Animated EV Charge Cable Enlightens Us

[ch00f] was searching for an idea to build for his father this Christmas, and cast his gaze across those novelty phone charging cables that have “flowing” LEDs along their length. Not one to stick to the small scale, he set out to create a flowing LED effect for a Tesla EV charger.

ch00f-led-ev-chargerThe basic components behind the build are a current transformer, a NeoPixel LED strip, and an ATtiny44 to run the show. But the quality of the build is where [ch00f]’s project really shines. The writeup is top notch — [ch00f] goes to great lengths showing every detail of the build. The project log covers the challenges of finding appropriate wiring & enclosures for the high power AC build, how to interface the current-sense transformer to the microcontroller, and shares [ch00f]’s techniques for testing the fit of components to ensure the best chance of getting the build right the first time. If you’ve ever gotten a breadboarded prototype humming along sweetly, only to suffer as you try to cram all the pieces into a tiny plastic box, you’ll definitely pick something up here.

Perhaps you’d like to check out this teardown of a Tesla Model S battery. Video after the break.

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Shocking Halloween Decoration

Sure, you could animate some Halloween lights using a microcontroller, some random number generation and some LEDs, and if the decorations are powered by AC, you could use some relays with your microcontroller. What if you don’t have that kind of time? [Gadget Addict] had some AC powered decorations that he’d previously animated with an Arduino and some relays, but this year wanted to do something quicker and simpler.

In another video, he goes over the wiring of a fluorescent starter to create a flickering effect with an incandescent light bulb. A fluorescent starter works because the current heats up a gas discharge tube which causes a bit of metal to bend and touch another, closing the circuit. A fluorescent bulb is a big enough load that the flowing current keeps the starter hot and, therefore, the circuit closed. If you wire the starter in series with a regular incandescent bulb, the starter heats up but the load isn’t big enough to keep the starter hot enough, so it cools down and the circuit breaks, which causes the starter to heat up again. This causes the bulb to flicker on and off. [Gadget Addict] uses two circuits with a fluorescent starter each wired to alternate bulbs in the decoration in order to get the effect to look a bit more random.

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Arduino Replaces Bad AC Thermostat, Hacker Stays Cool

Most of North America has been locked in a record-setting heat wave for the last two weeks, and cheap window AC units are flying out of the local big-box stores. Not all of these discount units undergo rigorous QC before sailing across the Pacific, though, and a few wonky thermostats are sure to get through. But with a little sweat-equity you can fix it with this Arduino thermostat and temperature display.

We’ll stipulate that an Arduino may be overkill for this application and that microcontrollers don’t belong in every project. But if it’s what you’ve got on hand, and you’re sick of waking up in a pool of sweat, then it’s a perfectly acceptable solution. It looks like [Engineering Nonsense] got lucky and had a unit with a low-current power switch, allowing him to use a small relay to control the AC. The control algorithm is simple enough – accept a setpoint from an encoder, read the temperature sensor, and turn the AC on or off accordingly. Setpoint and current temperature are displayed on an OLED screen. One improvement we’d suggest is adding a three-minute delay between power cycles like the faceplate of the AC states.

This project bears some resemblance to this Arduino-controlled AC, but it seems more hackish to us. And that’s a good thing – hackers have to keep cool somehow.

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Put a Reverse Engineered Power Meter in Your Toolkit

It seems that one can buy cheap power meters online and, well, that’s it. They work just fine, but to use them for anything else (like datalogging or control or…) they need a bit more work. The good news is that [Thomas Scherrer], alias [OZ2CPU], just did that reverse engineering work for us.

Inside these budget power meters, you’ll find an LCD driver, a power-monitoring chip, and an STM32F030, which is a low-cost ARM Cortex M0 chip that’s fun to play with on its own. [Thomas] traced out the SPI lines that the power-monitoring chip uses to talk to the microcontroller and broke in to snoop on the signals. Once he got an understanding of all the data, tossing an ATmega88 chip on the SPI line lets him exfiltrate it over a convenient asynchronous serial interface.

If you’re going to do this hack yourself, you should note that the internals of the power meter run at line voltage — the 3.3 V that powers the microcontroller floats on top of the 230 V coming out of [Thomas]’s wall plug. He took the necessary precautions with an isolation transformer while testing the device, and didn’t get shocked. That means that to get the serial data out, you’ll need to use optoisolation (or radio!) on the serial lines.

Now that we know how this thing works on the inside, it’s open-season for power-management hacks. Toss a mains socket and an ESP8266 in a box and you’ve got a WiFi-logging power meter that you can use anywhere, all for under $20. Sweet.

Google Contest Builds More Efficient Inverters

A few summers ago, Google and IEEE announced a one million dollar prize to build the most efficient and compact DC to AC inverter. It was called the Little Box Challenge, with the goal of a 2kW inverter with a power density greater than 50 Watts per cubic inch.

To put this goal into perspective, the DC inverter that would plug into a cigarette lighter in your car has a power density of about 1 or 2 Watts per cubic inch. Very expensive inverters meant for solar installations have a power density of about 5 Watts per cubic inch. This competition aimed to build an inverter with ten times the power density of what is available today.

Now, the results are in, and the results are extremely surprising. The best entry didn’t just meet the goal of 50 W/in³, it blew the goal out of the water.

The winning entry (PDF) comes from CE+T Power, and comes in a package with a volume of 13.77 in³. That’s a power density of 143 W/in³ for a unit you can hold in the palm of your hand. The biggest innovations come from the use of GaN transistors and an incredible thermal management solution.

Other finalists for this competition include Schneider Electric Team from France that managed a 100 W/in³ and a Virginia Tech team that managed a power density of 61.2 W/in³.

Thanks [wvdv2002] for the tip.

DIY AC for the Hot Shop

Working out in the shop is usually super fun but if it’s summertime, watch out, it can get hot! We’ve all been there and we’ve all wished we could do something about it. Well, woodworker and general DIYer [April] has stepped up to the plate and built a portable low-buck AC unit to cool her shop down to an acceptable temperature.

The unit is very simple and starts off with an old thrift store cooler. A hole is cut in the back of the cooler to make room for a fan that is directed to blow air inside the cooler and across blocks of ice. The air cools down as it passes over the ice and leaves out the top of the cooler through five 90-degree PVC elbows. After all the inlets and outlets were caulked, the entire unit was given a monochromatic black paint job.

[April] says you can feel the cool air blowing from about 5 feet away from the unit. She has measured the output air temperature to be 58-62ºF. If using loose ice cubes, the unit will work for 2-3 hours. Freezing milk jugs full of water gets about 5 hours of use.

Scope Noob: Bridge Rectifier

Welcome back to this week’s installment of Scope Noob where I’m sharing my experiences learning to use my first oscilloscope. Last week I started out measuring mains frequency using an AC-AC wall wart adapter. Homework, for those following along, was to build a bridge rectifier and probe the signals from it. Let’s take a look.

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