TIME TO DUST INDICATOR - Circuits designed by David A. Johnson, P.E.


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Circuits designed by David Johnson, P.E.

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Last Updated on: Friday, April 25, 2008 04:12 PM

Alarm Circuits Bistable Multivibrator or Flip/Flop Circuits Light Detectors or Optical Sensors

TIME TO DUST INDICATOR
I thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough. I have not yet built and tested this circuit completely but in concept it should work. The circuit draws very low current from a +3v battery and could be housed in a package similar to a small ashtray. The assembly might be placed in a suitable out of the way area to collect dust. It would alert a maid when it was time to dust the room. The circuit detects dust with an infrared LED that is pulsed so its light shines onto a smooth flat plate. Any dust settling onto the surface is detected by a phototransistor, mounted at a 90 degree angle from the LED. When the dust reaches a particular level, sufficient light is reflected into the phototransistor to change the logic state of the circuit to an alarm condition. The alarm output could be connected to a beeper, a flashing LED or to one of the LED flashing circuits in this hobby circuit section.

Click on Drawing Below to view PDF version of Schematic

Alarm Circuits Bistable Multivibrator or Flip/Flop Circuits Light Detectors or Optical Sensors
Master Schematic Category List - David A. Johnson, P.E.