How to use a relay multiple times

A much asked question is how can a relay used in 2 or more areas. By default this is not possible, due to the a relay can only be used once policy. This made it a bit easier to make sure that relays stays in the correct state. Even after power failures.

But there is a solution. In this FAQ we explain how to setup a relay to used in multiple areas. This can either be a relay or a dimmer. It should work for both.

Add original relay

First add the original relay to TerrariumPI and make sure it works. Enter the power usage and the water usage values. But never use this original relay in any area.

Create script relay code

1. Create a scripts folder if not exists: mkdir scripts
2. Copy duplicate_switch.py to the scripts folder: cp contrib/duplicate_switch.py scripts/

3. Edit the new script to set some settings: nano scripts/duplicate_switch.py

   • Edit the variables RELAY_ID, USERNAME, PASSWORD. The RELAY_ID can be found on the page: http://[TerrariumPI_IP]:8090/api/relays/

When this is all done, you can test if it al works by running the command: scripts/duplicate_switch.py 100 which should toggle on the original relay.

Duplicate the relay

Now it is easy to duplicate this relay a couple of times. Make sure you are on the scripts folder where the file duplicate_switch.py is placed.

Now by running the following command we will create a symlink to the original file. Now you will have 2 files with the same contents and will the same original relay.

ln -s duplicate_switch.py duplicate_switch_2.py

This can be done multiple times. Make sure you have a unique name for every new symlink.

Adding the new relays to TerrariumPI

Now add the new scripts as new script relay to TerrariumPI. Use as address /home/pi/TerrariumPI/scripts/duplicate_switch.py.

But here, do not enter the power and water flow values. Else the amount of used power and water will be counted double. Which is not correct.

Now you can use the new script relay in an area.