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Topic: Relay and LCD Issue (Read 3527 times) previous topic - next topic


[/quoLefty, what do you mean by "CAP to true Ground"?

To the negative side of the external power supply you are using to power the relay coils.


Mike Rice

The data sheets unfortunate choice of label for ULN pin 9 seems to be causing confusion.
Pin 9 is where all the diode anodes are connected together... thus the label 'diode common'.

Pin 9 should be connected to +5 volts of the relay board, not to ground.


I have wired the pin 9 to +5 and pin 8 to GND. Is that correct?

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