Superb Lab Power Supply

This hands-on laboratory guides students through assembling, calibrating, and packaging a complete benchtop linear DC power supply capable of providing an adjustable 0 to 30 V output with continuously variable current limiting from 2 mA to 3 A. Students populate and solder an analog regulator board featuring operational-amplifier control loops and a high-power bipolar pass transistor, alongside an Arduino-based monitoring shield equipped with a precision analog-to-digital converter, high-side current sense amplifier, output disconnect relay, and an I2C character LCD. Working with multimeters and test loads, learners condition the analog circuitry to zero the minimum output voltage, calibrate constant-current mode thresholds, and verify digital telemetry. Through complete chassis integration including AC mains step-down transformer wiring, thermal heatsinking with electrical insulation, and front-panel potentiometer controls, students gain practical experience in linear voltage regulation, overcurrent protection, power dissipation, and mixed-signal instrumentation.

linear power supply DC power supply benchtop power supply voltage regulator constant current constant voltage current sensing Arduino operational amplifier op amp power electronics PCB assembly soldering multimeter calibration instrumentation overcurrent protection thermal management heatsink

Uploaded by demo on 2026-07-09 · ready · Electronics · Original source ↗

Files: 00002A.brd · 00002A.sch · 00002A.zip · BOM_Assembly.pdf · DCmeter.ino · Schematic.pdf · WiringAndParts.pdf · frontPanel.svg · manual.pdf

Readiness checks

  • complete 2026-09-03 00:13 🛡 Cybersecurity: Could not check · 2 findings 85 searches · 5 pages
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  • running 2026-09-02 19:21
  • failed 2026-09-02 18:57 Judge exceeded 10 iterations without producing judgment notes.
  • complete 2026-07-09 02:04 🛡 Cybersecurity: not checked 39 searches · 0 pages
    view · PDF

Latest report — 2026-09-03 00:13

Readiness: Superb Lab Power Supply

Verdict: At risk · 2026-09-02 · est. parts cost $220–$420 Cybersecurity — software & network: Could not check

One part now blocks a clean build: R4, the Vishay WSL3637R0100FEA 10 mΩ four-terminal Kelvin shunt on the custom 00002A shield. It is out of stock at all five ECIA-authorized distributors that list it, with 40–55 week factory lead times, and every sibling in the same 3637 package (FEB, DEA, FBA) is out of stock everywhere too — so there is no drop-in to fall back on. That shunt sits in the full 3 A output path and the snapshot rates its substitution latitude "Low", so it cannot simply be swapped for a different package. The mains power switch and the chassis ground lug are also zero-stock with 3–15 week leads, though both have generic equivalents. Everything else is sourceable today, and where a part went obsolete (the relay, the 100 nF decoupling caps, the 1.8 MΩ divider resistor) there is a substitute below with its footprint checked against distributor parametrics. Note that the analog 0–30 V board is bought as a kit ($4.25–$17) that supplies its own parts — only the shield is built component by component, which is exactly where the shunt problem lands. The verdict has dropped from the previous report's Ready with caveats: in July the shunt was still in stock at a specialist distributor at $1.05, and the mains switch had not been checked. The cost estimate also rose sharply, because the previous report priced a generic $25.67 transformer rather than the specified DP-241-8-20 ($46–$49) and did not count the chassis consumables (wire, cord, fasteners, standoffs, lettering, ground lug) at all.

Action required

Part Problem Recommended action
R4 WSL3637R0100FEA New since July. Zero stock at all 5 ECIA distributors; 40–55 week leads. Every WSL3637 10 mΩ sibling also zero-stock. Order now against lead time, or source from a broker and verify authenticity. Do not swap to a 4527-package shunt — the board is drawn for the 3637 Kelvin pads.
C3–C7 GRM188R71H104KA93D Obsolete; zero stock everywhere; 42-week lead. Use C0603C104K5RACTU (KEMET), $0.13, 7.1 M in stock — verified 0603 drop-in.
C2 GRM188R61A106KE69D Zero stock at all 4 distributors; 19-week lead. Use C1608X5R1A106K080AC (TDK), $0.27, 160 k in stock — verified 0603 drop-in.
R5 ERJ-3EKF1804V Obsolete at DigiKey (30-week lead). Buy from Newark (10,828 @ $0.032) or use CRCW06031M80FKEA, $0.10, 27,898 in stock.
K1 G5LE-1-VDDC12 Obsolete (as in July), zero stock at DigiKey. Still stocked by Heilind/Sager/ICC/TTI. Or use G5LE-1 DC12 / G5LE-14 DC12 — footprint not verified, check the pinout.
IC1 MAX44284FAUT+T New since July. DigiKey stock fell to zero (22-week lead). Order from Mouser: 6,115 in stock @ $3.66.
Item 11 EG4397-ND switch New since July. Zero stock, 15-week lead, single distributor. Its 19.20 × 13.00 mm cutout also disagrees with the panel file. Back-order at DigiKey, or use a switched-and-fused C14 inlet (~$5–7) and drop the separate switch.
Item H L35-B2-5 ground lug New since July. Zero stock at all 5 distributors, 3–12 week leads, $14–$17. Any UL-listed 8–14 AWG mechanical copper lug works; electrical-supply houses list the base Blackburn L35 at $3.29.
Item 14 enclosure New since July. No enclosure checked meets the ≥200 × 210 × 90 mm envelope. Select manually against the envelope; the Hammond 1455ZT2201 is 34 mm too short.
Item 9 DP-241-8-20 Not a shortage — a price correction. Exact part is $46–$49, not the $25.67 assumed in July. Budget for it; must be an AC-AC chassis transformer, never a DC brick.

Cybersecurity — software & network

Could not check — All three software components are unpinned Arduino-side code with no vulnerability database covering them, so no security check was possible; the two problems recorded here are a dead download link and unpinned versions, not network exposure - this device has no network interface.

Component Version How known Support status
Arduino Core for AVR (arduino:avr) not determined unpinned (the lab ships no board-package manifest; the snapshot records no version) —
Arduino Wire library (<Wire.h>, I2C master) not determined unpinned (bundled with whichever AVR core is installed; included at DCmeter.ino line 1) —
LiquidCrystal_I2C (fmalpartida new-liquidcrystal fork) not determined unpinned (DCmeter.ino line 2 cites a bare Bitbucket downloads directory with no version; the maintained GitHub mirror's library.json currently publishes 1.5.0) —
Component Finding Severity Fix available?
Arduino firmware dependencies (AVR core, Wire, LiquidCrystal_I2C) None of the three firmware dependencies is pinned to a version, and the sketch uses a constructor that only this LCD fork provides, so a student who installs the Library Manager's LiquidCrystal_I2C instead gets a compilation failure rather than a working meter. posture Mitigation only - state the exact library and core versions in the build instructions and ship a vendored copy of the LCD library with the lab
LiquidCrystal_I2C (fmalpartida new-liquidcrystal fork) The library download location the firmware source cites returns HTTP 404, so anyone building this lab has to find the LCD driver somewhere else on the internet and cannot check that what they got is what the lab was written against. posture Mitigation only - take the library from the maintained GitHub mirror at github.com/fmalpartida/New-LiquidCrystal (its library.json publishes 1.5.0) and keep that copy with the lab materials instead of linking out

What this means for your lab

This power supply is not a networked device. The Arduino talks to a bench PC over a USB serial cable only, and the 0x3F and 0x68 numbers in the design are I2C chip addresses on a few centimetres of wire inside the box, not network addresses. So there is nothing here for someone else on your campus network to reach, log into, or read, and nothing needed to be cleared with IT before the supply is switched on. The real problem is where the firmware's code comes from. The one third-party library the sketch needs is fetched from a link printed in the source file, that link is dead, and nothing records which version the lab was written against - so each student ends up downloading some copy of the library from wherever they can find it, and the common one from the Arduino Library Manager will not even compile against this sketch. Before the next class, download the library once from the maintained GitHub mirror, keep that copy alongside the lab files, and write the version you used into the build instructions so everyone compiles the same code.

