Making a small wind turbine to charge phone whilst camping - Page 1
Forum section: electronics / beginners

author: seanspotatobusiness
author_rank: Regular Contributor
timestamp: July 23, 2015, 11:16:43 pm
content: I'm making a small wind turbine to charge my phone and/or external USB battery whilst camping. If I could get 2.5 W, that'd be okay; 5 W would be better.I've read that a stepper motor is a good thing to use (I'm not sure why) and I'm trying to find a broken printer with a stepper motor in it. I took two RS445PA14233R motors from a broken Epson but they're regular motors with specification:Supply Voltage: 12-42VSupply Current: 60mA - 1.5APower: 7.78WTorque: 81.8 mNmSpeed: 6500 rpmShaft diameter: 3.17mmI will try these motors while I wait to get my hands on another broken printer.My main question at the moment is what to do with the rectified current. I'm hoping to do something similar to this video (below) where the guy simply connects the rectified current to a cigarette lighter USB converter and that seems to be it.However I have concerns regarding what would happen should the conditions produce an input voltage of, say, 4V or even 40 V instead of the expected 12-24V of the adapter. The video does not address this possibility.

author: helius
author_rank: Super Contributor
timestamp: July 23, 2015, 11:41:43 pm
content: Stepper motors are used to move an output shaft to one of a set of defined angles. The angles are evenly spaced, and the shaft moves a whole number of steps according to the number of pulses it receives. They are rare on today's printers, because it is cheaper to use an ordinary DC motor with feedback from a position sensor. The place you have a chance of finding one is in the paper transport, not the print head assembly. Stepper motors are also completely impractical as electric generators.Not really sure what you mean by "rectified current": a DC motor used as a generator will always produce DC. You're not likely to find AC motors by taking apart old printers.

author: rs20
author_rank: Super Contributor
timestamp: July 23, 2015, 11:42:43 pm
content: I'm quite doubtful that a stepper motor will produce a significant amount of power let alone be the best thing to use, I'd be curious to see your source for that claim. Furthermore, with a small propeller and anything short of a gale, I wouldn't be all that surprised if the mechanical "stickiness/clickiness" or the stepper just locked the whole thing up.Making a regulator seems like a tricky proposition to me, because you need to provide 5V to the phone, while simultaneously drawing the correct amount of current from the generator (if you draw too little current, you're just not getting much power out of the wind; if you draw too much current, you'll just burn up your electricity as heat in the windings. There's an ideal amount of current to draw, which depends on the instantaneous wind speed). Solar panels have a similar issue, and use a technique called MPPT to continuously figure out what the best current to draw is.That's not a trivial undertaking.In short, I'm sure there's a clever technique out there that is nice and simple and works "well enough"; evidently I don't know of that technique.

author: seanspotatobusiness
author_rank: Regular Contributor
timestamp: July 24, 2015, 12:00:17 am
content: Quote from: helius on July 23, 2015, 11:41:43 pmThanks for the quick response.I thought the current would be the same as with a dynamo. The stepper motors require rectifiers according to the sources I've been reading.Quote from: rs20 on July 23, 2015, 11:42:43 pmHi. There are quite a few videos and tutorials that suggest using stepper motors. Here are some of the pages I've been reading:http://www.reuk.co.uk/Electricity-with-Stepper-Motors.htmhttp://www.freeonplate.com/how-to-build-cheap-wind-generator-using-floppy-drive/http://forum.allaboutcircuits.com/threads/type-of-stepper-motor-to-use-in-wind-generator.36002/http://www.c-realevents.demon.co.uk/steppers/stepmotor.htmlhttp://www.gotwind.org/diy/Projects.htm

author: mikerj
author_rank: Super Contributor
timestamp: July 24, 2015, 07:17:26 am
content: Quote from: rs20 on July 23, 2015, 11:42:43 pmWhy? It's simply a multi-phase permanent magnet alternator when used in reverse, and they can generate useful levels of power though efficiency probably won't be very high. There are dozens of projects on the web that have used steppers for small low power wind generators.The worst aspect of steppers for this application is the fairly high hold torque and "cogging", which means you need a higher wind speed to start things turning.

author: rs20
author_rank: Super Contributor
timestamp: July 24, 2015, 09:29:18 am
content: Quote from: mikerj on July 24, 2015, 07:17:26 amNice selective quoting there. I mean, real life wind turbines have conventional, not-that-many-poles generators, so it can't be optimal to use a stepper by any stretch. The best thing lying around a typical house? Sure, but I don't consider that a particularly high bar.

author: nowlan
author_rank: Frequent Contributor
timestamp: July 24, 2015, 10:06:26 am
content: Plenty of off the shelf solar panels and car chargers available. Unless you really want to build the wind turbine?

author: seanspotatobusiness
author_rank: Regular Contributor
timestamp: July 24, 2015, 11:35:13 am
content: Quote from: nowlan on July 24, 2015, 10:06:26 amThat might make sense in Australia but in Scotland the wind is far more reliable than the sun! Plus it continues to work outside of daylight hours.

author: Fraser
author_rank: Super Contributor
timestamp: July 24, 2015, 12:45:24 pm
content: From memory, a bike dyno hub is a well proven DIY generator for a wind turbine.IMHO a decent DC motor is the the alternative. I built a wind speed analyser as a student using a ball raced DC motor and it took very little wind to drive it. It is crucial to have a low cogging motor and reasonable size of fan. I believe I used a secondary fan assembly from car. It used to cool radiator when the A/C was on. That fan turned more easily than the main radiator cooling fan due to different power motors being used. Go visit a car scrap yard and see what you can find. I recommend a fan that has many thin blades like those of a turbine.I further recommend that you consider including a small battery in the system that is charged by the motor and acts as a reservoir from which power is taken via a conventional regulator. The battery need not be anything large, just a pack of AA Ni-Mh cells with current limiting resistor for charging and series diode to prevent reverse powering f the turbineGood luckAurora

author: seanspotatobusiness
author_rank: Regular Contributor
timestamp: July 24, 2015, 01:04:38 pm
content: Quote from: Aurora on July 24, 2015, 12:45:24 pmThanks a lot Aurora! I was thinking of using an external USB battery which I could then use to charge my phone. I'm hoping to be able to use an RC plane propeller.Regarding the electronics to provide a stable voltage, I'm not sure what kind of regulator to get. There are many different kinds on eBay. I also wonder what would happen if the turbine was spinning with no battery connected to take the power?http://www.ebay.co.uk/itm/LM2596-Voltage-Regulator-board-4-5V-to-35V-in-1-2V-to-30V-out-UK-STOCK-/190814696793http://www.ebay.co.uk/itm/DC-12V-24V-40V-to-5V-4-USB-Car-Charger-Step-down-Power-Module-for-MP3-Phone-GPS-/181199394975http://www.ebay.co.uk/itm/Buck-Step-Down-Converter-Module-Voltage-Regulator-Voltmeter-DC-6-35V-to-DC-5V-3A-/281748921203http://www.ebay.co.uk/itm/Brand-new-DIY-DC-6-35V-to-5V-3A-Double-USB-Voltage-Step-Down-Regulator-Module-/331411314192