Dimmer circuit for dc?
12v | | ,---------------------+------------+-------+ | | | | | 10K 1K Rload 10K | | | | 0.1 | | | | ,-----||-------|---10K------|-------+ | | | | | / | ,--1M------+ | |- \\ | | | ,--+----|| / | | |\\ | | |- \\----+-------| npn | \\ +---+--|-/ \\e | / | | |/LM2903 | | | | | | | | - 100K | | | ^ | | | | | | | | | | | | | | +---+--------------------|----------+ | | | | | Rs | | | '-------------------------------+----------' | | gndIt does okay running a very light load (like a car taillight bulb), but even driving a load of an amp or two, the mosfet gets warm. It oscillates too fast, so the mosfet never turns full on or off. At least I think so lol.
I actually want to use this circuit topology to run a 25 amp load, so I have somehow to get the circuit to do hard switching (also I have to get rid of the transistor/pullup resistor combo and replace it with a proper inverting fet driver). I don't have any drivers on hand but I do have a pile of 555's. I can make a 555 into an inverting driver, by tying pin 6 high and using pin
2 as the input for example. I only need very low frequency switching so a 555 should do it. Still figuring out how to make the circuit do hard switching. I thought instituting a delay in the signal between the comparator and the fet driver, or within the driver itself might accomplish it. This dimmer should switch pretty slow, between 10 Hz and 1 kHz. I'd appreciate any ideas how to slow it down.