Has anyone here just made one up?
I mean grabbing an LED, a photoresistor and holding them together with some light-resistive heatshrink?
Considering how variable commercial units seem to be and the efforts to make matching pairs as much as possible, I'm surprised I can't find any threads about making up your own.
ESP touched on this very topic here: Project 145
You can easily make them up at a fraction of the cost of industrial-made units, and you can probably play around with them a bit, tweaking distances, etc, to try and get matching pairs...
The other reason I started thinking about making up my own is that the two or three manufacturers I have found who make LDRs appear not to be RoHS compliant. The Advanced Photonix NSL-32SR and their variants aren't RoHS apparently. Neither are Excelitas Tech range...
For the cost of a few pennies, I'm going to put some together and will report back, but if anyone else has tried this, I'd love to hear your experience.
I mean grabbing an LED, a photoresistor and holding them together with some light-resistive heatshrink?
Considering how variable commercial units seem to be and the efforts to make matching pairs as much as possible, I'm surprised I can't find any threads about making up your own.
ESP touched on this very topic here: Project 145
You can easily make them up at a fraction of the cost of industrial-made units, and you can probably play around with them a bit, tweaking distances, etc, to try and get matching pairs...
The other reason I started thinking about making up my own is that the two or three manufacturers I have found who make LDRs appear not to be RoHS compliant. The Advanced Photonix NSL-32SR and their variants aren't RoHS apparently. Neither are Excelitas Tech range...
For the cost of a few pennies, I'm going to put some together and will report back, but if anyone else has tried this, I'd love to hear your experience.
A couple of reasons.
1. I'm putting together a product that may end up being part of a bigger commercial one.
2. It gives me warmer fuzzy feeling knowing it's approved by the sandal-wearing, tree-hugging european bureaucrats
I use nothing else
That said, I also guess that the actual non approved stuff is the cadmium sulfide itself.
Which would be very very ridiculous.
In a previous thread, I did explain that LDRs are nothing to do with LED.
Major guitar amp companies, Fender comes immediately to mind, use a neon as the light source, you may think that a neon is either on or off, you are correct. It uses the fact that an LDR is sluggish to give the vibrato effect.
Major guitar amp companies, Fender comes immediately to mind, use a neon as the light source, you may think that a neon is either on or off, you are correct. It uses the fact that an LDR is sluggish to give the vibrato effect.
Not long ago I made some tests with LDRs coupled to LEDs, or the other way around.
I went and ordered hundreds of CdS LDRs off from eBay, in China these seem to be very cheap, never mind the quality of these things. After checking the "universal" specifications for CdS LDRs, especially the spectrum response chart which shows the peak wavelength and the overall spectrum, I decided to try super bright white LEDs to illuminate the LDRs.
With 5mm "cold" white LED coupled to a selected CdS LDR I was able to get resistance down to 30ohms. Some "warm" white LEDs seem to be about equally good. That is something to experiment a bit more.
I concluded it is possible to DIY a photocoupler with low enough resistance, but the deviations of CdS LDR characteristics makes it laborious to match them.
If ordering the "usual" types from China, GL5506 seems to have the lowest on-light resistance, but I found there are at least two different variations, they are most likely from different manufacturer and "the other one" is better; lower on-light resistance and more consistent from part to part.
I have yet to experiment with 1W LEDs, which could be driven with higher current to get even lower resistance.
I went and ordered hundreds of CdS LDRs off from eBay, in China these seem to be very cheap, never mind the quality of these things. After checking the "universal" specifications for CdS LDRs, especially the spectrum response chart which shows the peak wavelength and the overall spectrum, I decided to try super bright white LEDs to illuminate the LDRs.
With 5mm "cold" white LED coupled to a selected CdS LDR I was able to get resistance down to 30ohms. Some "warm" white LEDs seem to be about equally good. That is something to experiment a bit more.
I concluded it is possible to DIY a photocoupler with low enough resistance, but the deviations of CdS LDR characteristics makes it laborious to match them.
If ordering the "usual" types from China, GL5506 seems to have the lowest on-light resistance, but I found there are at least two different variations, they are most likely from different manufacturer and "the other one" is better; lower on-light resistance and more consistent from part to part.
I have yet to experiment with 1W LEDs, which could be driven with higher current to get even lower resistance.
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Well, they say it's RoHS compliant.
LDR09 - VELLEMAN SA - 2-20k? Light Dependent Resistor | CPC UK
I've even downloaded my personalised RoHS compliance certificate for future use
Ahh so I'm not the only one thinking about this.I use nothing else
That said, I also guess that the actual non approved stuff is the cadmium sulfide itself.
Which would be very very ridiculous.
Yes, I think it's the cadmium that's the problem.Which is why I was looking for RoHS-compliant LED+LDR assemblies (to keep DF96 happy).
If, as you suggest, they don't really exist, then it's up to making your own out of components that don't contain any nasties. It looks like that LDR09 is OK for the troublesome LDR component. LEDs are of course OK.
Sorry, I know it's just the photocoupler part. But everyone else calls them LDRs to mean the (LED + LDR) assembly, so I'm guilty as charged. What would you want everyone to call them? Optocouplers?
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