Anemometer from CDROM motor, and plastic Easter egg halves

Written by: roboguru

Picture of Anemometer from CDROM motor, and plastic Easter egg halves

Anemometer from CDROM motor, and plastic Easter egg halves

I have a desire to build one or two small wind generators to charge lead acid batteries. To see if I have enough wind to make it worthwhile, I made an anemometer (wind measuring device) out of scraps and junk. (This cost me nothing except materials I had on hand) I have just completed calibrating and installing one I built using THIS as the inspiration. 

Materials needed:
1 old (preferably dead) CDROM from computer (source for motor)
3 plastic Easter egg half shells, the round ones.
3 popsicle or craft sticks.
1 very small fishing bobber
2 part Epoxy
16 to 18 inches of 3/4 inch schedule 40 PVC Pipe
1 PVC elbow, 1/2 thread X 3/4 slip (Glue)
1 PVC 1/2" pipe cap (slip)
1 PVC elbow, 3/4 X 3/4 slip (Optional)
1 PVC 1/2" pipe inch nipple; threaded one end at least 3 inches long will do
1 half inch PVC slip coupler.
1 Nylon screw/bolt, (I used a 1/4-20 coarse thread bolt, size is somewhat optional)
2ft minimum of 18 ga zip cord
2 #6 machine screws and 6 #6 nuts
4 crimp ring lugs for that fit the 18 Ga wire and #6 screws.
Dielectric grease
6x6 inch scrap of 3/4 or 1/2 plywood.
2 U-bolts to fit the 3/4 PVC pipe (and nuts and washers)
2 U-bolts to fit the mounting mast pipe (and nuts and washers) my mounting pipe was a plumbing vent on my roof...
Phone wire or CAT5/6 cable (Length depends on where mounted)
Paint (optional) primer, in whatever color(s) you chose to paint it.
Small cheap ass analog VOM (bargain bin type) with a scale for 50ma readings (other motors may need to use a different scale, but the motor I used works perfect with the 50ma scale)

Tools Needed:
Hack saw.
Exacto back saw
Hand drill or drill press
5/8 drill bit
1/4-20 tap
Drill bit for 1/4 -20 tap (#7)
1/8 drill (clearance hole for machine screws)
5/16 drill (clearance hole for plywood to clear the U-bolts)
Counter sink for deburring holes (Optional)
Center square
30/60 triangle
3 small clamps or welders vise grips. (Or combination of them)
Epoxy mixing tools (paper Dixie cups and craft sticks work well)
Sandpaper, (belt sander is a nice to have, but I used mine quite a bit)
Flush cutting wire cutters
4 lb peanut butter jar lid (used as a gluing fixture)
Wire strippers
Masking Tape
Digital VOM (for testing)
Obligatory warning: I used some power tools on this project. None are absolutely necessary strictly speaking, but if you chose to do so, you do so at your own risk. 

Step 1: Step 1 - Getting the motors(generators)

Picture of Step 1 - Getting the motors(generators)

Getting the CDROM apart is not too bad, and you will find there are 3 motors in one of these guys. One for the tray to come in and out, one to spin the CD and one to move the laser back and forth. All had a different form factor, All could have been used (meaning the generated current when spun) and two looked suitable for the anemometer, as they had a good gear hub on the shaft. 

I liked the tray motor as it slip fits inside a 1/2 inch PVC pipe perfectly once the pipe was drilled out slightly using the 5/8 inch drill. I wanted to house the motor in a way to weather, or at least rain proof it. Certainly there are many ways to do this. The motor had a small plastic beveled gear, with a flange that had slots in it (probably for a motor control bit&) and that provided a good place to epoxy the popsicle stick arms to. 

Once you have selected the motor, verify it will generate a current using your Digital VOM, (or the Cheap ass analog VOM) measure volts or milliamps, it matters not at this point, just make sure it does actually generate something. (You dont want to get done and find the motor was DOA) 

If it does, you have a miniature generator! 

Step 2: Step 2 - Making the Mount for the Motor

Picture of Step 2 - Making the Mount for the Motor

Mounting the motor is mostly described above, I cut my nipple section off a busted off sprinkler riser that I had from a sprinkler repair (darn skateboard Nazis...), one end still had good threads and I cut it to about 3 inches long (not critical at all). Drill out the 1/2" PVC nipple at one end (if needed) using the 5/8ths inch drill, this allowed my motor to slip in snugly. 

