Strobe control with op-amp output (solved)

Hey, all. Greetings.

I'm trying to build a strobe controller for a physics experiment. The arduino end is working perfectly. I have a sketch set up to fire the strobe when I want to, sends pin 12 from low to high, output verified with DMM.

Problem is the op-amp circuit. I have a TL082, and want to produce a 0-9v swing on output (not 0-5). So I tried using a common ground and a 3x non-inverting amplifier. This produced a constant 7V output regardless of the state of pin 12 (which was hooked into the +input for the amp.) So then I tried making a virtual ground at 2.5 v, using the other side of the op-amp and resistors from ground and V+. Hooked up the amplifier to reference virtual ground, so 0V on pin 12 should push output to negative saturation, and 5 into positive saturation. Still doesn't work, getting that flat 7V again.

Any experienced hands out there with a simple op-amp circuit to increase the voltage output from the arduino board? Would like to have this working for a class I'm teaching in 3 days. It should be possible to make this work without a dual supply, but I can use 2 9V batteries and do that if I have to.

Any advice appreciated - thanks in advance.

Regards, Martin

You're only going 0-9V? You don't need an op-amp for that. Just a simple NPN transistor and two resistors. Arduino pin to 1K resistor to NPN base. NPN emitter to gnd. 9V to 1K resistor to NPN collector, collector to strobe control. When Arduino output is Low, strobe control will be high. When Arduino outpit is High, strobe control wil be low.

Crossroads,

Thanks. The strobe is just a control line, so the current draw should be low. I'll stop by Radio Shack and get a NPN transistor today, and see if that works. Simple is good, and being able to control transistors with the arduino would be a good thing for me to pick up. Thanks for the speedy reply, I'll let you know how it works out.

(And obviously, if the circuit is inverting, I'll just change the sketch to make it work the way I want.)

Regards, Martin

Don't forget the resistors. Base resistor limits current flow out of the arduino pin. Keep it above (5V-0.7V)/.035A = 123 ohm. Can probably get by with a lot less if don't need to switch much current.

CrossRoads,

Thanks for the help. Works like a charm now, using your exact circuit for the strobe control. Doesn't draw much current, but running it at 5V was irregular, running at 8.2, from a lithium ion 9V, works great. I control the timing and number of strobe flashes.

Preciate the help. Later.

Regards, Martin

Cool.