Hydropower From Reuse





Introduction: Hydropower From Reuse

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:

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.  :-) 



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    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!

    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.



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

    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.



    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.


    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..

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

    Indeed, you could also use that type of turbine, but it is more adapted to flow in a confined conduit.

    Doesn't matter if the motor get wet?