best color LED for optos?

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best color LED for optos?

Postby RnFR » 22 Sep 2011, 02:09

I've heard many people say that yellow is the best color, but I could've sworn I saw RG post that they respond best to green light. anyone remember this?
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Re: best color LED for optos?

Postby DrNomis » 22 Sep 2011, 02:37

RnFR wrote:I've heard many people say that yellow is the best color, but I could've sworn I saw RG post that they respond best to green light. anyone remember this?




I seem to remember reading an article on RG's website about LDRs, LDRs respond to light similar to the human eye which has a peak sensitivity to green light, the actual response curve of the eye is kind of bell-shaped with green at the apex, and with the response dropping off either side of it, so if you're wondering what colour leds to use, I'd recommend green ones.... :hmmm:
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Re: best color LED for optos?

Postby DaveKerr » 22 Sep 2011, 02:40

This pretty much says "it depends"

The most commonly used photoresistive light sensors is the ORP12 Cadmium Sulphide photoconductive cell. This light depedant resistor has a spectral response of about 610nm in the yellow to orange region of light.
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Re: best color LED for optos?

Postby kleuck » 22 Sep 2011, 03:03

Don't use LDR, they vary too much and are almost always not a good choice for us (too high "on" res, too low "off" one, too slow, need too much light so you need too much current) etc etc, just use optocouplers.
CLM6000, NSL32, or VTL5C1 are fine.
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Re: best color LED for optos?

Postby .Mike » 22 Sep 2011, 05:00

I know this doesn't apply to every opto, but here are the datasheets for the two that Tayda sells:

Waitrony KE-10715.pdf


Waitrony ke-10720.pdf


It shows the best wavelength to use, so It could be a good guide for other photocells that are made out of the same materials. :)

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Re: best color LED for optos?

Postby kleuck » 22 Sep 2011, 08:31

In the past (20 years ago) i used to use LDR to make comps, and came with the same question.
So i tried green clear leds (no clear yellows available to me at the time) but soon switched back to red, because they had by far the best efficiency.
Color is not all, if you have a perfect 5500 Angstrom led that needs 4 times the current, it's useless.
Don't know if nowadays you can find a green Led with the same efficiency as a Red HR.
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Re: best color LED for optos?

Postby RnFR » 22 Sep 2011, 11:26

I think I actually ended up having the best results with a clear red, myself. I rolled a number of them with some different colored LEDs and some rat shack photocouplers to try in my circuit contest entry. i ripped put them together and ripped them apart, had some decent success, but eventually, I realized I had an old DOD 280 I never use lying around, so I pulled out the CLM-50. I think it worked a bit better in the end. what's the best place to get vactrols for cheap?
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Re: best color LED for optos?

Postby kleuck » 22 Sep 2011, 11:34

Don't know for you, i live in europe and buy them here : http://www.banzaimusic.com/Optocouplers/
Not cheap, but worth the price.
Banzai is very sloooooowwwwww to ship items, be aware.
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Re: best color LED for optos?

Postby mictester » 23 Sep 2011, 13:25

kleuck wrote:Don't use LDR, they vary too much and are almost always not a good choice for us (too high "on" res, too low "off" one, too slow, need too much light so you need too much current) etc etc, just use optocouplers.
CLM6000, NSL32, or VTL5C1 are fine.


The devices you list ALL contain LDRs!

I checked a recent batch of 40 of the cheap RPY52-type LDRs supplied to me by Rapid Electronics in Colchester, UK. In dark conditions, they all read 2.2 M (within 2%), and illuminated with a yellow, normal efficiency LED at 16 mA, they all were within 3% of 1k. These devices were better accuracy than the surrounding resistors (5%) and capacitors (10%).

Cost of a VTL5C1 = £2.80

Cost of yellow HE LED and LDR = £0.42 (plus a bit of black heatshrink tubing).

Response times of my homemade opto-coupler and the expensive, pre-made type are exactly the same. The linearity of my device is slightly better than the pre-made type. The range of control on my device is slightly larger than the expensive, pre-made type. Mine wins in every way, apart from construction time (mine takes about 30 seconds extra to construct!).

I like the way the LED/LDR combination reacts to the guitar envelope. The attack time is excellent for our purposes, because the initial peak of each note isn't squashed too much, which allows the instrument to sound more natural. This is why so many people like the "Really Cheap" compressor! Most users just switch the RCC on all the time and forget about it. They only notice when it's missing!
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Re: best color LED for optos?

Postby kleuck » 23 Sep 2011, 13:45

I want my optos to work with less than 2-3 mA and sorry, you cannot do that with LDR/Leds (16 mA !), but you can with Optos.
And the obscurity resistance alone is not significant, because with most LDRs the time they need to go back to 1 Mohms is about half a second, if not a plain second.
You have a much larger resistance ratio and short raise/recovery times with a limited consumption using a specialized opto than you can ever dream of with LDRs.

That's in the datasheets.
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Re: best color LED for optos?

Postby mictester » 25 Sep 2011, 15:00

kleuck wrote:I want my optos to work with less than 2-3 mA and sorry, you cannot do that with LDR/Leds (16 mA !), but you can with Optos.
And the obscurity resistance alone is not significant, because with most LDRs the time they need to go back to 1 Mohms is about half a second, if not a plain second.
You have a much larger resistance ratio and short raise/recovery times with a limited consumption using a specialized opto than you can ever dream of with LDRs.

That's in the datasheets.