Not checked

  • Arduino Core for AVR (arduino:avr): no vulnerability database covers Arduino board packages, and no version is pinned to check
  • Arduino Wire library (<Wire.h>): bundled with the AVR core; it has no version of its own and no advisory database
  • LiquidCrystal_I2C (fmalpartida new-liquidcrystal fork): no advisory database covers Arduino libraries, the lab pins no version, and the documented download location is gone
  • Arduino IDE and the avr-gcc toolchain: implied by the AVR core but not recorded with a version in the lab materials, and not tracked by endoflife.date
  • EAGLE (00002A.sch, 00002A.brd) and the SVG editor for frontPanel.svg: design-tool dependencies implied by the lab's file formats; no version recorded and no advisory database applies

Parts

Integrated Circuits and Active Semiconductors (00002A shield)

Part Spec/Package Status Stock Price Source Drift
IC1: MAX44284FAUT+T Current-sense amp, 1.7–5.5 V, SOT-23-6 Available (not at DigiKey) 6,115 (Mouser) $3.66 Mouser (ECIA); DigiKey $3.99, stock 0, 22-wk lead DigiKey 2,773 → 0; price held at $3.66
IC2: MCP3422A0-E/SN 18-bit ADC, 2.7–5.5 V, SOIC-8 Ready 2,599 $3.72 DigiKey 4,069 → 2,599; price flat
IC3: MCP6061T-E/OT Op-amp, 1.8–6.0 V, SOT-23-5 Ready 2,829 $0.84 DigiKey 574 → 2,829; price flat
Q1, Q2: BC817-25LT3G NPN 45 V / 500 mA, SOT-23-3 Ready 139,400 $0.17 DigiKey (9 distributors stocked) 3,187 → 139,400; price flat
D3: BAT54 Schottky 30 V / 200 mA, SOT-23-3 Ready 842,137 $0.14 DigiKey (BAT54LT1G single-die variant) 424,390 → 842,137; price flat
Z1: 824501361 TVS 36 V standoff, 400 W, DO-214AC Ready — polarity unconfirmed 4,033 $0.29 DigiKey (listed as SMAJ36CA); Mouser 2,631 on the exact number 4,611 → 4,033; price flat

Electromechanical and Relays (00002A shield)

Part Spec/Package Status Stock Price Source Drift
K1: G5LE-1-VDDC12 SPDT 1 Form C, 12 VDC coil, 10 A, through hole Obsolete — still stocked elsewhere 0 at DigiKey; 1,760 Heilind, 607 Sager, 586 ICC, 475 TTI $1.07 list; $0.67–$0.77 at stocking distributors ECIA Was "obsolete, no source"; four authorized distributors do hold stock

Precision Current Shunt Resistor (00002A shield)

Part Spec/Package Status Stock Price Source Drift
R4: WSL3637R0100FEA 10 mΩ, 1%, 3 W, 3637 Kelvin, 9.14 × 9.40 mm Hard to obtain 0 at all 5 ECIA distributors (40–55 wk leads) $1.46 DigiKey (back-order only) Was >100 @ $1.05 at a specialist distributor; now no stock anywhere

Passive Components — Resistors and Capacitors (00002A shield)

Part Spec/Package Status Stock Price Source Drift
R5: ERJ-3EKF1804V 1.8 MΩ, 1%, 0603 Obsolete — stocked elsewhere 0 at DigiKey; 30,000 TTI, 10,828 Newark, 2,169 Mouser $0.032/100 at Newark ECIA — (rolled into a "resistor kit" row in July)
R6, R7: RC0603FR-07100KL 100 kΩ, 1%, 0603 (×2) Ready 2,357,465 $0.10 DigiKey —
R1: RC0603JR-071K8L 1.8 kΩ, 5%, 0603 Ready 83,028 $0.10 DigiKey —
R2, R3, R11, R13, R15–R18: RC0603JR-07470RL 470 Ω, 5%, 0603 (×8) Ready 444,311 $0.10 DigiKey —
R8–R10, R12, R14, R19, R20: RC0603JR-074K7L 4.7 kΩ, 5%, 0603 (×7) Ready 1,151,400 $0.10 DigiKey —
C1: GRM1885C1H222JA01D 2.2 nF, 50 V, C0G, 0603 Available (not at DigiKey) 0 at DigiKey; 236,000 Avnet, 156,000 Future, 104,000 Newark $0.10 ECIA (4,000-pc price breaks) —
C2: GRM188R61A106KE69D 10 µF, 10 V, X5R, 0603 Hard to obtain 0 at all 4 distributors (19-wk lead) $0.17 DigiKey (back-order) —
C3, C4, C5, C6, C7: GRM188R71H104KA93D 100 nF, 50 V, X7R, 0603 (×5) Obsolete, no stock 0 (42-wk lead) no current price DigiKey (back-order) —
S1: PUENTE Printed solder-bridge net tie No purchase required — — — —

Connectors and Headers (00002A shield)

Part Spec/Package Status Stock Price Source Drift
X1: MKDSN 1,5/ 4-5,08 4-pos, 5.08 mm pitch, 10 A / 300 V Ready 3,166 $1.94 DigiKey (cat. no. 1729144) 144 → 3,166; price flat
X2, X3, X7: Molex 0022232021 2-pos, 2.54 mm friction lock (×3) Ready 87,682 $0.18 DigiKey was "not checked"
X5, X6: Molex 0022232031 3-pos, 2.54 mm (×2) Ready 114,189 $0.23 DigiKey was "not checked"
X4: Molex 0022232041 4-pos, 2.54 mm Ready 55,426 $0.28 DigiKey was "not checked"
SV1–SV4: PRPC040SAAN-RC 40-pin 0.1" breakaway strip Ready 48,820 $1.23 DigiKey was "not checked"

Active Devices — 0–30 V Analog Kit (supplied with Item 8)

Part Spec/Package Status Stock Price Source Drift
U1–U3: TL081CP JFET op-amp, 7–36 V supply, 8-DIP (×3) Ready 7,825 $0.70 DigiKey 10,105 → 7,825; price flat
Q4: 2SD1047 NPN 140 V / 12 A / 120 W, TO-3P-3 Available again, thin stock 174 $6.56 DigiKey (EVVO); ST's part still obsolete, 0 stock was obsolete with zero stock — improved
Q2: 2SD882 NPN 30 V / 3 A / 12.5 W, TO-126 Ready 8,003 $2.50 DigiKey 8,181 → 8,003; price flat
Q1: SS9014 NPN 45 V / 100 mA, TO-92 Ready (as SS9014CBU) 92,110 $0.04 DigiKey was priced retail at $0.08; now an authorized-distributor part
Q3: SS9015 PNP 45 V / 100 mA, TO-92 Obsolete (all variants) — huge stock 753,175 $0.04 DigiKey was priced retail at $0.08; lifecycle now visible as obsolete
D1–D4: 1N5408 1000 V / 3 A, DO-201AA (×4) Ready 11,006 $0.35 DigiKey 41,798 → 11,006; price flat
D11: 1N4004 400 V / 1 A, DO-41 Ready 199,396 $0.14 DigiKey 128,112 → 199,396; price flat
D5, D6, D9, D10: 1N4148 100 V / 200 mA, DO-35 (×4) Ready 763,524 $0.10 DigiKey 1 M+ → 1.49 M on the tape variant; price flat
D7, D8: 1N5231B Zener 5.1 V, 500 mW, DO-35 (×2) Ready 78,528 $0.18 DigiKey no baseline — July checked 1N4733A, a different part
D12: 5 mm red LED (WP7113ID) T-1 3/4, Vf 1.9 V Ready 145,555 $0.21 DigiKey was "not checked"

Analog Kit Resistors and Trimmers (supplied with Item 8)

Part Spec/Package Status Stock Price Source Drift
R7: SQP500JB-0R47 0.47 Ω, 5 W, ceramic axial Ready 535 $1.26 DigiKey 605 → 535; price flat
R1: RSF100JB-73-2K2 2.2 kΩ, 1 W metal oxide axial Ready 6,693 $0.20 DigiKey was "not checked"
R2–R6, R8–R22: 1/4 W 5% axial set 33 Ω to 270 kΩ, axial 0207 Ready (assortment) in stock $16.99 / 1,000 pc Altex Electronics (Xpart 250 pc $8.21) was a $9.95 RobotShop kit
RV1: 3296W-1-104LF 100 kΩ multiturn trimmer, 9.53 × 4.83 mm Ready 11,823 $2.73 DigiKey July priced a $2.38 Mouser listing; this is the Bourns part itself
P1, P2: 10 kΩ linear pot Panel mount, 6.0 mm shaft (×2) Ready — shaft not verified in stock $0.59 ProtoSupplies; Taiwan Alpha RV110F-40-15A-B10K, Mouser 968 @ $2.27 $0.95 → $0.59

Analog Kit Capacitors (supplied with Item 8)

