optoisolator bulb(trem roach)

[jeff]

 Hi guys I thinking of an effects project and I want to use the osc circuit but instead of controlling just one LDR I'd actually like to controll 8.

What type of bulb does the optoisolator use?
Can that one bulb be used to control more than one LDR?
Is there already such a product(1 bulb 8 LDRs)?
Is there a way to use 8 roaches without a seperate tube for each roach?

I got a couple of LDRs at radioshack maybe I could build something if I knew what type of bulb the fender roach used??? I'm thinking aim one bulb at 8 LDRs??? Probally have to get the spacing just right.
Thanks for the input.

[sluckey]

The Fender roach uses a neon bulb. Part # NE-2. Available everywhere.

[jeff]

Awesome! thank you very much.

 I'm thinking of building something along the lines of your warbler, but seeing as I don't have a sat. xfmr I'm gonna try using optoisolators, Waddaya think, possible???

Also I think maybe adding either one, or three more stage. If I understand the theory correctly each stage contributes to 90 of phase shift and every 2 stages causes a 180 phase cancelation "notch" so I think I'd like to try a multiple of 2 stages.(2,4,6 for 180, 360, 720) It would really be nice if I could get my hands on two of those Xfmrs so I could have 6 easily. Thoughts?

I gotta find one of those bulbs and see if I can build something that activates 6 LDRs at once.

Thanks again
 Jeff

[jeff]

 Just out of curiosoty have you ever tried bypassing the 3rd stage and only using the first 2 stages in chorus mode. Just wondering what the effect of having one less(or one more) stage would be with the dry singal added. 180(or 360) Vs. 270?

I think the Univibe uses 4 stages and I'm wondering if an even number makes a big difference over an odd number of stages(or if it doesn't really make much of a difference at all) when the dry is mixed back in. Maybe experiment with a 3rd stage bypass switch???

[terminalgs]

you can point multiple LDRs at a single neon.

It'll be a trick to get 8 (or even 6) LDR's to face a single neon light source in such a way as to fire them all equally.  Wrapping 8 LDRs and a neon with shrink wrap ALA Fender is, of course, out of the question.  an open arrangement, whereby the neon is in the middle and all the LDRs are positioned around it like Stonehenge might be doable,  but you'd need a plastic lid to affix over the top of such an arrangement, or you'll have do all your troubleshooting in the dark (I can imagine an eyelet board with the small plastic radio shack work box sitting on top of it).

Another option is use one neon with a single LDR, and use the LDR as a driver to fire another light circuit.  The "driver" LDR could light 4-8 LEDs for example, with a low voltage supply,, 1.5-5V depending on the LEDs. each LED could be wrapped with an LDR, or maybe two LDRs per LED.

you might do a hybrid, where a driver LDR fires supply voltage for a super bright LED, which fires 8 LDRs.  the advantage of this would be the exact proximity and direction of the LDRs might not be as critical with a super bright LED as it would be with an neon (a neon is not exactly omnidirectional in its light pattern), this would still be a stone henge arrangement.

All that said, using the neon as the light source would probably be more sinusoidal than using it to fire multiple LEDs. the LEDs would be more square wave I would think.

Also,  not all LDRs are the same.   They have a light resistance and a dark resistance.  This might vary from a 20M dark /5K light, to a 20K dark / 1K light.   obviously having a big variable in what resistance difference you get, as well as rise/fall speed and, in some cases,  binary like switching rise/fall.
 

I've got a tube based univibe circuit half built that has stumbled on the multiple LDR and light source issue.  Plus there are so many triodes! as compared to Shin-EI's compact transistor approach.  I think the univibe has four stages, so for that you'd only need 4 LDRs I suppose.

do yourself a favor and let the LDRs have plenty of slack with their leads as you tie it to a circuit so you can move and position the "face" of it in the direction and proximity of the light source.   if you line up eight on a eyelet board and stretch them out tight like resistors and caps,,  you'll have a hard time getting them all to pick up a single light source equally.

[jeff]

Yeah I dig it.
 Aranging them so they all get equal light/resistance may be a pain.

Does the univibe have 4 seperate light/LDRs or does it have one light controlling 4 LDRs? In other words I'm wondering if there is a multiple LDR with one light on the market. That would be ideal if I could get two of those. Maybe I'm getting over ambitious again but I'd like to build one with 6 stages and use one of the LDRs for tremolo.

[terminalgs]

univibe is a single light source, an incandescent, i believe.

It was a custom univibe only arrangement, certainly not an off the shelf part.

I've never seen a multi-LDR unit.  Certainly not one with a neon.   One exception is the X series of ampegs, which used a module with two LDRs sealed up with a neon.  a pricey unit considering you only get two LDRs..

[jeff]

Ok thanks.

Stonehenge it is. I'll have Nigel draw up some plans and hopefully I can fit it into a 1' X 1' X 2' box.
 

[sluckey]

I would not use a neon bulb for what you want to do. The neon switches off and on very quickly. Kind of choppy effect unless you use LDRs with a slow response time. You mentioned my warbler... Well look at the schematic. Notice the LED in the cathode circuit of the oscillator? That's all the light source you need. In fact, you could probably replace that LED with the vactec VTL5C1 opto switch that Doug sells. It has an LED driving an LDR in one package. I'm using one in the trem circuit of my Sunn Sceptre.

http://home.comcast.net/~seluckey/amps/warbler/warbler_rev2.pdf

[jeff]

Thanks
cool I'll check that out.

OK I didn't notice that. What is the LED used for, just as a rate indicator?

...Looking at the layout I think I see it now.