Trying to read voltage value from circuit to PC

[Tony Morelli]

Hello -
I have what I think to be a very simple task, however I am a little stuck and am unfamiliar with the terms so my searching has not provided any results.

I have a device with a knob on it and need to determine the position of the knob on a computer.
I have found 2 points on the board of the device where I can measure the voltage with a volt meter and it goes from 0 to 5v depending on the position of the knob.

Somehow I need to get that value into my computer. I could use an arduino which has an analog input pin, but I am unsure how to physically connect the 2. In the potentiometer example arduino circuit, +5 and ground are attached to the pot and then the output is attached to the analog pin.

In my case the device has its own +5 and ground, and at a certain point on the board I am measuring between +Xv and ground. Can I just take the +Xv and wire it into my analog input? That seems wrong, and I dont want to blow anything up

Any ideas? I am also not tied to arduino, that is just something I had laying around

Thanks for your thoughts!

 

[Gryd3]

Hello -
I have what I think to be a very simple task, however I am a little stuck and am unfamiliar with the terms so my searching has not provided any results.

I have a device with a knob on it and need to determine the position of the knob on a computer.
I have found 2 points on the board of the device where I can measure the voltage with a volt meter and it goes from 0 to 5v depending on the position of the knob.

Somehow I need to get that value into my computer. I could use an arduino which has an analog input pin, but I am unsure how to physically connect the 2. In the potentiometer example arduino circuit, +5 and ground are attached to the pot and then the output is attached to the analog pin.

In my case the device has its own +5 and ground, and at a certain point on the board I am measuring between +Xv and ground. Can I just take the +Xv and wire it into my analog input? That seems wrong, and I dont want to blow anything up

Any ideas? I am also not tied to arduino, that is just something I had laying around

Thanks for your thoughts!

Probably the easiest thing for you would be to grab an arduino. There are tutorials and documents everywhere on making your own mice, keyboards, and gamepads with the things. Get it to read the analogue input, and pretend to be a joystick
Otherwise you can use a USB to serial adaptor and communicate via a serial data connection to the microcontroller and pull numbers from it. I guess it depends on what you ultimately want to use it for?

 

[KrisBlueNZ]

You can get USB devices that provide generic analogue and/or digital I/O. The problem is that most of the Google hits for USB analog I/O are for audio interfaces. But they do exist - I found http://accesio.com/go.cgi?p=../cat/usb.html which I don't recommend but it should give you an idea of what to look for. You can probably find something similar for a low price on eBay.

What do you want to do with the value once you get it into the PC?

 

[Tony Morelli]

Thanks for your suggestions. I ended up using the ardiuno and just wired in the +Xv from the device to the analog in and it worked. I am not exactly sure why it worked but it does work. Maybe because both the arduino and the device are powered by the same USB hub and as a result share the same ground? I dont know, but it works perfectly for what I needed.

 

[BobK]

Yes, that would be correct. You can get a signal across if the sender and receiver share the same ground.

Bob