This circuit comes from some years ago as a part of a project we did to make it possible to keep a charger on a battery continuously without it overcharging.
It's mostly a junk box project, at least as far as the components used in the one I held onto. This is like late 1970's technology grafted onto 1960's.
The regulator board is a replacement for whatever was in an old Monkey Ward (that is properly Mongomery Ward) charger, rated at 15 amps. The components labelled T1, D1 & 2, Q3, SW1, the ammeter, and the circuit breaker are all part of the charger.
Other components:
Resistors R1 - 7 - 5% carbon 1/2 watt (1/4 watt should be fine)
Resistors R8 & 10 - 1% 1/4 watt. Oops, R10 should be 2.26K
Trimmer R9 - any multi-turn trimmer will do. Single-turn is not good.
Op amp Z1 - any Op amp should do, as long as it's better than a 741. It's used as a comparator, so good input impedance is better. The CA3140 was the hot op amp back when.
D3 - any 2.5 volt reference diode will do.
D4 - any 1N400X will do.
D5 - this is a 4.7 volt zener. $00 mw is fine - no tolerance necessary.
Q1 - we had cases of 2N1613's. Used them for everything. It's a switch, so 2N2222 is a good sub.
Q2 - had bunches of these, too. Just about any PNP will sub.
Operation:
The output from the full wave rectifiers is pulsating DC. The diode D4 isolates the op amp from these pulsations, and C1 filters it. Z1 is set up as a comparator with the D3 reference diode presenting 2.5 volts to pin 3. As long as the voltage on pin 2 is less than that, the output will be high.
In operation (with the switch in the regulated position) the voltage on pin 2 will reflect the charge on the battery during the low portion of the rectified waveform. If it is less than 2.5 volts, as set by the R9 trimmer, then Z1 output wil be high. That will turn on Q1. In turn, that will turn on Q2. As the rectified voltage increases, so will the voltage between R6 & 7. This will gate Q3 and allow charge to flow to the battery.
When the battery is up to charge (ideally, 13.6 volts), the voltage on pin 2 of Z2 will be high enough to make the output go low. This will leave Q1 & 2 off, and the SCR will not gate again until the battery charge falls a bit lower.
By using a meter, R9 may be adjusted for a very precise charge on the battery.
It's mostly a junk box project, at least as far as the components used in the one I held onto. This is like late 1970's technology grafted onto 1960's.
The regulator board is a replacement for whatever was in an old Monkey Ward (that is properly Mongomery Ward) charger, rated at 15 amps. The components labelled T1, D1 & 2, Q3, SW1, the ammeter, and the circuit breaker are all part of the charger.
Other components:
Resistors R1 - 7 - 5% carbon 1/2 watt (1/4 watt should be fine)
Resistors R8 & 10 - 1% 1/4 watt. Oops, R10 should be 2.26K
Trimmer R9 - any multi-turn trimmer will do. Single-turn is not good.
Op amp Z1 - any Op amp should do, as long as it's better than a 741. It's used as a comparator, so good input impedance is better. The CA3140 was the hot op amp back when.
D3 - any 2.5 volt reference diode will do.
D4 - any 1N400X will do.
D5 - this is a 4.7 volt zener. $00 mw is fine - no tolerance necessary.
Q1 - we had cases of 2N1613's. Used them for everything. It's a switch, so 2N2222 is a good sub.
Q2 - had bunches of these, too. Just about any PNP will sub.
Operation:
The output from the full wave rectifiers is pulsating DC. The diode D4 isolates the op amp from these pulsations, and C1 filters it. Z1 is set up as a comparator with the D3 reference diode presenting 2.5 volts to pin 3. As long as the voltage on pin 2 is less than that, the output will be high.
In operation (with the switch in the regulated position) the voltage on pin 2 will reflect the charge on the battery during the low portion of the rectified waveform. If it is less than 2.5 volts, as set by the R9 trimmer, then Z1 output wil be high. That will turn on Q1. In turn, that will turn on Q2. As the rectified voltage increases, so will the voltage between R6 & 7. This will gate Q3 and allow charge to flow to the battery.
When the battery is up to charge (ideally, 13.6 volts), the voltage on pin 2 of Z2 will be high enough to make the output go low. This will leave Q1 & 2 off, and the SCR will not gate again until the battery charge falls a bit lower.
By using a meter, R9 may be adjusted for a very precise charge on the battery.
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