A Pedal Powered Cinema

May 10, 2015 by Rick Osgood 10 Comments

When the apocalypse hits and your power goes out, how are you going to keep yourself entertained? If you are lucky enough to be friends with [stopsendingmejunk], you can just hop on his pedal powered cinema and watch whatever movies you have stored on digital media.

This unit is built around an ordinary bicycle. A friction drive is used to generate the electricity via pedal power. In order to accomplish this, a custom steel stand was fabricated together in order to lift the rear wheel off the ground. A 24V 200W motor is used as the generator. [stopsendingmejunk] manufactured a custom spindle for the motor shaft. The spindle is made from a skateboard wheel. The motor is mounted in such a way that it can be lowered to rub the skateboard wheel against the bicycle wheel. This way when the rear bicycle wheel spins, it also rotates the motor. The motor can be lifted out of the way when cruising around if desired.

The power generated from the motor first runs through a regulator. This takes the variable voltage from the generator and smooths it out to a nice even power signal. This regulated power then charges two Goal Zero Sherpa 100 lithium batteries. The batteries allow for a buffer to allow the movie to continue playing while changing riders. The batteries then power the Optomo 750 projector as well as a set of speakers.

Bike-Powered Everything

April 15, 2015 by Rich Bremer 37 Comments

It’s hard to argue that bicycles aren’t super handy. They get you from point A to B in a jiffy with little effort. Since these machines are so simple and convenient, why not use them for things other than transportation? Well, [Job] set out to do just that.

[Job’s] starts with a standard single speed bike and adds a few parts. First, a stand is installed to the back axle. When in the down position, it lifts the rear wheel off of the ground and provides support so the bike does not tip over. When flipped up into the ‘up’ position the stand creates a rack for holding goods and the bike can be pedaled around in a normal manner.

Next, a jack shaft made from a bike bottom bracket and crank is installed up front in between the top tube and down tube of the frame. On one side of the jack shaft is a sprocket and the other side is a large pulley. When converting to what [Job] calls ‘power production mode’, the chain going to the rear wheel is removed from the crank sprocket and replaced with a chain connected to the jack shaft.

With the rear stand down supporting the bike and the pedals now powering the jack shaft and large pulley, it is time to connect the bike to any sort of machine. A belt is slung around the pulley and connected to a matching pulley on a power-hungry machine. This dual-purpose bike has powered a rice thresher, peanut sheller, water pump, table saw and even a wood lathe!

[Job] set out to create a simple and inexpensive way to make a bike even more useful than just riding around town. We think he did just that. For more bike-powered stuff, check out this generator.

Retrotechtacular: Basic Telephony In The Field

March 24, 2015 by Kristina Panos 7 Comments

Here is a great introduction to a practical application of electromagnetic theory—the field telephone. It’s a training film from 1961 that covers the sound-powered, local battery, and common battery systems along with the six basic components they use: generators, ringers, transmitters, receivers, induction coils, and capacitors.

Clear illustrations and smart narration are the hallmarks of these Army training films, and this one begins with a great explanation of generator theory. The phone’s ringer uses electromagnetic attraction and repulsion to do the mechanical work of striking the bells. Similarly, the sound waves generated by a caller’s speech move an armature to create an alternating electrical current that is transmitted and converted back to sound waves on the receiving end.

In the local battery system, the battery pushes pulsating DC to carry the voice transmission. An induction coil increases the capabilities of this system, but capacitors are required to filter out the frequencies that would overload the receiver, passing only the higher speech frequencies.

In order for several stations to communicate, the use of a switchboard is required to patch the calls through. There are many advantages of a common battery system with regard to call switching: no local battery is necessary, nor is a generator needed at each station. Calls are easier to place, and communication is much faster.

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3D Printed Wimshurst Machine

February 6, 2015 by Rick Osgood 23 Comments

Steampunk extraordinaire [Jake von Slatt] has released his latest creation. This time he’s built a Wimshurst machine from mostly 3D printed parts. The Wimshurst machine is an electrostatic generator and was originally invented in the late 1800’s by James Wimshurst. It uses two counter-rotating disks to generate an electrostatic charge which is then stored in two Leyden jars. These jars are also connected to a spark gap. When the voltage raises high enough, the jars can discharge all at once by flashing a spark across the gap.

[Jake’s] machine has a sort of Gothic theme to it. He designed the parts using Autodesk’s 123D Design. They were initially printed in PLA. Skate bearings were used in the center of the disks to ensure a smooth rotation. The axle was made from the fiberglass shaft of a driveway reflector. The vertical supports were attached the base with machine screws.

The Leyden jars were made from sections of clear plastic tube. The caps for the jars were 3D printed and are designed to accept a short length of threaded 1/8″ pipe. Copper wire was used for the interior contacts and are held in place with electrical tape. The metal sectors on each disk were made from pieces of cut aluminum tape.

You may be wondering how this machine works if it’s almost entirely made out of plastic. [Jake] actually painted most of the parts with a carbon paint. This makes them electrically conductive and he can then use the parts to complete electrical circuits. Unfortunately he found this to be rather ineffective. The machine does work, but it only produces sparks up to 1/2″ in length. For comparison, his other machine is capable of 6″ sparks using similar sized Leyden jars.

