Two op amps, one is schmitt trigger and other is integrator, connected together at 12v supply and around 6vin creates triangle wave generator. Left OpAmp1 is Schmitt trigger creating a square wave and right OpAmp2 is integrator smoothing output of opamp1 creating triangle wave. Actual parts used lm358 dual OpAmp ic, and 2n3904 or tip120 transistor as led driver. Testing 11v and higher due to varying power supplies and project under construction.
