leanderseige / rapidohmmeter

Measure resistors really fast. No clamping, no waiting.

Rapid Ohmmeter

Measuring a single resistor with a digital multimeter or one of these (super useful) modern multifunction testers is way too slow and cumbersome for me. So I thought about how to build a really fast tool to measure resistors flying around on my workbench. Here is what I came up with.

(The case was made out of semi-transparent PLA which explains the coloring.)

I found a really old LCD display in my inventory an I also had a couple of cheap Arduino Leonardo "Pro Micro" clones flying around on my workbench. So I puzzled some components together, being inspired by this project: https://www.circuitbasics.com/arduino-ohm-meter/ For the contacts I used two large screws to make it easy to press the resistors against them. Now measuring a resistor is possible in the wink of an eye.

It also turned out that the right half of the LCD obviously was damaged but the left half is sufficient anyways.

Circuit diagram

Here is the schematic I finally used:

Controls:

Offset Button: short-circuit the two contacts so that there is a resistance of 0 ohms and press the Offset Button to calibrate the lower end of the scale.

Calibration Button: hold a 10k resistor to the screws and press the Calibration Button to improve scaling.

The potentiometer can be used to adjust the contrast of the LCD display.