Do you see any difference between LDA210 and LDA212?
Can it be that a factory produces the same product with different names?

LDA210 datasheet: link
LDA212 datasheet: link
Official comparison website: link
DigiKey comparison: link

I am trying to sense if lights are on or off with an ESP32. I am looking into an AC optocoupler with very high CTR ratio, so that I can reduce the current (Watts) as much as possible:

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I tried with the HCPL-3700 (link to my project), but the resistors get very hot, since I am wasting almost 0.6W per channel

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    \$\begingroup\$ Do you see any difference between LDA210 and LDA212? Yes, compare the pin configuration, the connections are different. I have my doubts if this is going to work propely as the current through the LEDs is going to be very small. It appears that about 300 kohm (in total so 4 x 75 kohm) would work though, see: smartsolutions4home.com/… \$\endgroup\$ Nov 25, 2021 at 11:14
  • \$\begingroup\$ lol! I checked those datasheets milion times and completely missed that. Thank you! \$\endgroup\$ Nov 25, 2021 at 11:16
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    \$\begingroup\$ ... If that 300 k is still too much power usage, consider a capacitive power supply circuit. See BigClive on Youtube demonstrating and explaining several types: youtube.com/watch?v=Q23uh7AjjXw \$\endgroup\$ Nov 25, 2021 at 11:21
  • \$\begingroup\$ Thanks @Bimpelrekkie! I have never built a capacitive PS. I am a bit constraint in size, and when i checked for those PS they seem to need a very large capacitor. Your link is really useful! \$\endgroup\$ Nov 25, 2021 at 11:24

1 Answer 1


The pins are wired differently on the units. This is common when you want your product to be compatible with existing products, to make it easy to use your product even if you originally designed it for the competitors or an older generation of optocouplers.


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