Auto Shutoff circuit

[Queball]

:?: I have a battery that I need to charge for 7-8 hours. I would like to build a circuit that cuts the power after 8 hours. I would also be nice to be able to move between 5-10 hours of charge time. Does any one have a design for this? The input would be a standard US 110v outlet, the load is a 8.4v 600mAh Nicad battery pack.

thanks for you help,
Queball.

 

[daviddoria]

i'm not sure what the max timing is....

somone let him know if you can use a 555 setup in monostable mode?

 

[Sebi]

Build a binary counter with 4040, use as clock signal the 60Hz.

 

[bogdanfirst]

what he means that you can generate a 60Hz frequency with the 555 and count the pulses with a 4040 counter and get the timing

 

[Sebi]

I think, the 60Hz mains freq. is a precise clock pulse for long timing.

 

[Queball]

Can any of you provide me a schematic?





Thanks,
Queball

 

[Gene]

Would it be better to stop the charger based on the condition of the battery being charged rather than on time?

 

[jriofrio]

auto shutoff

I guess a circuit that check when the batteries are full charged and then with a relay shut the power will be more efficent, rather that meassuring time....

use google.com to find the circuit, i have seen it, but i can not remember the site.

 

[gunny]

you might be able to use a comparator and a relay to turn on the input of your charging signal ..thay way when the potentional is met it will automaticly turn it off and visa-versa...