Hi all - I'm using one section of an LM324 quad comparator to regulate the output of a boost converter circuit by comparing the output to a reference voltage. The output of the comparator is connected to the "reset" pin on a 555, so when the voltage reaches the correct level the drive pulses are shut down. My problem is that the comparator just doesn't seem to swing high enough to fully turn on the 555 when it's supposed to, and doesn't swing low enough to shut it down. I think part of the problem is that when the circuit I have is used with a 9 volt battery, the supply voltage plunges to 5 volts. The output of the comparator never rises higher than about 2.5 volts, and never falls lower than about 0.8 volts.
Would using a switching transistor connected between the comparator output and the reset pin of the 555 help matters? The circuit seems to work properly when the reset pin is shorted to the supply or ground, so apparently that pin needs to really be pulled up or down hard. Or maybe there's something else happening? I thought I'd ask before I go desoldering things.
Would using a switching transistor connected between the comparator output and the reset pin of the 555 help matters? The circuit seems to work properly when the reset pin is shorted to the supply or ground, so apparently that pin needs to really be pulled up or down hard. Or maybe there's something else happening? I thought I'd ask before I go desoldering things.