Part Spec/Package Status Stock Price Source Drift
C1: UVR1H332MHD 3300 µF, 50 V, 18 mm dia, 7.5 mm pitch, 2.5 A ripple Ready 4,094 $3.18 DigiKey was rolled into a $5.99 "electrolytic kit"
C2, C3: ECA-1HHG470 47 µF, 50 V, 6.3 mm dia (×2) Ready 39,883 Mouser; 12,688 DigiKey on the "I" variant $0.44 DigiKey / Mouser $0.42 was rolled into a kit
C7: ECA-1HHG100 10 µF, 50 V, 5 mm dia Ready 10,612 on the "I" variant $0.31 DigiKey / Mouser $0.36 was rolled into a kit
C4: C315C104K5R5TA 0.1 µF, 50 V radial — 2.54 mm pitch (snapshot says 5.0 mm) Ready 7,195 $0.62 DigiKey was rolled into a $14.95 kit
C5: C320C224K5R5TA 0.22 µF, 50 V radial — 2.54 mm pitch (snapshot says 5.0 mm) Ready 1,157 $1.56 DigiKey; Mouser 5,973 @ $1.29 was rolled into a kit
C6, C9: D101K20Y5PH63L2R 100 pF, 100 V disc, 2.50 mm lead spacing (×2) Hard to obtain 0 at all 5 distributors (19-wk lead) $0.04 at 20 k DigiKey (back-order) was rolled into a kit
C8: D331K20Y5PH63L2R 330 pF, 100 V disc, 2.50 mm lead spacing Hard to obtain 0 at all 5 distributors (19-wk lead) $0.04 at 20 k DigiKey (back-order) was rolled into a kit

System, Chassis, Enclosure and Interconnect Hardware

Part Spec/Package Status Stock Price Source Drift
Item 1: 2004 I2C LCD 20×4 HD44780 + PCF8574, address 0x3F Ready in stock $4.13 BuyDisplay (eBay $8.25–$12.96) $4.50 → $4.13
Item 2: 10 kΩ panel pots (×2) Panel mount, 8 mm hole Ready in stock $0.59 ProtoSupplies $0.95 → $0.59
Item 3a: EG2045-ND (red) E-Switch PS1057ARED, SPST-NO, 12.60 × 11.30 mm cutout Ready — single distributor 979 $1.92 DigiKey was "not checked"
Item 3b: EG2041-ND (black) E-Switch PS1057ABLK, same cutout Ready — single distributor 7,640 $1.83 DigiKey was "not checked"
Item 4: banana binding posts (×3) 4 mm, ≥ 24 A, 9.5 mm panel hole Ready — M5 stud not verified in stock $2.70 Newark (Multicomp Pro 76-1502, 25 A) was "not checked"
Item 5: Arduino Uno R3 ATmega328P, 16 MHz, 5 V Ready in stock $4.99 Micro Center (CH340 board); genuine Uno Rev3 $30.95 PiShop $4.99 unchanged
Item 6: DC barrel pigtail 2.1 × 5.5 mm male to bare leads Ready in stock $0.95 Cable Leader was "not checked"
Item 7: 3590S-2-103L (optional, ×2) 10-turn 10 kΩ, 2 W, panel mount Ready — expensive 3,087 $18.39 DigiKey was "not checked"
Item 8: Vkmaker 0–30 V PSU kit 84 × 84 mm analog board kit Ready in stock $9.99 Banggood (AliExpress $4.25, eBay $16–$17) was never priced
Item 9: DP-241-8-20 115/230 VAC to 20 VCT @ 5 A chassis transformer Ready — price corrected 50 DigiKey, 25 Mouser $47.80 DigiKey / $46.10 Mouser ECIA July priced a generic 24 VAC unit at $25.67; the specified part is $46–$49
Item 10: IEC C14 inlet + fuse 250 VAC 10 A panel inlet, 5×20 mm fuse Ready in stock $4.95 Amplified Parts (switched+fused versions $5–$7) was "not checked"
Item 11: EG4397-ND mains switch E-Switch PB1973ABLKBLKEF0, SPST 15 A / 250 VAC, 19.20 × 13.00 mm cutout Hard to obtain 0 (15-wk lead, sole distributor) $2.63 DigiKey (back-order) was "not checked"
Item 12: off-board pass transistor See Q4 / Item 8 Available, thin stock 174 $6.56 DigiKey see Q4
Item 13a: heatsink TO-247, 100 mm, ≤ 0.8 °C/W (not verified) Ready — thin stock 45 Mouser, 10 DigiKey $7.60 DigiKey (Wakefield 694-100) $7.60 unchanged
Item 13b: ceramic insulator TO-264 alumina, 22 × 28 × 0.6 mm (size not verified) Ready in stock $3.60 eBay (innovasupplies $16.43) was "not checked"
Item 14: benchtop enclosure ≥ 200 mm deep × 210 mm wide × 90 mm high Not verified to spec 1 DigiKey / 26 Mouser on the Hammond unit $29.86 Newark (Hammond 1455ZT2201 — 222 × 85.6 × 56 mm, too short) $7.99 eBay box → nothing found that meets the envelope
Item A: 18 AWG silicone wire Stranded, ≥ 300 V Ready in stock $14.86 Performance-PCs was "not checked"
Item B: 24 AWG hookup wire Stranded, tinned copper Ready in stock $9.95 Jameco was "not checked"
Item C: laser-cut front panel 3 mm two-colour acrylic, 203.2 × 85.76 mm not checked — — — —
Item D: IEC C13 mains cord NEMA 5-15P to C13, 18 AWG Ready in stock $8.30 Best Buy was "not checked"
Item E: knobs (×4) 6.0 mm and 6.35 mm shafts, pointer Ready — shaft fit not verified in stock $3.13 eBay was "not checked"
Item F: PCB standoffs (8–12) Self-adhesive nylon, 25 mm, 4.0 mm hole Ready — 25 mm adhesive not verified in stock $3.90 keszoox (screw-in 25 mm nylon at DigiKey $1.67) was "not checked"
Item G: M3/M4/M5 fasteners Stainless screws, washers, locknuts Ready in stock $7.47 Walmart (Hyper Tough 182-pc) was "not checked"
Item H: L35-B2-5 ground lug Copper mechanical lug, 8 str – 14 sol Hard to obtain 0 at all 5 distributors (3–12 wk leads) $14.74 DigiKey (back-order); base Blackburn L35 $3.29 retail was "not checked"
Item I: dry-transfer lettering White rub-on, ~3 mm Ready in stock $7.99 HobbyTown (Woodland Scenics) was "not checked"
Item J: Faston terminals (6–10) 3/16" (4.75 mm) female crimp Ready in stock $5.98 Parts Express (50 pc) was "not checked"

