A video on photocell light controls

Enjoyed this a lot! Learned a ton from it. Liked the drawings too.

I would never have guessed that's how those sensor switches work. It's somehow both wildly disillusioning and heartening that at least I can follow the bouncing ball.

Buckaroo Bunny Slippers

There is apparently some debate on whether SCR is a tradename for a type of thyristor or something unique to itself. Upon seeing that, I just went with thyristor because that's what Big Clive called it when he toredown a nightlight circuit

Technology Connections

Unbelievable that you said “hysteresis” at almost the exact moment I said it (in my head). Also, is that thyristor not more specifically an SCR (silicon controlled rectifier)? You made me think of Triacs for the first time in decades, too.

Alan Medsker

I have a fun childhood story regarding streetlights!!! My Dad was an amateur astronomer. When I was around 10 the city put a street light in front of our house. Not good thought Dad! Well he found a plug in laser a laser at Goodwill. He mounted to a tripod and pointed it at the sensor on top of our streetlight and turned it off! After a year or so it started malfunctioning and would always switch on and off. He called the city and they fixed it. Funny thing though. Somehow it malfunctioned again in a year or so.

Joshua Rouw

If you want a clever design, I have one for you! LEDs are also photodiodes, so they _generate_ power when lit. So some of the "light-sensitive" bulbs use the LEDs themselves to detect the ambient light.

Aleksei Besogonov

Story time: Back when I worked at $COMPANY, we gave customers ZigBee gateways to form a mesh network of their end devices in order to gather our required data and send it up to our cloud. All of these gateways and devices shared the same network ID because if one neighbor's device joined another neighbor's mesh, the unique device IDs would all get sorted out cloud-side and it would work out fine in the end. No problem there. One day a customer's gateway just straight up died. Reported 99% CPU, 99% RAM then never checked in again. After a ton of work, I eventually got the gateway connecting to the last-resort OS-level debug platform. After some poking around I found out that the gateway was using all of its resources managing a mesh of hundreds of devices. Turns out, and this is where street lights come in, some other company was selling mesh networked IoT street lights to the city, and they happened to choose the same network ID as us for this specific installation. This customer was connected to ALL of the street lights. The amusing part was, with the exact framework we were both using I could not only use the OS-level debug connection to download and upload our source code to our devices, but any devices it connected to. So I was able to grab their IoT device's source. Unfortunately it was pretty bare bones and not exciting. In the end, I changed the customer's and their neighbors' network ID, which kicked the street lights off the network. TL;DR a customer's product stopped working because $CITY made their street lights smarter than necessary.

C222

You remind me of that "word of the week"-action we had in one of my study-internships: every week somebody should come up with some difficult, almost impossible-to-pronounce word (and Dutch, not even English where there is absolutely no relationship between spelling and pronounciation - https://monologues.co.uk/004/Chaos-The.htm), print it out in big letters including it's dictionary definition.

MrHammond

Very interesting thought, it consuming maybe some more power but to make a very simple and robust design... But I wonder if that is still used in modern LED streetlighting, especially the ones which decrease their brightness if nobody is around... Maybe an idea for a next video? ;-)

MrHammond

I did not know that there was a pressure campaign for you to say "hysteresis". I am glad you said it, as I do like the term, but I wonder why there was interest in you saying it? It's not *that* sesquipedalian, but the term is certainly a cromulent entry to embiggen a lexicon.

Jeremy

Solar cell plus normally closed relay. Done. Maybe a capacitor for hysteresis. But solar cells used to be much more expensive.

Jerrad Pierce

Autoincorrect. Bi-metal not numeral

Jim Hooke

FANTASTIC. Yes I'm shouting. One of my favourite little bits of technology. I happen to have a couple of Tyco branded PE cells tucked away. They are the chunkier but elegant numeral types. I'll send a pic via twitter. The voltage range is not just for International use but a lot of US streetlights can be 220/240 volts. In Australia there's been a move away from single PE cells and banks of lights. On overhead wiring it means they can be spliced into individual phases along the street, load balancing, and removing a single point of failure. Also removes the need for an extra pair of wires being strung. Areas with underground power now have an electrical box and power on separate lines. Utility companies have found out the hard way that the Chinesium PE cells are failing very quickly as they have caps and relays. Whi'd have thought. Lol. Lots of fittings have the PE on bottom of fitting as there's a little bit of UV protection, but more bird poop protection! Cheers

Jim Hooke