Risk of damaging the microcontroller. Badly designed circuit.

TG9541 / stm8ef

STM8 eForth - a user friendly Forth for simple µCs with docs

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Risk of damaging the microcontroller. Badly designed circuit. #462

Closed rtek1000 closed 1 year ago

rtek1000 commented 1 year ago

Hi,

As we can see in the electronic diagram, the LED of the relay can carry out a high voltage return if it fails in the reverse voltage, probably when using a power supply greater than the value that the LED supports in the reverse polarization (generally it is only 5V ).

See details in this issue: https://github.com/mister-grumbler/w1209-firmware/issues/22

Please disclose this design error to avoid unnecessary damage.

TG9541 commented 1 year ago

It's almost incredible that such an obvious design error has been copied hundreds of times and that maybe hundreds of thousands of W1209 boards have been sold!

I would suggest to simply remove LED "Red" or R7 and use one of the DPs of the 7S-LED display as a status indicator.