Substitutes

For part Substitute Differences Verified Judgment
K1 G5LE-1-VDDC12 G5LE-1 DC12 — $1.72, 6,012 at DigiKey, 9 distributors stocked Same SPDT (1 Form C) contact form, 10 A contacts, 12 VDC coil. DigiKey's own "Parametric Equivalent" for the obsolete part verified: contact form, contact rating, coil voltage (DigiKey parametric-equivalent entry vs the original's parametrics); not verified: pin layout, lead pitch, body dimensions Recommended — check the pinout against the board before soldering
K1 G5LE-1-VDDC12 G5LE-14 DC12 — $1.73, 24,375 Every listed parameter identical to the original: through hole, 12 VDC coil, SPDT 1 Form C, 10 A, 33.3 mA coil, 9 VDC must-operate, AgSnO contacts, -25 to 85 °C verified: mounting type, coil voltage, contact form, contact rating, coil current, contact material (DigiKey parametrics, both parts); not verified: pin layout and body dimensions Recommended — best-evidenced option. Do not use G5LE-1A4 DC12 or G5LE-1A-E DC12: those are SPST-NO, the wrong contact form
R5 ERJ-3EKF1804V CRCW06031M80FKEA — $0.10, 27,898 1.8 MΩ ±1% both; 1/8 W vs 1/10 W (exceeds — acceptable); TCR ±100 ppm/°C both verified: package 0603 and body size on both (1.60 × 0.80 mm vs 1.55 × 0.85 mm, both standard 0603), resistance, tolerance, power (DigiKey parametrics) Recommended
C2 GRM188R61A106KE69D C1608X5R1A106K080AC — $0.27, 160,024 None found: 10 µF, ±10%, 10 V, X5R on both verified: package 0603 and body size 1.60 × 0.80 mm identical on both, plus value, tolerance, voltage, dielectric (DigiKey parametrics) Recommended — drop-in
C3–C7 GRM188R71H104KA93D C0603C104K5RACTU — $0.13, 7,158,308 None found: 0.1 µF, ±10%, 50 V, X7R on both verified: package 0603 and body size 1.60 × 0.80 mm identical on both, plus value, tolerance, voltage, dielectric (DigiKey parametrics) Recommended — drop-in
C1 GRM1885C1H222JA01D C0603C222J5GACTU — $0.40, 63,798 None found: 2200 pF, ±5%, 50 V, C0G/NP0 on both. 4× the unit price, but buyable in ones verified: package 0603 and body size 1.60 × 0.80 mm identical on both, plus value, tolerance, voltage, dielectric (DigiKey parametrics) Recommended when you don't want a 4,000-piece reel
C6, C9 D101K20Y5PH63L2R D101K20Y5PH63L6R — $0.43, 473 Electrically identical (100 pF, 100 V, Y5P, 5.00 mm disc) but lead spacing 6.35 mm vs the original's 2.50 mm — the snapshot specifies a 2.5 mm pitch verified: lead spacing on both from DigiKey parametrics — this is a mismatch, not a match Rejected — footprint hard stop. The 2.5 mm-pitch siblings DigiKey suggests all show no stock
C8 D331K20Y5PH63L2R D331K20Y5PH63L6R — $0.43, 28,162 Same story: 330 pF, 100 V, Y5P, 5.00 mm disc, but lead spacing 6.35 mm vs 2.50 mm verified: lead spacing on both from DigiKey parametrics — mismatch Rejected — footprint hard stop
Q4 2SD1047 TIP35CG — $3.65, 5,809 TO-247-3 vs TO-3P-3; 25 A vs 12 A (exceeds); 125 W vs 120 W (exceeds); 100 V vs 140 V VCEO — short of the identity spec but within the snapshot's stated ≥ 100 V latitude, and the rail is only 30–34 V; hFE 15 at 15 A vs 35 at 5 A, so the driver must supply more base current verified: package designation, collector current, power rating, VCEO from DigiKey parametrics on both; the snapshot explicitly permits TO-247. not verified: bolt-hole position and pin pitch (mounted off-board on flying leads, so this is a heatsink check) Recommended as the fallback; the exact 2SD1047 is back in stock (174 pcs) if you prefer it
Q3 SS9015 2N3906 — $0.14, 25,866 PNP TO-92 both; 200 mA vs 100 mA (exceeds); 625 mW vs 450 mW (exceeds); 40 V VCEO vs the snapshot's stated ≥ 45 V — falls short, though the snapshot itself names 2N3906 as acceptable verified: package TO-92 (TO-226-3), collector current, power rating (DigiKey parametrics, both). not verified: pinout (E-B-C ordering), and the 45 V requirement is not met Only if the obsolete SS9015 stock (753,175 pcs) runs out — check the node voltage and pinout first
Z1 824501361 SMAJ36A — $0.48, 39,166 36 V standoff both; 40 V min breakdown vs 42.1 V typ; 58.1 V clamping and 400 W identical; DO-214AC (SMA) both verified: package DO-214AC/SMA, standoff, breakdown, clamping and peak pulse power on both (DigiKey parametrics) — all meet the snapshot's spec. not verified: unidirectional vs bidirectional, which the snapshot requires Acceptable on ratings; confirm polarity on the datasheet, for this part and for the Würth part DigiKey lists as SMAJ36CA
Item 11 EG4397-ND Switched + fused IEC C14 inlet — $6.95 Replaces Items 10 and 11 with one rear-panel part; listing states 10 A / 250 VAC, meeting the snapshot's "SPST ≥ 250 VAC, 5 A". Removes a front-panel hole not verified — Google Shopping links resolve to redirects, not to a fetchable product page, so the mains rating comes from the listing title only Plausible, unverified — confirm the rating and cutout on the seller's own page before ordering
Item 14 enclosure Hammond 1455ZT2201 — $32.27, stock 1 222.00 × 85.60 × 55.98 mm against the required ≥ 200 mm depth / ≥ 210 mm width / ≥ 90 mm height — 34 mm too short verified: body dimensions from DigiKey parametrics — they do not meet the requirement Rejected on evidence. Select an enclosure manually against the envelope

Verify any substitute against its datasheet before ordering.

Other dependencies

  • Custom shield PCB "00002A" — 2 layers, 55.88 × 53.34 mm, 111 plated holes across 5 drill sizes, 8/8 mil track and space, solder mask both sides, top silkscreen; Gerbers in 00002A.zip. Not checked — no fabrication quote was obtained this run. The specifications are routine for any 2-layer prototype service.
  • Analog PCB (84 × 84 mm) — no separate fabrication needed; it comes with the Item 8 kit.
  • Front panel — frontPanel.svg, 203.2 × 85.76 mm, 3 mm two-colour acrylic (white on black), with an LCD window, 4 pot holes, 2 pushbutton holes, a power-switch hole and 3 binding-post holes. Not checked: the Ponoko material page the snapshot cites returned no extractable text when fetched this run, so neither availability nor price was confirmed. Note also that the mains switch specified as Item 11 needs a 19.20 × 13.00 mm rectangular cutout, larger than any hole in this cut list — reconcile the panel file with the switch you actually buy.
  • eBay / AliExpress listings cited in the snapshot (2004 LCD, Vkmaker kit, multiturn pot, enclosure, ceramic insulators, banana sockets) — not checked. A fetch of the Vkmaker listing was blocked by eBay, so these 2016–2017 listing IDs could not be confirmed alive. Every product they point at is currently purchasable from other sellers, priced above.
  • DigiKey links cited in the snapshot (EG2045-ND, EG2041-ND, EG4397-ND, 595-1088-ND) — all four resolve to current catalogue parts; see the tables.
  • Calibration — RV1 must still be trimmed until the output reads 0.00 V at the minimum setting.
  • Input constraint — 24 VAC AC-AC only. A DC power brick is forbidden by the design; this remains the easiest way to destroy the build.

Watch list

  • R4 WSL3637R0100FEA — the whole Vishay WSL3637 10 mΩ family is out of stock across authorized distribution with 18–55 week leads and a High supply-chain risk rating. If it has not restocked by the next check, the shield needs a redesigned sense footprint.
  • Item 11 EG4397-ND mains switch — zero stock, 15-week lead, and only one distributor lists it. A single-sourced mains part on a student-operated control is worth replacing pre-emptively.
  • Item 3 pushbuttons (PS1057ARED / PS1057ABLK) — also single-sourced at DigiKey. Fine today (979 and 7,640 in stock), but there is no second source if that changes.
  • C6, C8, C9 Vishay disc capacitors — zero stock everywhere, 20,000-piece minimum pricing, and the only in-stock siblings have the wrong lead spacing. Harmless while the Item 8 kit supplies them; a problem the day someone needs a replacement.
  • Q3 SS9015 and Q1 SS9014 — obsolete lifecycle across every variant. Stock is enormous today (750 k+), so this is a multi-year horizon, not a next-check one.
  • Item 9 DP-241-8-20 transformer — only 50 units at DigiKey and 25 at Mouser, at $46–$49. Low stock on the single most expensive line in the build.
  • Item 14 enclosure — no in-evidence box meets the stated envelope; the next check should be run against a specific chosen enclosure rather than a generic search.
Snapshot What the lab depended on when it was uploaded — the baseline the readiness checks research against.

This document provides an exhaustive snapshot of all physical hardware, components, off-the-shelf modules, software libraries, and fabrication specifications for the Superb Lab Power Supply.

System Overview and Operating Rails

The Superb Lab Power Supply is an adjustable 0–30 V, 2 mA–3 A linear benchtop DC power supply with digitally controlled overvoltage (OV) and overcurrent (OC) protection. The architecture integrates an analog linear regulator board (powered by a 24 VAC mains step-down transformer producing an unregulated internal DC rail of approximately 30 V to 34 VDC) with a custom microcontroller shield (designated "00002A") mated to an Arduino Uno R3.

The system logic operates on a regulated +5 V rail supplied by the Arduino Uno. The protection relay coil operates on the Arduino VIN rail (nominal +12 VDC supplied via an external DC barrel jack). High-side current sensing is performed directly on the 0–30 V output rail across a 10 mΩ shunt resistor using an amplifier with a 36 V common-mode rating, while output voltage sensing uses a resistive divider scaled to the 0–5 V ADC input range.

Component Inventory: 00002A Digital DC Meter Shield PCB

The custom Arduino Uno shield ("00002A") contains 47 distinct schematic/board elements. All surface-mount passives are in standard 0603 imperial packages unless explicitly specified.

Integrated Circuits and Active Semiconductors

  • IC1: High-side current-sense amplifier, fixed gain 50 V/V.

    • Identity: Maxim Integrated / Analog Devices MAX44284FAUT+T (BOM lists MAX44284FAUT+, DigiKey: MAX44284FAUT+TCT-ND).
    • Quantity: 1.
    • Footprint: SOT-23-6 (SOT23-6).
    • Electrical constraints: Supply voltage: 1.7 V to 5.5 V (runs on +5 V rail). Common-mode input range: -0.1 V to +36 V (sits on the 0–30 V output rail). Gain accuracy: 0.2%.
    • Substitution latitude: Low. Must have identical pinout, fixed 50 V/V gain, and a common-mode input range covering at least 32 V to monitor the full output range.
    • Operated control: No.
    • Sourcing plan: distributor lookup: MAX44284FAUT+T

  • IC2: 18-bit dual-channel delta-sigma ADC with I2C interface and internal reference.

    • Identity: Microchip MCP3422A0-E/SN (DigiKey: MCP3422A0-E/SN-ND).
    • Quantity: 1.
    • Footprint: SOIC-8 (SOIC-8).
    • Electrical constraints: Supply voltage: 2.7 V to 5.5 V (runs on +5 V rail). I2C fixed address 0x68 (A0 address variant). Differential input range: ±2.048 V.
    • Substitution latitude: None without rewriting DCmeter.ino I2C register configuration and state machine routines.
    • Operated control: No.
    • Sourcing plan: distributor lookup: MCP3422A0-E/SN

  • IC3: Low-power rail-to-rail input/output operational amplifier (voltage buffer).

