On 25/10/12 12:00 Chris Green wrote:

I'm looking for reasonably priced and reasonably easy to implement ways to measure voltages with a computer. To be more specific:-

The computer will either be the existing eeePc running Ubuntu (but no GUI) or a raspberry pi.

I need to monitor at least four and preferably eight or so voltages, some of these are 12 volts (i.e. lead acid batteries) and others are current transducers giving an output around 2.5 volts with a +-0.5 volts swing.

I don't need *incredible* accuracy but something around 2% or better is necessary for it to be useful in monitoring battery charge state.

I want it to be cheap!

Sample rate can be slow, once an hour would be fine.

I built myself a home power monitor using a Freescale 8-bit HCS08 series micro-controller and an FTDI USB/serial interface chip, both powered from USB. I'm running two ADC channels @1kHz sample rate to take differential samples from either side of a biased current detector clamp. I'm sure something similar would be ideal for battery monitoring.

Total cost - micro-controller free - obtained as a 'sample', FTDI chip you might get a 'sample' for free, but more likely to pay ~ £5, PCB ~ £0.50 if you use 0.1" DIP pinout devices and stripboard.

The fun bit is writing the code :)

P