SORTING TIMEOK so some more stuff to sort... this time OPTO stuff.... I like opto stuff, it's just cool.
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1h20AM, I have just finished Googling and sorting all my photo couplers
52 total. 3 of them were scrapped as I can't read what's on them. Then 2 of them I can read perfectly but Google can't find me anything. See pic below, if you know what they are, I am all ears.
So that left me with 47 I could actually research.
I thought it would be boring but it was not at all... because there was much more diversity in these things than I had imagined was possible.
Other than a couple Fairchild and one NEC, 90% of the stuff is split evenly between only two manufacturers : Sharp and Toshiba.
Great variety as I said...
- Some have photo transistor
- Some have photo darlington
- Some have a photodarlington with a built-in reverse protection diode between Collector and Emitter.
- Some have a photo diode associated with a regular transistor
- Some give you access to the base of the transistor, so you can drive it yourself should you want to for.... I don't know what reason.
- Some have Faraday shield between the emitter and detector.
- Some can be driven with AC signals : inside there are TWO LEDs, wired in // in reverse polarity.
The one thing they have in common though, is just how slow they are, and how highly unpredictable their speed is. rise and fall times, turn on and turn off... vary so immensely from the factory, and are also affected so greatly by how much voltage and current you use for the output transistor...
some datasheet don't even mention the "storage time", even though it's super important as it ruins every hope you had at fast switching, if you only looked at the rise and fall times...
Some DO show the storage time in the timing diagram BUT... in the tables of parameters it does NOT tell you how much it is ! SO basically the thing is useless, as this parameter is what makes or breaks you max speed... since it appears to be usually much slower than the rise and fall times.
It was cool looking at all that diversity... I felt like a biology student flipping a rock on the beach and looking closely with his microscope to marvel at just how much life there can be under there, and taking notes to write a report for his professor...that would be TEA jury for me.
Now that gives me an idea for yet another little experiment. I have dozen of the TLP559 and PC817, two different manufacturers then.
I could measure the timing characteristic of all of them, using obviously the same operating conditions stated in the datasheet, and makes statistics to see how real life correlates to the numbers we see i the datasheet. Are they realistic.. too optimistic... or too pessimistic.
I gather that the LED in photocouplers can "wear out" over the years, so I anticipate that I might eventually get results in average a bit worse than when they were new.
If you want to do that experiment, press #1. If you don't want it, press #1 as well, because I will do it regardless !