    • Identity: Microchip MCP6061T-E/OT (DigiKey: MCP6061T-E/OTCT-ND).
    • Quantity: 1.
    • Footprint: SOT-23-5 (SOT23-5).
    • Electrical constraints: Supply voltage: 1.8 V to 6.0 V (runs on +5 V rail). Input offset voltage ≤ 150 µV. Unity-gain stable.
    • Substitution latitude: Any precision rail-to-rail I/O 5 V op-amp in SOT-23-5 with matching pinout.
    • Operated control: No.
    • Sourcing plan: distributor lookup: MCP6061T-E/OT

  • Q1, Q2: NPN general-purpose small-signal bipolar switching transistors.

    • Identity: ON Semiconductor BC817-25LT3G (DigiKey: BC817-25LT3GOSCT-ND). Note: Board file (00002A.brd) uses footprint value BC817-16LT1SMD, while the BOM specifies gain grade BC817-25LT3G. Both are functionally compatible.
    • Quantity: 2.
    • Footprint: SOT-23 (SOT23-BEC).
    • Electrical constraints: VCEO ≥ 45 V, IC ≥ 500 mA. Q1 switches the 12 V relay coil; Q2 senses the analog board constant-current LED line into digital pin D12.
    • Substitution latitude: Any standard NPN switching transistor in SOT-23 with VCEO ≥ 45 V and IC ≥ 500 mA (e.g., MMBT2222A, BC817-40).
    • Operated control: No.
    • Sourcing plan: distributor lookup: BC817-25LT3G

  • D3: Fast switching / Schottky barrier diode (relay flyback suppression).

    • Identity: Diodes Inc. / onsemi BAT54 (DigiKey: BAT54FSCT-ND).
    • Quantity: 1.
    • Footprint: SOT-23 (SOT23).
    • Electrical constraints: VR ≥ 30 V, IF ≥ 200 mA, forward clamp across 12 V inductive relay coil.
    • Substitution latitude: Any Schottky diode in SOT-23 rated for VR ≥ 30 V.
    • Operated control: No.
    • Sourcing plan: distributor lookup: BAT54

  • Z1: Transient Voltage Suppressor (TVS) diode, 36 V standoff.

    • Identity: Würth Elektronik 824501361 (DigiKey: 732-9957-1-ND). Note: The schematic/BRD library part name references package 824501401, but the component value and official assembly BOM explicitly require the 36 V variant 824501361.
    • Quantity: 1.
    • Footprint: DO-214AC / SMA SMD (824501401).
    • Electrical constraints: Reverse Standoff Voltage VR = 36 V, Breakdown Voltage VBR ≥ 40 V, 400 W peak pulse power dissipation. Protects output terminals.
    • Substitution latitude: Any 36 V unidirectional TVS diode in SMA/DO-214AC footprint.
    • Operated control: No.
    • Sourcing plan: distributor lookup: 824501361

Electromechanical and Relays

  • K1: Single-Pole Double-Throw (SPDT / 1 Form C) 12 VDC miniature power relay.
    • Identity: Omron Electronics G5LE-1-VDDC12 (DigiKey: Z3672-ND).
    • Quantity: 1.
    • Footprint: Through-hole 5-pin SPDT relay (G5LE).
    • Electrical constraints: Coil voltage: 12 VDC (nominal coil power 400 mW). Contact ratings: ≥ 5 A at 30 VDC / 250 VAC. Switched in series with output power rail.
    • Substitution latitude: Form-fit-function compatible through-hole relays with identical "Sugar Cube" footprint (e.g., Song Chuan 833H, TE Connectivity OEG SRD).
    • Operated control: No.
    • Sourcing plan: distributor lookup: G5LE-1-VDDC12

Precision Current Shunt Resistor

  • R4: Precision 4-terminal/Kelvin high-power surface-mount shunt resistor.
    • Identity: Vishay Dale WSL3637R0100FEA (DigiKey: WSLI-.01CT-ND).
    • Quantity: 1.
    • Footprint: 3637 SMD (WSL3637R0100FEA).
    • Electrical constraints: Resistance: 0.010 Ω (10 mΩ), ±1% tolerance, 3.0 W power rating, low TCR (±50 ppm/°C). Sits directly in the primary 3 A output current path.
    • Substitution latitude: Low. Must match the 3637 4-terminal/Kelvin-sense pad layout and sustain 3 A continuous dissipation (0.09 W nominal, but up to 3 W short/fault dissipation).
    • Operated control: No.
    • Sourcing plan: distributor lookup: WSL3637R0100FEA

Passive Components (Resistors and Capacitors)

  • R5: Thick film chip resistor, 1.8 MΩ, 1%, 0603.
    • Quantity: 1. Footprint: 0603 (R0603). Part number: Panasonic ERJ-3EKF1804V (DigiKey: P1.80MHCT-ND). High-side element of 20:1 precision voltage divider.
    • Sourcing plan: distributor lookup: ERJ-3EKF1804V
  • R6, R7: Thick film chip resistors, 100 kΩ, 1%, 0603.
    • Quantity: 2. Footprint: 0603 (R0603). Part number: Yageo RC0603FR-07100KL (DigiKey: 311-100KHRCT-ND). Low-side elements of 20:1 precision voltage divider.
    • Sourcing plan: distributor lookup: RC0603FR-07100KL
  • R1: Thick film chip resistor, 1.8 kΩ, 5%, 0603.
    • Quantity: 1. Footprint: 0603 (R0603). Part number: Yageo RC0603JR-071K8L (DigiKey: 311-1.8KGRCT-ND). Output RC filter on IC1.
    • Sourcing plan: distributor lookup: RC0603JR-071K8L
  • R2, R3, R11, R13, R15, R16, R17, R18: Thick film chip resistors, 470 Ω, 5%, 0603.
    • Quantity: 8. Footprint: 0603 (R0603). Part number: Yageo RC0603JR-07470RL (DigiKey: 311-470GRCT-ND). Input shunt filtering (R2, R3), pushbutton ESD/fault limiters (R11, R13), potentiometer protection (R15, R16, R17, R18).
    • Sourcing plan: distributor lookup: RC0603JR-07470RL
  • R8, R9, R10, R12, R14, R19, R20: Thick film chip resistors, 4.7 kΩ, 5%, 0603.
    • Quantity: 7. Footprint: 0603 (R0603). Part number: Yageo RC0603JR-074K7L (DigiKey: 311-4.7KGRCT-ND). I2C pull-ups (R9, R10), transistor base/pull-ups (R8, R19, R20), pushbutton pull-ups (R12, R14).
    • Sourcing plan: distributor lookup: RC0603JR-074K7L
  • C1: Ceramic capacitor, 2.2 nF (2n2), 50 V, C0G/NP0, 0603.
    • Quantity: 1. Footprint: 0603 (C0603). Part number: Murata GRM1885C1H222JA01D (DigiKey: 490-1459-1-ND). Filter capacitor for current sense.
    • Sourcing plan: distributor lookup: GRM1885C1H222JA01D
  • C2: Ceramic capacitor, 10 µF, 10 V, X5R, 0603.
    • Quantity: 1. Footprint: 0603 (C0603). Part number: Murata GRM188R61A106KE69D (DigiKey: 490-3896-1-ND). Shunt input bypass.
    • Sourcing plan: distributor lookup: GRM188R61A106KE69D
  • C3, C5, C6, C7 (and C4): Ceramic capacitors, 100 nF (0.1 µF), 50 V, X7R, 0603.
    • Quantity: 5 (or 4 if C4 is fitted as 47 nF). Footprint: 0603 (C0603). Part number: Murata GRM188R71H104KA93D (DigiKey: 490-1532-1-ND). Power rail and IC bypass decoupling.
    • Discrepancy Note: Schematic 00002A.sch and board 00002A.brd assign C4 = 47n (47 nF) across the low-side voltage divider, whereas the official assembly BOM (BOM_Assembly.pdf) specifies C3, C4, C5, C6, C7 = 100n (DigiKey: 490-1532-1-ND). Either 47 nF or 100 nF is electrically acceptable as an anti-aliasing RC filter on the ADC input.
    • Sourcing plan: distributor lookup: GRM188R71H104KA93D
  • S1: Printed solder bridge / net tie (PUENTE). Connects analog ground (AGND) to digital ground (GND) at a single star point. No purchase required.

