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Can a cadnium sulfide turn a transistor on

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mrel

Member
Hello
I would like to know if cadnium sulfide photocell hookup to a transistor have enough voltage or current to turn a transistor on to cause a relay coil to pull the contract close , as long as the cadnium sulfide photocell have light shine on the photocell, without using any outside battery power to transistor or the relay.
If can be done ,can you tell me where can I find a circuit like that.
mrel
 

dknguyen

Well-Known Member
Most Helpful Member
It will definately not produce enough current and not at a high enough voltage to close a relay coil at any size. And it might barely be able to turn on a small transistor directly. The turn on speed would be very slow and things would depend on whether it was a BJT or FET.
 

jbeng

Member
Cadmium sulfide cells are light-dependent resistors. The resistance of the cells change when light shines on them. They don't produce current flow of their own like photovoltaic (solar) cells do and require external power to operate.

Jeff
 

Sceadwian

Banned
The CDS cell isn't meant to produce a voltage, you set it up as a voltage divider with another resistor to bias a transistor. They do produce a voltage of some kind, that's how they alter their resistance, how much I don't know but it can't be directly used for anything that I know of, no reason to, just attach to a voltage source add another resistor and it'd work many times better.
 

MikeMl

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Most Helpful Member
...
If can be done ,can you tell me where can I find a circuit like that.
mrel
Here you go. Component values left to student :D
 

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