Motion sensors are not omnipresent – they can’t be all-seeing because they are, to an extent, directional.
They are designed to cover a specific area that you have them pointed at.
Otherwise, they would be triggering all the time.
But what if you have one light that you want to be activated depending on whether there’s movement in different places?
You can’t cover everything with one sensor, but can you wire one light (or set of lights) to two sensors?
You can wire two motion sensors to the same light, but not in series; otherwise, both would need to be triggered for the light to work. You can wire the sensors to the light separately in a parallel circuit, and they will work independently.
To explain in a bit more detail, let’s take a look at:
- Whether it’s possible to have two motion sensors working on the same light
- Why you can’t daisy-chain motion sensors
- How to wire multiple motion sensors on one circuit
Can I Have Two Motion Sensors To The Same Light?
It is possible to wire two motion sensors to the same light, provided you wire them correctly.
This can be really useful.
For indoor sensors, you might want the staircase lighting attached to a motion sensor at the top and bottom of the stairs so that the lights switch on when you’re approaching them from either floor.
Outside, you may prefer to wire all your lights to motion sensors covering the front and rear of your home.
Using your outdoor lights to deter potential intruders, you’ll have more coverage without needing to double-up on lights – just multiple sensors.
In theory, you can have as many sensors as you want on a circuit, which could be good for outdoor lights if you want to cover more than two directions and you have an expansive garden.
What matters is how they’re wired up, so let’s look into that more.
Can You Daisy Chain PIR Sensors?
To be clear, daisy-chaining motion sensors would be where you put them on the same circuit in a single loop.
This is called a series circuit – where the current travels from the power source through each component.
That wouldn’t work if you wanted multiple motion sensors on one circuit.
That’s because a motion sensor is like a light switch that is naturally in the ‘off’ position.
When there’s no movement, the motion sensor is in its own ‘off’ position, and the circuit is broken.
As soon as there’s movement and the sensor is triggered, it closes the circuit, just like when you switch a light switch into the ‘on’ position.
Except after a set period, it’ll automatically flick back into the ‘off’ position and break the circuit.
Current will only flow on a complete circuit, so if there is a break anywhere in the circuit, none of the devices wired into the circuit will be powered.
This means that if you have two motion sensors on one circuit, they will both be in the off position when there is no movement, and no current will flow.
If only one sensor is triggered, the other will still break the circuit, so the light won’t work.
So technically, yes, you can daisy-chain PIR sensors and wire them in series, but only if you want the lights to work when both sensors are triggered, and not if only one is.
And I can’t think of a scenario when that would be useful – but let me know if you can!
How Do I Wire Multiple Motion Sensors On One Circuit?
So, I’ve said that you can wire more than one motion sensor into a circuit but can’t just wire them in series.
How do you do it in a way that’s therefore useful?
It’s simple enough, though it might mean more wiring work. You need to wire them in parallel.
Wiring them in parallel essentially creates two separate circuit loops.
As long as you have the motion sensors on different loops, then there will always be a fully closed circuit when one of the sensors is triggered.
Simply you would wire the power supply to the two motion sensors separately and then connect them both to the light(s) before closing the circuit from there.
Here is a diagram:
As soon as the motion sensor is triggered, the circuit will close, and the lights will turn on.
The only downside to this – and it is very minor – is that if you trigger both motion sensors, one after the other, the lights will remain on for a few seconds longer than they otherwise would.
Let’s use the example from above with the staircase. As you approach the bottom of the stairs, you trigger the sensor on that floor, and the lights come on.
Then as you reach the top of the staircase, you trigger the upper-floor sensor.
When the lower-floor sensor deactivates, the upper-floor sensor will still be closed. So the lights will remain on for a few extra seconds before that sensor deactivates again and the circuit re-opens and breaks the flow.
Like I said, a really minor inconvenience with the lights staying on ever so slightly longer than they otherwise would, but worth mentioning.
Also read: Do Motion Sensors Work Through Glass?
The simple answer is that you can wire multiple motion sensors onto one circuit but only in parallel.
Wiring them in series isn’t going to be helpful, and if you did, then you might as well only have one sensor anyway.
But multiple sensors wired in parallel can be useful for ensuring your lights always turn on when you need them and not just when you pass one specific area where a single motion sensor would be aimed.
How do you set your motion sensors up, and have you had any issues wiring them into the circuit?