Oznog
Active Member
I want to make a strobe out of a series string of 3x 3.9V, 1 amp Luxeon emitters, powered by a 12.6 car battery, which of course can go up to 14V or so. I will be flashing it with another one of my microcontrollers, probably at 5V again.
12.6V- 3*3.9V = 0.9V to control the regulation.
Since there's not a lot of voltage room here, the currents are high, and the pulses will be sharp which makes feedback tricky, I figured just an NPN and an emitter resistor would do it.
So I think shooting for 0.3 Vcesat would mean a maximum of 0.6 ohm for the emitter resistor.
I don't know if this is such a good idea, I now need a fairly tightly regulated voltage of 1.2V, depending on gain might be 3 to 10 mA. And it has to switch on and off really fast.
Any good way to do this? Or should I think about using an op amp to drive the NPN (or MOSFET) and use the voltage on the resistor as feedback to the op amp?
12.6V- 3*3.9V = 0.9V to control the regulation.
Since there's not a lot of voltage room here, the currents are high, and the pulses will be sharp which makes feedback tricky, I figured just an NPN and an emitter resistor would do it.
So I think shooting for 0.3 Vcesat would mean a maximum of 0.6 ohm for the emitter resistor.
I don't know if this is such a good idea, I now need a fairly tightly regulated voltage of 1.2V, depending on gain might be 3 to 10 mA. And it has to switch on and off really fast.
Any good way to do this? Or should I think about using an op amp to drive the NPN (or MOSFET) and use the voltage on the resistor as feedback to the op amp?