I'm an artist working on a interactive installation. I'm a beginner in electronics and I'm feeling a little bit lost here, can you help me?

I have a 5v circuit with a PIR sensor activating a LED and a sound module. The minimum output from the PIR sensor is HIGH for about 3 seconds and then LOW for another 3 seconds. I need to flash the LED quickly, not stay on HIGH for 3 seconds.

The LED is just to demonstrate what I am trying to do. This is actually to trigger the sound module that I am using, which is triggered only by a short pulse. If it stays HIGH for 3 seconds it doesn't trigger it (just changes the volume). Basically, I'm trying to use the PIR sensor as a momentary button.

I know I could use an Arduino for this, but I need very cheap pieces for this project (cheaper than Arduino) as I will have many copies of the same circuit. What do I need for this? A timer or switch module, capacitors?

I really appreciate any help from the community!! Thanks!

  • \$\begingroup\$ You could use a cheap microcontroller. There are 6 pin 8 bit microcontrollers under $1. That would require skills in programming it though... \$\endgroup\$
    – Szidor
    Apr 3, 2016 at 11:46
  • \$\begingroup\$ How quick is quick? Are we talking human perception quick? (That would be ages in electronics ) maybe you can use a high pass filter. \$\endgroup\$
    – Christian
    Apr 3, 2016 at 11:57
  • \$\begingroup\$ Quick as the push of a button...probably anything less than 30ms will work. \$\endgroup\$
    – Emerson
    Apr 3, 2016 at 18:44
  • \$\begingroup\$ Is there a solution that doesn't involve a microcontroller? It seems to be such a simple thing..it's only necessary to stop the energy flow just after the LED has been activated.. \$\endgroup\$
    – Emerson
    Apr 3, 2016 at 19:00

1 Answer 1


Maybe a 555 oscillator? It can be triggered by a rising edge and the duration of les flash is configurable by a resistor and a capacitor.

I don't know if is the cheapest solution but is the most classical approach.

  • \$\begingroup\$ Thank you for your answer! I will try this solution soon and let you know if I managed to do it. \$\endgroup\$
    – Emerson
    Apr 6, 2016 at 12:42
  • \$\begingroup\$ I can confirm this method works, although I found out another problem (the LED works OK, but the sound module button connects to ground...but I will sort this out later). Thanks! \$\endgroup\$
    – Emerson
    Apr 11, 2016 at 11:23

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