Wednesday, October 13, 2010

P.S.A. that can be viewed from Outer Space!

This is what my front lawn currently looks like from across the street. A giant reminder of every citezen's civic duty. (I'm hoping that those americans on the Mir space station have a way to mail their ballots, since online voting will not be available anytime soon. )

Supplies for the project:
  1. x-mas lights
  2. extension cords
  3. a light-sensetive power switch
  4. Coat hangers

I found it helpful to start with a scale drawing, and some quick estimaions on how many lights you need. The coat hangers will be turned into cord-steaks, to keep the lettering in place. Cut off the hook, and cut the middle of the flat bottom to end up with something resembling a mini croquet hoop. If you do not have enough coat hangers, go to the local cleaners and buy a dozen for a couple bucks. I used sheet-metal snips to cut the wire, but pliers would work too. The light-sensetive power switch costs $20 or so at your local hardware store - mine has options to turn on at dusk, and stay on for 2,4,6,8 hours, or until dawn. Be sure to pay attention to how many light strings you connect in series - this maximum should be listed on the packaging. Hopefully people will not try to steal/vandalize this rig. I have a Kieth Ellison sign, and so far have caught one potential thief red handed, have put it up after having it knocked over, and had to retrive it from the alley down the street after it was stolen.

Remember; Vote aerly, and vote often!

Wednesday, September 29, 2010

Turn your Computer into an Electric Space Heater

Need a little extra heat in your house? Want to solve all of the worlds problems with minimal effort? Try leaving your desktop computer on all the time, while donating the would be wasted processor cycles to scientific research.

Go to Progress through processors to download the app and get started. The BOINC program automatically downloads and executes smaller pieces of a larger problem, and sends the results back to the lab. The program can be run with lowered security credentials, and has features that will suspend the projects when the computer is active (have it run as a screen saver). Be sure to turn off hibernation or auto-suspend.

And while you are saving the world, try signing up for WindSource (or similar program), to balance out any carbon guilt you might experience.

Note: you can only use the "house heating" argument if you live in a cold climate, and at that, only half the year. If you live in a hot climate, chances are you are paying twice as much to do the same number of calculations. Although, you may find some of these projects worth the cost and donate the energy anyway.

The waste heat from computers escapes into the room, and is just as energy efficient as any space heater. If you have the AC running, the waste heat will just make your AC run longer.

I live in Minnesota, so this is a win-win for 10 months out of the year!

Sunday, August 22, 2010

DIY Baby Toy Suspension

So, I got this baby, and she likes to reach for things, but my arm gets tired of holding toys over her, so I built this toy holder thing. I've seen these at Target for $40, but you could build this for $11 (cloth cover not included).

I purchased 2 6ft rectangular steel stock: 1/2" x 1/8" for $4.69 each.
Also, a #6 bolt , washer and wing nut for $1 .

JC sewed these green cloth covers, and secured them with bows.

The toy suspender collapses for easy storage.

The steel needs to be bent into a smooth arc, for which you will need a jig. I used a workbench with a couple of bearings bolted to it. I made the mistake of trying to bend this by hand, which put a couple of kinks in the metal. Once the jig was set up, I fed the metal through the 2 bottom rollers (pictured left) and bent it to the left of the top roller. When feeding it into the jig, The first bend made a kink in the metal, but at least it is the same for all 4 legs. The result was having 4 sections of straight metal on the ends, with the center sections having a smooth arc.
Steel will retain a camber with a curvature less than that of the jig you feed it through. If you can, increase the curvature with multiple runs. (I was not able to do this with my setup... since the adjustment knobs were maxed out with the exact curvature I needed.)

Here is the center bolt+wing nut. Use a drill bit with the same gauge as the bolt for a snug fit.

I wrapped the feet in electrical tape for safety.
If you plan on using this on wood floor, you will need to tie the opposite ends of the rods together. The downward pressure from gravity and baby grabs will cause the legs to spread out. Putting this on carpet creates enough friction on the feet.

