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LED based optoisolator that can work from 5V 150uA 300Hz signal
Psi:
--- Quote from: wraper on November 22, 2020, 04:20:47 am ---LDA111 Darlington should work as well according to the graph. https://www.ixysic.com/home/pdfs.nsf/0/66F34A78811BAA3985256A2C00693C54/$file/Lda111.pdf
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Thanks!
Looks promising.
mikeselectricstuff:
Another option may be to use a small pulse transformer.
On the primary side, have the input switch a transistor to short the winding.
On the secondary, feed it with a ~1-10MHz squarewave via a resistor, and measure the loading cause by the transistor being on or off.
BrianHG:
--- Quote from: Psi on November 22, 2020, 03:30:29 am ---
Digital optos would work, but the person doesn't have easy access to 5V to power it on the input side.
Does such a thing exist?
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Digital isolators exist without that 5v supply input. They are a little slower than the ones with the dedicated VCC pin, yet still at least 10x faster than the typical opto. Need to search TI.com. I also believe that some of the 1 channel TI parts allow the input VCC to be connected to the input data and power the 2 of them together to switch on, and 0v on both pins for off on the output side with some degradation on switch-on time.
Here is a normal 40ua input normal LED opto, but slower than the data isolator and pricey at 3$:
https://www.digikey.com/en/products/detail/broadcom-limited/ACPL-K70A-500E/11594302
BrianHG:
I tried googling 'led simulated optoisolator'.
Silicon Labs make some, but they require at least 1ma at the input to work, though they are fast.
Check their 'Si873x' series. Though, I cannot tell is the 1ma requirement is the activation minimum current, or, if that figure is due to the simulated input current diode curve. Maybe it will switch on before the current reaches 1ma.
Psi:
--- Quote from: BrianHG on November 25, 2020, 08:02:35 pm ---Here is a normal 40ua input normal LED opto, but slower than the data isolator and pricey at 3$:
https://www.digikey.com/en/products/detail/broadcom-limited/ACPL-K70A-500E/11594302
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I think you have found the one. :)
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