Circuit produces high current (very bright) pulses through led. Circuit built using 3mm and 5mm clear type leds (red, white, blue, yel, etc). Xstrs were general purpose 2n3904, 2n3906 types. Est peak current limit to be approx 2x to 3x continuous current rating. Adjust the output duty ccycle to keep the equivalent ave led current below the continuos rating (20ma or less in most cases). Pulse duration can be changed by adjusting 20k resister, rep rate mostly affected by 1.8meg resister. Peak led current afjusted through source voltage and led current limit selection. For the circuit shown, the hardware measurements were rep rate approx 1.4 Hz, pulse duration approx 58 ms, peak led current approx 70 ma, output duty cycle = 0.8%.