Now for hours of baby overstimulation!

Saturday, April 24, 2010

Power your bike lights with Faraday's law!

Is this a UFO? Why do the lights blink so consistently as a function of distance? Why not just get a battery?

A project of mine for a while has been to set up a lighting system for my bike that did not require batteries. You have seen the old-fashioned Schwinns with the generator on the back wheel going to the headlight. This is the same idea, except the entire back wheel becomes the generator. As the magnets pass by the coils, the changing field generates a (small) current, in quantities defined by Faraday's law

The materials needed for this setup:

4 cheap guitar pickups
8 neodymium bar magnets (I got mine here)
8 x Nylon 1/4" bolts w/ nuts
8 nuts and 8 bolts (bolts must have high iron content.)
2 Aluminum bars 1/8" x 1/2" X 5" long to attach the guitar pickups
20' of cheap speaker cable
16 rectifier diodes
1 box of LED color christmas lights
1 x 6000uF - 15000uF 20V Capacitor (axe-man)
1x 50uF 50V capacitor
1 x magnetic reed switch
6 x 800 - 1500 ohm resistors
1 x 100 ohm resistor
soldering iron / solder
wire strippers
a breadboard for testing configurations
a volt meter
lots of spare time
I have mounted neodymium magnets on the spokes, and mounted 4 cheap guitar pickups on the rear horizontal fork. The rusty bolts seen to the left were selected for their high iron content, which helps to conduct the field to the coils (a little wd-40 would have helped stop the rust). The other side has 2 aluminum support bars, with 2 copper pipe holders to attach it to the bike frame. Aluminum was not the best choice, since the field-effect will slow down the wheels. If you find a strong plastic, use that instead.
Believe it or not, the hardest part of this whole operation was getting the magnets to stay on the spokes while riding. I used nylon bolts, since I could saw them in half and put the nut on the other side of the spoke to clamp on to the spoke. The head of the bolt is mighty-puttied to the magnet. The ones that did not fall off within a week have lasted 2 years , and I have 4 of 8 left. The wheels get jerked around when you ride, so what ever method you use to attach these has to be good. If you use glue or putty, be sure to score the magnet and bolt surface before gluing.

The other consideration is the distance from the magnet to the coil as it passes by. The closer the better, but you will find that the wheel flexes when you turn, which will change that distance and maybe even cause the parts to collide. I keep mine about 5-8mm away.
Once the coils and magnets are mounted in place, the next step is to start on the circuitry.

Step 1: build a rectifier circuit that will take the AC pulses from the coils, and smooth them out with a low-pass filter to a safe DC voltage for that mega-capacitor you bought. Here is a crude circuit diagram (anyone have a good free circuit-drawing tool that runs on xp?)

The squiggles are the coils (there are 4, but I only drew 2...), representing an AC voltage source.

The arrows with the lines are the rectifier diodes. Each wire from a coil gets 2 diodes opposing in polarity. match all the diodes of 1 polarity together to form 2 main leads coming from the coils (a + and a -)
Step 2: the low-pass filter
The 1st capacitor on the left is the 50V/50uF - make sure this has a rating of 50V or more, since the coils can produce spikes that will short out smaller caps. The 100ohm resistor drains the voltage to the main cap between spikes.
Step 3: charge the main capacitor:
The Main cap should have a rating of 20V or more, with 6000uF of capacitance (for those confused while shopping, MFD is the same as uF ) Get the capacitors attached to the breadboard , and get the polarity figured before you solder anything.
Step 4: the magnetic reed switch:
Attach the magnetic reed switch on the rear fork somewhere in the vicinity of a passing magnet. This will be the strobe driver for the lights. As you can see on the left, electrical tape works just fine to secure this light-weight component. When in the presence of the magnetic field, the switch is pulled to the closed position.
Step 5: testing out the lights:
This next photo shows the breadboard in use. You can mix-and-match to a certain degree with LED's, but using only the LEDs from the xmas lights will allow you to assume that all of the lights have the same voltage drop and current draw. The 6 800-Ohm resistors are for equally dividing the current between all the LEDs, and keeping the lights from draining the capacitor right away. To organize this, I soldered a collection of 5 resistors to the positive lead of the main capacitor, and attached the wires going to the diodes from there. The advantage here is that a pair of diodes can share a negative lead, requiring only 3 wires for 2 led's. I put 2 LEDs in the back, 2 in the middle, and 1 in the front.

