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I am working on an ESP32 prototype project which uses two SW420 vibration sensors.

On this board there are two (fairly bright) SMD LEDs, their function is not only not necessary but also unwanted, therefore I wish to remove these LEDs.

I have found the schematics of the board in a datasheet.

As far as I understand (I am not so good at "reading" schematics,) I can remove the D2 power LED without issues to the function, but I am worried about the D1 status LED because of the parallel resistors, which would increase the total functional resistance as R4 would be unneeded I think. If so, would this be as issue, as this would also be the case when the diode is not emitting?

As far as I can see, there are four possible options (for both LEDs) the last one the least favorable:

  1. Just remove both LEDs.
  2. Remove and short the remaining patches to re-create continuity.
  3. Remove and replace with non-light emitting diodes, but if so what type?
  4. Cover up the diodes.

They are not valuable, but I would like to finish this part of the project this weekend. If I mess the sensor up I would have to re-order, which is a fairly huge delay that I'd like to avoid.

Schematics

JRE
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Matthieu Kints van
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    From personal experience, my recommendation is to get some black nail polish, and paint it over the offending LEDs in repeated layers until it's opaque enough to block them (or dim them to the desired level.) – Glenn Willen Dec 18 '22 at 18:24

1 Answers1

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The power LED can certainly be removed, but your intuition is correct about the status LED - it is part of the pull up network that allows the comparator to output a high signal. The comparator used on this board is an LM393 open collector output type, here’s a schematic of the comparator guts from it’s website (https://www.ti.com/product/LM393 )

product info snip with schematic and output type

Since this output can sink up to 20mA you can simply get away with shorting the status LED and allowing R4 to pull up the output.

Bryan
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