hassmaschine wrote:all the LEDs are grounded. the current limiting resistor(s) are built in as well. I'm providing power to turn them on, and they're all powered at the same voltage source. from testing it appears they want around 5v (all the others are run off 5v, but I don't have the light contol module to activate the LED backlights the "normal" way).
basically I don't care about the gain of the OP-AMP- it's purpose is to invert the voltage from the light switch/dimmer, which I always run at full brightness. I'll fine tune the voltage output at the op-amp for the brightness I want.
Any chance you could post a schematic or wiring diagram of what you think you have ? I gleam you're taking the voltage off a pot that's used to dim lights somewhere and when that voltage goes lower and lower you want the LEDs to get brighter and brighter ?? Thus you've got some inverting op-amp circuit to (try to) do that. That op-amp then drives a bunch of resistor+LEDs that are in parallel. So what you seem to need is an amp that can supply more current at about the same output voltage as the present op-amp circuit. You might be able to find a "power amp" to replace the op-amp in your circuit or one that follows it (op-amp output goes into power amp input).
OTOH when you say that "
it's purpose is to invert the voltage from the light switch/dimmer, which I always run at full brightness," it sounds like you have a fixed voltage, that's either there or not, and the problem is just that it's not the correct voltage for the LEDs. There may be a much better and simpler way to make the LEDs turn on if this is the case. But I do need to know the circuit as best a you can and what the "wrong" voltage from this switch/dimmer is. Depending on the current involved, you might be able to get rid of this op-amp circuit and just use a reasonable power dropping resistor (though a DC-DC converter would be less wasteful and run cooler and a linear regulator+resistor would split the difference btw these 2 approaches).
hassmaschine wrote:btw, even if I crank up the op amp to say, 7v output, it still only gets about 3v to the LEDs.
If my understanding is correct, that's to be expected. The op-amp can't provide all the current needed by the LEDs. They are in effect shorting the output of the op-amp to ground (even if it's not a "hard" short). But let's be very clear with the terms used so there's no mistake. When you said "
about 3v to the LEDs", did you really mean ~3V between the connector pins that go to the
resistors+LEDs and ground ? The actual voltage across
just the LEDs themselves should only ever be 1.5 to maybe a little over 2 V, even when driven at their max current levels.
Can you measure what the current draw needed by all the resistors+LEDs is ? I'm thinking you could put an ammeter inline with an ~ 4.8V battery pack and connect the resistors+LEDs to that. With that measurement, we could know what's needed for a "driver" of some sort.