| T O P I C R E V I E W |
| augustin87r |
Posted - Dec 20 2005 : 3:25:58 PM
I have a problem with the schematic. Can anyone tell me if the normal position of the led is on? When the charger is not connected to the battery the led is on , after i connect the battery, the led switches off and doesn't turn on again. What is the purpose of that switch? If i push that switch when the battery is not connected the led turn off, when i release it, the led turns on.............. Can anyone telle me why the led does not indicate the batery charged ? Thanks
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| 2 L A T E S T R E P L I E S (Newest First) |
| Aaron Cake |
Posted - Dec 22 2005 : 09:36:53 AM
There's a much better charger schematic available that is fully automatic. Search this forum for "battery charger as promised".
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| OutToLunch |
Posted - Dec 21 2005 : 10:55:39 AM
The circuit is behaving properly. If you do not have the circuit connected to a battery, then there is no current flowing through R7, so the voltage that is being placed on the inverting input to the op-amp is the output of the linear regulator.
The voltage on the non-inverting input of the op-amp is going to be slightly less than than the voltage on the inverting input in this situation. The op-amp is being used as a comparator and if the inverting input is higher than the non-inverting input, the output is pulled low - which turns on the LED.
When you have the circuit tied to your battery, the battery voltage is such that the voltage on the inverting input is lower than the voltage on the non-inverting input. In this situation, the comparator forces the output high and the LED is off.
Once the battery voltage has risen to a point where the current being fed into it is very low, the comparator will trip and the LED will be turned on.
Since the LED is off when you have it connected to your battery, it means your battery is being charged.
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