If things had gone to plan we would have had another video out by now, and talking about another peripheral that I want to add to my automation project.
Regrettably, though, I’ve had a family bereavement which has halted most things Arduino and Pi for this week and next, as I fly out to Germany for my dad’s funeral. He’s been suffering from Alzheimer’s for a couple of years or so which meant he had difficulty understanding some concepts – which meant I was saving news and photos of my new workshop for a face-to-face when I went over this weekend for his birthday. Now it will be for his funeral instead and I’m sad because he never got to know about it. In many ways, he was responsible for nurturing my practical, hands-on nature which allows me to “build stuff”. He would have been absolutely fascinated by my new workshop, that’s for sure.
But he would have been the first to say that life goes on for the rest of us, so I’ll give you a brief preview of what it is I plan to include as part of my next video.
It’s a three-channel, optocoupler (aka optoisolator) mains detector, that can be interfaced to an Arduino or Pi without any danger of zapping that unit should things go awry.
The concept is simple enough: you supply a line (L) wire to any of the three channels (on the right in the above picture), from a light perhaps, a neutral to the common neutral and the power is dropped by a rather chunky resistor, rectified via an MB2M bridge rectifier and fed into an optoisolator chip (an EL817) that can then be used to bring a µcontroller pin high. Simples. And safe for your receiving device.
The actual optoisolator unit can be potentially fatal though, and as we are now talking DC line-level voltages (albeit at tiny currents) that makes it even more so. So not a board for the risk-takers or those uncomfortable with mains electricity. I will be taking extra care when I do the video as I don’t want to be the next one in the Bacon family to go to the great breadboard in the sky. Not just yet, anyway. The whole area enclosed in the white box on the circuit board is at mains potential and must NOT be touched when connected.
I bought this from a UK supplier on eBay, moore_estates, but if you’re not in the UK you can probably pick them up from other local or Far Eastern outlets if you’re prepared to wait a few weeks. Single units are also available from them if you don’t need the three channels, and are cheaper, of course, but I will need 3 channels, as I want to detect my lighting, heating and something else, but I haven’t decided on it yet!
So thanks, dad, for giving me the genes and the opportunities to explore the practical nature of my life – and perhaps you’ll now see my workshop from above. Tempus Fugit.