I did some soldering tonight, and it felt good.
I haven't really done much soldering since I built my cat water bowl monitor, and that's going back to the last decade.
My apartment building has an intercom-triggered release to the common front door, and the latch has been sticking a bit lately. It stuck today when Megan's Dad came to pick her up, and it stuck when Sarah came to pick up Zoe. It's annoying to have to trek all the way downstairs to let them in and then walk back up again. I decided I'd try and look into what the problem was today after everyone left.
A visual inspection of the latch showed nothing obvious, and no one else was home to push the door unlock button for me while I was at the front door, so I decided to have a look at how it worked from within my apartment.
I pulled the intercom phone off the wall and identified the two wires that got shorted when you pressed the unlock button, and shorted them by hand with a wire, and sure enough, I could hear the door solenoid releasing.
I was thinking to myself, "if only there was a way to trigger this with my phone". I have a RaspberryPi and an Arduino board at my disposal, but I didn't really want to risk frying either of them. Then I remembered that I had a BoArduino that I'd bought at the Maker Faire years ago, but never assembled. I figured it'd make a good sacrificial lamb.
So I rummaged around and found it, and busted out the 240v soldering iron I bought recently, but haven't used yet, and set about slapping it together. Man, it was fun. I had it half built before yoga, and finished it off when I got home. It even worked first go. I felt such a sense of accomplishment.
The problem is, my general electronics fu is so weak, I'm not sure where to go from here, and my multimeter needs a new battery. I think the voltage on the wire for the intercom is higher than the BoArduino likes. I'd naively thought I could just connect the two wires of interest, one to ground and the other to one of the digital I/O pins, and have the BoArduino act as a switch, but that's not working. If I wire it one way, it unlocks the door instantly, even with the board powered off, and if I wire it the other way, it seems to half power up the board just using the power of the intercom system. So I'm obviously doing something wrong.
My plan is to just have the BoArduino simulate pressing the button for 5 seconds at a time, every 10 seconds or so. Then I can be downstairs wiggling the latch to see what's up with it.
Or I could just place a maintenance request with the Body Corporate.
At least I had fun assembling the BoArduino, and now I have a spare one. It was nice to be able to go from problem to idea to execution in one night, even if the execution failed.