VTL5C3 alternative?

[Kevin Mitchell]

I'm back to working on my tube phaser (or the Tube O Vibe) and I don't feel like paying $6 each for the optocouplers. I'd use the simple LED/LDR in heatshrink but for this project I don't think the common LDR is going to be well enough for this project.

The VTL5C3 cell is rated at 250v max while most common LDRs are rated at 100v. Any inexpensive LDRs around that fits the bill?

I guess I'm open to trade if anyone has 4 or so of these optocouplers they don't know what to do with  .

More about this project soon! I've mentioned it last year (if someone recalls  ) but have made some changes getting back into it.

[Kipper4]

$6 dollars sounds like a steal.
Get them while you can they won't be around forever and this is diy so the build time cost can be absolved if it's for a unique effect specific to you.
Hopefully your peers will be jealous and commission you to make their dream pedals which will help keep future developments cost neutral at least.
Happy vibing.

Just my two pence.

[George Moore]

  What does it need to do ?
  I had N/T getting high resistance from photocells [470k or so] low R is where photocells ''mattered'' in my circuits.
  I used to get lower minimum R by paralleling 2 photocell resistors [which also of course divides the max resistance.
  Even though I got fine results [for the purposes of phasing and env. filter, tremolo, etc] rolling an LED into dark pak facing photosensative cells, I still ordered the VTL packages, IIRC their rate of R sweep is quicker than what I could roll.
  I used cells whose chemicals were most responsive under green light.
  By the time the cells are tested, sorted, matched and rolled into dark rooms with opto units though, the VTL units start seeming less expensive, if you watch polarity and limit current [you can't see the LED light} and orient them correctly.

[digi2t]

$6??

WHERE!!!!

[smallbearelec]

http://smallbear-electronics.mybigcommerce.com/photocoupler-xvive-vtl5c3-work-alike/

http://smallbear-electronics.mybigcommerce.com/photocouplers-macron-mi1210clx-series/

Both the Macron "F" and the XVive have been vetted, are known to work and come in under $6 in small lots.

[blackieNYC]

Just used the macron in a compressor that calls for the VTL5C3. perfect.

[digi2t]

http://smallbear-electronics.mybigcommerce.com/photocoupler-xvive-vtl5c3-work-alike/

http://smallbear-electronics.mybigcommerce.com/photocouplers-macron-mi1210clx-series/

Both the Macron "F" and the XVive have been vetted, are known to work and come in under $6 in small lots.

Oh.. the workalikes. Yeah, already knew about those. Read good things about them too. I thought there was a line on some real Ecelitas/Perkin Elmer/Vactec VTL5C3's for $6. That would be like saying "I found stock of $25 SAD1024's". 

[bean]

The current Xvive 5C3 on smallbear do work pretty well...at least in the limited testing I've done. Not to be disagreeable but there are differing opinions on the Macron F's.

A 9203 photocell and red LED at least get you in the ballpark of a 5C3 though it's not exactly the same.

[garfo]

The current Xvive 5C3 on smallbear do work pretty well...at least in the limited testing I've done. Not to be disagreeable but there are differing opinions on the Macron F's.

A 9203 photocell and red LED at least get you in the ballpark of a 5C3 though it's not exactly the same.

This is really interesting, I'm looking at trying to make my own VTL5C3 replacements opto's and acquired a Xvive one. Teo things I've noticed was, with it on it had around 11k resistance, that's on spec. With it off it went past 30M; from what I understand, that is way off. Also, I've cut it open and the LED is Green, diffused. I was trully expecting to see a Red Bright LED.

Having said this, assuming I can find that specific LDR, what type of red LED should I use to simulate, as close as possible, a VTL5C3?

[Kevin Mitchell]

This thread has been stale for almost 5 years 
I can vouch that the old VTL5C3 devices had dark red diffused LEDs - or the one's I've seen did. Since they are of an older design I'd assume they require more current and refract light a little differently than modern LEDs.

My opinion is to use the common stuff and decide what works best for you. Review the datasheets of the LDR you use to know what spectrum works best. That being said, the most reactive color may not be the favorable one.

[ElectricDruid]

This thread has been stale for almost 5 years 

...so it must be time to revive it!! Anyway, recycle to save the planet, right?!?

Presumably the LED colour you'd use would depend on the characteristics of the LDR you use. So it would at least be theoretically possible to make an exact VTL5C3 clone with a blue LED and some weird LDR that made that match the response of the original with a red LED.

That said, I don't think Xvive really care that much about matching the original spec exactly. Their own datasheets are very sketchy. To be fair, vactrols have alway varied enormously anyway, so that's not as much of a big deal as it might seem. Vactrols and JFETs are similar like that - you might need to think that you're probably going to finish up tuning the circuit to the device you have at hand.

On the FilterFX design, I used the Xvive VTL5C3 and I haven't had any complaints about the filter range, depite the variation in vactrols. This was because the LDR is used with a 120K resistor in parallel which massively limits the maximum off resistance and essentially forces all the vactrols into a much narrower range (1M in parallel with 120K is basically the same as 12M in parallel with 120K!). I didn't add any minimum value series resistance, but I *did* try a selection of vactrols on the prototype and found much less problems at that end of the range, so it didn't matter.

Decent "depth" and "offset" controls deal with the majority of these problems anyway, even if that means people will argue over exactly where the sweet spots are Lol