Thermochromic Treatment Keeps Solderless Breadboards Smokeless

There’s a point in a component’s thermal regime that’s between normal operation and overloaded to the point of obvious failure. That’s a dangerous region, because the component isn’t quite hot enough to release the Magic Smoke, but hot enough to singe any finger you poke around with the see if everything’s running right. So if you’re looking to keep your fingerprints unmodified, but you don’t want to invest in a thermal camera, you might want to let this thermochromic breadboard point the way to overloaded components.

We’re not sure where this tip came from, but judging by the look of the website it was sometime in the late 90s. We’re also not sure who’s behind this little hack, so we’ll just credit [improwis]. The idea is pretty simple — white acrylic paint is mixed with thermochromic pigment, and the mixture is carefully painted onto the plastic surface of a standard-issue solderless breadboard. Care is taken to apply thin coats, lest the paint gets into the contacts and really muck things up. Once the paint is dry you’re ready to build your circuit. We have to admit we’re surprised at how sensitive the paint is; judging by the pictures, the heat coming off a 1/4-watt resistor dissipating 350 mW is plenty, even when the body of the resistor is well above the surface of the breadboard. We’d imagine the paint would point out not only hot components but probably the breadboard contacts too, if things got really toasty.

This seems like such a great application of thermochromism, one that’s a bit more useful than clocks and Pi Day celebrations. If you’re going to try this yourself, you’ll have to track down your own supply of thermochromic pigment, though — the link in the article is long dead. That’s not a problem, though, as Amazon sells scads of the stuff, seemingly aimed mainly at nail salons. The more you know.

Tripping Out: A Field Guide To Circuit Protection

My introduction to circuit protection came at the tender age of eight. Being a curious lad with an inventive – and apparently self-destructive – bent, I decided to make my mother a lamp. I put a hose clamp around the base of a small light bulb, stripped the insulation off an old extension cord, and jammed both ends of the wires under the clamp. When I plugged my invention into an outlet in the den, I saw the insulation flash off the cord just before the whole house went dark. Somehow the circuit breaker on the branch circuit failed and I tripped the main breaker on a 200 amp panel. My mother has never been anywhere near as impressed with this feat as I was, especially now that I know a little bit more about how electricity works and how close to I came to being a Darwin Award laureate.

To help you avoid a similar fate, I’d like to take you on a trip (tee-hee!) through the typical household power panel and look at some of the devices that stand at the ready every day, waiting for a chance to save us from ourselves. As a North American, I’ll be focusing on the residential power system standards most common around here. And although there is a lot of technology that’s designed to keep you safe as a last resort, the electricity in your wall can still kill you. Don’t become casual with mains current!

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