Supercapacitors In A Servo: The “Forever” Flashlight

May 30, 2018 by Ben James 21 Comments

The principle is well understood: use a motor in reverse and you get a generator. Using this bit of knowledge back in 2001 is what kick-started [Ted Yapo]’s Hackaday Prize entry. At the time, [Ted] was searching for a small flashlight for astronomy, but didn’t like dealing with dead batteries. He quickly cobbled together a makeshift solution out of some supercapacitors and a servo-as-a-generator, hacked for continuous rotation.

A testament to the supercapacitors, 17 years later it’s still going strong – leading [Ted] to document the project and also improve it. The original circuit was as simple as a servo, protection diode, some supercapacitors, and a LED with accompanying resistor; but now greater things are afoot.

A DC-DC boost converter enables constant power through the LED, regardless of the capacitor voltage. This is achieved by connecting the feedback pin of an MCP1624 switcher to an INA199 current-shunt monitor. The MCP1624 kicks in at 0.65V and stays active down to 0.35V. This is all possible due to the supercapacitors, which happily keep increasing current as voltage drops – all the way to 0.35V. Batteries are less ideal in this situation, as their internal resistance increases as voltage drops, as well as increasing with age.

When testing the new design, [Ted] found that the gears on his servos kept stripping when he was using them to charge capacitors. Though at first he attributed it to the fact that the gears were plastic, he realized that his original prototype from 2001 had been plastic as well. Eventually, he discovered the cause: modern supercapacitors are too good! The ones he’d been using in 2001 were significantly less advanced and had a much higher ESR, limiting the charging current. The only solution is to use metal gear servos

Want to read more about boost converter design? We have the pros and cons of microcontrollers for boost converters, or this neat Nixie driver for USB power.

Delightful Electromechanical Build Of A Jet Engine Model

February 24, 2018 by Steven Dufresne 9 Comments

[InterlinkKnight]’s jet engine model is a delight to behold and to puzzle out. Many of us have been there before. We know how to build something, we know it’s not the most up-to-date approach, but we just can’t help ourselves and so we go for it anyway. The result is often a fun and ingenious mix of the mechanical and the electrical. His electric jet engine model is just that.

Being a model, this one isn’t required to produce any useful thrust. But he’s made plenty of effort to make it behave as it should, right down to adding a piece of plastic to rub against a flywheel gear in order to produce the perfect high-pitched sound, not to forget the inclusion of the flywheel itself to make the turbine blades gradually slow down once the motor’s been turned off. For the N1 gauge (fan speed gauge) he built up his own generator around the motor shaft, sending the output through rectifying diodes to a voltmeter.

But the most delightful of all has to be the mechanical linkages for the controls. The controls consist of an Engine Start switch, Fuel Control switch and a throttle lever and are all built around a rheostat which controls the motor speed. The linkages are not pretty, but you have to admire his cleverness and just-go-for-it attitude. He must have done a lot of head scratching while getting it to all work together. We especially like how flipping the Fuel Control switch from cutoff to run levers the rheostat with respect to its dial just a little, to give a bit of extra power to the engine. See if you can puzzle it out in his Part 3 video below where he removes the cover and walks through it all.

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16-Cylinder Stirling Engine Gets A Tune Up

December 20, 2017 by Dan Maloney 33 Comments

Tiny catapults, kinetic sculptures, a Newton’s Cradle — all kinds of nifty toys can adorn the desk of the executive in your life. On the high end of the scale, a 16-cylinder butane-powered Stirling engine makes a nice statement, but when it comes equipped with a propeller that looks ready for finger-chopping, some mods might be in order before bestowing the gift.

We don’t knock [JohnnyQ90] for buying a rotary Stirling engine from one of the usual sources rather than building, of course. With his micro Tesla turbine and various nitro-powered tools, he’s proven that he has the machining chops to scratch-build one of these engines. And it wasn’t just the digit dicing potential of the OEM engine that inspired him. There was a little too much slop in the bearings for his liking, so he machined a new bearing block and shaft extension. With a 3D-printed shroud, a small computer fan, and snappy brass nose cone, the engine started looking more like a small jet engine. And the addition of a pulley and a small generator gave the engine something interesting to do. What’s more, the increased airflow over the cold end of the engine boosted performance.

Need the basics of Stirling engines? Here’s a quick look at the 200-year history of these remarkable devices.

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Smart DC Tester Better Than A Dummy Load

November 12, 2017 by Brian McEvoy 31 Comments

Testing DC supplies can be done in many ways, from connecting an actual load like a motor, to using a dummy load in the manner of a big resistor. [Jasper Sikken] is opening up his smart tester for everyone. He is even putting it on Tindie! Normally a supply like a battery or a generator would be given multiple tests with different loads and periodic readings. Believe us, this can be tedious. [Jasper Sikken]’s simulated load takes away the tedium and guesswork by allowing the test parameters to be adjusted and recorded over a serial interface. Of course, this can be automated.

