Measuring Voltage of 2V batteries

djh82uk

Hey Guys

it's been a little while (been playing with my new cnc machine)

I have an SX48 Board that I am hoping to use. I want the circuit to basically monitor the voltage coming out of 8 2V rechargable Batteries sepratley, when one of them drops below say 1.5V, I want to trip a relay (via npn transistor to keep the ampage down ont he sx pins), the relay will connect the battery to the charger.

Now I guess i could calculate how long it would take the battery to charge up then switch the realy off, or could i measure the actual voltage and switch it off at 2V?

I also wanted to have a red and green led for each battery, one to say OK and the other to say "charging".

Im still struggling to move over from the propeller, the SX is cheaper so would rather use it for this project.

Question is, how do i start, i guess I need a divider of some sort, but do not know how to figure it out. Also im struggling to get started with the code, i guess it depends on how I measure the voltage (analog/digital), i guess I could measure it digitally (cmos?). How many pins can use analogin?

I guess the whole system would be a loop, check all input pins, trigger any relays/led's, wait a few secs, start loop again.

Any Advice?

Once I have this one figured (hopefully with your help), then i can move onto the 6V and 12V batteries (one SX board for each i guess)

Thanks

DJH

Bean

You need 2 I/O pins for ANALOGIN so with 16 pins you could read the 8 voltages.

Bean.

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djh82uk

thats good to know, i'll do some reading up on analogin

thanks [noparse]:)[/noparse]

DJH

Sparks-R-Fun

You did not mention the type of 2V rechargeable batteries you want to charge. Many rechargeable batteries require a charging voltage that is higher than the operating voltage of the battery. If that is the case then sensing the charging voltage probably will not be very helpful.

I believe many smart chargers actually sense the charging current. The current tends to decrease as the battery reaches full charge. You could look into that possibility or, since you are using an SX, you could apply the charger for a while, perhaps allow the battery to rest a bit, then check it again. If you are not in a hurry to charge the batteries a Charge-Rest-Test cycle might work well for you.

- Sparks

djh82uk

yes I was going to calculate roughly how long they too to charge from say 1.5V, then disable the charging via relay, then check voltage, or something along those lines

thanks


DJH