Connectors and Headers

  • X1: 4-position 5.08 mm pitch through-hole screw terminal block.
    • Identity: Phoenix Contact MKDSN 1,5/ 4-5,08 (DigiKey: ED2611-ND).
    • Quantity: 1.
    • Footprint: 5.08 mm pin spacing (MKDSN1,5/4-5,08). Rated 13.5 A / 400 V. Terminals: Power IN (+/-), Power OUT (+/-).
    • Substitution latitude: Any standard 4-pin 5.08 mm (0.2") pitch PCB terminal block.
    • Sourcing plan: distributor lookup: MKDSN 1,5/ 4-5,08
  • X2, X3, X7: 2-position 2.54 mm (0.1") friction lock headers ("Molex style" / KF2510-2P).
    • Quantity: 3. Footprint: 2-pin 0.1" (22-23-2021 / KF2510-2P). Interfaces: ON pushbutton (X2), OFF pushbutton (X3), Analog board CC status LED pickoff (X7).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Molex 0022232021
  • X5, X6: 3-position 2.54 mm (0.1") friction lock headers ("Molex style" / KF2510-3P).
    • Quantity: 2. Footprint: 3-pin 0.1" (22-23-2031 / KF2510-3P). Interfaces: Overcurrent threshold pot (X5), Overvoltage threshold pot (X6).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Molex 0022232031
  • X4: 4-position 2.54 mm (0.1") friction lock header ("Molex style" / KF2510-4P).
    • Quantity: 1. Footprint: 4-pin 0.1" (22-23-2041 / KF2510-4P). Pinout: SCL, SDA, 5V0, GND (to external I2C LCD display).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Molex 0022232041
  • SV1, SV2, SV3, SV4: Breakaway pin headers, 0.1" (2.54 mm) pitch, gold plated.
    • Identity: Sullins PRPC040SAAN-RC (BOM DigiKey: S1011EC-40-ND).
    • Quantity: 1 strip (cut into 8-pin SV1, 8-pin SV2, 6-pin SV3, 10-pin SV4). Mates shield directly to Arduino Uno headers.
    • Sourcing plan: distributor lookup: PRPC040SAAN-RC

Component Inventory: 0–30 V Analog Linear Power Supply Kit

The analog power supply relies on the widely distributed "0-30V 2mA-3A Adjustable DC Regulated Power Supply DIY Kit" (Vkmaker / Hiland PCB layout 84 mm × 84 mm).

Active Devices (Diodes, Transistors, ICs)

  • U1, U2, U3: Single JFET-input operational amplifiers.

    • Identity: Texas Instruments / STMicroelectronics TL081CP or TL081IP.
    • Quantity: 3.
    • Footprint: DIP-8.
    • Electrical constraints: Supply voltage ratings up to ±18 V (36 V total rail). Sits across a split rail formed by the unregulated DC rail and a -5.1 V negative substrate pump.
    • Substitution latitude: Must tolerate up to 36 V to 40 V total supply voltage (e.g., TLE2071, OPA134, LF356). Standard 30 V op-amps (e.g., NE5534, LM741) may fail under high mains conditions.
    • Operated control: No.
    • Sourcing plan: distributor lookup: TL081CP

  • Q4: NPN high-power audio/linear power pass transistor.

    • Identity: Unisonic / Sanyo 2SD1047 (or generic D1047).
    • Quantity: 1.
    • Footprint: TO-3P / TO-247 through-hole (mounted off-board to an external heatsink via flying leads).
    • Electrical constraints: VCEO ≥ 140 V, IC ≥ 12 A, PC ≥ 100 W. Sustains full load drop: in worst-case short circuit at 3 A, dissipation is approximately (34 V × 3 A) = 102 W.
    • Substitution latitude: Any robust NPN power transistor in TO-247/TO-3P with VCEO ≥ 100 V, IC ≥ 15 A, PC ≥ 125 W (e.g., TIP35C, 2SC5200).
    • Operated control: No.
    • Sourcing plan: distributor lookup: 2SD1047

  • Q2: NPN medium power driver transistor.

    • Identity: 2SD882 (D882).
    • Quantity: 1.
    • Footprint: TO-126 through-hole (mounted with onboard mini aluminum heatsink).
    • Electrical constraints: VCEO ≥ 30 V, IC ≥ 3 A, hFE = 160–320.
    • Substitution latitude: BD139 (verify pinout: BD139 is E-C-B, 2SD882 is E-C-B), 2SD882S.
    • Operated control: No.
    • Sourcing plan: distributor lookup: 2SD882

  • Q1: NPN small-signal bipolar transistor.

    • Identity: SS9014 (9014) or equivalent.
    • Quantity: 1.
    • Footprint: TO-92.
    • Electrical constraints: VCEO ≥ 45 V, IC ≥ 100 mA.
    • Substitution latitude: Any general-purpose NPN transistor (e.g., 2N3904, BC547).
    • Operated control: No.
    • Sourcing plan: distributor lookup: SS9014

  • Q3: PNP small-signal bipolar transistor.

    • Identity: SS9015 (9015) or equivalent.
    • Quantity: 1.
    • Footprint: TO-92.
    • Electrical constraints: VCEO ≥ 45 V, IC ≥ 100 mA.
    • Substitution latitude: Any general-purpose PNP transistor (e.g., 2N3906, BC557).
    • Operated control: No.
    • Sourcing plan: distributor lookup: SS9015

  • D1, D2, D3, D4: 3 A, 1000 V silicon power rectifier diodes (mains full-wave bridge).

    • Identity: 1N5408.
    • Quantity: 4.
    • Footprint: DO-201AD axial.
    • Electrical constraints: VRRM = 1000 V, IF(AV) = 3 A.
    • Substitution latitude: Any 3 A to 6 A axial rectifier diode with VRRM ≥ 100 V (e.g., 1N5402, 1N5404, 6A10).
    • Operated control: No.
    • Sourcing plan: distributor lookup: 1N5408

  • D11: 1 A, 400 V silicon rectifier diode.

    • Identity: 1N4004.
    • Quantity: 1.
    • Footprint: DO-41 axial.
    • Electrical constraints: VRRM ≥ 400 V, IF = 1 A.
    • Substitution latitude: Any 1N400x series diode (1N4004, 1N4005, 1N4007).
    • Operated control: No.
    • Sourcing plan: distributor lookup: 1N4004

  • D5, D6, D9, D10: High-speed small-signal switching diodes.

    • Identity: 1N4148.
    • Quantity: 4.
    • Footprint: DO-35 axial.
    • Electrical constraints: VR = 100 V, IF = 200 mA, trr ≤ 4 ns.
    • Substitution latitude: 1N914, 1N4448.
    • Operated control: No.
    • Sourcing plan: distributor lookup: 1N4148

  • D7, D8: 5.1 V, 0.5 W Zener diodes.

    • Identity: 1N5231B / BZX55C5V1 (5.1V ZD).
    • Quantity: 2.
    • Footprint: DO-35 axial.
    • Electrical constraints: VZ = 5.1 V ±5%, PD = 500 mW. Used in negative supply generator.
    • Substitution latitude: Any 5.1 V 0.5 W Zener diode in DO-35.
    • Operated control: No.
    • Sourcing plan: distributor lookup: 1N5231B

  • D12: 5 mm Red diffused LED.

    • Quantity: 1.
    • Footprint: T-1 3/4 (5 mm through-hole).
    • Function: Indicates when current limiting (CC mode) is active. Note: In this project, leads are wired to shield connector X7.
    • Substitution latitude: Any standard 5 mm red LED (Vf ≈ 1.8 V to 2.2 V).
    • Operated control: Visual indicator.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Kingbright WP7113ID

