Building an Intrusion Alarm part 2

I had to scale down the circuit that I had built before because the perf board that I’m going to use is pretty small (Adafruit Perma-Proto 1/2 Sized Breadboard). I also decided to change the relay that I used for another type. I previously used the SRC-S-12VDC which works fine but the pin layout is different from the relay used in Make:Electronics. So I used the FTR-F1 CD 012 which is one of the recommended relays in the book. Once I built the circuit everything worked fine except for one thing. Once the alarm is triggered by the magnetic sensor the alarm should be locked even if the magnetic sensor is closed again. This is not the case. I went over the circuit several times but I couldn’t fix the problem. I don’t want to waste to much time on this so I think I will build the alarm without the lock.

Image of the circuit with the new relay.
Close-up of the circuit.

Experiment 15: Building an Intrusion Alarm

A couple of years ago I started working with electronics as a hobby. The reason was that it seemed cool to create electronics gadgets and learn about electronics in the process. I had limited training in electronics so I decided to start with simple electronics kits. These kits contain a PCB, electronic components and a simple step by step instruction. So I built a FM radio, an amplifier and some simple LED gadgets but apart from enhancing my soldering skills I didn’t learn much about electronics. Then at I came across the Make:Electronics book by Charles Platt. The book from 2009 but it looked very hands-on and I ordered it. By now I have almost finished the first three chapter and I arrived at experiment 15 which proved to be the most challenging so far.

In experiment 15 I have to build a alarm circuit. After some setbacks I have a working circuit on breadboard.

Two breadboards with on top the magnetic sensor, the breadboard with the noisemaking circuit and the loudspeaker. At the bottom the relay circuit that triggers the noismaking circuit.
A closer look at the relay circuit


DIY bar table

I finished a bar table for our kitchen today. I found a design for a table made of scaffolding wood. This wood is probably the cheapest that one can get but it is sturdy and it looks nice (at least that’s what I think). The local DIY shop where the wood was bought also cut it at the desired length. Building it was easy. Just build the table top B, by attaching the 62mm stave lath (D) to the table top and attach it to the table leg A with the 30mm width stave (G). The planks of leg (A) were connected with the stave (E). Some of the 195mm wood was slightly curved but the staves straightened it nicely.
The bill of material was:

  • 6 pc scaffolding wood 2500 x 195 x 30mm
  • 2 pc scaffolding wood 2500 x 62 x 30mm
  • 2 pc scaffolding wood 2500 x 30 x 30mm
  • 1box (100pc) clipboard screws.
The parts list  for the 195mm width wood was:
  • 8 pc scaffolding wood 1070 x 195 x 30mm
  • 4 pc scaffolding wood 780 x 195 x 30mm
Drawing of the table.
Image of the finished bar table.

Image of the finished bar table.
Image of the table top’s bottom side.