Triaxis LDR Part Numbers?

[tbryanh]

The thread I pointed to contains interesting information on this subject.
Concerning the LDRs there are what I call regular LDRs and custom made. Icall regular all those that you can buy freely from various web sites. They include:

1/ 2-terminal LDRs /the photcell terminals are interesting only/ built from one LED and one photcell.
2/ 3-terminal LDRs built from one LED and one center tapped photocell /or two photocells sharing a common termnial/.

2/ can be used in vacuum tube circuits as Middle and Presence control in a regular passive tone stack and amp. For the Bass you'll need a 4-terminal LDR /one LED and two independent photocells/. To imitate a regular pot with a taper however you'll need 2 of those 4-terminal LDRs. Since they're available only in wholesale quantities for DIY projects you'll have to build them yourself by using regular LEDs and photocells available online. This way they'll cost you $2 the piece and you can forget about the wholesaler.

Enjoy!

I went to the "LDRs as pots?" discussion. It is lengthy and has numerous URL links, so if there are links to the devices you are talking about, I am having a hard time finding them.

I am very interested in the devices you mention. Can you post links here to them? Thanks.

[Gregg]

Which devices exactly do you mean?

[tbryanh]

I am under the impression you are making LDPs (light dependant potentiometers) from LDRs (light dependant resistors) or some other divice.

If this is correct, please send me the link(s) to the devices.

Thanks

[Gregg]

For dual cell /center tapped/ LDRs and other photocells check out Allied Electronics:

http://www.alliedelec.com

Search for VTL5C3/2, Silonex and Vactec.

[tbryanh]

Thanks for letting me know they existed.
I thought they weren't available.

The one with the 100v rating looks pretty good.

Have you seen any of the LDR pots with a 250v or so rating?

[Gregg]

Check out Silonex for photocells with higher voltage rating but I don't think you need more than 100V. The highest voltage /signal/ I measured across a fully open Middle pot was ~60V .

[tbryanh]

There are spikes that can occur during power up, when the guitar come unplugged, etc.

Silicon is a wimp when it comes to that.

A read something about the composition of LDRs a while back. I am pretty sure they are silicon.

[Steve Conner]

No, they are made of a material called cadmium sulphide. And yes, that other thread does deal with ways of making what you call "LDPs" out of LDRs, since there is no single component available off the shelf that performs the function you call "LDP".

In a previous life I was involved in the design of a Numark DJ mixer with VCA faders. The VCA was implemented with a pair of 4-terminal LDRs. (Actually 6 terminals if you count the LED too.)