John Walker wrote:

>Hi all! Long time lurker, first time poster.
>
><SNIP>
>  
>

>I'm sure there are several other ways to accomplish this and could use 
>your recommendations. To recap, I want to detect when a bulb is in a 
>socket using the filament as a switch. I will use a PIC pin to monitor 
>this and will use another PIC pin to turn the light on/off. The light 
>will be an incandescent type operating at 120VAC and be rated at 25W.
>
>Thanks in advance.
>
>  
>
If  the light is wired correctly in the USA the Neutral or white wire 
should have the same electrical potential as ground (earth).

Put a small SPDT relay in series with the blub.  Throught the N.C. 
contact run a wire from PIC PIN to the other side of the bulb socket 
that the PHASE wire would connect to.  Test it for ground allowing for 
the resistance of the bulb filament.

If for some reason the bulb is energised the relay will close and keep 
120V from going to the PIC PIN.

Recon

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