Hackaday Prize 2022: DIY Brushless Hand Cranked Generator

A standard part of travel kit for the 2020s is now a battery pack — a hefty lithium-ion cell with onboard electronics for USB charging, that ensures all of our devices stay topped up while we’re out of range of a socket. But what happens when there is no handy mains supply to recharge it from? Step in [Chleba], with a hand cranked generator.

There are plenty of hand cranked generators to be found online, from tiny devices intended to top up a single phone to sturdy metal boxes intended for battery charging. This one differs from those in that most use a brushed DC motor as a cheap generator, while here that function comes from a stepper motor feeding a rectifier pack and thence a DC-to-DC converter. A step-up gearbox provides the necessary shaft speed, and a neat 3D-printed case rounds everything off.

The result is about as neat a generator as you could imagine, and would certainly be of use shoved into any off-grid backpack. Meanwhile it’s not the first we’ve shown you, we’ve even see one that could start a car.

12 thoughts on “Hackaday Prize 2022: DIY Brushless Hand Cranked Generator

  1. Cranking uphill into a 25:1 gearbox, and also having a current-hungry LED voltmeter as a load, with a max power output of less than 5 watts. Ouch. My arm is sore already.

    I wonder how many kWh per pizza it gets? (with a nod to Steve Roberts’ notion of ‘miles per pizza’ on BEHEMOTH)

    1. Well, a short circuit can be interpreted as no load: there’s zero power dissipated in it.

      So, 25-30V open circuit, 0.7A short circuit means maximum power output is at the impedance match: 14V at 0.35V = 5 watts.

  2. That’s not much more than the German standard of a bike dynamo, 3 watts. they’re AC too.
    The second set of diodes would refer to using 2 of the 3 windings to use in parallel. All 3 should give 3 times the current.

  3. I have one of those hand cranked flashlights from 20 years ago. It has a jack for charging a cell phone. So when I tried it, each time I turned the crank, the phone screen would light up, resulting in zero net charge.

  4. Maybe try one of those 3 phase out-runner motors like they use for drones and model planes? Also in a case like this it might be worth it to use one of those ‘intelligent’ rectifiers that uses MOSFETs to avoid the power loss you get with the classic bridge rectifiers.

  5. Yeah, I researched different hand crank radios for emergency use, with USB out for charging a phone, and they were all USELESS!

    I setteled for a powerbank with a foldable solarpanel instead, and a radio that charges from USB.

    I left the solar panel in the sun (inside a window), and the radio connected to the powerbank, and it has been running all summer, fully charged, I even charged my phone from it a couple of times and it seems to be enough for both charging the phone every day and keeping the radio running indefitenly.

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