Hydropower From Reuse




About: Send me a message if you're interested in Technology or Science Workshops in Flanders, Brussels or the Southern of the Netherlands. I have over 20 years of experience in developing and giving creative worksh...
Last fall we were staying at a holiday cottage generating its own electricity from a water wheel. We reproduced that in a little workshop with the kids, powering a LED with a miniature water wheel.

We made several attempts, a number of which worked, but those based on a stepper motors from a discarded printer proved to be the fastest an easiest to make. Furthermore, apart from some glue it was completely built out of discarded parts, thus combining the demonstration of renewable energy with reuse.

We had a great time building and playing. Check out the video to see the result in action:

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Reusing Parts and Materials

a small stepper motor as found in a printer
2 discarded CD-ROMs
a foam tray
some long stick (I used a piece of 20mm diameter  PVC tube from demolition)
one or two tie-wraps
a small piece of scrap paper

Non-reused: The only non-reused part is the hot melt glue (I recommend the low temp type, especially when working with kids).

Tools: scissors, screwdriver to disassemble the printer (not shown), cutting pliers or desoldering tools for (optional, not shown).

Stepper motors make very easy generators, as they produce relatively high voltages (I’m talking 5V range) at low rpm. Small DC motors (toy motors) need high rpm and still produce only a low voltage (1V range). Stepper motors do not need gears and/or electronics to power a LED (compare it to my junior wind turbine). I was worried about blowing up the LED at first, but that did not happen. The current generated being pulsating very probably contributes to that.
I doe not bother to waterproof anything (motor or electronics). Repeated use for several minutes, on several occasions, showed no need for that.
If found two stepper motors in an old Lexmark inkjet printer for which first the ink heads were no longer available and which later did not survive more than a couple of refills of the last ink head. I guess most inkjet printers will have two stepper motors, one for moving the paper and one for moving the head. The way to disassemble the printer will differ for each model. As in this case the printer should be a discarded one and there is no need to put it back together, you can’t do much wrong by simply unscrewing al screws you can find until you can free the stepper motors. Just keep the pinion gear and the connector they come with on the motors. To give you an idea on what to disassemble, you can go looking for an exploded view of your printer, like this one.

With a bit of luck the LED can also be found in the discarded printer. With even more luck you can find some discarded electronics with a LED standing tall on a printed circuit board, with most of its legs still intact, instead of mounted flush on the board. This makes it easier to remove from the print (leave the legs as long as possible) and easier to connect to the stepper motor by simply inserting it in the plug. As alternative you either us a new LED or desolder one and solder it to the stepper motor leads (I guess it is hard to tell if the ecological impact smaller for using a new led or for (de)soldering).

To keep within the spirit, you can also reuse tie-wraps: when you cut them loose carefully near the “ratchet”, you end up with a shorter, but still usable tie wrap.

Now to start building, see the next step.

Step 2: Wheel to Motor Connection

The wheel is made as light as possible. This makes any unbalance or eccentricity less critical.

One of the discarded CD-ROMs is put flat on the working surface. The glue will stick best on the printed side. Taking this in account we started with the printed side facing downwards.

The working surface as “seen” through the hole of the CD-ROM should be completely covered.  With the working surface protected like that, put a good blob of hot melt glue. The stepper motor is put with its pinion in this blob and kept in place by hand, while the glue sets (takes a minute or so). Before it has set look from above to check if it is positioned in the middle of the CD-ROM. Check from several sides to check it is level.

When you are two to do this, it is not hard to achieve a reasonably good alignment this way. The pinion gear helps and we found no spacers or templates were needed.

When the glue has set the scrap paper is peeled off.

With one stepper motor with a metal pinion gear, the wheel came off when using it. The pinion gear was glued back in the hot melt glue cavity, with superglue.

Step 3: Sandwiching the Vanes

8 vanes, roughly 3 by 3 cm are cut from the flat parts of a foam tray. You could try to use the curvature of part of the foam tray to your advantage (as a kind of scoop type vanes) but I chose not to and kept the water wheel and bidirectional.

