Hand-cranked dynamo alternative to Shutter Precision SV-9 for LED lighting system

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#1 21680792 03 Oct 2018 19:03

Michelle OBrien Michelle OBrien

Anonymous

Post #1
21680792 03 Oct 2018 19:03

Julian Edgar's excellent article "Dynamo bicycle LED lighting system" got me very interested in the November issue of EPE magazine just out:

I want to try my hand at this. BUT MINUS THE BIKE.

So can anyone suggest a small dynamo with the same specifications to substitute for the Shutter Precision SV-9 hub dynamo or the smaller, cheaper "bike bottle dynamo" in the set-up described by Julian in the article

What I'm looking for is most probably though not certainly a hand-cranked affair.

Michelle O'Brien
SE London
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#2 21680793 03 Oct 2018 20:28

Rick Curl Rick Curl

Anonymous

Post #2
21680793 03 Oct 2018 20:28

Hi Michelle-If you're doing this without the bike, you probably don't need a dynamo specially made to go in a bike wheel hub. FYI- any permanent-magnet brush-type DC motor will make a fine dynamo. Also, small stepping motors will generate a lot of power, but if you're looking for a DC output you will need to add rectifier diodes to each of the coil windings.What will you be using to turn the dynamo? How much voltage and current do you need? -Rick
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#3 21680794 03 Oct 2018 23:03

Michelle OBrien Michelle OBrien

Anonymous

Post #3
21680794 03 Oct 2018 23:03

Hello Rick
Thanks for your interest.Rectified from AC to DC and smoothed, the dynamo's output will be fed into a small DC/DC buck-boost module that can output from 1.25 - 35V.

Julian says in his article that this requires a supply voltage anywhere from about 3 - 32V. And he adds: "A realistic input current maximum is 1A" for the intended LED lighting system.

All the details are given in his stuff in the November issue of Everyday Practical Electronics magazine.

Hand cranking will most likely be my means to turn the dynamo but steam power might also be a possibility.Michelle
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#4 21680795 04 Oct 2018 03:15

Rick Curl Rick Curl

Anonymous

Post #4
21680795 04 Oct 2018 03:15

If I were you I think I'd start with a stepper motor. Either cannibalize one out of an old printer or buy an inexpensive NEMA 17 motor on eBay. Look for a bipolar motor with 4 wires. These will have two windings with two wires each. Use an ohmmeter to determine which wires go to each winding. Then connect the AC side of two bridge rectifiers to the wires coming from each winding. For the highest efficiency, use Schottky rectifiers, like SP260TA in the bridges (most any silicon rectifiers will do, though). Connect the positive sides of both bridges together. That will be your positive output. Connect the negative side of both bridges together for the negative output. Spin the motor with your fingers and you should see some voltage come out.If you're going to hand-crank it, you'll need to add a couple of gears to increase the speed of the motor. Alternatively, you could use belts and pulleys, or even sprocket gears and a sprocket chain. I would think you'll need maybe a 4X to 10X speed increase.-Rick
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#5 21680796 04 Oct 2018 03:18

David Ashton David Ashton

Anonymous

Post #5
21680796 04 Oct 2018 03:18

Hi Michelle. I love the idea of a steam-driven electricity generator... Suggestion - you get hand-cranked torches that you could maybe take apart, though I don't think you'd get an amp out of them. Also, you'll probably have to use some gearing, most motors are designed for fairly high speeds and you'd have to get them up to near those speeds to generate a reasonable amount of power. One of my suppliers coincidentally just offered a geared motor here, but it's very highly geared (around 300:1) and that would probably be too much.
#6 21680797 04 Oct 2018 13:33

Julian Edgar Julian Edgar

Anonymous

Post #6
21680797 04 Oct 2018 13:33

Hi Michelle,
First, thanks for the nice compliments about the original article. As others have said, any DC motor run backwards as a generator will work, as will a stepper motor with appropriate rectification. But it depends what you want to run - and you haven't said that!It's actually fumy that you say that you want to run it 'without the bike' because today I was buying some parts to try to achieve that, such has been the success of the bike system. (I am looking at using a geared-up stepper motor.)I did a story for EPE on a hand-cranked LED torch some years ago - and that also might be worth a look. Finally, the Shutter Precision generator is pretty impressive, so you might not so easily achieve the same output from something else. On the bike the drag feels like zero (it's not, but...).
Julian Edgar
#7 21680798 04 Oct 2018 14:40

Alan Winstanley Alan Winstanley

Anonymous

Post #7
21680798 04 Oct 2018 14:40

You might be able to get a small sterling engine from Ebay and hook it to a small d.c. motor? This could become very steam-punky!
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Topic summary

The discussion centers on finding a hand-cranked dynamo alternative to the Shutter Precision SV-9 hub dynamo for powering an LED lighting system as described in Julian Edgar's article in Everyday Practical Electronics magazine. The required electrical specifications include an input voltage range of approximately 3 to 32 V and a maximum current of about 1 A, feeding a DC/DC buck-boost converter outputting 1.25 to 35 V. Several suggestions highlight that any permanent-magnet brushed DC motor can function as a dynamo, and small stepper motors, especially bipolar types with four wires, are effective generators when combined with appropriate rectification using bridge rectifiers and Schottky diodes for efficiency. Hand cranking will likely require gearing or pulleys to achieve sufficient rotational speed for adequate voltage and current output. Alternatives such as repurposed motors from old printers (e.g., NEMA 17 stepper motors), hand-cranked torches, or even steam-powered setups using small DC motors or sterling engines were proposed. The Shutter Precision SV-9 is noted for its low drag and high efficiency, making it challenging to match with generic motors without gearing or specialized design.
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Hand-cranked dynamo alternative to Shutter Precision SV-9 for LED lighting system

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