Sorry for the long post but I'm hoping someone can give me some advice about using an ADC on my RasPi.
I'm building a monitoring server for systems on my boat and looking to monitor the voltage on two battery banks (house and starter), current in/out of the house bank, and current out from three solar panels and a wind generator (using the BB-ACS756 hall effect current sensors from Cytron).
I bought a couple of Delta Sigma Pi ADC converters (http://www.abelectronics.co.uk/products/3/Raspberry-Pi/14/Delta-Sigma-Pi-18-bit-Analogue-to-Digital-converter
) from AB Electronics and set up the house bank current in/out with no problems using an existing shunt.
However, monitoring voltages caused me major headaches. I used a voltage divider on the inputs with 10k and 1k resistors giving me a voltage of about 1.2 volts on the differential inputs of the original boards (which should have been good up to something like 20 volts) but that didn't work. I tried putting a capacitor across the inputs thinking it might suppress any spikes but that didn't seem to make much difference. I ended up letting the smoke out of one chip on each board and blowing some individual inputs on the other chips. Expensive mistake!
I think my problem is with spikes on the voltage of the battery banks maybe by loads from pumps etc as they seemed to work for a while then failed badly but I'm not at all sure.
Anyway, I've just bought a couple of slightly different ADC boards (http://www.abelectronics.co.uk/products/3/Raspberry-Pi/17/ADC-Pi-V2---Raspberry-Pi-Analogue-to-Digital-converter
) from the same source. I chose these boards instead as they already have a voltage divider which I think (well hope actually) makes them slightly less fragile and allows for up to 5 volt inputs instead of the 2 volts on the original board.
So I'm hoping someone can help me with designing a method of safely measuring voltages between (say) 10 and 16 volts using the new boards. I'm sure I'll need another voltage divider but I'm not sure of the values to use and how can I protect the ADC inputs from unknown spikes or surges?
Thanks in advance.