Arduino ESR Meter for Capacitor Testing

It uses the DC-pulse method: a short current pulse is driven through a known precision resistor into the discharged capacitor, and the ADC samples the voltage step at the pulse edge. At that instant the capacitor behaves as a short, so the step equals pulse current × ESR — Ohm law, no AC source needed. The firmware repeats and averages the pulse for stability.

No, and the project does not claim so. Commercial meters inject a ~100 kHz AC signal, which is the industry-standard ESR condition; this build approximates ESR with a DC pulse. The design target is approximately ±10% of reading after calibration — good enough to spot a dried-out capacitor on a repair bench, and the report states the method's limits honestly.

Unreliably. Parallel capacitors and other circuit paths distort the measurement pulse, so an in-circuit reading can look fine while the cap is bad (or vice versa). The honest answer is to test out-of-circuit, or with one leg lifted — the report explains why.

Approximately, yes. The firmware measures the RC charge time to ~63% of the drive voltage and reports a capacitance estimate — an expected ±10–20% sanity check, not an LCR-meter replacement. The interesting viva point is that a dried capacitor often still reads near its rated capacitance while its ESR has soared.

The firmware holds a table of datasheet-typical ESR values per capacitance/voltage family and shows an OK/HIGH hint. It is guidance, not an absolute verdict — the report explains the family trends (larger capacitance and higher voltage rating generally mean lower typical ESR) so the student can defend the judgement.

Yes — for Electronics and Telecommunication Engineering programs. It demonstrates analog measurement with a microcontroller ADC, applied Ohm law, averaging and calibration methodology, embedded C++ firmware, and real capacitor failure physics — every part defensible in a viva. problem: Electrolytic capacitors are among the most failure-prone components in power supplies and audio equipment, and they rarely fail open or short — they dry out. A capacitor can still read near its rated capacitance on a multimeter while its equivalent series resistance (ESR) has climbed many times over, causing excess ripple, overheating and faults that look like anything but a bad capacitor. The failure mode is invisible to a basic multimeter: you need an ESR measurement. Commercial ESR meters exist but cost more than a student can justify for a repair bench, and ordinary capacitor testers measure capacitance only. This project gives students an instrument to build and demonstrate themselves: an Arduino-based ESR meter that fires a short, controlled current pulse through a known precision resistor into the capacitor under test and computes ESR from the resulting voltage step, with an LCD readout, probe calibration and a good/high judgement. concept: The capacitor under test is clipped between alligator probes. On the test button press, firmware first discharges the capacitor through a 1 kΩ discharge resistor until the ADC reads below approximately 0.1 V. A digital pin then drives 5 V through the known precision series resistor (10 Ω, 1%, design choice); the ADC samples the capacitor-side voltage within microseconds of the pulse edge, where the capacitor behaves as a short and the measured step ΔV is set by the ESR. Firmware computes ESR = ΔV × Rseries / (Vdrive − ΔV), repeats the pulse 16 times (design choice) and averages. The stored short-probe zero offset is subtracted, the corrected ESR is compared against a datasheet-typical family table, and the result is shown on the 16x2 LCD in ohms with an OK/HIGH hint. A capacitance estimate follows from the RC charge time. features:

