3 Pin LDRs

[KerryF]

Anyone see those 3 pin LDRs.  Usually they are 2 pins and can only be used as a variable resistor, but I found ones with 3 pins that can be used as pots.  I ordered and recieved them to.  I cant wait to try them out.  Here they are:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G15180

I also ordered and recieved some regular 2 pin ones:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G15181

Any experiences?  Anyone ever seen them? 

[Seljer]

"Small .29" x .26" CDS cell features 3 leads. Between the outer leads the resistance in the dark is over 100Mohm. In light the resistance between the outer leads is less than 1Kohm. The center lead is connected as a tap to the 2 outer leads, however it does not divide the resistance between the outer leads in equal values."

If I understand that, it just works like 2 LDRs hooked up in series (and not even precisely split in half), not like a pot

[oldrocker]

Will those work for the DOD 440?

[Paul Perry (Frostwave)]

http://www.goldmine-elec-products.com/prodinfo.asp?number=G15429
Guys, THIS is what you want!! Electrolytic tilt sensor!! WOOHOO!! Strap it on the ax!

[darron]

http://www.goldmine-elec-products.com/prodinfo.asp?number=G15429
Guys, THIS is what you want!! Electrolytic tilt sensor!! WOOHOO!! Strap it on the ax!

duel axis isn't necessary. but that's an awesome idea Paul. Another idea might be to put a mercury switch on the guitar so that it will only activate when you have it fully upright. This could:

Mute the guitar when it's on your rack.
Give a volume/drive boost for %^&*-rock style solo-ing

damn... i'm gunna do that!

any other applications?

[darron]

just thought of another use... disable your active electronics when you are not holding the guitar in an upright position (e.g. when you put it on the rack) to not worry about your battery. you'd also have another one setup to send the signal to ground.

[petemoore]

  I had a mercury switch kinda like that, had two leads, it had very reliably switched a trunk light on/off in an AMC Ambassador's trunk lid. I called the vehicle an "AMBlastadoor" .
  I put it in a gooseneck lamp, it came from the dashboard on my 68 Galaxie, made a great map light.

[Ge_Whiz]

Up comes the big solo - you arch your back - throw your hair off your face - point your axehead at the skies and... the sound cuts out. 

[KerryF]

Ok now I have some questions...

1. The 3 pin LDRs.  Ok, not that you say they cant work as a pot type thing.  Well, what would happen if I connected it up like a pot?  Use all 3 pins.

2. I got a Photodiode sample.  Its the shape of an LED.  How does this work, or how is it used?  Can it replace an LDR?  Whats the difference between an LDR and a Photodiode?

Thanks.

[KerryF]

^-Anyone?  I would like to know because I am doing something with it tomarrow... 

[Seljer]

Think of your 3 pin LDR as 2 regular LDRs connected in series, its basically just like 2 regular resistors correct in series and when it gets darker the resistance of both of them goes up. It doesn't work like a pot where when one side gets larger the other side gets smaller.


What you can however do if you want to use LDRs as a regular pot is to hook up a resistor (something between 10k and 100k depending on the specs of your LDR) onto one side of the LDR. So as the light the changes the entire resistance does change (instead of staying put like on a pot) but the ratio between the resistor and LDR changes greatly (from 100k/10M to 100k/2k) which could work pretty well depending on the circuit your using.


A photodiode is a slightly different thing, when light shines upon it generates a small current (a solar cell is actually just a bunch of photodiodes) and I think some other things happen, I'm not really good at that side of photoelectronics stuff...
I believe you can even use regular LEDs as photodiodes as well http://www.diystompboxes.com/smfforum/index.php?topic=45323.0

[KerryF]

Thanks Seljer.  That resistor idea sounds good to me.  If I am using this LDR: http://www.goldmine-elec-products.com/prodinfo.asp?number=G15180 what value resistor should I use and which 2 pins?

I guess the 3 pin ones are sort of like a dual pot, but instead a dual LDR