skulenov
New Member
Hello all,
i'm new to the forum but not new to electronics
i have a problem and i have a feeling that it's something trivial but i just can't get through it!
I'm trying to build a NiMH battery charger that is temperature controlled so when batteries get full they start to heat up, and when temperature rises to 35°C the LM35 sends 350mV to inverting input of uA741. The 741 in turn switches it's output from 14.3V(high) to 2V(low) and switches relay driving transistor off. Relay should break flow of current to 741 but that just don't happen!
It stays in on state, the pin 6(Output) of 741 is 14.3V and won't go down no matter what! maybe it just don't want to kill itself!?
I tested this part of circuit on a breadboard and it worked (i put a LED in place of relay and 741 and transistor worked ok and switched on and off depending on the state of '+' and '-' input levels of op-amp)
anyway, here's the schematic so please take a look and give me comments and any critics are welcomed!
i'm new to the forum but not new to electronics
i have a problem and i have a feeling that it's something trivial but i just can't get through it!
I'm trying to build a NiMH battery charger that is temperature controlled so when batteries get full they start to heat up, and when temperature rises to 35°C the LM35 sends 350mV to inverting input of uA741. The 741 in turn switches it's output from 14.3V(high) to 2V(low) and switches relay driving transistor off. Relay should break flow of current to 741 but that just don't happen!
It stays in on state, the pin 6(Output) of 741 is 14.3V and won't go down no matter what! maybe it just don't want to kill itself!?
I tested this part of circuit on a breadboard and it worked (i put a LED in place of relay and 741 and transistor worked ok and switched on and off depending on the state of '+' and '-' input levels of op-amp)
anyway, here's the schematic so please take a look and give me comments and any critics are welcomed!