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Weird I2C problem stm32f4 switch 230V coil

Question asked by Kenny on Jul 22, 2013
Latest reply on Jun 29, 2015 by kourid.ikrame
Hello everybody

I have the weirdest problem on my i2c....

I have some pcf8574's connected on my stm32f4Discovery and the work like a charm
(thanks Clive1.....)

But now i have connected some 5V relays which also work fine and they have to switch on some 24V relays and everything there works perfectly untill i let the 24v relays switch a 230VAC coil. Then my PCF will just switch all outputs high and when i switch a few times than the I2C hangs on EV6 flag...
This also happens when i switch the coil by pressing the relay so it's some kind of inductance :s

Any ideas?

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