Instructables

Sensor Question

This is a hypothetical electrical circuit question, I'll try to clarify as best as possible.

If you had a circuit hooked up to a light bulb, but controlling a the light bulb were two sensors wired into the circuit. One sensor turned the bulb on when there was no light, and the other turned it off when there was light. I'm not sure if that would be all one sensor, but garden lights work somewhat like that. Anyway, what if the sensors were mounted directly in front of the light bulb, facing it, so they worked based on its light. What would happen when you turned it on? Would it act like a strobe light or just explode, and would the effect be different with LED's? Also, would you need to put some other mechanism in to slow the sensor's signals?

Goodhart4 years ago
IF the sensors did not "sense the state" of the light, but just flipped the circuit on or off; I would think that the first one to react would be the last state it'd be in....that is, if the first sensor turned the light on because it was faster, and the second one turned it off, since the first one has already "acted" it will not "reverse" the second state. To me, it might react much like a "3-way switch" one switch turns the bulb on, the next one turns it off.....so it stays off.....or the other way around if the first switch turns it off. I don't know how else you'd be able to wire this circuit but in this manner.
seandogue4 years ago
I'd suggest that you try it and report back with your results. This is something best determined by you via empiricism.
caarntedd4 years ago
We have a night light with a sensor in our bathroom. If it is switched on with the main light on , it doesn;t glow as it detects the main light. If you put your thumb over the sensor the light glows as it no longer detects any light. Pretty obvious, however if I pass my hand in front of the sensor the nightlight flickers as it switches on when the shadow passes over, but switches off again as soon as it detects it's own light reflected off my hand.
Re-design4 years ago
It depends on how fast your circuit worked.

If it worked too fast the light might look continuous by flashing so fast you saw it as solid. 

Or it might turn on and off so fast that it never really has time to light up much.  Probably not this way though.

It would probably just blink at a certain rate.  You could put in a delay mech. and have it blink slower.