Rolling your own vactrol

[Timko]

I am going to try my hand at making some vactrols, but wanted to ask about exactly how to seal them up.  I was going off of this site:  http://sound.westhost.com/project145.htm.  I purchased a couple of sizes of heat shrink to go around the led and the sensor, but wasn't quite sure how to seal it up.  I noticed they used something called hot-melt aheasive.  If someone has also made vactrols this way, where do I find this stuff?  I checked at both my local electronics supply store and an art store and they had no idea what I was talking about. 

If you seal your vactrols another way, I would love some help with this one.  I need to make 7 for the various projects I have in flight, and figure this is a good skill to know.

[flanagan0718]

I actually just did some of my own. 5mm diameter heat shrink tubing. If you stretch the end that the LED goes in it works quite well. I used small needle nose to stretch it just a little.


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[Timko]

Where did you get hot-melt?

[flanagan0718]

Where did you get hot-melt?

I didn't use any "hot-melt". When the tubing shrank it almost shrank enough around the LED to seal it. I think that Hot Melt stuff is available on Amazon...see link

http://www.amazon.com/Bohning-Ferr-L-Tite-Adhesive-Stick-12-Gram/dp/B0009TUDRW/ref=sr_1_7?ie=UTF8&qid=1462587476&sr=8-7&keywords=hot+melt+adhesive

[Timko]

It's good to hear about the heat shrink being good enough to seal it; I think I'll give that a shot.

[BrianS]

I did the same thing and just squeezed the heat shrink with my fingers. I suppose you could also use a smaller piece of heat shrink at both ends and push it inside the bigger piece. Mine worked just fine though.

[dbp512]

I read someone suggest to use a plastic LED bezel with the diode installed backwards so it points into the hollow tube. Fit the photoresistors in the other end then seal it in heat shrink. I haven't rolled any of my own yet so I don't know how well it works or if its unnecessary, but I thought I'd bring it up.

[Jules]

I use a black plastic drinking straw and cut of a small segment, stick the LED in one end and the LDR in the other and shrink tube it. There is only 1 store in the town I live in that has straws thick enough to fit a 5mm Led in it.
I think you are fine just to wrap the led and Ldr by themselves though. But if you give it to much heat the wrap can get so tight around the components it actually seals some light away in places you want it, so watch that.
I guess that is the advantage of having a structure around the assembly to let all the light out.
I bought some square LEDs recently from mouser and put the LDR flush with one side of it and blacked out the others like on Madbeans 1590g Wygl vibe, that worked well.
I will have to see if I can use a plastic bezel to make one next like was mentioned before, that's one of the cool thing about rolling your own vactrols, there are no rules.
You can use your own imagination and see what you come up with.

[EBRAddict]

Are you guys using those LDR from Tayda? Or something else?

[Jules]

It depends on the circuit. The Tayda ones from memory are 20k - 500k.
The light and dark specs are what makes them different from each other.
The last build where I needed 4 ldr specified 20meg dark resistance.
Because the tayda are only 500k they wouldn't have worked in that build.
There are a few circuits around that state any ldr should work but a lot require specific LDRs.
The Taydas do work fine if that has the specs you need.

[Timko]

I got my vactrol built last night, and I was curious if there's a way to test it before I put it on my modulation board.  Is there a simple circuit I can breadboard to test with?

[sturgeo]

i could be barking up the wrong tree but as they are effectively resistors, use a multi meter and measure the resistance with the LED off, then power the LED and measure the resistance again.

[Timko]

Sorry to resurrect this post, but I noticed that some people don't roll their vactrols at all.  For example, this post:

http://www.madbeanpedals.com/forum/index.php?topic=21447.msg218049

Simply has the LDR and the LED attached to the board with no shrink wrap.  I'm curious about this because I'm about to complete my Mercury Phaser, and I don't want to have to un-fasten the double layer boards if I get something wrong.  I understand in theory that more light will escape without shrink wrap, but what's the practical effect of it?  Does it have an impact on the effect?

[Willybomb]

It means you can test it in a room with the lights on.  An LDR is sensitive enough in a darkened room that flickering from the TV in a room with the lights off can set it going so you pretty much need to mount it up and close the box to test it.

IU've rolled my own in the past.  Just push the LED into shirnk wrap from one end, and the LDR in from the other.  Shrink the wrap.  i don't think i bothered sealing the ends as I had enough overhang.  Vactrols are way easier.

[matmosphere]

Sorry to resurrect this post, but I noticed that some people don't roll their vactrols at all.  For example, this post:

http://www.madbeanpedals.com/forum/index.php?topic=21447.msg218049

Simply has the LDR and the LED attached to the board with no shrink wrap.  I'm curious about this because I'm about to complete my Mercury Phaser, and I don't want to have to un-fasten the double layer boards if I get something wrong.  I understand in theory that more light will escape without shrink wrap, but what's the practical effect of it?  Does it have an impact on the effect?

Once it's in the box and all plugged in no outside light is coming in so the only light is coming from the led, so everything works the same way as it would if the ldr and led were rolled so no light gets in. If you don't roll them then you can't test it outside of the box, but that's the only difference.