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Last Updated on: Thursday, December 07, 2017 02:05 PM

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

It's Time to Dust Indicator
Also see Circuit Solutions


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

Circuit Battery Powered Dust Monitor designed by Dave Johnson, P.E. (July 6, 2000)



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

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