[Caleb] was given a tiny LED flashlight which has a crank used to charge it. Unfortunately it wasn’t holding a charge, and constant cranking didn’t work very well either. He cracked it open to find a single lithium button cell. Instead of using a drop-in replacement he soldered in his own super capacitor.
The stock device is remarkably simple. It uses a standard DC motor as the generator. It’s connected to the crank using a set of gears, with the two red wires seen above connecting it to the control board. Four diodes make up a bridge rectified and apparently feed directly into the battery. No wonder that cell went kaput!
But this orientation isn’t bad for using capacitors. They can be charged directly and the switch which attaches the LEDs to voltage doesn’t interfere with their operation. The last problem was making room for them in the case. [Caleb] considered a few different approaches, but ended up just heating the plastic enclosure until it could be deformed to make room for the additional parts.
This project is in one of our favorite categories; the kind where asking “why?” is the wrong question. [Berto A.] built the device after observing some power generation by placing a large magnet next to a mechanical relay coil and quickly clicking the relay’s lever. From this humble beginning he built up the RattleGen, a bicycle spoke driven generator.
To get the most power possible he searched around for a massive relay and found one which was originally meant for telephone exchanges. He cut the case open and strapped a big bar magnet to the side of the coil. Next he fabricated an arm which will press against the relay’s lever. To that he added a small wheel which is pressed each time a spoke from the bicycle passes by it. This repeated clicking of the relay lever generates a current (and a rattling sound) that is harvested by the joule thief circuit built on some protoboard. An LED is illuminated, with excess current stored in the capacitor bank. Don’t miss the build and demonstration video after the break.
Continue reading “Rattle generator is a new type of dynamo for a bicycle”
Here’s a thermoelectric generator which [x2Jiggy] built. The concept uses heat from a flame, biased against cooler temperatures produced by that huge heat sink making up the top portion of the build to produce electricity via the Peltier effect.
The build is passively cooled, using a sync assembly that takes advantage of heat pipes to help increase the heat dissipation. A nearly flat heat sink makes up the mounting surface for the hot side, which faces down toward a flame driving the generator. [x2Jiggy] started the project by using a can, wick, and olive oil as the heat source. He managed to get about 2V out of the system with this method. What you see here is the second version. It swaps out the olive oil lamp for an alcohol stove. The cans with holes punched in them act as a wind screen while also providing a stable base. This rendition produces about 3V, but it doesn’t sound like there are any precise measurements of what it can do under load.
This is the control and monitoring hardware which [Jack] built for his campfire electricity generator. He’s done an amazing job to get this far. You can see he’s pulling 1 Amp at 14.2 Volts off of the system. But there one gotcha that’s still plaguing him.
The rig uses a big metal plate as a heat sink over the campfire (which is simulated by a cooking stove for testing). On the back of that plate is an array of Peltier coolers which generate electricity based on the temperature difference from one side to the other — it’s the same theory behind candle generators. The cold side has a heat sink with water running through it. What you see above are three relays which switch between using the Peltiers in series or in parallel based on their voltage output. You can’t really make it out there but there’s a radiator and recirculating pump to the right which are used to cool the water. The gotcha we mentioned is that the radiator can’t quite keep up with the heat of the fire. To get the results seen above [Jack] is running cold water from the tap through the radiator. But maybe if this were used in the winter the water could be circulated through a big box full of snow. Just keep shoveling it in to keep up the electrical potential!
After the break we’ve embedded part four of the project video as it shows off the array of peltier coolers quite well. You will also see part five (radiator and recirculating pump testing) from which this image was taken.
Continue reading “Peltier campfire generator put out 14W (kind of)”
We’re not really interested in building a dummy load like this one for ourselves. But the concepts behind its design make for a nice little mental exercise as you read your way through the build description. [Pabr] wanted to build a dummy load which could be used to test a cheaply made gas generator. He wanted it to be as simple as possible, while providing a range of different loads. What he came up with is this monotonically adjustable load tester which uses gray codes for switching.
The video after the break does a good job of explaining the motivation for the design. Grey coding ensures that just one bit changes at a time. The example he uses to show the importance of this is when binary code transitions from 7 (0b0111) to 8 (0b1000). Three digits have been turned off and one has been turned on. Since he’s using light bulbs for his load this will turn off 700 Watts and then switch on 800W. That sudden jump in power draw can cause all kinds of problems with the generator’s engine. But the system he wired up will ensure that each flip of a switch moves in smaller steps.
Continue reading “Dummy load uses gray code to adjust load in small steps”
It seems like tinkerers are always being tapped to build or repair exhibit hardware. This time around it’s [Dino’s] turn. He’s been asked to alter a light bulb efficiency demo so that it includes an LED option.
The idea here is that you crank a generator to power different types of light bulbs. There’s an ammeter built in, but possibly the best feedback is knowing how hard you have to crank to illuminate the most inefficient choice. As it stands there is a toggle switch to choose between incandescent and CFL bulbs. [Dino’s] solution is to use a three-position rotary switch. He removes the toggle switch and replaces it with a socket for the LED bulb. A new location for the rotary switch is chosen and he does a bit of work to get it mounted securely. If you haven’t worked with this type of switch before he takes the time in the video after the break to explain how they work.
Continue reading “Light bulb efficiency exhibit updated with LED bulb option”
[Niklas Roy] is at it again. He’s applying wind power to his projects by using umbrellas. He was inspired by the shape of an anemometer, and umbrellas turned out to be a great choice because they’re cheap and easy to find.
Anemometers measure wind speed by capturing it with egg-shaped sails (in fact, we’ve seen them built from plastic Easter eggs before). The umbrellas have a much larger area and will capture more wind. Still it’s a big jump from measuring wind speed to generating energy. That’s why he’s not trying to generate electricity, but instead using the mechanical force directly. He took a page from one of last year’s projects and used the dual umbrella setup to power a music box, thereby reinventing the wind chime. The triple-umbrella unit seen above serves as a bubble machine, driving a series of plastic rings through a soapy solution and letting the wind do the rest. We’ve embedded his demo video after the break.
Continue reading “Umbrella-based windmills”