I am building a model railroad and would like a way to interface a model railroad with my computer preferably using a USB port but I can use a serial port if I must.
The basic requirements are that I be able to detect DC current flowing EITHER way (polarity change=direction change in model railroading). I have thought about Bruch Chubb's CMRI but that is kind of expensive for me. Basically I just need a card that can accept inputs and outputs.
I'm kind of describing and stuff from scratch here.
Thanks,
Zatnikitelman

 

Greetings Zatnikitelman,

http://www.usbmicro.com/odn/documents/555CE987BEF556101735F5D26CE4356BD3400BDC.html

I googled this link that looks like it could serve as the basis of the type of interface you are seeking.

It is set up to take digital IO so some sort of current sensing circuit will be required to complete the effort.

You could try introducing a small valued current sense resistor in-line with your power source but to measure current in a non-invasive way you will need some sort of clamp on current sensor.

hgmjr