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I've created a small circuit to sense the voltage of the batteries, both charging and power, and switch when one of two conditions is met. Either A) the power battery drops below a certain voltage, or B) the charging battery reaches a voltage.
However I'm not all that great as a circuit designer, I found a few ideas off the net and threw them together. If any one sees any obvious flaws, or definite improvements I would very much appreciate it. Also I could use a little help with selecting the right values for the resistors, etc.
First we start with the main circuit. We have an SCR supplying the power to the charger, and the SCR is triggered by voltage from a Zener Diode (D1). The Zener diode is hooked up across a voltage divider (R1 & R2) to fine tune the cutoff voltage.
An NPN Transistor (q1) is also in line for sensing/switching from the charging battery side. It's isolated frome the charging battery by an opto-isolator (The 4n25 diagram was the only one the program had) which is controled by the PNP (q2) and NPN (q3) switch on the charging side. In that situation, the Zener diode is used to send the base of the PNP transistor high, which would cut off the NPN transistor (q3). The NPN transistor is set up in a self powered loop to keep itself triggered so long as it has power and once turned off will have to be reset by the momentary NO switch.
Under normal charging situations, once the reset switch is pressed, the circuit will continue to keep Q1 open until the battery reaches whatever charge your looking for, at that point the PNP is biased and cuts power to the circuit which will not reset without the switch and power from the PNP transistor.
I'm also looking to design a circuit that will interface with the computer.. (though I have to learn to program first).. So that some A/D converters can be read directly into the computer, log the data and even control the switching of the circuit as well.
However I'm not all that great as a circuit designer, I found a few ideas off the net and threw them together. If any one sees any obvious flaws, or definite improvements I would very much appreciate it. Also I could use a little help with selecting the right values for the resistors, etc.
First we start with the main circuit. We have an SCR supplying the power to the charger, and the SCR is triggered by voltage from a Zener Diode (D1). The Zener diode is hooked up across a voltage divider (R1 & R2) to fine tune the cutoff voltage.
An NPN Transistor (q1) is also in line for sensing/switching from the charging battery side. It's isolated frome the charging battery by an opto-isolator (The 4n25 diagram was the only one the program had) which is controled by the PNP (q2) and NPN (q3) switch on the charging side. In that situation, the Zener diode is used to send the base of the PNP transistor high, which would cut off the NPN transistor (q3). The NPN transistor is set up in a self powered loop to keep itself triggered so long as it has power and once turned off will have to be reset by the momentary NO switch.
Under normal charging situations, once the reset switch is pressed, the circuit will continue to keep Q1 open until the battery reaches whatever charge your looking for, at that point the PNP is biased and cuts power to the circuit which will not reset without the switch and power from the PNP transistor.
I'm also looking to design a circuit that will interface with the computer.. (though I have to learn to program first).. So that some A/D converters can be read directly into the computer, log the data and even control the switching of the circuit as well.
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