Author:masynmachien author's websiteMy main hobby is developing creative workshops for children. Since several years now I have been organising those, mainly voluntary at the school mydaughter is attending: Leefschool Klavertje Vier. My workshops most often involve a scientific or rather technical topic: rockets, mousetrap cars, solarpowered vehicles, hovercrafts...Another hobby of mine is sculpting things, mainly dolls...
Yvon Masyn
Intro: Mass producing LED powering wind turbines in a kids workshopThe Junior Wind Turbine project. For my latest workshop in my daughter’s school I wanted to let the children each make a wind turbine. It wanted it to be functional, powering a small light and it neededto be cheaper than 6 Euro a piece, which ruled out any commercial kits.
The workshop was for 20 kids, which ruled out scavenging hard discs motors or stepper motors and such. Low cost “toy” motors on the other hand need really high rpmto light up a small bulb or a led. Fortunately the type of motors used in solar cell driven toys and kits work better. And these are still available for under 2 Euro.
A small flashlight bulb was actually easier to get to glow than lighting a LED, when driving a 6 to 1 gear on a “solar grade” motor by hand. But it required too muchtorque for a small and simple wind turbine.
A LED worked with a turbine and a single step 6 to 1 gearing, but only at really high wind speeds, needed to get a high enough voltage. But I wanted the kids see itfunctioning, without having to wait for a strong wind. To apply a higher gear ratio in one step needed a larger gear wheel which I could not find at a low price. A two stepgearing gives to much friction with the cheap and simple construction techniques suitable for a kids workshop (remember we are talking about gearing up, which is morecritical to build quality).
But our good friend the Joule Thief came to the rescue. With this little circuit added, the LED lights up at a breeze. Moving the wind turbine by hand easily lights up theLED. I estimate it starts at wind speeds below 10km/h. And everything still holds up at strong winds.
Apart from attaching leads to the motor/generator in advance (“solar” motors are often sold with leads anyway) the circuit is built up without soldering, as I prefer toavoid that when working with 20 kids aged 6 to 12.
All that was left was making some “templates” for the steps that need accuracy and gathering the materials and I was ready for the workshop. Check the result in thevideo below and read how we built the wind turbines in this Instructable. If you like it, please give it your vote in the MakerBot Challenge.
My special thanks goes to Emma, for her assistance when taking extra pictures showing the detailed construction steps.
Step 1: Materials and toolsFor the turbine and tail vane:1 piece of 2mm thick balsa 10 cm by 40 cm or 4 pieces 10 cm by 10 cm4 bamboo (meat) skewers 30 cm long, about 3mm diametersome cellotape, at least 19mm widesupergluelarge gear (about 60 mm diameter, Opitec part 840088)a piece of scrap wood, 3 cm thick and about 6 cm by 6cm in size.some non-stick paper,1 small stick of hotmelt glue (low temp type when working with kids)a cabinet screw with an unthreaded part, fitting loosely the gear hole (4mm for the gear mentioned above), about 35 mm long. A brass screw will last longer in humidconditions, I found out screws with a nominal diameter equal to the gear hole, actually fit loosely.4 washers fitting the screwpaint and varnish (optional)
For the generator:a “solar grade” toy motor with 7cm leads (FF 130 “solar motor”, Opitec part 224176 works great, but needs leads to be soldered to the motor. The RF 300, Opitec224154, comes with leads, but is less resistant to rain)a small pinion gear of the same module as the large gear (Opitec 841187 with adapter 842022)a (steel spring) clamp fitting the motor/generator (Opitec 225074)a 25 mm long bolt and nut. I choose M3, allowing for all drilling to be done with a 3 mm bit.
For the Joule Thief:a ferrite toroid (e.g. Conrad 507997 or 508039)a 2N3904, BC 337 or equivalent transistora 1kOhm resistor1 to 3 LEDs (the clear ones are easiest to see lighting up in sunlight)2 times 20 cm of insulated thin gauge electrical wire (twisted strands from telephone or network cable are perfect)5 small cabinet screws, preferably brass (more durable contact). I choose shortest 3 mm diameter ones I found, allowing for all drilling to be done with a 3 mm bit.
For the masta 27 cm piece of 20mm diameter PVC electrical tubea 75 cm to 1 m long piece of 16 mm PVC electrical tube2 tie-wraps (pretty small ones are OK)a marble
a junior hacksawa flat working surface (theoretically 31 by 31 cm, but take double to work with some comfort)a hotmelt gun (low temp type when working with kids)a drill (preferably column-type) and a 3mm drill bitscrewdrivers fitting the screws and bolts usedsome templates can be made out of scrap wood as explained in the following steps
Image Notes1. For the workshop I cut these in four 10 cm by 10cm squares in advance>2. At one end the 16mm long diameter tube is cut with a sharp angle. This to helpsit being inserted into the soil.3. brass cabinet screws4. washers5. 30 cm bamboo skewers6. marble7. pinion gear8. joule thief parts9. 3 mm drill bit10. sawing template (see step 20)11. drilling template (see step 4)12. 3 cm by 6cm by 6 cm block of scrap wood (see step 3)13. non-stick paper
Step 2: Making the Turbine BladesThe turbine blades are made by sawing three of the balsa squares as shown. Keeping the turbine very light makes it very forgiving for inaccuracy’s and unbalance, butto help make the blades all the same size, I did make sawing templates.Three of the skewers are cut in half (it is a good idea to cut of a couple of mm of the sharp point, to limit the risk of anyone hurting herself or himself). Take care of thegrain of the wood. It should be close to perpendicular to the cut, or the blades will break easily.
