Autorange Capacitor Tester

In this instructable I describe my autorange capacitor tester, made with just a few components.

I have a bunch of unknown capacitors for my electronic projects. Most of these capacitors are leftovers from previous projects or salvaged from scrap pcb's. Many printed surface codes are faded or completely gone.

So I searched for a small tester. The one I found uses the Arduino serial monitor and is indeed very very small. It only needs an Arduino UNO R3, 3 wires, two Dupont test plugs, a pushbutton and an Arduino proto shield. (and of course a laptop to see the Arduino serial monitor).

See here for two websites where I found (and then updated) this tester:

https://www.circuitbasics.com/how-to-make-an-arduino-capacitance-meter/

https://codewriteuk.wordpress.com/2014/01/21/cap-meter-with-arduino-uno/

a laptop with the Arduino IDE installed

3 small pieces of insulated wire

2 female Dupont connectors, each with 10 connections

1 Arduino proto shield with male Dupont connectors

1 small pcb pushbutton

There are a zillion explanations on the internet about the theory of capacitance metering.

Stoppi71 here on instructables published a clear story explaining this in detail. Thanks for that Stoppi71!

See here: https://www.instructables.com/Simple-Autorange-Capacitor-Tester-Capacitance-Mete/

The voltage U (t) at the capacitor increases according to the formula U (t) = U0 * (1-exp (-t / (R * C))) and the capacitance can be calculated.

The diagram is indeed very minimal. Only two connections to the test contacts to insert the capacitor to be tested (connected to the Arduino analog pins A2 and A0) and a small pushbutton connected between digital pin D12 and GND.

Easypeasy.

The wiring, pushbutton and test contact are soldered on an Arduino proto board to be connected to the Arduino UNO R3. The test contacts each have 10 connections so you can insert diffent types of capacitors.

Download the attached sketch to your laptop and upload it to the Arduino via the Arduino IDE.

Open the serial monitor.

IMPORTANT: Check the capacitor to be tested, it MUST be discharged to avoid damaging the Arduino.

Mount the capacitor you want to test and press the pushbutton.

The capacitance value will appear on the screen.

Testing large capacitors (>50 uF) it will take a few seconds before the value will appear on screen.

When no capacitor is connected, no value will be shown.

The program automatically shows the value in picoFarad, nanoFarad or microFarad.

Happy testing!