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Strange PCF 8575C problem

Topic last updated 16 Jun 2011, by David Cornish. 2 replies
David Cornish
15 Jun 2011

Mbed Community

I have the following circuit:

/media/uploads/pinballer83/pcf8575_connections.gif

I have the outputs connected to the GND of 5V relays.

As it is it doesn't work.

But when I touch the soldering iron to GND the circuit works.

Why is this?

Cheers David

Hexley Ball
16 Jun 2011

This might be as simple as a floating ground connection for one of the supplies. Double check that the mbed supply and the +5 relay supply share a common ground.

David Cornish
16 Jun 2011

Thank you for your help.

You were right, I connected the mbed GND to the 8575C GND and presto.