The forth square and skewer are kept aside for the tail vane.
With some cellotape the skewers are provisionally attached to the blades as shown. The assembly is laid down on some anti-stick paper and some superglue is run in thejoint, (something I do myself for the younger kids). When the glue has set the rest of the tape is bent over and attached.
Step 3: Turbine ConstructionThe 3 x 6 x6 cm piece of scrap wood is prepared with a top of anti-stick paper and a central hole. With a small screw the large gear is attached to it. A washer is put inbetween to keep some distance from the hub, when the skewers are pushed in between as shown. With the skewers evenly distributed under the holes, tighten the screwjust enough to keep them in place when the assembly is on the table.
Make sure all the blades are pointing the same direction (clockwise or counter clockwise) and touch the flat working surface with their tip. This is obviously very importantto get a good angle. Now, pour hotmelt glue in the hole, taking care not to spill any on the gear's teeth (see how a piece of scrap cardboard can be used the help preventthat). Check if all blades are in the right position and let the glue set, before removing the screw.
You might want to reinforce the glued connection on the other side, but to my experience that is not needed unless the turbine is accidently dropped or something likethat.
Step 4: DrillingThe 27 cm piece of 20mm diameter PVC tube is prepared to be the central “support” onto which all other parts are attached. This means first some drilling has to bedone. All holes are 3 mm
Only one hole needs to be in an accurate position from one other, the others holes are not critical. First the hole for the motor/generator mount is drilled about 5 cm fromand goes completely through. The motor/generator mount is attached with a bolt and nut. There's a little trick to that: first the mount is attached hand tight, with the curveof the metal following the curve of the tube. When it is twisted to its final position the spring metal provides tension, locking the assembly into place.
Now comes the critical hole. It needs to be drilled perpendicular to the first one, and at a distance along the tube determined by the gears and motor/generator used (18mm with the Opitec parts mentioned above). The motor/generator mount can be bent a little to adjust for small errors, but taking care with this drilling will avoid this.Therefore a template fitting the tube and motor/generator mount was made as shown. This hole goes completely through also.
Now five holes are drilled near the top of the tube, roughly in the pattern shown. These holes need only to go through the tube wall once (don't worry if they go throughcompletely). I adapted the template to help positioning these holes, but that was an overshoot.
Image Notes1. See how the clamp fits the template, positioning the tube exactly for the secondhole.2. This stuff was suposed to help positioning the other holes, but proved to be anovershoot, as those do not need to be exact.
Step 5: The Generator Joule Thief (1)The basics of making a Joule Thief are described in a number of Ibles, so I won’t go into detail, but stick to explaining the solderless construction used here. It is helpfulto check out the circuit at Evil Mad Scientist to have some idea of what connections you are making. Obviously the motor/generator replaces the battery.
Prepare the double wound toroid by coiling the pair of twisted wires. Four to five windings should do it.
Loosen the wire ends and put two opposite ends back together (twist them together for now).
Put the pinion gear onto the motor/generator and put it in the clamp as show (pinion facing the other side than the five holes pattern).
Step 6: The Generator Joule Thief (2): electrical connectionsThe electrical connections are made by inserting the right wire ends in the pattern of five holes and fixing them with the small brass screws. Not only is this an alternativefor soldering, we also do not need to strip the wire. The thread of the screws cuts right through it, making the connection.
If you are not sure which one is the positive one, just go ahead and check for what rotating direction the LED lights up after finishing all connections. Switch the motorleads after step 7 if it happens to be the wrong direction.
At the workshop it showed the first insertion of the screw was difficult when connecting more than two wires. This is easy to solve by enlarging the hole slightly with abradawl.
To test it after assembly, turn the pinion gear quickly as shown in the video in the introduction. You might need to check both directions of rotation to find one working.
Image Notes1. Do not use this hole, It's for the turbine axle screw.2. We start out by connecting the two joined wires from the wound toroid withthe lead from the motor/generator.3. Next we put in the transistor (check which leg is which the for the type oftransistor) and the LED(s) in the top holes.
Image Notes1. Next we connect one of the loose toroid leads with the collector leg of thetransistor and the anode ( ) leg(s) of the LED(s).
Image Notes1. Next, connect the base leg of the transistor with the resistor in the middle hole.The other end of the resistor is connected to the remaining lead of the toroid inthe remaining bottom hole. Make sure the blank resistor wire is not touchinganything else.
Image Notes1. Next, connect the base leg of the transistor with the resistor in the middlehole.
