How i ken read 7.2v with pic

[serandre]

Hi,

I need to read a car battery, it ranges from 10v to 14.8v. In my circuit i have used a zener 10v to drop the voltage to 0-4.8v.

Should i modify it to use voltage divider (10K/5K) instead ?

Sorry eletronic is just a hobby to me, just learning :-)

[mister_e]

You should use the voltage divider with simple resistor... also add a 10-100nF at the PIC a/d input to smooth the results. It's amazing how much noise you can remove. Also, doing multiple reading then average them to avoid odd results it's just a better practice in, at least, car application.

[Acetronics2]

Hi,

I need to read a car battery, ...i have used a zener 10v to drop the voltage to 0-4.8v.

Should i modify it to use voltage divider (10K/5K) instead ?

Sorry eletronic is just a hobby to me, just learning :-)

Hi, Serandre

Your Zener idea is not so bad ... but zener voltage is not stable with temp .!!! so, your measurement will be somewhat false ( in a car temp is not so constant ...).

There would be a simple solution : use a cheap TL431 trimmable "zener" instead of the diode. see TL431 datasheet for that.

http://pdf1.alldatasheet.com/datashe...OLA/TL431.html

Alain