photoresistor question.....

[dminner]

I have, hopefully, a simple question.

I was doing some of the mods on this site to my big muff:

http://rkerkhof.ruhosting.nl/Taas/Mods/Big%20Muff.htm


I recently did the "feedback loop" mods.  If you look on the site, the feedback mods just involve attaching 2 points with a switch so that the feedback loop can be turned on and off.  You can see on the sight also says: "Great addition: add a 1M potmeter in the loop (wired as a variable resistor) or, even better!!, a LDR (light dependent resistor)."

So, I got a cheap pack of photoresistors (LDRs) from radio shack and mounted and wired up a photoresistor into the loop.  However, when the resistor is wired in, the loop does not work.  It does not feedback at all and acts like the switch is not flipped.  I just simply wired the photoresistor in line with the loop.  Is that wrong???

I know the photoresistor works because the I can use a multimeter and wave my hand in front of it and see the resistance change.

Do i need someting else in line besides the resistor?  Right now I just have a wire going from one point on the board, through the switch, through the photoresistor, and back to the other point of the board.

thanks for the help!!!


(oh yeah, I added the LDR to "feedback loop 1" on the site, not sure if that matters...)

[PRR]

Try a VERY bright light. (Sunlight.)

Try the loop-2 variation.

But the lack of details on that mod makes me wonder if all proposed variations were actually bench-tested.

[petemoore]

  The description is probably more complicated than...
  a resistive feedback path...+ or - ?
  Photocells...easier to see what the resistances'd be, then simulate the photo part with resistors or pot until it starts making sense to the point that the photocell part seems required/prepared and ready for further progress.
  When the 'plunk in' didn't work, especially on prototypes, I find it's easier to provide X value resistance [especially when the R needs to be low like, <100k] with anything except a photocell.
  Otherwise I often found the + lead, -lead, DMM and wires, Light, Photocell, circuit and power supplies extremely difficult to handle/rely on with only 2 hands and 1 set of eyes.