• [One-press ESR measurement] Clip the probes across the capacitor and press the test button — the meter discharges the capacitor, fires the measurement pulse, averages the readings and shows ESR on the LCD. No oscilloscope or manual math needed.
• [DC-pulse ESR method] The capacitor under test is driven with a short current pulse through a known precision series resistor; the Arduino ADC samples the voltage step at the pulse edge, where the capacitor behaves as a short and the step is set by ESR alone: ESR = ΔV × Rseries / (Vdrive − ΔV).
• [LCD readout with good/high judgement] A 16x2 LCD shows the measured ESR in ohms alongside an OK/HIGH hint, judged against a firmware table of datasheet-typical ESR values per capacitor family.
• [Short-probe zero calibration] Shorting the probes runs a zero-calibration that stores the lead and contact resistance offset in EEPROM, subtracted automatically from every measurement.
• [Reference-resistor verification] The kit includes 1 Ω and 10 Ω (1%) reference resistors; a verification mode measures them so the student can confirm the meter's accuracy themselves.
• [Automatic capacitor discharge] Before each test the firmware discharges the capacitor through a discharge resistor until the residual voltage is negligible — a safety habit built into the instrument.
• [Approximate capacitance readout] The same charge path gives a capacitance estimate from the RC charge time (time to reach ~63% of the drive voltage), shown alongside ESR as a sanity check.
• Optional customization: serial CSV logging of batch measurements to a PC, buzzer for out-of-spec capacitors, Li-ion battery pack instead of 9 V battery.
• Future scope: 100 kHz AC test-signal version for standard-comparable ESR readings, guarded in-circuit test fixture, SMD tweezer probes for board-level caps. requirements:
• Arduino Uno (ATmega328P, 10-bit ADC)
• 16x2 LCD (HD44780) with I2C backpack
• Known precision series resistor: 10 Ω, 1% metal film (design choice)
• 1 kΩ discharge resistor + push button (test trigger)
• 1 Ω and 10 Ω (1%) reference resistors for verification
• Alligator-clip test probes with leads (approximately 60 cm, expected)
• Practice set of electrolytic capacitors (various values) for the calibration procedure
• Breadboard or perfboard, hookup wire, base plate
• 5 V USB supply or 9 V battery with barrel adapter
• Computer with Arduino IDE for firmware deliverables:
• Assembled ESR meter prototype (Arduino Uno + LCD + measurement front-end on board, test probes fitted)
• Arduino firmware source with comments (discharge sequence, pulse timing, ADC averaging, zero-offset handling, family-table judgement)
• Wiring diagram and measurement-theory notes (the ΔV = I×ESR derivation, error sources)
• Buyer-run calibration procedure: short-probe zero cal + 1 Ω / 10 Ω reference-resistor verification
• Reference ESR table card (datasheet-typical values per capacitance/voltage family)
• Kit extras: 1 Ω and 10 Ω (1%) reference resistors + a practice set of electrolytic capacitors
• Project report PDF (ESR theory, capacitor failure modes, methodology, the student's own calibration results)
• PPT presentation for final review
• Viva Q&A preparation document (ESR vs capacitance, ADC resolution, calibration, why dried caps still read capacitance) limitations:
• This is a DC-pulse approximation, not a 100 kHz AC bridge: readings are a repair go/no-go aid, not standard-comparable ESR values — a commercial meter will differ, and the report states this plainly.
• In-circuit testing is unreliable: parallel capacitors and circuit paths distort the pulse, so trustworthy readings need the capacitor removed or at least one leg lifted.
• The design accuracy target is approximately ±10% of reading after calibration on the low range; the real figure depends on lead resistance, probe contact and the zero calibration, and the buyer verifies it against the supplied reference resistors.
• Large or energy-storage capacitors must be pre-discharged externally before clipping on — the meter's own discharge handles small caps but is not a substitute for safe practice around charged power-supply banks.
• Only electrolytic/large-value capacitors are in scope: film and ceramic capacitors have ESR far below this method's useful floor (lead resistance alone is comparable), so they are excluded.
• The good/high judgement uses datasheet-typical family values as guidance, not an absolute pass/fail — borderline readings need the student's interpretation, which the report explains. timeline:
• Typical built-to-order delivery: component procurement in the first week, measurement front-end assembly and wiring in the second, firmware (discharge sequence, pulse timing, averaging, LCD judgement) in the third, with the zero-calibration and reference-resistor verification run on the finished build before handover. Exact schedule is confirmed at order time. support:
• Explanation support covers the full chain: ESR theory and capacitor failure modes, the DC-pulse measurement derivation, ADC resolution and averaging, the zero-calibration procedure and reference-resistor verification — so the student can answer viva questions on every part. Report, PPT and viva Q&A are included; firmware walkthrough provided on request.