How to connect an external siren to AlertMe

After waiting a while for AlertMe to release an external alarm, I decided to investigate making my own one. Since the release of the SmartPlug I could see this might be possible. I found an alarm on the maplin website that I thought might be able to do the job. After finding the instruction manual on the Lyntech website, I decided it was worth buying even though I wasn't entirely sure if it was going to work. After some initial testing (while the alarm was wrapped in a blanket to keep the noise down) I worked out that connecting the siren and stobe to the 0V line would activate them. Here is my intial wiring test:

Based on this initial test my basic principle was to have a 12V supply powering the alarm, and have another 12V supply plugged into a SmartPlug connected to a relay that would switch the alarm on. Here is the basic circuit diagram:

Here are the details of how I went about making it, in case anyone else wants to make one. Here is a list of all the components required from Maplin: (scroll down lots as blogger doesn't seem to like tables)

Description	Code	Quantity	Price
External Bellbox Siren/Strobe	YS09K	1	£39.99
16A PCB-Mounting Terminal Blocks	RH77J	1	£0.59
Stripboard	FL17T	1	£5.38
AC/DC Multi-Voltage 1250mA Switched Mode Power Supply	L49BR	2	£17.99
5A DPDT 12Vdc PCB Relay	N31AW	1	£1.98
Min Extra Flex Red	XR69A	1m	£0.69
Box 321	FK73Q	1	£1.89
2.1mm Single-Hole-Fixing DCSocket	JK09K	2	£1.59
3-Core 3A Mains Cable	XR02C	5m	£0.99

The 3 core mains cable is to run from the circuit near the SmartPlug through to where ever the bell box is, so obviuously your length might be different. Also most 3 core cable would do, and doesn't necessarily need to be this thick.

These are most of the tool you will need:











Most important tool of all!



Here is the top of the board with the relay and screw terminal placed on




And in the box




Here is the back of the board where you can see the pins coming through and where I cut the board with the stanley knife to break the track in the wrong place. If you cut it in the same way but where indicated instead it will make things a lot easier!




Here it is soldered with a few extra blobs from where I made a mistake in cutting the track



Here is the box with the 8mm holes cut for the 12V power connectors and the 3 wire cable leading to the alarm








Here is the completed circuit in the box. As you can see the 3 core cable going to the alarm was a bit of a squeeze to get in, so it might be best to put the hole for the cable nearer the centre of the box



Outside of the box with the lid on and the power supplies connected. They look different, as they didn't have 2 of the 12V power supplies I have listed above in stock, so had to get to slightly different one



This shows the alarm connections without any wires so you can tie it up with the next image to see which cable goes where

This shows the connections in the alarm. Note the loop going from TG- to STB-, that is making the strobe go off at the same time as the alarm.


I hope this is enough information for anyone intrested in making something similar. I will try to create a clearer image of the underside of the circuit board and where it is cut and where things should be soldered, but hopefully you should be able to work it out from the circuit diagram.