Step 6:
Solder the connections and manage the wires. - Be sure that the wires do not interfere with the break or shifting cables. Electrical tape works well. Get the wires in place and taped before soldering. wires that ware twisted together will not stay that way (and the oxidize too), so soldering is mandatory.

  • The LEDs are polar, so be sure to keep track of this when soldering.
  • mark the polarity on the wires to save time. (often I will use copper for positive, and steel for negative)
  • If people start conversations with you about how this is "green", inform them that far more energy went into the manufacturing these components than will ever be generated by them. My computer has even surpassed the amout generated while writing this blog. If your friends want to be green, have them all write a letter to our delegates urging them to cover Minnesota in windmills and solar panels, and to pay for it by taxing carbon.
  • don't try to look at the lights while riding, as this can be distracting and cause accidents.
  • have someone take a long exposure photo of you going by at different speeds.

Saturday, February 13, 2010

Fractal Koch Curve Radio Antenna

Want a radio antenna that will perform better than an antenna of similar size, and look pretty too?
Fractal antennae have been around since 1988, and can now be found in most cell phones. The basic idea is that any self-similar shape will produce better results for broad-band antenna design. See more information on this invention from the inventor himself.
This antenna is based on the koch curve, which is a special case of the DeRahm curve .
To start, download the graphic from wiki, and edit the 4th iteration to fit on a 8.5x11 sheet of paper. (I like to use Gimp, but you may have another preference.)
Print the rsult, and pin it to a cork board. Using pins, place a pin at each point on the curve. You will need to find a wire that is at least 8x((4/3)^3) + x inches long (about 18.96 + x"), x is to reach the radio, 3 feet , so make it 4 or 5 feet long. 8*(4/3)^3 represents the length of the triangle side at the first iteration, 8", multiplied by 4/3 for each iteration. Three iterations will increase the length by a factor of 4/3 to the 3rd power.
Next, you will put a pin at each point, and wrap the wire around that point. try to keep the wire exactly on the printed design. It helps to tape it down as you go to solidify your work. (I used packaging tape so the design is visible) This will take some time to complete (I took 2 hours or so...)
If you want to play around with self-similar shapes, there are some free fractal generators out there. Perhaps a 3d-fractal, a 3d printer with conductive plastic, and bam, youve got a 3d fractal antenna!

Thursday, January 21, 2010

Build your own Van de Graaff generator!

Last year I set out to build a van de graff generator, and after a year of tweaking, I have something that works (most of the time).

The first step in building these is understanding the principles of how it works. I will attempt an explaination here, but please check out the wikipedia here.

The charges for this machine accumulate on smooth conductive surfaces, which is the reason for the large metal globe at the top. Generally, the larger the globe, the higher the voltage. Inside the tube, there is a belt with 2 rollers. The belt is made from some electrically neutral material that is also an insulator (latex). The rollers are made from materials that have opposite polarizations in the triboelectric series. I chose aluminum(+) and silicone rubber (-).

When the belt comes in contact with one of these materials, electrons are either pushed to one side of the belt, or pulled from one side. In the case that electrons are pulled from the other side, the metal brush is there to provide replacement electrons. (the reverse is collecting the extra electrons). The belt moves along over the roller, and eventually seperates from the roller. When the belt is seperated from the roller, it will then have a charge on the outside of the belt. (for those concerned about the conservation of energy, dont worry. The work of seperating the clingy-belt from the roller equals the charge on the belt.)

