I completed the projectbox yesterday. It is looking good (well good enough) and I was eager to wrap-up the project. Just a few solder joints and it was finished. Before I started soldering, as I final test, I screwed the circuit board in the box and plugged in the power, I opened the magnetic sensor and… nothing happened, at least no audible sound either from the relay or the loudspeaker. I checked the voltage on the noise making part of the circuit, nothing. Then I checked the relay part. I measured voltage but the relay will not energize. Probably something has happened when I screwed the circuit board. Now I’m stuck with a nearly finished projectbox and an apparently broken circuit.
When frustration builds up I have learned to leave a project alone. You might end up throwing the project out of the window. On the up-side this may be a learning opportunity. On page 139 of Make:Electronics is an explanation how to trace faults in a circuit. I had no need for that until now. It is also an opportunity to use the minigrabber (see Figure 3-6 of the book) that I had recently bought.