Heat shrinking LED/LDR combos

[Jdansti]

One thing that may help eliminate the issue of shrink tubing wrapping around the LED is to file the front of the LED flat.

I crazy glue the LED and LDR together before I shrink tube it. Filing the LED serves two purposes: it's much easier to get a good bond with a flat surface rather than a round one, and the overall footprint of the DIY optocoupler is reduced.

When applying heat to the LED/LDR combo, concentrate on the ends to seal the component leads and less on the junction of the LED/LDR.

Good idea. I've filed LEDs for other reasons and it works fine. I use polishing compound and a Dremel polishing wheel to remove the file scratches from the flat surface.

[armdnrdy]

I finish the filed surface with sand paper or emery cloth and the crazy glue sort of "reanimates" the gloss from the opaqueness caused by sanding.

[Jdansti]

Not to stray off topic, but has anyone tried aiming a red laser diode (or red laser pointer/cat toy) at an LDR to see what happens?

[puretube]

I can imagine it would indeed so that.
I once pulled apart a LED/LDR combo from an EHX pedal and they put the LDR/LED inside a sort of semi-rigid tube made from polyester-cloth before putting them inside the heat-shrink, to prevent the problem you just described.

confirmed
(best/cheapest way to get consistent results...)

btw.: while colaborating with Mike Beigel on certain products I sadly discovered that some
Silonex optocouplers wheren`t as light-tight as neccessary for my purposes...
(straylight from working/daylight influencing measurement)

[Jdansti]

^ You bring up another good reason for shielding the DIY optocoupler from stray light. If you're doing R&D, testing, or troubleshooting, you will probably be working on a breadboard or have to work with an open enclosure. Mucho stray light!

[deadastronaut]

something which is not talked about much here is led/ldr proximity...

indeed...depending on the effect it can be better to be seperated a little..or butted up...a matter of taste i guess.

use flat top leds..or like larry suggested, sand them..this also diffuses it too..

from what ive read, ldrs like 'yellow' apparently..

[Liquitone]

I can imagine it would indeed so that.
I once pulled apart a LED/LDR combo from an EHX pedal and they put the LDR/LED inside a sort of semi-rigid tube made from polyester-cloth before putting them inside the heat-shrink, to prevent the problem you just described.

confirmed
(best/cheapest way to get consistent results...)

btw.: while colaborating with Mike Beigel on certain products I sadly discovered that some
Silonex optocouplers wheren`t as light-tight as neccessary for my purposes...
(straylight from working/daylight influencing measurement)

Sorry for pulling apart your creation Puretube, it where my first steps in DIY and The Worm was my first victim.
I modded the hell out of it to make it sound more like a Uni-Vibe and messed it up so bad it started making noises all by itself during rehearsal-breaks. (like it was asking us to put it out of it's misery )

So apart from The Worm itself, those optocouplers where your design as well?, nice! they where quite clever and sturdy, and indeed different from that other pedal you mentioned.

^ You bring up another good reason for shielding the DIY optocoupler from stray light. If you're doing R&D, testing, or troubleshooting, you will probably be working on a breadboard or have to work with an open enclosure. Mucho stray light!

That's a good point Jdansti, it would make prototyping testing  a lot easier.

on a related note, since I've been using incandescent lamps a lot instead of LED's; Does anyone know how they made the optocouplers in the old days? like fender and such?
as I've mentioned earlier, when I tried it the heat of the lamp sort of melted the heat-shrink.

[puretube]

Yes - when I invented my "Envelope-Followah" (a.k.a.: "Tube Zipper") in 1971/-72,
I used a bulb and several LDRs inside a black film-can

[Govmnt_Lacky]

Just to give a better idea...

I am planning on building the Flanger with no name by Lovetone 

If you look at the pics online, you can clearly see that ALL 4 of the LED/LDR combos that they use are NOT sealed.

