I want to use one of those tilt-ball switches on an interrupt with a microcontroller that can only trigger an interrupt on a signal FALLING from high to low, in a low power circuit.

The tilt ball switch is normally closed but this cannot be relied upon.

Basically it needs to trigger a low pulse whenever the signal from the switch changes from high to low or low to high but normally be high or high-Z, and not burn significant current in the long periods of time waiting for this to happen.

  • \$\begingroup\$ So, whenever the input to the solution circuit changes state, H to L or L to H, its output must generate a negative going pulse, H to L to H? \$\endgroup\$
    – James
    Jun 21 at 20:07
  • \$\begingroup\$ James, that's right \$\endgroup\$ Jun 22 at 18:12

1 Answer 1


Use a dual monostable multivibrator such as a 4528B (MC14528B). Use both monostables within the package, one triggering on the positive going edge and the other triggering on the negative going edge. Connect the two monostables' outputs (positive going pulses) via resistors into the base of a npn transistor such as a BC547 or BC548 with its emitter grounded and its collector connected to Vdd via a resistor. Output to microcontroller comes off of transistor's collector.


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