Relay node hangs sometimes when toggling a fan

[chris021]

Hi,

I have a sensor node driving a fan and sometimes when toggling the relay the node locks up. I am using a nano board and when it locks up the TX led stays solid.

The relay board is opto isolated. I have done some research about the interference that can be caused by a relay switching a motor, but I don't understand the solutions and given its 240v I don't want to make changes to the 240 side unless I fully understand them.

I have tried swapping out the radio, the nano and the relay.

I have not been able to reproduce the fault when the fan is disconnected.

My skills are quite basic so any simple advice would be very much appreciated!

Chris021

[hek]

Do you feed the relay from your arduino?

[chris021]

I have D3 signal low to trigger the relay. The same 5V source powers the relay, but this works fine if no load is connected.

[BulldogLowell]

@chris021 said:

The same 5V source powers the relay

what kind of power source are you using?

[TimO]

I've the same problem with a 4 relay board. After a few times switching on and off, the Atmega hangs.
Especially if more than one relay on the board is switched.

I'm currently swithing the power source.

[chris021]

@BulldogLowell im using one of these onto the 5v pin of the board:

http://www.aliexpress.com/item/5-pcs-AC-DC-85V-265V-700mA-Isolated-Switching-Power-Board-Module-Industrial-Power-Supply-Built/1260239970.html

I have also tried feeding it via USB of a 2.1 amp supply with the same results.

[BulldogLowell]

So you are powering both the relays and the arduino in parallel from the transformer?

have you tried isolating the arduino's power from the transformer with a capacitor?

the power surge of the relays (even though you have an opto-isolator from arduino to relays) may cause issues for the arduino.

perhaps start with a regular 4.7µF across the Vin and ground of the arduino

[chris021]

its worth a try, however this works 100% fine when there is not a fan connected I might try a different AC device to see if that is just as reliable as no AC device connected.

[BulldogLowell]

@chris021 said:

however this works 100% fine when there is not a fan connected

motors draw a tremendous amount of current when they start... Try isolating the arduino's power from the transformer, or using the capacitor.

[chris021]

@BulldogLowell I have powered it off an external battery pack. Same story!