My daughter got a co-curricular school activity in early September about renewable energy models. The students were tasked with making a model depicting one of the three renewables: solar energy or wind energy or hydroelectric energy. A link to a sample video was provided for some inspiration too. Included was also a reminder note: The model can be non-working. (Emphasis was the school’s.)
We chose wind energy and decided to make a non-working model with a couple of windmills, a house and farming land around it. As she and her mother started working on making the actual model, I started wondering, “Can a working model be made?”. I mean it seemed like just sticking a pinwheel fan on a dynamo generator should do the trick of lighting up a single measly LED! How hard could it be, right? As it turns out, it is actually quite a pain to make a working model of a windmill out of just those 3 things! I list here all of my failed attempts to make a working “windmill” with the help of a ceiling fan providing the required wind.
Attempt 0: Her mother likes my “grand” idea for the “project” and agrees to source the electronics components. She gets 10 green LEDs, wires and two motors used in toy cars (cuboid shaped with a red plastic end). As it turns out, this motor can be used as a generator (the same working principle in reverse) but I did not know this fact at that time so I ask her to source a generator specifically. She gets two dynamo generators similar to those used in bicycles (I guess), one of which we use till the end of this “project”. (As it turns out, the red one could not have worked for our purposes anyway!)
Attempt 1: We make a couple of pinwheels (we discard the idea of a 3 blade proper-looking windmill quite early on because we can not make it aerodynamic enough!) and source a plastic stub from Sakura’s toy collection (a kids’ science kit for electrical stuff) to fix the pinwheel to the generator’s axle. We switch on the ceiling fan, turn it to max and let the pinwheel rotate away. The LED does not turn on. No surprise there!
Attempt 2: I search about what can be done and settle on Gemini’s suggestion to spruce up the pinwheel to make it more sturdier and rotate faster and even use gears to rotate the axle of the generator even faster so that enough voltage is generated to light up the white LED.
As it turns out, these LEDs need ~3V to turn on and no way was the pinwheel’s rpm enough to generate any voltage close to that. I buy a toy gear set and make a cardboard enclosure for the gear mechanism but at the end of the day the pinwheel does not rotate the geared generator at all. This is because (it is obvious now) more power is required to turn a 5:1 gear set than just the generator’s axle directly. So this is a complete failure.
Attempt 3: I am back to the pinwheel directly attached to the generator’s axle. I finally “painstakingly” use a battery tester to measure the voltage being generated by the generator and it is a disappointing ~0.6V! The 5:1 gear box idea was quite good as it would have really given ~3V to light up the LED if the pinwheel had rotated as required. Another idea strikes: let me replace this bulky generator with a sleek drone motor (which can also be used as a generator). Another day, another order for the drone motors and while I am at it, let’s buy a proper multimeter too.
With 4 drone motors in hand, I make a smaller pinwheel for this smaller generator and no prizes for guessing, this also does not work because the voltage generated now is measly ~0.06V… 10× lower! Arrgh! But then it is post-priori obvious that this would not have worked because these drone motors are rated for very high rpm (~50K) for ~3.5V and the bulky generator is rated for just ~5K worth rpm for ~12V so from pinwheel’s low (100-500) rpm, no wonder the voltage drops so drastically. (The “red motor” mentioned above would not have worked either exactly for this reason.) This is utter disaster.
Attempt 4: Back to the pinwheel directly attached to the bulkier generator which is happily generating ~0.6V at max ceiling fan speed. Gemini finds technical specifications of this generator and “calculates” from the generator’s 0.6V that the pinwheel must be performing ~150 rpm, which is nice to know but utterly unhelpful for my purposes! Because the rpm of the pinwheel cannot be increased any further so I need to boost 0.6V to 3V. I ask Gemini for simple DC voltage step up circuits. It talks about “Joule thief” circuit and suggests a ready-made circuit to buy. This circuit requires minimum input voltage of 2V so I call it quits on sourcing another product that might not work! Also there is no way of making a Joule thief circuit on my own as I am not salvaging a ferrite core and transistor from anything in my surroundings in a million years.
Attempt 5: After having a few sleepless nights with ever-increasing urge to get this “windmill” light up a single LED, I decide to follow the maxim: Go Big or Go Broke! I order ₹4K worth of electronic components (including the Arduino Uno board kit for later use by Sakura, hopefully!). With the above tutorial video running in loop in front of me and having ransacked Sakura’s toy closet to get my hands on two ring magnets (instead of the ferrite core), I cobble up this JT circuit and with a “dead” AAA cell, it lights up the red LED (to “match” with the red ring magnets)! WOW! So this circuit is definitely boosting 1V to 3V.
Now is the moment of truth. The moment way past the actual co-curricular day where Sakura had to present her non-working model. The moment when I replace the cell by the “windmill”: WHhhaaattt!!! WHhhyyyy??? The LED does not light up. So apparently, this circuit is not able to boost 0.6V to 3V or was it just luck that the magnet “worked” with the AAA cell. Anyway, we now know what needs to be done.
Attempt 6: I order the final missing component: the ferrite core. What’s ₹400 more having spent ₹4K already? They arrive in a pack of 5 after what seems like ages. I pick out one, wrap wires around it (in a slightly different way) and remake the JT circuit. It works with the dead AAA cell. Good! Now again is the moment of truth. Nothing else matters because this is the brink of all that has transpired for the last few weeks. This is the moment when I replace the dead cell with the live “windmill”…
Our faces light up along with the red LED!
The final setup is shown below with a green LED to match the colour scheme of the ferrite core and the overall theme of green energy.
Finally, we should take stock of what all we did and what all we spent to achieve that. We did make a Joule thief circuit (barely worth ₹200) to boost low voltage output of a generator (~0.6V) powered by a “windmill” to a level that can turn on a standard (green, red, white) LED requiring ~3V. As for what we actually spent to get there, here is the itemized breakdown:
- Motors, LEDs, wires – ~₹400
- Toy gear set (unused) – ~₹350
- Multimeter – ~₹1400
- Electronics components – ~₹4000
- Ferrite cores – ~₹400
- Project time – ~1 Month
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Sakura’s lit up face when windmill worked – Priceless
Here’s the proper finale for those who have reached till the end.