Image Notes1. Connect the remaining motor lead to the remaining transistor leg (emitter)and the cathode (-) leg(s) of the LED(s).
Image Notes1. The remaining lead of the resistor is connected to the remaining lead of thetoroid in the last bottom hole.
Image Notes1. Make sure the blank resistor leads do touch anything else than their pointsof connection.
Image Notes1. Check on the inside of the tube if none of the screws or blank wires aretouching each other.
Step 7: Mounting the TurbinePut in the axle screw in the turbine gear from the side of the blades. With 4 washers in between screw it in the tube, taking care the gear aligns with the pinion on themotor/generator. Again, slightly enlarging the hole with bradawl might help. When the screw reaches the second hole, on the other side of the tube, take care to guide itnicely through the hole, or the gear will not be angled correctly.
Check if it runs smoothly and adjust. The gears should have a fairly loose grip on each other. Check if the LEDs light up by moving the assembly through the air by hand(as shown in the video in the introduction). Again, check the other direction if the first one does not work.
The correct direction of rotation is the one with the turbine facing downwind from the tube. If it only works the other way around, switch the motor/generator leads.
Image Notes1. Shift the motor/generator to get the gears to loosely grip eachother.
Step 8: Tail VaneGlue one end of the 30 cm skewer to the last 10 by 10 cm balsa square, taking care of the direction of the grain of the wood. The skewer should be glued across the grainof the wood, protecting the balsa from snapping along the grain.
Attach the other end of the skewer to the bottom of the tube with two tie-wraps in cross. Align the tail vane in such a way that it keeps the turbine facing down wind.
Step 9: InstallingPut a marble on the top of this tube and slide on the turbine assembly. The axle screw inside the tube, resting on the marble provides a bearing for the turbine to turnsmoothly into the wind. Obviously the wind turbine should be positioned vertically for that.
Step 10: Ideas for Further DevelopmentsThis basic junior wind turbine works well, but can use some improvements.
One idea is to in weather proof all electrical connections with something like Plasti Dip. Do not worry about the motor/generator to much. Most toy motors resist rain quitewell. To make sure you can put some grease to the axle and all openings.
Varnishing the blades or replacing them with plastic sheet and possibly also the skewers will make it more durable. Although the bamboo skewers and balsa keep quitewell.
A furling tail vane could turn the turbine out of too strong winds. A classic furling vane mechanism with counterweight should not be too difficult to make.
A bearing that keeps the turbine attached to the long tube could be helpful in strong winds. A longer 20mm diameter tube would help already. Another idea is to put themarble on a large screw inserted in a plug into the top of the 16 mm diameter tube. Then a small screw is inserted through the wall of the outer tube, locking just underthe head of the large screw.
An alternative attachment/bearing with a phone untangler could allow for the generated power to be transferred to an application separated from the rotating turbine.Another idea is to store the energy in a rechargeable battery, to power the LED(s) at windless evenings.
Image Notes1. I tried water based varnish, insteaed of Plasti Dip, which made the brass turn green. It still works though.
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Comments
11 comments Add Comment
JoshuaZimmerman says: May 2, 2011. 7:23 AM REPLYAwesome! I'm going to have to try this with my science club!
masynmachien says: May 2, 2011. 9:34 AM REPLYThanks. Please keep informed on the result.
JoshuaZimmerman says: May 2, 2011. 10:40 AM REPLYNow I just need to find a source of cheap gears...
masynmachien says: May 2, 2011. 11:29 AM REPLYIn the States I guess www.kelvin.com is the classic source.
scraptopower says: May 2, 2011. 4:07 AM REPLYBrilliant! If you don't want to make the joule thief circuit, you can buy emergency mobile phone chargers from ebay from around £1.50 each, they are just ajoule thief with a battery holder. That might make it even simpler and easier.
masynmachien says: May 2, 2011. 9:47 AM REPLYThanks.
Very interesting tip! I have been scavenging Joule Thief circuits from cheap solar garden lights, but unless one has a good use for the solar cell, that isnot the cheapest solution.
Of course, making the Joule Thief is fun in itself, but depending on the group or the project it could be very welcome to simplify things.
scraptopower says: May 2, 2011. 10:14 AM REPLYI used them on my thermoelectric generator, they're good and cheap. Here's one in for $1.37 : http://cgi.ebay.com/Emergency-Battery-Charger-Nokia-SAMSUNG-phone-Mp3-/250643464754?pt=PDA_Accessories&hash=item3a5b83c232
Takes a while for shipping though, as all the cheap ones ship from China.
Ronak360 says: May 2, 2011. 8:47 AM REPLYcool but bit unstable
masynmachien says: May 2, 2011. 9:40 AM REPLYThanks.
The wind was very unstable the day of filming, and of course the simple and light construction is indeed very sensitive to any changes in the wind.Actually, the kids like that.
construction-lawyer says: May 2, 2011. 9:18 AM REPLYWow that's amazing.
masynmachien says: May 2, 2011. 9:34 AM REPLYThanks