Analog Kit Resistors and Trimmers

  • R7: 0.47 Ω, 5 W ceramic cement wirewound power shunt resistor.
    • Quantity: 1. Footprint: Radial/Axial ceramic rectangular power package (5W0R47J).
    • Electrical constraints: 0.47 Ω, 5 W, ±5%. Sets analog current limiting threshold.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo SQP500JB-0R47
  • R1: 2.2 kΩ, 1 W metal oxide power resistor.
    • Quantity: 1. Footprint: Axial 1 W. Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RSF100JB-73-2K2
  • R17: 33 Ω, 1/4 W, 5% carbon film / metal film resistor.
    • Quantity: 1. Footprint: Axial 0207.
  • R2: 82 Ω, 1/4 W, 5% carbon film / metal film resistor.
    • Quantity: 1. Footprint: Axial 0207.
  • R3: 220 Ω, 1/4 W, 5% carbon film / metal film resistor.
    • Quantity: 1. Footprint: Axial 0207.
  • R15, R16: 1 kΩ, 1/4 W, 5% carbon film / metal film resistors.
    • Quantity: 2. Footprint: Axial 0207.
  • R14: 1.5 kΩ, 1/4 W, 5% carbon film / metal film resistor.
    • Quantity: 1. Footprint: Axial 0207.
  • R9, R19: 2.2 kΩ, 1/4 W, 5% carbon film / metal film resistors.
    • Quantity: 2. Footprint: Axial 0207.
  • R22: 3.9 kΩ, 1/4 W, 5% carbon film / metal film resistor.
    • Quantity: 1. Footprint: Axial 0207.
  • R4: 4.7 kΩ, 1/4 W, 5% carbon film / metal film resistor.
    • Quantity: 1. Footprint: Axial 0207.
  • R5, R6, R13, R20, R21: 10 kΩ, 1/4 W, 5% carbon film / metal film resistors.
    • Quantity: 5. Footprint: Axial 0207.
  • R8, R11: 27 kΩ, 1/4 W, 5% carbon film / metal film resistors.
    • Quantity: 2. Footprint: Axial 0207.
  • R12, R18: 56 kΩ, 1/4 W, 5% carbon film / metal film resistors.
    • Quantity: 2. Footprint: Axial 0207.
  • R10: 270 kΩ, 1/4 W, 5% carbon film / metal film resistor.
    • Quantity: 1. Footprint: Axial 0207.
    • Sourcing plan for commodity 1/4 W resistors (R2–R6, R8–R16, R17–R22): distributor lookup (representative example — sources give spec only): Yageo CFR-25JR-53-series
  • RV1: 100 kΩ top-adjust multiturn cermet trimmer potentiometer.
    • Identity: 3296W-1-104 (Bourns 3296W style).
    • Quantity: 1.
    • Footprint: 3/8" square through-hole trimmer (3296W).
    • Function: Adjusts op-amp offset to calibrate minimum output down to 0.00 V.
    • Operated control: Set-once internal adjustment.
    • Sourcing plan: distributor lookup: Bourns 3296W-1-104LF
  • P1, P2: 10 kΩ linear potentiometers (Type B).
    • Quantity: 2.
    • Footprint: Panel-mount / PCB solder pin, 6.0 mm round shaft.
    • Function: Analog control of Voltage (P1/V) and Current limit (P2/A).
    • Operated control: Student-operated rotary knobs.
    • Sourcing plan: retail shopping search: 10K linear potentiometer 15mm shaft

Analog Kit Capacitors

  • C1: 3300 µF, 50 V aluminum electrolytic capacitor.
    • Quantity: 1. Footprint: Radial leaded, 18 mm diameter, 7.5 mm lead pitch.
    • Electrical constraints: Must handle 100 Hz ripple current ≥ 2.5 A RMS. Voltage rating ≥ 50 V (rectified 24 VAC peak is ~34 VDC).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Nichicon UVR1H332MHD
  • C2, C3: 47 µF, 50 V aluminum electrolytic capacitors.
    • Quantity: 2. Footprint: Radial leaded, 6.3 mm diameter.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Panasonic ECA-1HHG470
  • C7: 10 µF, 50 V aluminum electrolytic capacitor.
    • Quantity: 1. Footprint: Radial leaded, 5 mm diameter.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Panasonic ECA-1HHG100
  • C4: 0.1 µF (100 nF / marking 104), 50 V ceramic disc or film capacitor.
    • Quantity: 1. Footprint: Radial leaded, 5.0 mm pitch.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): KEMET C315C104K5R5TA
  • C5: 0.22 µF (220 nF / marking 224), 50 V metallized film or ceramic capacitor.
    • Quantity: 1. Footprint: Radial leaded, 5.0 mm pitch.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): KEMET C320C224K5R5TA
  • C6, C9: 100 pF (marking 101), 50 V ceramic disc capacitors.
    • Quantity: 2. Footprint: Radial leaded, 2.5 mm pitch.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Vishay D101K20Y5PH63L2R
  • C8: 330 pF (marking 331), 50 V ceramic disc capacitor.
    • Quantity: 1. Footprint: Radial leaded, 2.5 mm pitch.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Vishay D331K20Y5PH63L2R

System, Chassis, Enclosure, and Interconnect Hardware

Hardware items identified by numerical and alphabetical indices in the master wiring manifest (Wiri_SDARgkc.pdf) and front panel laser cutting profile (frontPanel.svg):

  • Item 1: 4×20 I2C Character LCD Display module ("2004").

    • Identity: 2004 character LCD (HD44780 compatible) pre-soldered with PCF8574 I2C daughterboard (yellow-green or blue backlight).
    • Quantity: 1.
    • Interface: 4-pin I2C (VCC, GND, SDA, SCL) set to fixed hardware I2C address 0x3F.
    • Dimensions: Cutout window 98.0 mm × 40.0 mm on front panel.
    • Sourcing plan: retail shopping search: Yellow 2004 20x4 I2C LCD character display module Arduino

  • Item 2: Two 10 kΩ, 270° linear potentiometers (included in kit Item 8; used for OV and OC protection limits on shield).

    • Quantity: 2.
    • Footprint: Panel-mount, 8 mm mounting hole.
    • Operated control: Student-operated control knobs.
    • Sourcing plan: retail shopping search: 10k linear potentiometer B10K panel mount

  • Item 3: Momentary On/Off Pushbuttons.

    • Identity: E-Switch TL2201 or equivalent panel-mount momentary SPST switches. Red actuator (ON) DigiKey: EG2045-ND; Black actuator (OFF) DigiKey: EG2041-ND.
    • Quantity: 2 (1 Red, 1 Black).
    • Footprint: Panel cutout diameter 12.6 mm.
    • Electrical constraints: 5 V logic level switching to GND.
    • Operated control: Student-operated pushbuttons.
    • Sourcing plan: distributor lookup: EG2045-ND and EG2041-ND

  • Item 4: Binding posts (banana jacks), heavy duty copper M5 threaded studs.

    • Identity: 4 mm banana chassis jacks rated ≥ 24 A, 30 VAC / 60 VDC.
    • Quantity: 3 (1 Red: Positive Output, 1 Black: Negative Output, 1 Green: Earth Chassis Ground).
    • Footprint: 9.5 mm panel mounting hole.
    • Sourcing plan: retail shopping search: M5 stud 4mm banana jack binding post 24A copper

  • Item 5: Host Microcontroller Board.

    • Identity: Arduino UNO R3 (ATmega328P with 16U2 or CH340 USB interface, 16 MHz, 5 V logic).
    • Quantity: 1.
    • Sourcing plan: retail shopping search: Arduino Uno R3 ATmega328P

  • Item 6: Arduino DC Power Jack Cable.

    • Identity: 2.1 mm ID × 5.5 mm OD male DC barrel plug to 2-wire pigtail cable.
    • Quantity: 1.
    • Function: Connects external 9–12 VDC supply to Arduino Uno power input jack.
    • Sourcing plan: retail shopping search: 2.1mm x 5.5mm DC male plug pigtail cable

  • Item 7: Multiturn 10 kΩ linear potentiometers (optional replacement for analog voltage/current controls).

    • Identity: 3590S-2-103L 10-turn wirewound precision potentiometers (10 kΩ).
    • Quantity: 2.
    • Footprint: Panel-mount bushing 9.0 mm / 3/8".
    • Operated control: Student-operated multiturn knobs.
    • Sourcing plan: retail shopping search: 3590S-2-103L 10K multiturn potentiometer

  • Item 8: Analog Linear Power Supply DIY Kit.

    • Identity: Vkmaker / Hiland 0–30 V, 2 mA–3 A adjustable regulated DC power supply kit.
    • Quantity: 1.
    • PCB Dimensions: 84 mm × 84 mm.
    • Sourcing plan: retail shopping search: 0-30V 2mA-3A adjustable DC regulated power supply DIY kit

  • Item 9: Power Transformer (115 V / 230 V Primary to 20–24 VAC Secondary).

    • Identity: Signal Transformer DP-241-8-20 (DigiKey: 595-1088-ND).
    • Quantity: 1.
    • Specifications: Primary: 115/230 VAC 50/60 Hz. Secondary: 20 VCT @ 5 A (100 VA) or 24 VAC @ 3.5–4 A.
    • Sourcing plan: distributor lookup: DP-241-8-20

  • Item 10: IEC AC Mains Power Inlet.

    • Identity: IEC 320 C14 panel-mount male inlet with integrated 5 mm × 20 mm fuse holder.
    • Quantity: 1.
    • Ratings: 250 VAC, 10 A or 15 A. Fuse: 2 A to 3 A slow-blow 250 V fuse.
    • Sourcing plan: retail shopping search: IEC 320 C14 power inlet socket with fuse holder

  • Item 11: Main AC Power Switch.

    • Identity: E-Switch pushbutton or rocker switch, mains rated (DigiKey: EG4397-ND).
    • Quantity: 1.
    • Ratings: DPST or SPST rated ≥ 250 VAC, 5 A.
    • Operated control: Student-operated main power switch.
    • Sourcing plan: distributor lookup: EG4397-ND

  • Item 12: Off-board Power Transistor (2SD1047 from Kit Item 8). Mounted directly to heatsink.

    • Sourcing plan: Accounted for in Kit Item 8 / active parts list.

