Geiger Pulse Simulator PUBLIC

Circuit to interface a Lego RCX brick to a Geiger Counter.

Final Working circuit for interfacing Lego RCX brick to Geiger Counter.

This circuit takes a 100us pulse from the LED of a Geiger Counter, and converts it to a >20ms signal usable by a Lego RCX brick input port configured as a touch sensor, enabling the Lego controller to count Geiger "ticks".

NOTES: First Transistor is NOT 2N3904, it is an H11A2 Opto (transistor side). The H11A2 diode side REPLACES Geiger Counter LED to produce a clean signal. Output after Q2 is to RCX, be careful about polatity on Input port connection for correct signal sensing. R1 and C1 form charge time circuit. Discharge through Q2 measured at >20ms.