Dude about to pull a fire alarm

Fire Alarm Disco Party

What should your first instinct be when the room catches on fire? Maybe get out of the room, pull an alarm, and have a disco party? Not your first instinct? Well, this seemed pretty obvious to [Flying-Toast], who retrofitted an old fire alarm to activate a personal disco party.

After finding a fire alarm being sold on eBay, [Flying-Toast] couldn’t resist the urge to purchase one to use for his own purposes. He immediately gutted the life-saving internals to fill the shell with his own concoction of ESP goodness to be activated by the usual fire alarm mechanism. This sends a signal to the next elements of the party system.

Every part of the party system receives this activation signal, including the most important part, the party lights. Using a generic crystal disco ball and its own ESP, the party lights are more than sufficient to create the proper panic party. Of course, what is a party without music? With another ESP board and salvaged speakers, the proper atmosphere can be set right before the venue burns to the ground. The final touch is the additional hacked WIFI relays to turn off the lights in the room.

Priorities are important in emergencies, and that is exactly what [Flying-Toast] gave us with this project. Learning from this expertise is important, but how about learning from the near misses? For some risky decision making, be sure to check out the near nuclear war that was almost caused by a false alarm!

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The Scourge Of Fake Retro Unijunction Transistors

We all know that it’s easy to get caught out by fake electronic components these days, with everything from microcontrollers to specialized ASICs being fair game. More recently, retro components that were considered obsolete decades ago are now becoming increasingly popular, with the unijunction transistor (UJT) a surprising example of this. The [En Clave de Retro] YouTube channel released a video (Spanish, with English dub) documenting fake UJTs bought off AliExpress.

These AliExpress UJTs were discovered after comments to an earlier video on real UJTs said that these obsolete transistors are still being manufactured and can be bought everywhere, meaning mostly on AliExpress and Amazon. Of course, this had to be investigated, as why would anyone still manufacture UJTs today, and did some Chinese semiconductor factory really spin up a new production line for them?

Perhaps unsurprisingly, some tests later and after a quick decapping of the metal can, the inside revealed a bipolar transistor (BJT) die (see top image on the left). Specifically, a PNP BJT transistor die, packaged up inside a vintage-style metal can with fake markings claiming it is a 2N2646 UJT.

The video suggests that scams like these might be because people want to get vintage parts for cheap, and that’s created a new market for people who would rather get scammed than deal with the sticker shock of paying for genuine new-old-stock or salvaged components. For example, while programmable unijunction transistors (PUTs) like the 2N6028 are still being manufactured, they cost a few dollars a pop in low quantities. UJTs used to be common in timer circuits, but now we have the 555.

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