[Jake] actually tried rebuilding this project using ABS, thinking that the PLA may have been collecting moisture from his breath, but the result is still only 1/2″ sparks. He suspects that the bumpy surface of the plastic parts may be causing the charge to slowly leak away, preventing a nice build up. He’s released all of his designs on Thingiverse in case any other hackers want to give it a whirl.

[Mike] Shows Us How To Use An Armature Growler

February 2, 2015 by Adam Fabio 24 Comments

[Mike] has put up a great video on his [SmallEngineMechanic] YouTube Channel about a tool we don’t see very often these days. He’s using an armature growler (YouTube link) to test the armature from a generator. Armature growlers (or just growlers for short) were commonplace years ago. Back when cars had generators, just about every auto mechanic had one on hand. They perform three simple tests: Check armature windings for shorts to other windings, for open windings, and for shorts to the armature body. [Mike’s] particular growler came to him as a basket case. The wiring was shot, it was rusty, and generally needed quite a bit of TLC. He restored it to like new condition, and uses it to help with his antique engine and genset ~~addiction~~ hobby.

Growlers essentially are a transformer primary with a V-shaped frame. The primary coil is connected to A/C mains. The armature to be tested sits in the “V” and through the magic of induction, some of the windings become the secondary coils (more on this later). This means some pretty high voltage will be exposed on commutator of the armature under test, so care should be taken when using one!

Testing for shorts to the ground or the core of the armature is a simple continuity test. Instead of a piezo beep though, a short will trigger the growler to turn on, which means the armature will jump a bit and everything will emit a loud A/C hum. It certainly makes testing more interesting!

Checking for open windings is a matter of energizing the growler’s coil, then probing pairs of contacts on the commutator. Voltage induced in the windings is displayed on the growler’s meter. Open windings will show 0 volts. Not all the armature’s windings will be in the field of the growler at once – so fully testing the armature will mean rotating it several times, as [Mike] shows in his video.

The final test is for shorted coils. This is where things get pretty darn cool. The growler is switched on and a thin piece of ferrous metal – usually an old hacksaw blade, is run along the core of the armature. If a short exists, the hacksaw blade will vibrate against the core of the armature above the shorted windings. We’re not 100% clear on how the coupling between the growler’s primary and two windings causes the blade to vibrate, so feel free to chime in over in the comments to explain things.

Most commercial shops don’t troubleshoot armatures anymore, they just slap new parts in until everything works again. As such the growler isn’t as popular as it once was. Still, if you work with DC motors or generators, it’s a great tool to have around, and it’s operation is a pretty darn cool hack in itself.

Click past the break for [Mike’s] video!

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Cordless Drill Turned Into Bicycle-Powered Generator

December 6, 2014 by Rich Bremer 27 Comments

The bicycle is a great invention. It is an extremely efficient method of transportation, even more so than walking. So why not harness that efficiency for other things? [Tony] had that same thought so he ordered a bike generator but after waiting too long for the company to send it, he decided to make his own.

[Tony] is an bicycle enthusiast so he had an old bike and an old training stand he could use for the project. Generating electricity from pedaling the bike requires some sort of generator. Lucky for him, [Tony] happened to have a cordless drill that stopped going in reverse. Since he had since upgraded, this was the perfect candidate for the generator. The drill was mounted to the training stand so that a pulley inserted in the chuck pressed against the rear wheel. Wires were added to connect the drill’s battery connectors to a 12vdc to 120vac inverter. As the bike is pedaled, the rear wheel spins the drill, which spins the drill motor creating DC voltage. That DC voltage is then converted to AC by the inverter. With a multimeter connected to the output from the drill, it is easy to adjust the pedaling speed to keep the output in the 11-14v range which is required by the inverter.

In the photo above, you can see a light bulb being powered by the bike. However, the bike powered generator could not power the larger load of a computer. The remedy for this was to purchase a solar charge controller and a 12 volt battery. The bike charges the battery and the battery can power the computer through the inverter.

Hydropower From A Washing Mashine

September 1, 2014 by Marsh 53 Comments

Living off the grid is an appealing goal for many in the hacker community, perhaps because it can fulfill the need to create, to establish independence, to prepare for the apocalypse, or some combination of all those things. [Buddhanz1] has been living off the grid for awhile now by harnessing power from a nearby stream with an old washing-machine-turned-generator.

He started with a Fisher & Paykel smart drive, which he stripped down to the middle housing, retaining the plastic tub, the stator, the rotor, the shaft, and the bearings. After a quick spot check to ensure the relative quality of the stator and the rotor, [Buddhanz1] removed the stator and rewired it. Unchanged, the stator would output 0-400V unloaded at 3-4 amps max, which isn’t a particularly useful range for charging batteries. By rewiring the stator (demonstration video here) he lowered the voltage while increasing the current.

The key to this build is the inclusion of a pelton wheel—which we’ve seen before in a similar build. [Buddhanz1] channeled the water flow directly into the pelton wheel to spin the shaft inside the tub. After adding some silicon sealant and an access/repair hatch, [Buddhanz1] painted the outside to protect the assembly from the sun, and fitted a DC rectifier that converts the electricity for the batteries. With the water pressure at about 45psi, the generator is capable of ~29V/21A: just over 600W. With a larger water jet, the rig can reach 900W. Stick around for the video after the break.

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