You're mostly right - I built an RCC last night with a high efficiency yellow LED, and checked the LDR resistance vs LED current. The LDR got down to 3k with 2.7 mA through the LED. Response time (3k to 2M2) was 450 ms (a pretty good release time for a compressor for a guitar) and attack time (2M2 down to 3k) was 35 ms which is pretty quick! In use, with real guitar levels into the pedal, the minimum LDR resistance (calculated) would be around 10k and the gain of that controlled stage would almost always be in compression in real use. The current draw of the HE LED and the rest of the circuit is only 4.5 mA on average which is certainly acceptable for battery use!

If you want the expense (but the ease of use) of a pre-made LED / LDR combination, you'll get great results. However, you'll more than double the component cost, thereby moving away from the original "Really Cheap" concept.

I've also built compressors using the "linear" H11F3 opto-FETs and achieved great results. Unfortunately, these devices seem to be made of unobtanium these days (or I would put my H11F3-based phaser into the competition!).
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Re: best color LED for optos?

Postby KindaFuzzy » 25 Sep 2011, 15:14

I remember reading that yellow was the best too, and they work well for sure. I usually go back to red too, since they're cheaper, the clear ones that aren't too bright are usually the best, but if it's for a choppy trem or something like the clairinot, a real high brightness one gives a wider swing with the no name LDRs I get locally.
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Re: best color LED for optos?

Postby kleuck » 25 Sep 2011, 16:15

mictester wrote:
I've also built compressors using the "linear" H11F3 opto-FETs and achieved great results. Unfortunately, these devices seem to be made of unobtanium these days (or I would put my H11F3-based phaser into the competition!).

I made one with an SSM2166, wich was surprinsingly good once tweaked for the guitar level, but another unobtainium IC now.
It's a pity, cause it was really easy to use, with a expansion capability very usable and useful to combine comp and noise "gate"

H11F1 are still on the market : http://www.banzaimusic.com/H11F1.html
I would love to see your schematic.
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Re: best color LED for optos?

Postby LaceSensor » 25 Sep 2011, 17:49

I tend to use 3mm LEDs and LDRs from Futurlec. They have a variety of types.
The standard one from BitsBox is also fine too.

Ive built a number of pedals with different colour LEDs.
Easy vibe x 3 with different brands of Red LED works really nice.
Flatline comp with a standard yellow LED works fine.
Tremulus lune with a yellow LED works fine
Just done a Ringstinger with a bright clear green LED and that works a treat too.

I did make a meatball with an NSL-32 because I got some cheap for a pound each. They work too.
I think if you are lazy and dont mind paying a lot, the VCL5c1 or NSL-32 are good devices, but I see no reason why an LED/LDR wont work just as well, depending on the application...

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Re: best color LED for optos?

Postby earthtonesaudio » 26 Sep 2011, 11:49

I've used high efficiency white with good results. I figure even though it's not "true" white it's close enough to contain the wavelengths the CdS cell wants. I think I've never ran more than 3mA into one.
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Re: best color LED for optos?

Postby Dr Tony Balls » 26 Sep 2011, 15:17

when you say "high efficiency" do you mean the bright, clear packaged LED?

I've built my optos out of many different color LEDs but never spent too much time experimenting with what I like best. Last opto project I built was a tremulus lune using a plain red 5mm LED with a radioshack LDR, and it worked great.

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Re: best color LED for optos?

Postby earthtonesaudio » 26 Sep 2011, 18:04

Dr Tony Balls wrote:when you say "high efficiency" do you mean the bright, clear packaged LED?


Yep.
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Re: best color LED for optos?

Postby Pruttelherrie » 25 Jan 2012, 21:23

kleuck wrote:I made one with an SSM2166, wich was surprinsingly good once tweaked for the guitar level, but another unobtainium IC now.
It's a pity, cause it was really easy to use, with a expansion capability very usable and useful to combine comp and noise "gate"

The SSM2166 can still be had in SMD. This week I populated a pcb I designed last autumn and had in the drawer for a couple of months, based on the Quick and Dirty Compressor by Matt Armstrong, which was based on the Jack Orman SSM2166 compressor and some other forum discussion.
I added a Tillman phantom power thingy on a second inputjack, so you can choose with or without FET preamp cable. Components and jack can be left out of course. SMD is certainly doable at home, and the circuit works! Haven't boxed it up yet, I'm trying to get it into a 1590B.

schema.png


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Re: best color LED for optos?

Postby atreidesheir » 04 Jan 2013, 03:47

.Mike wrote:I know this doesn't apply to every opto, but here are the datasheets for the two that Tayda sells:

Waitrony KE-10715.pdf


Waitrony ke-10720.pdf


It shows the best wavelength to use, so It could be a good guide for other photocells that are made out of the same materials. :)

Mike

DaveKerr wrote:This pretty much says "it depends"

The most commonly used photoresistive light sensors is the ORP12 Cadmium Sulphide photoconductive cell. This light depedant resistor has a spectral response of about 610nm in the yellow to orange region of light.



To save some moments, the optimum wavelength is @600 nm, so orange. both sources agree.
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Re: best color LED for optos?

Postby atreidesheir » 04 Jan 2013, 03:53

atreidesheir wrote:
.Mike wrote:I know this doesn't apply to every opto, but here are the datasheets for the two that Tayda sells:

Waitrony KE-10715.pdf


Waitrony ke-10720.pdf


It shows the best wavelength to use, so It could be a good guide for other photocells that are made out of the same materials. :)

Mike

DaveKerr wrote:This pretty much says "it depends"

The most commonly used photoresistive light sensors is the ORP12 Cadmium Sulphide photoconductive cell. This light depedant resistor has a spectral response of about 610nm in the yellow to orange region of light.



To save some moments, the optimum wavelength is @600 nm, so orange. both sources agree.

I will try this one in th ecoming months and give a report with orange leds.
http://www.taydaelectronics.com/resistors/photoresistors/photo-conductive-cell-resistor-ldr-650nm-radial-ke-10720.html
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