Lead Acid Battery voltage monitor

[ZeleC]

HEllo
i want to feed a logic signal to a Pic16F84 to notify me when the batteray is lower than a certain voltage , what kind of Opamp to use and if anyone one can give me the circuit
thank you.

 

[DrWhoF]

PIC16F84 doesn't have AD converter.
Better choose PIC with ADC and connect battery to AD input pin through resistor voltage divider.

 

[ZeleC]

I made this comparator circuit and it worked fine when its left alone,and it flips between 0V and 3.66V but when connected to the PIC input a drop from from 3.66 to 1V what might be the problem ,???
I think it might help if to add a 74hc00 in between but im trying to avoid that due to the PCB space.
Thank you .

 

[vsgiri]

Hi Zelec

Most likely you would have configured that pin as an output. Check the TRIS register!

Also, why don't you consider a 311 comparator instead of the 358? Since it is open collector output you wouldn't have problems with the logic levels like 3.66V!


Giri

 

[ZeleC]

You r right vsgiri i have already checked it and it was an output ,plus i added a simple 2n2222 transistor at the output of my opamp to get a 0 - 5V flip at my PIC input
Thank you guys