Switching 24V with Arduino


I have a system that switches a 24 Volts (AC) wire with a relay, the relay is been switched by the Arduino with use of a transistor and a alternative power supply for the relay. On the PCB are 6 relay's wich each of them switch a 24 Volts (AC) wire. When I make an input high, to let the relay switch, it sometimes occurs that the other relay's (not specific one) become high and switches the 24 Volts (AC) wire. I've tested the system without the 24Volts circuit, and it works just perfect. Can I change something in the circuit to let the 24 Volts (AC) wire have no influence? I have already connected 10K resistors from the input to the ground, but it seems nog enough.

I hope my explanation makes sense.

An odd occurrence indeed. Is there any way you can sketch up a diagram of how you have the system wired up? Specifically how you have the transistor connected to the Arduino and this “alternative power supply”?

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Do the relays have a diode parallel over the contacts ?

When I make an input high,

You do mean output not input. Are these initialised as outputs in the setup part of the code? Resisters go between the output and the transistor's base, not where you said.