Greetings one and all!

I am trying to find what distance you can run an LDR away from the circuit.

I have a 12 Volt day night switch using a 741. I want to mount the control unit right next to the battery and the LDR outside about 5 meters away from the control unit.

Is this possible?

 

hi Rodney,
If you use a twisted pair or screened pair of wire to the LDR, 5mtrs is not a problem.
I would add a 10nF or 100nF across the local end of the wire pair,[the 741 end] to reduce air borne interference.
E

 

hi Rodney,
If you use a twisted pair or screened pair of wire to the LDR, 5mtrs is not a problem.
I would add a 10nF or 100nF across the local end of the wire pair,[the 741 end] to reduce air borne interference.
E

Would I need to solder the screen to the negative or to an earth spike

 

Would I need to solder the screen to the negative or to an earth spike

That would be good.

 

If you use a screened pair, connect the screen to the 0V/Common of your project supply.

 

If you use a screened pair, connect the screen to the 0V/Common of your project supply.

Unless the LDR part of the divider is ground referenced, the OP might have to use screened twin.

 

Originally Posted by ericgibbs
If you use a screened pair, connect the screen to the 0V/Common of your project supply.

Unless the LDR part of the divider is ground referenced, the OP might have to use screened twin.

hi,
If one end of the LDR is at 0V, surely if he followed my suggestion, all that would happen is that one inner conductor and the screen would be connected together to 0V at the 741 end.?
E