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Garage door opener puzzle
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isw
Aug 2, 2016, 1:52:56 PM8/2/16
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Trying to find out why operation is erratic, I measured the voltage
across the hard-wired pushbutton in the garage.
The button is illuminated by a red LED, which is in series with a 1k
resistor across the switch. The LED is always on. Pressing the switch
shorts the resistor-LED pair and operates the door.
The puzzle is that when I disconnect the LED-switch assembly and measure
the voltage across the wires from the opener unit, I get only a couple
hundred millivolts DC, and less AC.
How is it possible for the LED to light with only 200 mV across it?
Isaac
across the hard-wired pushbutton in the garage.
The button is illuminated by a red LED, which is in series with a 1k
resistor across the switch. The LED is always on. Pressing the switch
shorts the resistor-LED pair and operates the door.
The puzzle is that when I disconnect the LED-switch assembly and measure
the voltage across the wires from the opener unit, I get only a couple
hundred millivolts DC, and less AC.
How is it possible for the LED to light with only 200 mV across it?
Isaac
frank
Aug 2, 2016, 3:32:38 PM8/2/16
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isw
Aug 2, 2016, 11:57:07 PM8/2/16
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In article <nnqsgg$43t$1...@usenet.itgate.net>, frank <fr...@invalid.net>
wrote:
Hmm. Could be. Time to limber up the ol' wiggle tube.
Isaac
wrote:
Isaac
ohg...@gmail.com
Aug 4, 2016, 7:43:07 AM8/4/16
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