I still didn't like the weather exposure the motor had, so using a hacksaw I cut the 1/2 coupler in half, and using the largest countersink I have, chamfered the inside cut edge so water would dip off the outside edge, and using my belt sander, clamped upside down in my vise, beveled the upper edge so it would not hold water drops. The coupler was then epoxied onto the cut end of the nipple. This could be done with PVC cement, but the epoxy leaves a nice bead and can be smoothed out. 

I then (with the motor removed) drilled and taped the pipe with the 1/4-20 tap so the nylon bolt would hit the motor and hold it in. 

The idea is the motor will be mounted facing down so it will not collect rain inside, and any water drips off the housing. A thin plastic sheet could also be cut and glued in place to act as a shield, but I haven't done this as yet. Cut a thin sheet the ID of the coupler drip edge, punch a small hole in the center that will clear the motor shaft, cut with scissors from the outside to the center hole (the cut is needed as the gears are on to stay I've found) and slip this cut ring over the motor shaft, then glue in place with RTV to the coupler. This leaves a very small space for moisture or bugs to get inside, and still is a no drag solution. 

OK, The motor housing assembly is now ready for assembly, set it aside. 

Step 3: Step 3. Cups and arms

Picture of Step 3. Cups and arms

I took flush cutting wire cutters and trimmed off the stepped lip Easter egg cups had. It is a 50/50 chance whether you will need to do this... I then used the belt sander in the vice to carefully sand them even. You could remove this step with just the belt sander, but trimming first is faster. 

The 3 popsicle/craft sticks (now called arms forward from here) I sanded smooth, and beveled both long edges; both sides to minimize any wind drag. Again this was done on the belt sander. 

I notched the Easter egg shells on one side to fit the arms using the Exacto Back saw. Again using the Exacto back saw, I cut the arms at one end to match the shallow curve of the egg cups, leaving a nub slightly longer than the cup wall (See pics) opposing the arm notch on the cups I drilled a small hole to mate with the arms nub. This provides a mechanical lock so the cup isnt relying entirely on the epoxy. 

Before epoxying the arms to the cups, I notched the opposite arm end to match the gear hub of the motor. (Jump ahead to the next step to see how the arms align to the motor hub, as it may also be required to trim the arms to clear each other at the hub. This is best done before drilling the clearance hole in the peanut butter jar glue fixture.) 

The arms were a press fit into the cups when done, and I epoxied all six (per arm) facing joint surfaces, leaving a small radius of epoxy filling the joints. A small dab was put into the hole to cap it. The arm cup assemblies were all primed and painted except where they would get epoxied onto the hub and flange of the motor. (I don't believe in epoxying structural joints over paint). 

I think it important to paint/seal the wood arms to keep them from warping. 

Step 4: Step 4 Assemble the arms and cups to the motor’s hub

Picture of Step 4  Assemble the arms and cups to the motor’s hub

This is where the 4 lb peanut butter jar lid comes in. (You may want to do some of this while making the arms, especially for getting them to a tight fit on the hub and to each other) I used a center square to find the center of the top of the lid. I also marked one line across to use as a base line. Using a 30/60 triangle, I accurately marked out lines at 120 degrees from each other (360/3 =120). Then I marked parallel lines to these three lines so I could see to clamp the arms to the lid at the required 120 degree spacing.

Before gluing, but after laying out the arms and making them, you need to drill a good size clearance hole in the center of the lid. This allows you to glue the arms without gluing anything to the lid (see pic). Clamp the arms to the marked lines (actually for the gluing Masking Tape will do the trick, I did use the clamp and vice grips when I was trimming the ends of the arms however) , and align to the motor's hub. BE SURE TO GET ALL THE CUPS FACING THE SAME DIRECTION ROTATIONALLY!

Once you are sure all is correct, lift the motor out, coat the arm surfaces that will contact the hub with epoxy, and the hub where the arms will go, and place the motor/hub back firmly onto the arms. I added epoxy to the back side of the hub so the epoxy thoroughly saturated the tiny holes in the hub. This is to insure the arms and hub stay together. Remember this thing will have to withstand high winds/stress at times. (I estimate as high as 1867 rpm in about 50 mph winds, assuming no frictional losses)

Let dry overnight. 

