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A project log for Commercial home automation

Home automation using the Loxone series of home automation products along with hacks to extend functionality and reduce cost

Ian NortonIan Norton 04/14/2015 at 20:0110 Comments

So following on from my previous post about switches at let's talk about Passive Infra Red (PIR) sensors.

Loxone Presence Sensor

Summary: No way in hell I'm buying one at that price
Supplier: Loxone

Wow, the price of this is staggering. It's got a light level sensor and a PIR in it. I'm not going to buy one, but I'm including it here without much comment.

Manufacturers site -

Generic presence sensor

Cost: Low (£10)
Summary: Not quite what I'm after, but I can hack this.
Supplier: Low Energy Supermarket Ebay shop

I purchased this with the thought that I would place them in some rooms outside of the automation system like the toilet and possibly the kitchen. I ran it in the kitchen for a while until it finally started to annoy me. There's an adjustable timer and light level sensor which means that once the light drops below a certain level the PIR will activate the light until no presence is detected and the timer runs down. It's 240v mains, which isn't great for working with, so having gotten annoyed with it and removed it (Claire nearly cut herself after the lights in the kitchen went out) I took it apart for a looksee.

So what's the black tube? It's a fuse, that's a good thing. Otherwise not much of interest.

Oh hello! That's a 24v relay. That means that we're looking at a 24v DC supply. *grin* The Loxone kit is 24v DC, which I don't think I've mentioned so far. The two circuit boards are a mains power supply and the combined PIR and logic board with the two variable resistors on. Removing or modifying the back board *should* give us a board that we can power with 24v and will trigger a 24v line when activity and suitable light level are detected. We don't actually care about the light level or the timer so we can turn both right down. Now we have something we can connect directly to a Loxone digital input and feed into a lighting controller block for a fraction of the cost of the official presence sensor. This I like :)

Purchased from Low Energy Supermarket Ebay Shop -

Hacking the generic PIR

Some time after writing the top half of this post, I got to the testing. Tests on the generic PIR revealed that indeed it was 24v as expected. A simple full wave rectification circuit with four 1N4007 diodes, a couple of capacitors, a signal diode and a couple of resistors.

Surplus components removed from the PCB

PCB with surplus components removed - attempt 1

PCB with surplus components removed - attempt 1 with links

Turns out the signal diode was mostly redundant as far as I can tell, it's included to eliminate back EMF but that's actually dealt with by one of the power diodes without need for it. Eh, I put one of the power diodes back in and removed the signal diode.

PCB with components removed - attempt 2

So testing! Lets see what the current consumption is like on this after the modification

Voltage 24.1v, current 7.3mA with PIR off

Voltage 24.1v, current 21.9mA with PIR on

Huzzah! 24v DC PIR with low current consumption and low cost. Our terminals are now switched 24v DC, 0v and +24v DC enabling us to use this on an input as suggested above. The input can then be mapped to the sensor input on the lighting controller and programming via the Loxone as documented.

I'm very happy with this money saving hack and will be buying a few more of these sensors in the very near future!


Ian Norton wrote 09/10/2016 at 18:47 point

Latest post now up with the new PIR design at

Hope that helps peeps!


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Ian Norton wrote 09/05/2016 at 10:46 point

Turns out that the manufacturer changed the design for the PIR I used, a couple of people have contacted me to ask about this. I've ordered a new one today so as soon as I'm able I'll get a fresh post up with the new design.


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Mihai Margineanu wrote 04/03/2016 at 12:42 point

Therefore it works also on 0-10v?

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Ian Norton wrote 04/03/2016 at 15:35 point

No, the PIR is 24v

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JJPinch wrote 07/06/2016 at 19:25 point

@Thebays,  how did you handle the 28v alarm output of the paradome pir?

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thebays wrote 07/06/2016 at 21:35 point

just used 24v and it worked. have had it in the hallway for 3 years, switching light on, no issue

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Andrew wrote 05/26/2015 at 15:28 point

Cool, I look forward to them!

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Andrew wrote 05/26/2015 at 11:05 point

As someone who is a novice Loxone programmer I am loving this series, any more posts coming?

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Ian Norton wrote 05/26/2015 at 11:43 point

Hi Andrew!

Yes, I have a couple planned. One on implementing your own light level sensor using a Raspberry Pi and the sensor module in the list for the project and another on cabling and how I've done mine. The sensor one might be a while off as it needs some software writing and some hardware building which is a bit more time than I have
free right now.

Hit a bit of a stop getting stuff done on the house renovation :)

Thanks for the comment, acts as a reminder I need to write some more stuff!


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