The vanes are glued to the CD-ROM already on the stepper motor. We did not mark their position beforehand. Following the pattern show in the pictures, each time putting a van “in the middle” works accurate enough.

Some practical testing showed a second CD-ROM on top is needed to make the wheel-vane construction robust enough. When the glue has set, check the “height” of all vanes and trim those that are longer than the others. All vanes get some glue on top (working quickly) and the second CD-ROM is put on top.

Step 4: On a Stick and Into the Water

One or more tie-wraps are run through the stepper motor mounting holes and are used to attach it to the end of a stick. Take care the tie-wraps d not hinder the wheel of moving freely.

Connect the LED to two leads of the stepper motor by either inserting its legs in the plug or by soldering. The polarity of the LED does not matter as the current will be alternating. You will need to check which two leads work by spinning the wheel by hand. Several combinations will work, but (depending on the type of stepper motor) not all.

We were able to test our build in the feed to a real water wheel, but you can use any water running at a reasonably high speed. Be careful at the bank: don’t risk falling in the water.  :-) 

Be the First to Share


    • Book Character Costume Challenge

      Book Character Costume Challenge
    • Made with Math Contest

      Made with Math Contest
    • Cardboard Speed Challenge

      Cardboard Speed Challenge

    48 Discussions


    3 years ago

    Hi! I'm a senior in highschool and doing a project related to this as a part of a project. For mine, I am making a portable hydropower generator that can be used to charge mobile devices when camping. I was planning on making a stator and rotor to produce the electricity but seeing that I could use a motor, I am thinking of doing that. I am just confused about the motor getting damaged from the water because to generate enough power to charge a phone, the generator will have to be in the water for a very long time. You seem like you're much more knowledgeable on this topic so I was basically wondering if you had any tips on how you would go about doing my project. If so, please respond to this or email me at sonnyp99@gmail.com. Thanks!

    1 reply

    Reply 3 years ago

    Hi Sonnyp99,

    Cool project!

    First, using a motor as generator is much simpler than build your own stator and rotor. Even commercial small charging devices (think crank torches, some of which can charge cell phones) are often based on an existing motor used as a generator. For a more high end applications it is very often a device specifically built with specs as a generator, but still with the same technology and on the same production lines as motors.

    Most low voltage motors, including stepper motors do keep working in clean sweet water for days, weeks and even longer.
    It does depend on the type of motor and it is hard to tell in advance.
    But most do last quite a while, so if you only need to explore and demonstrate a working principle you can omit any waterproofing.
    Dirty and in particular salty water will probably shorten the motor's lifetime considerably.

    If however you want to demonstrate how a real reliable product could be made, you should waterproof your motor.
    An accessible approach is using waterproof prop shaft assemblies as sold for RC model boats.




    3 years ago

    Hi. How long should each of the stator coils be in length? Thanks.

    1 reply

    Reply 3 years ago

    Sorry, no idea.
    I just scavenged a printer and used the steppers available from that.
    I think it is not very critical if you just want to power an LED.


    4 years ago



    4 years ago on Introduction


    Hot melt glue is pretty common in DIY and in crafts shops. And Amazon is very reliable.

    But you can use other glue, as long as it is water resistant, reasonably gap filling and doesn't attack the foam. If you use another light material instead of foam, you don't need to worry about the latter. You could make even use Duck Tape for the wheel and attach a piece of wood in the middle, with a hole that fits the motor axle or pinion.



    4 years ago

    Hi there,
    Great instructable! Indeed..
    Can u give me an alternative for hot glue as it is not available here. And i do not rely on amazon.com and etc... No online shopping..


    4 years ago on Introduction

    Great Instructable. Have you ever looked into the Tesla Turbine? This would be a neat project for it.

    1 reply

    Reply 4 years ago on Step 4

    Indeed, most motors will survive being wet, even being immersed, for a long time.

    And the current lost through the conductivity of the water is negligeable at these low voltages.


    5 years ago

    Hi just a quick question.

