What USB device can I use to check for voltage on or off? [closed]

Question

I am looking for a device (ideally a USB device) which I can use to check automatically if there is some voltage (3.3 V) at an electrical connection.

The idea is to automatically test (with a python script) if a LED would be ON or OFF, instead of manually checking it by looking at the LED. I want to be able to connect this device to a computer to see with the python script of there is some voltage applied or not.

What would work is maybe a multimeter with USB connection, but maybe there are simpler devices that can be used to just check if at some connection there is some voltage or not.

Any suggestions?

Answer 1

You don't give much information, such as frequency with which you want to check, whether the ground reference for the 3V3 signal is the same as the computer, or operating system of the computer.

However, in broad terms you are looking for a GPIO (General Purpose Input Output) module, possibly with galvanic isolation.

There are a multitude of options you could choose from, but assuming you need only low frequency checks (as you are replacing human viewing an LED), and that you want to stick with USB, I'd suggest something like this unit FTDI Isolated GPIO.

FTDI are probably the leaders in USB interfacing for serial and simple GPIO, with very wide spread driver support on many platforms. The use of a galvanically isolated product will stop you having fun with different ground references.

If your computer was a Raspberry Pi, and you needed galvanic isolation, I'd suggest you just use an IO pin with an optocoupler like the H11L1. Put the input in parallel with the LED + resistor in the target circuit, with its own resistor at say 1K to limit current, and the just use the output to one of the GPIO pins on the RPi.