  • Item 13: Heatsink and Electrical Insulator Sheet.

    • Identity: Extruded aluminum chassis heatsink (thermal resistance ≤ 0.8 °C/W) + TO-264 / TO-3PL alumina ceramic insulator sheet (22 mm × 28 mm × 0.6 mm) with thermal grease and insulated bushing.
    • Quantity: 1 heatsink, 1 ceramic insulator.
    • Sourcing plan: retail shopping search: TO-264 ceramic transistor insulator sheet 22x28 and extruded aluminum heatsink 100mm TO-247

  • Item 14: Benchtop Enclosure.

    • Identity: Extruded/folded aluminum instrument enclosure (chassis depth ≥ 200 mm, width ≥ 210 mm, height ≥ 90 mm to accommodate transformer DP-241-8-20 and 84x84 mm boards).
    • Quantity: 1.
    • Sourcing plan: retail shopping search: aluminum project box enclosure 200x90

  • Item A: High-Current Hookup Wire (Heavy gauge).

    • Identity: 18 AWG to 16 AWG stranded copper wire (rated ≥ 300 V, 5 A). Used for AC secondary, bridge, pass transistor, and output binding posts.
    • Sourcing plan: retail shopping search: 18 AWG stranded silicone hookup wire

  • Item B: Low-Current Signal Wire (Thin gauge).

    • Identity: 24 AWG to 26 AWG stranded hookup wire. Used for I2C bus, potentiometers, and logic buttons.
    • Sourcing plan: retail shopping search: 24 AWG stranded hookup wire spool

  • Item C: Custom Front Panel.

    • Identity: Laser-cut two-color acrylic sheet (matte black face, white core / white on black engraving), 3.0 mm (1/8") thickness.
    • Dimensions: 203.2 mm × 85.76 mm (cut from vector profile frontPanel.svg).
    • Fabrication plan: general web research: Laser cutting service 3mm two-color acrylic white on black

  • Item D: IEC AC Mains Power Cord.

    • Identity: Standard 3-prong grounded IEC C13 power cable (NEMA 5-15P to IEC C13 or regional equivalent).
    • Sourcing plan: retail shopping search: IEC C13 power cord grounded 18AWG

  • Item E: Potentiometer Knobs.

    • Identity: Collet or set-screw knobs with indicator pointer. Two for 6.35 mm (1/4") shafts (red/multiturn), two for 6.0 mm knurled/D-shafts (green/OV-OC).
    • Quantity: 4 total.
    • Sourcing plan: retail shopping search: potentiometer pointer knobs 6mm and 6.35mm

  • Item F: PCB Standoffs.

    • Identity: 3M self-adhesive nylon support spacers / standoffs (L = 25 mm, hole diameter = 4.0 mm).
    • Quantity: 8 to 12 pieces.
    • Sourcing plan: retail shopping search: 3M self-adhesive nylon PCB standoff 25mm

  • Item G: Mechanical Fasteners.

    • Identity: Assorted M3, M4, and M5 stainless machine screws, washers, and locknuts.
    • Sourcing plan: retail shopping search: M3 M4 M5 machine screw and nut assortment kit

  • Item H: Protective Earth Ground Lug.

    • Identity: Blackburn L35-B2-5 (or Ilsco / Burndy equivalent) mechanical copper ground lug for 8 to 14 AWG solid/stranded wire. Bolts directly to aluminum chassis.
    • Quantity: 1.
    • Sourcing plan: retail shopping search: Blackburn L35 copper mechanical ground lug

  • Item I: Panel Lettering.

    • Identity: Dry transfer lettering / rub-on decal sheet (white letters, 3 mm / 1/8" height).
    • Sourcing plan: retail shopping search: dry transfer lettering sheet white

  • Item J: Crimp Terminals.

    • Identity: 3/16" (4.75 mm) female Faston quick-disconnect crimp terminals.
    • Quantity: 6 to 10 pieces.
    • Sourcing plan: retail shopping search: 3/16 female faston disconnect terminal crimp

Software and network dependencies

Runs no network services. The microcontroller connects only via USB serial (ATmega16U2/CH340) for programming and telemetry, and does not join any local or wide-area network.

  • Arduino AVR Core / Runtime:

    • Component: Arduino Core for AVR Microcontrollers (ATmega328P).
    • Source: Official Arduino AVR Board Package (arduino:avr).
    • Version: not stated.
    • Where the version came from: not stated.
    • Pinning status: Unpinned.
    • Manifest location: None.
    • Network exposure: None. Operates entirely as an embedded offline controller.
    • Check plan: not checkable: vendor core without security tracking advisory database.

  • Wire Library:

    • Component: Arduino standard <Wire.h> Two-Wire Interface (I2C) master driver.
    • Source: Bundled with Arduino AVR Core.
    • Version: not stated.
    • Where the version came from: not stated.
    • Pinning status: Unpinned.
    • Manifest location: Built-in include in DCmeter.ino, line 1.
    • Network exposure: None.
    • Check plan: not checkable: bundled core utility.

  • LiquidCrystal_I2C Library (Francisco Malpartida branch):

    • Component: new-liquidcrystal / LiquidCrystal_I2C.h (specifically the custom I2C port expander driver written by Francisco Malpartida).
    • Source: Bitbucket repository download archive cited in DCmeter.ino line 2: https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads/.
    • Version: not stated.
    • Where the version came from: not stated.
    • Pinning status: Unpinned (bare link to an unversioned Bitbucket download directory).
    • Manifest location: Cited in source comment of DCmeter.ino line 2.
    • Critical compatibility note: This code uses the constructor LiquidCrystal_I2C lcd(0x3F, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); which defines the raw PCF8574 bit-mapping. Standard Arduino Library Manager versions of LiquidCrystal_I2C (such as Frank de Brabander's) do not implement this constructor and will result in compilation failure.
    • Network exposure: None.
    • Check plan: not checkable: unpinned version, hosted on Bitbucket download archive with no formal package registry advisory feed.

External URLs and Remote Assets

The project documentation and source code reference the following temporal download links:

  • Bitbucket LCD Library: https://bitbucket.org/fmalpartida/new-liquidcrystal/downloads/
  • Ponoko Acrylic Material Spec: https://www.ponoko.com/make-and-sell/show-material/608-acrylic-two-color-white-on-black#main-image
  • DigiKey Product Links:
    • Pushbutton Switches: http://www.digikey.com/products/en?keywords=EG2045-ND, EG2041-ND, EG4397-ND
    • Transformer: http://www.digikey.com/product-detail/en/signal-transformer/DP-241-8-20/595-1088-ND/952958
  • eBay / AliExpress Listings:
    • 4x20 LCD: http://www.ebay.com/itm/Yellow-2004-20X4-IIC-I2C-TWI-Character-LCD-Display-Module-For-Arduino-/172181792364
    • Vkmaker Kit: http://www.ebay.com/itm/Vkmaker-0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-Short-/162321443727
    • Multiturn Potentiometer: http://www.ebay.com/itm/261965763785
    • Aluminum Enclosure: http://www.ebay.com/itm/121967934560
    • Ceramic Insulators: http://www.ebay.com/itm/Ceramic-Sheet-Insulator-TO-264-TO-3PL-22-28-0-6mm-Transistor-Heatsink-x5-pcs-/351980427050
    • Banana Sockets: https://www.aliexpress.com/item/4pcs-lot-30VAC-60VDC-MAX-24A-banana-socket-Pure-copper-large-current-binding-post-M5-studs/32474336380.html

PCB and Laser Cutting Fabrication Specifications

  1. Custom Meter Shield PCB ("00002A"):

    • Layer Count: 2 copper layers (Top, Bottom).
    • Dimensions: 55.88 mm × 53.34 mm (2.20 in × 2.10 in). Form factor matches Arduino Uno R3 shield footprint with side mounting notches.
    • Drill Hole Count: 111 plated holes across 5 tool diameters (0.0236", 0.0394", 0.0400", 0.0512", 0.0520").
    • Minimum Track / Spacing: 8 mil / 8 mil.
    • Solder Mask: Both sides.
    • Silkscreen: Top overlay.
    • Source Gerber files: Included in archive 00002A.zip.

  2. Analog Linear Power Supply PCB:

    • Layer Count: 1 or 2 layers through-hole.
    • Dimensions: 84.0 mm × 84.0 mm (3.31 in × 3.31 in).

  3. Front Enclosure Panel:

    • File: frontPanel.svg.
    • Outer Dimensions: 203.2 mm × 85.76 mm.
    • Material: 3.0 mm two-color acrylic (white on black).
    • Cutouts:
      • 1× LCD window: 98.0 mm × 40.0 mm.
      • 4× Potentiometer holes: 8.0 mm diameter.
      • 2× Pushbutton holes: 12.6 mm diameter.
      • 1× Power switch hole: 11.3 mm diameter.
      • 3× Binding post holes: 9.5 mm diameter.