DIYbanter - View Single Post - Using varying 5VDC signal to control voltage on 110VAC circuit

(David P. Kleinschmidt) wrote in message om...
(Larry) wrote in message om...

I
would much rather use this varying current to ... dim my 75W, 110VAC
desk lamp [it's a long story]. So I figure there's got to be
something like a dimmer switch that, instead of being controlled by a
knob, is controlled by varying voltage. Can anybody help?

You can use a small 6.0 V (5.0V) lamp and light couple it to a Photo Cell
with heat srink tubeing,tape ect.
Open up a cheep 120.0VAC light dimmer and connect the photo Cell only across
the the 2 used (soldered connections) of the pot.
This way you are isolated from computer to lamp dimmer.

That's a good idea. What should I look for in the photo cell? Should
I try to match its resistance range to that of the pot? And are you
suggesting that I replace the pot with the photo cell, or connect it
in parallel? [Sorry if these are dumb questions; I want to be certain
before I go blowing things up.]

- Dave
You can use a wide range of photo cells (Cad cells is a common type)
most are 3/8 to 1/2 inch dia and I have not had any big problem with
dark to light resistance of the cells.
You connect the photo cell across the two used leads of pot.
In use you leave pot in off(dim) and let the cell drop the resistance and
turn on the dimmer or you can override it by turning up the dimmer pot.