VTL5C4/2 Part Substitution

[mikealbert]

Hi All,

I've started building an Aion Electronics Convex compressor (https://aionfx.com/app/files/docs/convex_documentation.pdf). The build calls for 2 x VTL5C4, but I accidentally purchased the "dual" version (VTL5C4/2) from Small Bear. Is it possible to use VTL5C4/2 I purchased and if so, which 2 of the 3 legs on the photoresistor side should I use? https://www.alliedelec.com/m/d/350b8613fa7c1e545249ca9cecf75d88.pdf

Thanks in advance for the help!

[rankot]

Try it and find out - connect LED side of the vactrol normally, and make sure not to miss LDR pinout - the middle one is common.

[iainpunk]

welcome to the forum

use the outer legs of the vactrol, you might want to snip away the middle leg.

cheers, Iain

[Kevin Mitchell]

With the VTL5C4 having a lower resistance spectrum than that of a VTL5C3, I'd say that you may have a better chance of successfully using hand made optos for this. You could use the common KE-10720 or GL5516 LDRs.

Worth a shot IMO.

[duck_arse]

also cheers, and welcome.

the bible:
http://www.ka-electronics.com/images/pdf/Perkin_Elmer_Photocell_Vactrol_Catalog.pdf

I can't see it said, but I thought the dual/split/double ldr vactrols used a 'pair' of ldrs with a common lead, so a VTL5C4/2 would behave as two VTL5C4 elements. that would make the middle and either one of the outer leads.

[Kevin Mitchell]

I can't see it said, but I thought the dual/split/double ldr vactrols used a 'pair' of ldrs with a common lead, so a VTL5C4/2 would behave as two VTL5C4 elements. that would make the middle and either one of the outer leads.

Yes of course. Though the Convex Compressor has separate drive circuits for each LED which makes the dual opto not so useful for this build.

Is it a pair of LDRs in series or one center tapped LDR?

[duck_arse]

I can't see an actual description in the specs linked for the vactrol gizzards.

[mikealbert]

Thanks for all the replies. I found another thread which seems to indicate I can use an outer leg and the center leg.

https://www.diystompboxes.com/smfforum/index.php?topic=27657.msg185937#msg185937

Could I drop the vactrol on a breadboard, power the led and measure the resistance between the photoresistor legs to find which ones I should use?

Thanks again for the help!

[idy]

Yes breadboarding may tell what you need to know. Be sure to use a current limiting resistor on the LED. Circuit uses 2.2k. You would need more than that to mimic performance in circuit.