Heathkit, the storied purveyor of high-quality DIY electronics kits that inspired a generation of enthusiasts and launched the careers of many engineers, has returned from the dead. We think. At least it seems that way from this build log by [Spritle], an early adopter of the rebooted company’s first offering. But if [Spritle]’s experience is any indication, Heathkit has a long way to go to recreating its glory days. Continue reading “Heathkit’s Triumphant Return?”
Here at Hackaday we see a lot of technological hoaxes looking for funding. Some are on Kickstarter, others are firms looking for investors. And unlike a lot of the press, we’re both skeptical and experienced enough to smell the snake oil. When you read about a laser-powered razor blade that looks too good to be true, you know we’ve got your back.
The background: [Zachary Feinstein] is a professor at Washington University in St. Louis who studies financial engineering, and in particular systemic financial risk in the banking sectors. So he’s just exactly the guy you’d tap to write a paper on the financial repercussions of the destruction of the Death Stars in Star Wars (PDF). Wait, what?
The central argument of the paper is that, since the Empire has so much money wrapped up in building the Death Stars, it’s economic suicide for the Rebels to destroy it. To quantify any of this, [Feinstein] runs financial crisis models. The idea is that the Rebels win, but they inherit an economy that’s so dysfunctional that they’d have been better off not destroying the Death Stars.
We’re not saying that the rest of the press is gullible, but we are saying that they’re not putting their best economists onto articles about financing Death Stars. But here at Hackaday, we are. And we’re calling it a hoax. So let’s look into what the paper gets right, and what makes less sense even than Chewbacca’s infernal growling. Spoiler: we’ll get wrapped up in numbers because it’s fun, but the whole thing is moot for Econ 101-style reasons.
With a computer in every pocket, being tethered to large mains-powered appliances is a bit passe. No longer must you be trapped before the boob tube when you can easily watch YouTube on your phone. But you might be jonesing for the big screen experience in the middle of a power outage, in which case learning to build a simple battery bank built from cheap cell-phone power packs might be a good life skill to practice.
Looking more for proof of concept than long-term off-grid usability from his battery bank, [Stephen] cobbled together a quick battery bank from 18650 lithium ion batteries and a small 300W inverter. All the hardware was had on the cheap from an outfit called Cd-r King, a Phillipines-based discount gadgetorium we’d like to see in the states. He got a handful of USB power packs and harvested the single 18650 battery from each, whipped up a quick battery holder from 1/2″ PVC pipe and some bolts to connect the inverter. With four batteries in series he was able to run a flat-screen TV with ease, as well as a large floor fan – say, is that a Mooltipass on [Stephen]’s shelf in the background? And what’s nice about the gutted USB power packs is that they can still be used to recharge the batteries.
As [Stephen] admits, this is a simple project and there’s plenty of room to experiment. More batteries in parallel for longer run times is an obvious first step. He might get some ideas from this laptop battery bank project, or even step up to Tesla Li-ion battery hacking – although we doubt Cd-r King will be of much help with the latter.
We love a good tear-down, and last week’s “Enginursday” at Sparkfun satisfied our desire to see the insides of AC-DC switching power supplies, accompanied by knowledgeable commentary. [MTaylor] walks us through how the basic circuit works and then points out why various other elaborations are made, and how corners are sometimes cut, in a few power supplies that he’s taken apart.
What struck us in the comparison was that some of the power supplies were very minimal designs, while others had “features” that were obviously added after the fact. For instance, the Li Shin supply (about half-way down the page) has an extra circuit board tacked on to the bottom of the real circuit board to act as EM shielding.
Rather than declare this a dodgy hack, as we would have, [MTaylor] declares it to be “Good News!” because it means that they’ve probably run an emissions test, failed it, and then added this bit on to make it pass. This is of course in contrast to the other makers who’ve probably never even considered emissions testing. Sigh.
If you’re interested in seeing more inner bits of power bricks, Sparkfun forum reader [sgrace] passed along this field guide to various power supplies, which is also worth a look. And if you’re interested in building yourself the ultimate bench power supply, look no further than this Hackaday.io project by [The Big One].
When [hkdcsf] was a teenager, he made a Christmas star with an up counter driving decoder logic and using transistors to light LEDs in festive patterns. He’s revisited this project using modern techniques including a microcontroller, a DC/DC converter, and constant current LED drivers.
The project uses two AA batteries, and that’s what makes the DC/DC converter necessary. Blue LEDs have a forward voltage of just over 3V, and the LED driver chip requires about 0.6V of overhead. Two fresh AAs will run a tad above 3V, but as they discharge, or if he’s using rechargeables, there just won’t be enough potential. To make sure the star works even with whatever LEDs are chosen, the converter takes the nominal 3V from the batteries and converts it to 3.71V.
Converting mains voltage down to 12 or 24VDC to drive a heating element makes no sense. To get 120 watts at 12 volts requires thick wires that can handle 10 amps, whereas at 120V, tiny 1A wires will do. If you’ve ever felt the MOSFET that switches your heated bed on and off, you know it’s working hard to pass that much current. [Makertum] is of the opinion this is a dumb idea. He’s creating a 110 / 230 V, mains-powered heated bed.
Creating a PCB heat bed isn’t an art – it’s a science. There are equations and variables to calculate, possibly some empirical measurements by measuring the resistance of a trace, but Ohm’s Law is a law for a reason. If you do things right, you can make a PCB heat bed perfectly suited for the task. You can even design in safety features like overcurrent protection and fuses. It can’t be that hard. After all, your house is full of devices that are plugged into the wall.
However, there’s a reason we use 12V and 24V heated beds – they give us, at the very least, the illusion of safety. Therefore, [Makertum] is looking for a few comments from specialists and people who know what they’re doing.
Although a mains powered heated bed sounds scary for a hobbyist-built 3D printer, there are a number of positives to the design. It would heat up faster, thin down a few parts, and significantly reduce the overall cost of the printer by not requiring another 100 Watts delivered from a 12V power supply. It’s a great idea if it doesn’t burn down the house. Anyone want to help?
So you’ve successfully taught your cats to use your toilet, just like little furry humans. Congratulations! But you can’t quite teach the cat to pull the flush lever? You might want to automate it for them instead! (Editor’s note, 2019. Link seems to be dead. Try the Wayback Machine.)
[Joycelin & Dan] are in the final stages of teaching their cats to use the toilet. Unfortunately they had a snowboarding trip coming up, and were worried about the cats losing progress when they couldn’t flush the toilet for them. Rather than have a bit of a setback in their toilet training, they improvised — and automated the toilet.
There are commercial solutions available, but they cost several hundred dollars. You could strap a geared motor to the side of your toilet with a stick screwed to it like this guy did, but who wants to pay for the water bill of flushing your toilet every few minutes??
Continue reading “Toilet Automatically Flushes For Your Bathroom Trained Kitty”
