I have been using a battery indicator from Nigel Goodwins tutorials which simply divides the voltage across the battery by an amount which switches on an LED when the divided voltage drops below 0.7V


I have to modify this circuit for another application.

The important differences are:
My new circuit does not have a proper isolation switch, so I need to be able to stop the battery indicator drawing current using the software of the PIC.

My new circuit only has one LED controlled by the PIC, so I need to feed the battery information back into the PIC in order to display the battery status on the one remaining LED at the right time.


I had a go at modifying the circuit, I would appreciate any input you guys
have on it.


The idea is that the battery test controller output is used to turn on the indicator, or turn it off to save power and the battery status is fed into the battery status input of the PIC

Will it satisfy the constraints of my new circuit?
Will it work at all ???



I am going to test it, but I appreciate what you guys think.

Attached Images

batterytester.jpg (26.1 KB, 301 views)

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I don't see why not, but what PIC are you using?. Also, how low are you trying to get the current consumption?.

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get rid of Q2 and connect emmiter of Q1 to collector of Q3.
if you want to keep both Q2 and Q3 (i don't see why),
run separate resistors to base of each transistor.

 

Nigel,

I am using the 16f628. I would have used the comparator but it is already used for something else.

This application is run from a 9V PP3 but there is no isolating on-off switch. I want to be able to turn everything off (or as near as possible) using the PIC, so that after a period of inactivity the PIC powers everything down and goes to sleep.





Panic Mode,
Thanks for the tip I overlooked that idea, space is an important issue for me and you have saved me a transistor. Thanks




I love this forum :lol: :lol: :lol:

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