A couple of mechanical challenges when building this:

  • Attaching the bearings to the pvc pipe so they do not move.
  • keeping the belt on the rollers
  • keeping the brushes in place
  • attaching the bottom roller to the motor

These are not really challenges for those that are mechanically inclined, but I found mighty-putty to of use in a couple of places.

Lets start with the metal globe at the top. This is essentially 2 14" steel salad bowls from ikea. a hole is cut in one of them for the pvc pipe to fit into, and they are taped together inside and out with aluminum tape. after you cut the hole, use a file to take off any sharp edges with a file.

The globe will be detachable, and connected to the brush by alligator clip. The wire must be inside the globe; The reason being, that the globe becomes the center of an electric field. If it has conductive points on the outside of the globe that are not smooth, they will spew electrons in a process called corona discharge. What you really want is electrical breakdown, which is more impressive.

Get a PVC pipe, and cut to about 4 or 5 feet. (if you have high ceilings, use a 6 foot pipe)

Cut a U shape into each end to mount the bearings on. Make sure the u-shaped cuts are lined up, which will line up the belt rollers for less friction. The bearings should fit snugly, so they do not vibrate.
Keep in mind you will be putting the metal globe over the top roller. For that reason, I used mighty-putty on the top roller to attach the axle to the bearing:
To make the roller, I used a 5/16" x 6" carraige bolt as the axle. For the top roller, I cut off the head. The bearings are held in place by bolts. (btw, axeman is a good place to get cheap bearings) The roller was made from a rubber sanding drum drill attachment, which was cut to size, and then screwed onto the bolt. The drum is then wrapped with electrical tape (or any tape you like) to give it the right shape. You want a "crown" in the middle of the roller, as the belt will naturally tend towards the center of the crown. (this is how you keep the belt on the roller)
The bottom roller (above) has an extra rubber roller with a notch to hold the drive-belt.
Aluminum Tape, usually used for ventilation ducts. Used to cover the bottom roller, and seal the globe halves together.
Silicone tape, used for plumbing, used to cover the top roller.

A toilet flange holds the pvc pipe upright. This is bolted to a wooden base, purchased from the IKEA damaged goods section. The brushes are made from braided copper grounding wire. Aluminum tape holds the brush in shape, and a screw/washer attaches it to the pipe, allowing you to align the brush before assembly.

The bearings for the bottom roller are held in place by plastic inserts.

The latex belt is made from one of those pilates yoga straps, but get the heavy-duty-tension version, for more durable, thicker latex. After the rollers and the bearings can be mounted, you will have an idea of how long to cut the belt. Make the belt 10% shorter than it needs to be, so that it will stretch and have some tension when it is on the rollers.
Use rubber cement to glue one end to the other. Cut on the diagonal for a stronger bond and less of a chance it will catch on a brush. When you put the belt on, make sure it is facing in the direction in which the seam will not catch on the brush.

Next, the electronics
Go to axeman or other surplus/hobby store to get a 120V AC 2-pole motor. Most hardware stores will have dimmer switches. You can buy 3-prong plugs and wire, but most likely you have this already. Be sure to look up which wire is hot, neutral, and ground. The hot should go to the switch first.
The wire on the left leads to the bottom brush. The right side attaches to the grounding leads on the other components.
The aluminum plate keeps he motor in place, acts as a heat-sink, and is conductive for grounding.
I attached the drive-belt-pulley with mighty putty.

You can use smaller serving bowls to make an electrode. drill a hole for a conductive handle, and attach handle to grounding wire.

With some aluminum tape and a jar, you have a Leyden jar. This will make the sparks 50% more painful.

Well, once you are finished, show it to your friends after they have had a couple, and they will be more likely to volunteer for shock therapy.