I wanted to replace my old, ordinary PIR-activated outdoor security lighting around the house with newer, smaller, LED floodlights. I still want to keep the PIR-based motion activation, but I also want to be able to control the lights from Home Assistant.
I spotted a couple of Zigbee floodlights, but they were kinda pricey, especially in comparison to the thousands of very cheap security light options out there. So I opted for modifying “dumb” security lights to make them a bit smarter, which cost less than 10 quid, all in.
Turns out it wasn’t a complicated task at all, either. I opted for a separate PIR and floodlight, rather than a combined unit, as I decided to run two lights from one PIR. But you could do this with ordinary security lights too.
Parts List
- 20W LED Floodlight
- Standard external PIR
- Zigbee light switch relay module (could be WiFi or Z-Wave or Matter, either)
- [Optional] External adaptable box
- [Optional] 3 core flex
Operation
The PIR is mains powered, the same as the light, and the Zigbee relay.
Normally, when the PIR is activated by motion, is sends a 240V output to the light, switching it on. Super simple.
The Zigbee relay is most often used to make an ordinary light switch smart. It has a relay that sends 240V to the light when activated, just as the PIR does. It also has a switch (S1) input, so you can manually activate it with your existing light switch.
Note: Some of these smart switches require you to input 240V into them to “turn it on”, while others want dry contacts from your light switch (no voltage applied to the S input on the relay). For this project, you need the former - a 240V-activated input on the relay. That’s because the PIR outputs 240V. So make sure you choose the correct option.
I just rewired this very simple circuit slightly, so that switched 240V from the PIR goes into the switch (S) input on the Zigbee relay instead of directly powering the light. This way, when the PIR detects motion, it activates the Zigbee relay using its switch input, and the relay then turns the light on. This means the relay can also be activated remotely, giving us both automatic PIR control, and Home Assistant control.
Assembly
Connect live and neutral to the PIR and the Zigbee relay unit, and neutral to the light.
Connect the live to the light to the Zigbee relay unit’s L1 terminal. This terminal outputs 240V when the relay unit is activated swtiching on the light.
Connect the PIR’s 240V output wire to the S1 terminal on the relay unit. When 240V is applied to this terminal (as it is when the PIR detects motion), it activates the relay. When the PIR turns off, so does the relay when the 240V is removed from S1.
Other than pairing the Zigbee relay, that’s everything. The relay unit even fits inside the PIR housing.
I didn’t actually do that in the end, as I decided to run two lights from one PIR, and I wanted to reposition where the PIR was mounted around the house. So I put the relay unit in an IP65 adaptable box box and rand all the wiring into that. But you may want it all contained inside the PIR housing for neatness - you have options!
Bonus
It also has the advantage of giving you a sensor in Home Assistant whenever the PIR detects motion (the relay status switches on and off with the PIR). So you can trigger automations from motion detection, too, should you want to.
