On Fri, Oct 26, 2012 at 11:10:14PM +0100, Wayne Stallwood wrote:
If you want quick and dirty just use something like the ADS7830, it runs on i2c so if you want minimal soldering just run it direct from a i2c bridge or even a bus pirate and have the monitoring app as a daemon on the pc. 8bit so 0.05v step resolution if you were wanting to monitor 0-12v.
You'll need to set up some lot tolerance potential dividers to cope with the 12v and you may run into problems with shared grounds depending on what you are monitoring. I *think* the 7830 has an isolated analogue signal ground so you may just end up needing a couple of them running on different ground planes but you'll need to check that on the datasheets. Otherwise it probably supports 4 channels of differential measurement so you could do the ground isolation that way.
Yes, I'm conscious of the grounding problem. While the boat wiring (the batteries are on a boat) is quite well behaved in having a single earth point to the hull etc. the length of the wires to the voltages being measured are such that there may be problems.
Alternatively pick any microcontroller platform and build a standalone monitor that buffers and spits out the data via serial or whatever. Doesn't matter what really, could be PIC, AVR, or even just an Arduino shield, the right Arduino shield/AVR has 8 ADC inputs on chip but then you have more work to do on ground isolation probably.
I was thinking about Arduino (I already have one) but it gets a bit 'messy' to have something like:-
Desktop PC (where Arduino code would be written/built) | V eeePc (or Raspberry PI) on the boat | V Arduino
If I can instead have some hardware read/written by a Python script (or something similar) that can be done 'locally' on the boat eeePc then life would be simpler.