    Do you think it might be possible to attach 3 LEDs and have them light up when a different voltage is reached so kids can see how much energy is being generated and how fast the water is moving?

    Oh yes thanks for the amazing instructables! Great ideas!!

    1 reply

    Reply 5 years ago

    Thank YOU!
    Great idea! That shoul probably work. If needed you can increase the difference in minimum voltage for different colours by adding diodes in series, like I did in this project: https://m.instructables.com/id/Disarming-Game/
    Please keep me posted on your results.

    AnnMarie Ha

    5 years ago on Introduction


    I'm not sure If this is too late but my daughter is making this for her school project and I was wondering if I could find such stepper motor on Amazon.com. I was also wondering what type of foam tray I needed since we do not own any foam trays in our home and if we could buy any on Amazon.com. Also, how long would this project take? My daughter has about a week to complete it.

    Thanks, AnnMarie

    3 replies


    you can probably find a stepper motor on Amazon. Make sure is is not a geared one, those are less suitable.
    If a bottom price is not required, I would recommend this one: https://www.sparkfun.com/products/10551
    At only $7 it not that expensive and I used that model with success.
    The same product is also available through amazon, but at $9: http://www.amazon.com/SparkFun-Small-Stepper-Motor/dp/B007R9UMFU/ref=sr_1_8?ie=UTF8&qid=1392836223&sr=8-8&keywords=sparkfun+stepper
    The shipping options might be better, but amazon and ebay are usually more expensive than buying directly from online suppliers. In this case Sparkfun is a certainly a serious company.

    Once you know how to do it, building a working example takes only about an hour. But experimenting, improving and rebuilding it, can keep you busy for days.

    As for the foam tray: you need a light and stiff material, that is water resistant for at least a while. So cardboard would not do. Any stiff foam in thin sheet or that you manage to cut in sheets under 1 cm would do. Foam board (stiff foam covered with paper) can work if you carefully peal off the paper. Light wood (balsa or poplar) will work too and should last a while at least.
    Stiff plastic sheet, like cut from sturdier plastic bottles should work to. The curved shape can work well.
    Please experiment. Anyway, be ready to repair the wheel once in a while. keep the glue gun at hand when the time for a demonstration is ready.



    Also, If I can't find a foam tray is there any other alternative as to foam? Like cardboard or maybe plastic?


    5 years ago on Introduction

    Hello!, So this is my first time playing with electronics therefore struggling a little, I think i brought the wrong component ----> http://www.ebay.co.uk/itm/Arduino-compatible-5V-4-phase-DC-Gear-Stepper-Step-Motor-Driver-Board-/130860581877? could you please recommend one with a pinion gear as im finding it difficult, without having to ruin my printer?! Would this be suitable? - http://www.maplin.co.uk/motors-97341 Many thanks, Abi.

    2 replies

    Reply 5 years ago on Introduction

    Hello Abi,

    The stepper motor you bought would be useable if only the gears didn't slip when you turn the axle. I altered one once, but that is not a beginner's job.

    The maplin motors aren't stepper motors, so they will not do in the concept of this Ible.

    this one will work: http://robosavvy.com/store/product_info.php/products_id/2861
    I used one exactly like it once.

    You do not need a pinion gear. If you have a piece of plastic or wood with a hole that fits the shaft tightly you can work from that. Or drill a hole. Even a drill bit with a diameter equal to the shaft will probably work to make a hole tight enough, if needed with some glue carefully added.

    Still, if you ask around there is a good chance someone has a discarded printer lying somewhere.




    Reply 5 years ago on Introduction

    Hi Yvon,

    Thanks alot for the response, help and link to the website. Yep the axle on the original stepper motor doesn't move. I was shown a miniature gearbox and brought that before i saw your comment from a local-(ish!) shop, would that be ok?!

    http://www.mfacomodrills.com/gearboxes/multiratio.html (trying to not open it, as im a student so funds are tight!!).

    I was going to solder or wrap some bell wire to the end of the motor then wrap it around the LED.

    Thank you