The March Muppet
Member
Happy New Year - although mine started exceedingly poorly - My silly GSD with a ball lodged in his throat at 5AM, wondering why everyone was trying to suddenly kill him trying to get it out. We got it, he's fine, I was rattled but have also recovered.
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I am doing my "homework" - but there's a lot out there that just looks wrong.
Lots of LM317 based DIY drivers, some wired CC, some CV, some with bizarre component valuers, and some just incorrect.
I suspect the reason that many of them appear to work for their creators is that they're playing with high current diodes that the 317 doesn't have enough output to blow up.
I just want to muck about with a pile of (likely 0.5 - 2 mW max) older LD's in bits of various optical bits I've salvaged over the years - for example a bar code scanning head.
Not really certain how to set up for it though. Seems a typical Vfwd for red is 2 to 2.3 V with current anywhere depending on the device. I don't believe that I have any violets, but probably have some drives that contain them so may want to play in that sand box eventually.
Presumably "any" diode will safely operate (if nowhere near optimal) series current limited to say, 20mA? - so it would appear that a setup with adjustable voltage regulation and a simple series resistor should light anything up without killing it..
But also presumably, once the diode is lit, I'd then want to regulate current.
Of course to what level - as I recall they achieve a certain subjective intensity and then die with an increase in current. You only know you're too far when you just fell through the ice - though seem to also recall that once the device was lasing, additional current had little effect on intensity.
Can you even daisy chain adjustable CC and CV circuits?
I happen to have a nice old 500 Ohm wire wound pot - toss this on the end of a 317 adjustable voltage reg, bring the voltage up until it just lases, and then use the pot to increase current?
Anyone have much experience playing with unknown diode "open loop" play?
As well, are they "tougher" than they once were - or just cheaper? I recall red diodes being in the $450 range in the early 90's: handling precautions as if they were full of nitro, and feedback "mandatory" - pretty sure the dollar pointers must be just running a resistor.
Any help appreciated.
...
I am doing my "homework" - but there's a lot out there that just looks wrong.
Lots of LM317 based DIY drivers, some wired CC, some CV, some with bizarre component valuers, and some just incorrect.
I suspect the reason that many of them appear to work for their creators is that they're playing with high current diodes that the 317 doesn't have enough output to blow up.
I just want to muck about with a pile of (likely 0.5 - 2 mW max) older LD's in bits of various optical bits I've salvaged over the years - for example a bar code scanning head.
Not really certain how to set up for it though. Seems a typical Vfwd for red is 2 to 2.3 V with current anywhere depending on the device. I don't believe that I have any violets, but probably have some drives that contain them so may want to play in that sand box eventually.
Presumably "any" diode will safely operate (if nowhere near optimal) series current limited to say, 20mA? - so it would appear that a setup with adjustable voltage regulation and a simple series resistor should light anything up without killing it..
But also presumably, once the diode is lit, I'd then want to regulate current.
Of course to what level - as I recall they achieve a certain subjective intensity and then die with an increase in current. You only know you're too far when you just fell through the ice - though seem to also recall that once the device was lasing, additional current had little effect on intensity.
Can you even daisy chain adjustable CC and CV circuits?
I happen to have a nice old 500 Ohm wire wound pot - toss this on the end of a 317 adjustable voltage reg, bring the voltage up until it just lases, and then use the pot to increase current?
Anyone have much experience playing with unknown diode "open loop" play?
As well, are they "tougher" than they once were - or just cheaper? I recall red diodes being in the $450 range in the early 90's: handling precautions as if they were full of nitro, and feedback "mandatory" - pretty sure the dollar pointers must be just running a resistor.
Any help appreciated.