Protect PIC's input against "high" voltage using AD

[flotulopex]

I'll try with a SCR then - good links, thanks Joe.

I'm using either a 16F88 or a 16F690 (I would prefer to use a 16F690 because it's cheaper than the 16F88 here in Switzerland).

[chuck]

flotulopex they are some batteries there,
I did a battery anayliser to test 6V batteries based on the alphabat pro, It works really well, The only real way to test batteries is the discharge method, It uses a pic18f4520,GLCD & SD_CARD for recording the date,time,battery and current draw, This unit works very well.

If you want accuracy then have a look at the attached file, It's part of a schematic from a fluke meter and it ues a 10bit A/D converter, You could can control the auto ranging through the PIc and if need be you could always use a 12-24Bit A/D chip. If I rmember the max DC voltage is 600V, This is one of my next projects.

have you thought about hard wiring the unit to the batteries and using RF or RS232 way, You could have one or two master units then salves units to send data and why not go all the way, Use a SD_Card so log the voltage and you can upload the data into EXcel These are just some ideas but it would amake it cool project

[flotulopex]

Hi Chuck,

Thanks for the FLUKE shema.

For my daily job, I use this kind of tool http://www.programma.se/se/battery.php.

And for keeping track of every and each battery, the TMC is the best complement http://www.electricnet.com/product.m...?VNETCOOKIE=NO.

I'm actually trying to make a kind of TMC recorder, smaller and handyer.

[sougata]

Hi,

A low leakage zener diode can always protect your ADC input from high as well as negative voltages. Find the proposed solution as attachment. I recommend using a MCP1541 as your voltage reference.

Thanks to the low impedance of the battery as a voltage source. Otherwise the circuit would not work on any source. As the source would get loaded and change itself.

Ensure proper acquisition delay. Try to use RC osc (ADC Clock) and execute @ SLEEP after setting go/done bit.

Best of Luck.

P.S. - I never got paid for the project. I accept Paypal.