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magicshine and dynamo?

3008 Views 6 Replies 5 Participants Last post by vroom9, Dec 17, 2009

elpresidente

Discussion Starter · Dec 15, 2009

hey guys, since im now doing a cycling commute everyday 6 miles each way, im considering buying a dynamo hub, as i like the idea of not having to faff around connecting/disconnecting lights at each end. Ive been running a a magicshine since june-ish and am thrilled to bits with it, giving me a level of lights i couldn't afford otherwise.

Now, could i run this off a hub, i know theres driver circuitry in there, what would the result be? Would i be able to supply enough power for a p7?

I could perhaps take the driver out and replace it with a bridge rectifier and a smoothing capacitor (itd be a squeeze) but then i wouldn't be able to use it on my mtb as it wouldn't have a hub. so this option wouldn't be practical unless i were too move the driver to the battery pack somehow.

or am i just faffing and should i just cope with batteries?

oh i was thinking of buying a SHIMANO DH-3N30 btw

any thoughts appreciated,

Andrew

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znomit

· #2 · Dec 15, 2009

You would need to gut the magicshine, replace the P7 with an MCE and find room for a DIY circuit.
A decent dyno light is not much more than 100$ anyway.
http://www.peterwhitecycles.com/schmidt-headlights.asp

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mtb_robs-x

· #3 · Dec 16, 2009

think the hub is AC,... aka coils an magnet,...
so it would fry your light, also not enough juice, since those are in the 6w range,
and the voltage too, fluctuating,....
need to push them to the 12V hub, they are considering it,....

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elpresidente

Discussion Starter · #4 · Dec 16, 2009

i know a dynamo is AC hence me mentioning the need for a bridge rectifier, just wonderin what would happen if i fed the rectified current into the driver, seeing as the driver board takes a 7.4v li-ion i was wondering wether the 6v would be enough.
Andrew

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allport

· #5 · Dec 16, 2009

elpresidente said:
i know a dynamo is AC hence me mentioning the need for a bridge rectifier, just wonderin what would happen if i fed the rectified current into the driver, seeing as the driver board takes a 7.4v li-ion i was wondering wether the 6v would be enough.
Andrew

I'd have thought that if you get the 6v dc input into the driver you should be ok, as the P7 only need's 3.7v it must be using a buck driver if the battery pack is 7.4v. But without knowing what the driver is I couldn't say it would be ok.

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znomit

· #6 · Dec 17, 2009

allport said:
I'd have thought that if you get the 6v dc input into the driver you should be ok, as the P7 only need's 3.7v it must be using a buck driver if the battery pack is 7.4v. But without knowing what the driver is I couldn't say it would be ok.

You would need to build a complete 7.4V power supply. Theres a few commercial ones out there(they probably don't put out 2A though). The dyno will put out a much higher voltage than the MS can tolerate, so simply rectifying it will not work.

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vroom9

· #7 · Dec 17, 2009

That hub just doesn't generate enough power. No need for a driver since the power is so low. Basically just a bridge rectifier to the P7. Couldn't figure the output vs rpm for that hub, but at whatever speed it's rated for you only get 1/2 an amp. That will only give you a wimpy 150 to 200 lumens from your P7.

Two R5 XP-G's in series with one of those circuits that switches from a voltage doubler to a normal bridge rectifier as the speed increases could give up to 350 or so lumens with that same hub at the same speed.

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