Just the LED butted up against the LDR out in the open (or inside the enclosure if you will)

[Liquitone]

Ah,. like they do in Uni-Vibes.
What I meant is in the case of using only one LDR and lamp and wrapping it in heat-shrink.
I found 2 pictures that indicate it's only a lamp and LDR in the heatshrink (no additional tubing) and they put the LDR on the side of the lamp instead of in front of it.
http://www.tubeampdoctor.com/images/products/thumbs/FVIB---x_640-y_480.jpg
http://www.offsetguitars.com/personal/mike/74twin21.jpg
I'm guessing they used heat-shrink that can resist more heat? or they don't bother with it getting sticky/melting?
How did you do it in your Black-Finger compressor? as it seems to have a lamp setting as well.

the reason I started using the bulb in the tremolo was that I wanted that old fender trem sound,
and figured using the same sort of lamp would help in getting closer to the same fluid response.

Just to give a better idea...

I am planning on building the Flanger with no name by Lovetone  

If you look at the pics online, you can clearly see that ALL 4 of the LED/LDR combos that they use are NOT sealed.

Just the LED butted up against the LDR out in the open (or inside the enclosure if you will)

Ah I see, I guess with the closed jacks there's no stray light, but if they're not in sync I can see some would affect each other.
What I'm more worried about in those pictures is how the LDR's are connected to the PCB with wires running so close to it.
I can Imagine you can easily knock an LDR out of alignment with the LED this way, and that would change the response a lot.

p.s. You are really into the huge effects these days huh? can't wait to see it finished! that Ludwig Phase build was truly awesome.

[Govmnt_Lacky]

@Liquitone

On the Flanger you can see they used some form of sockets to mount the LEDs and LDRs

[Liquitone]

yeah that had me worried as well, I don't think sockets are a good idea for this,
although I think these are more a sort of guide-blocks (don't know what they're called) like they used on transistors in some of the old stuff I saw, and that the leads are in fact soldered to the board.
but still it seems way to easy to accidentally bend it out of alignment with the wires running so close to it.

[Jdansti]

Re lamps, heat, and melting heat shrink, it seems that the lamp's power rating (watts) and the voltage applied would determine the heat dissapated. Heat shrink tubing can be purchased with various temperature ratings, from 100C to 260C ( see this ).

[Liquitone]

Thanks! the lamp runs on a univibe LFO running on 24V and the lamp gets quite hot. I guess getting high temp. resistant heat-shrink would do the trick then.

[Kipper4]

I'm guessing here because ive never seen an ldr but would it not be possible or practical to put the two componants inside a piece of plastic airline tubing and easl both ends with shrink and hotmelt glue?

[duck_arse]

I'm late, but ....

pen tubes. ball point or felt tip, cut to length, shove parts in with a dob of sillicone behind each and heatshrink as needed.

I've also used the internal metal runners (I dunno what they are, they look like pillars and the tape runs across them) from disassembled video cassettes, w/ leads insulated and silliconed in.


can someone tell me what "crazy" glue is? is it like styrene cement?

[armdnrdy]

can someone tell me what "crazy" glue is? is it like styrene cement?

They include methyl 2-cyanoacrylate, ethyl-2-cyanoacrylate (commonly sold under trade names like "Super Glue" and "Krazy Glue"), n-butyl cyanoacrylate and 2-octyl cyanoacrylate (used in medical, veterinary and first aid applications). Octyl cyanoacrylate was developed to address toxicity concerns and to reduce skin irritation and allergic response. Cyanoacrylate adhesives are sometimes known as instant glues.

[petey twofinger]

+1 on the pen tubes , i used a clear plastic pen cut with a hot knife , plastic end caps from biros with lil holes drilled for the leads . thing is they end up being a bit long . i extended the leads with cut capacitor lead trimmings , put tiny heat shrink on those , then soldered it into the socket ... a bit of a hassle really but ... i am saving my one and only vactrol for the gristlizer .

[Govmnt_Lacky]

Damn! Cant believe I didn't think of the pen tube idea!  

I happened to find one here that will work. Although the LDR fits nice and tight, the LED wiggles quite a bit.

Would some super glue or the likes be a good idea to tighten up the fit of the LED in the tube? Super glue dries opaque and could let some ambient light in behind the LED -OR- is that something that could be considered negligable?

[Govmnt_Lacky]

p.s. You are really into the huge effects these days huh? can't wait to see it finished! that Ludwig Phase build was truly awesome.

Thanks for the comment!   

Not really into BIG effects as much as a challenge and/or effects that are a LOT cheaper to build than to buy 

Last I saw, the original Lovetone Flanger was going for anywhere between $700-1000