How to add Relay


I have recently purchased and emontx v3 + rfm12b and RFM12Pi + raspberry Pi. I would appreciate it if somebody could explain to me how to control a 3 channel relay using the aformentioned combination. 

Thanks in advance

ukmoose's picture

Re: How to add Relay

What do you want to use the relay for?


Where do you want the relay to be located?  EmonTX or Pi


hannsl's picture

Re: How to add Relay


I would like to connect the relay to control a mains electricty signal. It would actually be the same signal that the emon tx 3 is sampling. It can be located at either the pi or the emon tx.

bernamorillo's picture

Re: How to add Relay

I am interested too, We want to switch off the power supply remotely via Emoncms. Is it possible?


Robert Wall's picture

Re: How to add Relay

The easy answer is to add the output interface used here: Diverting surplus PV Power, by Robin Emley

It is not a relay, it is a triac, but when constructed correctly according to the instructions you have isolation between the mains and the low voltage circuit, and it can switch up to 40 A when equipped with the appropriate heat sink. Robin can supply PCBs and possibly the complete kit.

For 3 channels, you would need three identical units.

To control this from emonCMS, you would need to send a control signal back. I think there is a separate thread about that.

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