Testing caps with a DIY ESR meter

ESR

There’s a problem with collecting old tube amps and vintage electronics – eventually the capacitors in these machines will die. It’s not an issue of a capacitor plague that causes new electronics to die after a few years; with time, just about every capacitor will dry out, rendering antique electronics defective. The solution to getting old gear up and running is replacing the capacitors, but how do you know which ones are good and which are bad? With [Paulo]‘s DIY ESR meter, of course.

An ideal capacitor has a zero equivalent series resistance, and failure of a capacitor can be seen as an increase in its ESR. Commercial ESR meters are relatively cheap, but [Paulo] was able to build one out of a 555 chip, a small transformer, and a few other miscellaneous components.

The entire circuit is built on stripboard, and if you’re lucky enough to find the right parts in your random parts bin, you should be able to build this ESR meter with components just laying around.

Sonic Screwdriver meets TV-B-Gone

sonic

[furrysalamander] has a friend that is a really big Doctor Who fan. It happens that this friend has a birthday coming up, and [furrysalamander] wanted to get her something amazing. A Sonic Screwdriver is always a great gift, but [furrysalamander] wanted to put his personal touch on it. He ended up adding a TV-B-Gone to [10]‘s screwdriver, turning a fictional deus ex machina into a functional device.

The body of the Sonic comes from this replica of [10]‘s screwdriver from Think Geek. Inside, the screwdriver has space for a battery a circuit board to control the lights and sound normally expected of a sonic screwdriver. [furrysalamander] added a freeform circuit composed of an ATtiny85, a transistor, LED, and a few resistors to add the ability to turn just about any TV off.

Of course [furrysalamander] needed to program the ATtiny with the TV-B-Gone firmware, and lacking any AVR development tools he used a Raspberry Pi’s GPIO pins to write the firmware to the microcontroller. That’s something we’ve seen before, but [furrysalamander] is a champ for including the process in his Instructable.

The end result is a Sonic Screwdriver that doesn’t work on wood and can’t break a deadlock seal. It turns off TVs just fine, though, and looks great to boot. You can check out a demo of [furrysalamander]‘s sonic in action after the break.

[Read more...]

AC vs DC human pain test

AC-vs-DC-human-pain-test

Ever wondered just how much being zapped by electricity hurts? Curious if AC is worse than DC? Want to know just how many volts a human body can take? Although many people might cringe at the shear thought of it, [Mehdi Sadaghdar] is an electrical engineer who decided to turn himself into a human guinea pig and find out.

[Mehdi] measured the electrical resistance of his dry skin, his wet skin, and finally his tongue.  He found that his tongue had the least resistance, so it would feel the electricity at much lower levels. Using a bench power supply, he then used his tongue as a testing ground – slowly turning the voltage up and up until he could no longer take the pain. He tested the levels at which: he could first feel the electricity, when it began to get annoying, when it felt like torture, and when he could no longer stand the pain. He tried both AC and DC, and reports that AC is much worse.

Check out the informative, yet admittedly hilarious at times, video after the break. [Mehdi] seems like one awesome engineer! Remember – don’t try this at home.

[Read more...]

Midwest RepRap Festival

We’re a US-centric site, but aside from events in New York or California, we don’t see many hacker, maker, or 3D printer events aimed at the parts of the country filled with corn and WalMarts. The 1st annual Midwest RepRap Festival aims to change that with enough events, speakers, and activities to make Elkhart, Indiana look like the hoppingist place around.

Officially, the festival started yesterday but the schedule of events really ramps up today. [Josef Prusa] will be taking the stage talking about the state of the RepRap, and a ton of 3d printing vendors will be there showing off their wares and selling some really cool stuff. There’s also tons of experienced RepRappers available to help you tune your machine to perfection; just as well, because the festival is going for the world record for the greatest number of 3D printers printing simultaneously.

If you’re around northern Indiana, you might want to check out the festival and send us a few pics or videos.

Follow

Get every new post delivered to your Inbox.

Join 93,718 other followers