EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: RPBCACUEAIIBH on May 18, 2013, 03:29:44 pm
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I'm trying to design a circuit which switches my other circuits between adapter and battery power, without interruption, charges the battery, and also stops when it is charged, and I came up with this.
It will be probably be used with some Li - Ion/Li - Po battery(a bigger one, that can supply about 1 A for a few hours). This is the lowest cost smart charger that I could came up with so far... I have made one more with an ATTINY microcontroller, but that's a little overkill I think... This should do what I need it's simple, cheep, and doesn't require any program to work.
Switching: When the Adapter is connected R2 set 4.8 V to the Q1's base which is normally pulled down, causing Q3 to turn off, while the IC1starts to supply the necessary current for the circuit.
Charging: IC2 Supplies current to the charger circuit so that is not powered when the device is powered from battery R7 sets the upper limit which stops the charging, R8 sets the lower limit under which the charger turns on. Between the 2 limit the battery is full. The 555 timer is used to switch the charging on and off. For setting the charging current the R4 should be changed.
The circuit is not tested yet, but I thought I share it. I'll replay when I test it, but that will be a little further, because I already have a charger, this just came to my mind while I was working on another project. :)
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This is more the direction I was looking at for my 9-Volt charger/supply. I like the LED circuit posted there, but question I have on that is whether it cuts off charging when the battery is fully charged.
Thanks for posting this thread.
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The 9v LED regulated charger stops charging when the battery if fully charged, at which point it will give the battery a tiny trickle charge(a few mA at most).
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Thanks, Paul.
Now I still want to see what else I can do with this; I'll return to my thread for that.