To cap the hub, (totally unneeded, I just wanted to make it look cleaner) I disassembled a red white bobber, and using the belt sander setup, ground one side (the one with the big hole) until it would fit over the glued hub joint. Then I plugged the remaining small holes (Epoxy) and painted it. It was then epoxied in place; I gave the cup/arms a spin and adjusted until I was satisfied the cap was centered, and let it dry.

The last step prior to final assembly is to attach enough 18 ga. zip wire to replace the way too weak wires on the motor (Both fell of just in handling it.), a fairly simple and very quick solder job.

Step 5: Step 5 Semi final assembly of the motor housing to the support structure

Picture of Step 5  Semi final assembly of the motor housing to the support structure

I used epoxy instead of PVC cement to glue the elbow to the 3/4 inch pipe section then screwed the motor housing into the threaded part of the elbow. I had originally planned on mounting the 3/4 PVC to a vertical mast, but if you use another 3/4 x 3/4 slip elbow, you can also use more 3/4 PVC pipe to make the riser. (20-20 hindsight...) Either way, you need to cap the pipe assembly, but before doing so, drill two 1/8 holes on the cap so you can use the machine screws to make contact studs for wiring the thing. 

Before going further and gluing the cap on, I painted most of the pipe assembly (except for the end the cap goes on) using both primer and paint. If you skip this step the PVC will deteriorate in the sun. 

Once the paint is dry, run the motor wire through the pipe (this could get tricky if you have the added mast, so run a drag wire inside as you assemble it), and crimp in the lugs. Since this is going to be outside, and corrosion is a factor, coat the wire with dielectric grease before crimping and coat the lugs before screwing the lugs down inside the cap. Double nut the outside (locking them solidly) and leave the screws long enough so you can put wire lugs and nuts on the outside. 

Mask the connector lugs off and complete painting the capped pipe. 

Step 6: Step 6 Calibration

Picture of Step 6 Calibration

I made a test to see how much resistance I could measure in the expected 30-40 feet of phone wire, and I checked it by measuring the voltage drop across a AA battery for that distance. It was less than one 1/1000 of a volt, so I'm not too worried about it. 

I set my completed anemometer up, taped to a length of metal conduit, and temporarily wired to the cheap ass analog VOM. I did try various scales and even the DC voltage scales, but the 50ma scale worked the best. Once we got past the preliminary testing to see how to use it (in a car with it hanging out the passenger window; dont hit something when you are moving, it could be disastrous to both you and whatever you hit), I waited for a morning that was dead calm. 

I also learned we needed to find a street with no trees, houses or other obstructions nearby. At anything over about 10-20 MPH, passing even a side street causes the thing to surge, I think due to the car's frontal wave and stationary objects reflecting it back. 

Once we had all that, (as well as no traffic, again other cars can affect this thing, it is REAL sensitive) we tested at 10 MPH (had to estimate 5 MPG) 20, 30 40 ad even 50 MPH. Then we double checked it. I had previously cut a white label so I could see the arc of the reflecting scale, and made a tic mark for each test speed. 

What I found was that for 20, 30, 40, and 50 MPH the meters 0-50 scale matched exactly, (YMMV), and that 5 and 10 MPH do not match any standard step. 
The scale is constant from 20 to 50 MPH, at 5 and 10 MPH the marks read differently, probably due to low rotation efficiency fall off. (At those slower speeds it is barely rotating...)

Step 7: Step 7 Mounting it up high

Since I live in a suburb,with other houses, trees, (I planted lots of big ones twenty years ago&) and my two story addition around, I didnt have a lot of good choices. Ideally a pole taller than the house or surrounding trees would be used.

I wound up mounting onto a sewer vent pipe (temporarily, the bloody thing is plastic I discovered), and ran the phone wire down to the wife's office. 

The Analog VOM back cover got removed and two holes were drilled; one smaller above a larger one just bigger than the head of the small box nail I used to hang it on. (I had to do this twice, the first hole set was exactly where the back of the meter assy was...)

And it works great!

Here is a little video of the anemometer in action one with the wind barely moving (0-5 MPH).


My future plan is to get it on its own pole, and higher than the trees around my house.

I'm also going to try seeing if this will fire a small red LED using the Joule Thief  technology, (I seriously doubt the voltage gets high enough to fire it without it), to use as a high wind signal. It would be great if this kicked in at around 30 MPH or so (We normally get quite a bit of wind, hence my interest in a wind generator.)