In the video after the break, you can see an adjustment in the constant-current mode from 0mA to 1000mA. His supply, meter, and serial data all track to within one significant digit. If you are testing any kind of power generator, super-capacitor, or potato battery and want a data log, this might be your ticket.

We love testers, from a feature-rich LED tester to a lead (Pb) tester for potable water.

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Typhoon-proof Wind Turbine

October 9, 2017 by Bryan Cockfield 35 Comments

While wind energy is rapidly increasing its market share across the world, wind turbines are not able to be constructed everywhere that they might be needed. A perfect example of this is Japan, where a traditional wind turbine would get damaged by typhoons. After the Fukushima disaster, though, one Japanese engineer committed himself to building a turbine specifically for Japan that can operate just fine within hurricane-force winds. (YouTube, embedded below.)

The “typhoon turbine” as it is known works via the Magnus effect, where a spinning object directs air around it faster on one side than on the other. This turbine uses three Magnus effect-driven cylinders with a blade on each one, which allows the turbine to harvest energy no matter how high the wind speeds are. The problem with hurricanes and typhoons isn’t just the wind, but also what the wind blows around. While there is no mention of its impact resistance it certainly looks like it has been built as robustly as possible.

Hopefully this turbine is able to catch on in Japan so they can reduce their reliance on other types of energy. Wind energy has been getting incredibly popular lately, including among hikers who carry a portable wind generator, and even among people with just a few pieces of scrap material.

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Power Through A Hurricane

October 5, 2017 by Bryan Cockfield 45 Comments

When living in an area that is prone to natural disasters, it’s helpful to keep something on hand for backup power. While a large number of people chose to use generators, they are often unreliable (or poorly maintained), noisy, produce dangerous carbon monoxide, or run on a fuel supply that might not be available indefinitely. For truly reliable backup power, [Jay] has turned to a battery bank to ride through multi-day power outages.

While the setup doesn’t run his whole house, it isn’t intended to. One of the most critical things to power is the refrigerator, so this build focuses on keeping all of his food properly stored through the power outage. During the days following Hurricane Irma, the system could run the refrigerator for 10-11 hours, and the thermal insulation could keep everything cold or frozen overnight. Rather than using solar panels to charge the batteries, the system instead gets energy from the massive battery of his electric vehicle. [Jay] was out of power for 64 hours, and this system worked for him (and at a better cost) than a generator would have.

With the impact of major storms on many areas this year, we’ve been seeing a lot of interesting ways that people deal with living in areas impacted by these disasters. Besides riding through power outages, we’ve also seen the AARL step in to help, and also taken a look at how robust building codes in these areas help mitigate property damage in the first place.

Reviving A $25 Generator

September 22, 2017 by Adam Fabio 35 Comments

[Jennies Garage] found a used and abused inverter based generator in the clearance section of his local home improvement store. The generator had been returned on a warranty claim and was deemed uneconomical to fix. Originally $799, [Jennies Garage] picked it up for just $25. He documented his quest to get the device running with a trio of videos.

The generator had spark, but didn’t want to fire. The only obvious problem was the fact that the machine had been overfilled with oil. There was little or no compression, but that is not uncommon with modern small engines – many of them have a compression release mechanism which makes them easier to start.

With all the obvious problems eliminated, the only thing left to do was tear into the engine and figure out what was wrong. Sure enough, it was a compression issue. The overfull oil condition had forced engine oil up around the piston rings, causing them to stick, and snapping one of the rings. The cylinder bore was still in good shape though, so all the engine needed was a new set of rings.

That’s when the problems started. At first, the manufacturer couldn’t find the rings in their computer system. Then they found them but the rings would take two weeks to ship. [Jennies Garage] isn’t the patient type though. He looked up the piston manufacturer in China. They would be happy to ship him complete pistons – but the minimum order quantity was 5000. Then he started cross-referencing pistons from other engines and found a close match from a 1960’s era 90cc motorcycle. Ironically, it’s easier to obtain piston rings for an old motorcycle than it is to find them for a late model generator.

The Honda rings weren’t perfect – the two compression rings needed to be ground down about 1/2 a millimeter. The oil ring was a bit too thick, but thankfully the original oil ring was still in good shape.

Once the frankenpiston was assembled, it was time to put the repair to the test. [Jennies Garage] reassembled the generator, guessing at the torque specs he didn’t have. The surgery was a complete success. The generator ran perfectly, and lit up the night at the [Jennies Garage] cabin.

If you’re low on gas, no problem. Did you know you can run a generator on soda? Want to keep an eye on your remote generator? Check out this generator monitor project.

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