Cheap(er) dynamo to USB power option

[DoctorRad]

So run the lights all the time then?

You could do, but you'll be most likely be reducing your charge current considerably.

[jameso]

The issue is more subtle than it appears, and it's taken me a while to get to the bottom of why so many of these regulator units appear to be quite fragile, electrically at least.

Many modern 5v regulators will handle input voltages of typically 7-36v which will cause no issue from a rectified dynamo output while there is a load on the regulator. The problem comes when the device is fully charged and the regulator is no longer pulling power from the dynamo. In these circumstances, the regulator presents a very high resistance to the dynamo, and the voltage across the dynamo can reach much more than the maximum input voltage of the regulator (and indeed the smoothing capacitors). Fried components can easily result.

A protection circuit is therefore needed, see my comments and links here:

http://forum.ctc.org.uk/viewtopic.php?f ... 41#p777550

Useful, thanks. Initially I though 'I'll just turn off the charging circuit before a big hill' but that won't always happen when I'm tired or enjoying myself and a road bike in the Alps will see some high speeds. So this point applies to a charged device or an inline battery.. all the same when full and presenting no resistance. Beginning to understand the basics of this now, A-level Physics and owning anything needing a soldering iron to work on was a long time ago.

At some point, I plan to pull all this together and do a DIY guide.

From your CTC post .. I for one would really appreciate something like that as I simply don't understand electronics well enough to figure all this out, yet I'd like to get something customised to work with the bike arranged this summer. I don't want to fry stuff learning how though, normal product<>user error risks aside : )

[DoctorRad]

This has not been tested in anger, but I think all you really need is:

Dynamo -> Full Wave Rectifier -> Crowbar Protection Circuit with Blocking Diode -> Smoothing Capacitor -> 5v Switching Regulator -> USB socket

Then, if the dynamo kicks out anything greater than the breakdown voltage of the zener, the thyristor will short the dynamo output until the end of the half-wave output and then reset before the next half-wave.

Use a thyristor rated for at least 3A and mains voltages and everything should be fine with anything a dynamo can throw at it. The smoothing capacitor voltage rating should be at least as large as the maximum input voltage of the regulator. Not sure how beefy the zener diode needs to be, but its breakdown voltage should be a few volts lower than the maximum input voltage of the regulator for safety.

[johnnystorm]

So run the lights all the time then?

You could do, but you'll be most likely be reducing your charge current considerably.

I was thinking more for big descents. Not that it's going to be a big problem for me........in Suffolk.

[Taylor]

This has not been tested in anger, but I think all you really need is:

Dynamo -> Full Wave Rectifier -> Crowbar Protection Circuit with Blocking Diode -> Smoothing Capacitor -> 5v Switching Regulator -> USB socket

Then, if the dynamo kicks out anything greater than the breakdown voltage of the zener, the thyristor will short the dynamo output until the end of the half-wave output and then reset before the next half-wave.

Use a thyristor rated for at least 3A and mains voltages and everything should be fine with anything a dynamo can throw at it. The smoothing capacitor voltage rating should be at least as large as the maximum input voltage of the regulator. Not sure how beefy the zener diode needs to be, but its breakdown voltage should be a few volts lower than the maximum input voltage of the regulator for safety.

Did anybody understand that? ^^^^^^

[Bearbonesnorm]

Did anybody understand that? ^^^^^^

Made sense to me ... but I once plumbed in a solid fuel Aga and oil fired boiler so they'd run side by side

[jameso]

I failed the electronics test above : )

Apologies for possible topic drift but I think this applies to any charging box -
For now I'm about to order a Sinewave to go with my SP hub, decided on a std front light for keeping lighting and charging etc separate. Also hoping that the Sinewave could be detached and used on another bike if needed in future, or removed for shorter rides.

So one Q - is it possible to splice or divide the wire from the SP hub to the light (Edelux II I expect) so that there is a connector for the Sinewave part-way along it? The light wire will go up the fork leg internally and exit under the fork crown (threading that will be fun..!). I don't want the Sinewave cable to be external but internal is too much faff to remove once fitted. But a M-F plug for the Swave hidden in the steerer-fork crown area would be easy to fit when needed, well protected and allow the Swave cable to exit the top of the steerer and the box then sits in a bar bag or a Stem-cell. Pretty neat if it can work that way? I think charging anything will pull current from the light if it was on but during the day that's no issue. No probs with day=charge / night=lighting.

[jameso]

A possibly dumb Q - if I plug a rechargeable power pack only into my dynamo, am I right in thinking that under 25-30ish mph or before the battery is charged fully, the unregulated input isn't a risk, or the worst that happens is you may burn out a cheap power pack if left on charge when full or at higher speeds?
My Garmin charges well off the power pack I have and I think plugging the dynamo into either the light or the battery only, and then charging things from the pack when disconnected from the dynamo, may work for keeping navigation charged on a longer ride.

[johnnystorm]

On my commute my hub>recharge>battery is always connected (35 mins ride) and used to charge my phone every other trip. No big descents of course but nothings caught fire yet.

[johnnystorm]

In related news I've just bought a 10000mAh battery pack from Amazon (£12.99) with two usb out. The classic chinese cree lamps can now be had with USB plugs too. Still, I've bought a Revo now!

[mountainbaker]

I think this is what you need

[Zippy]

I think this is what you need

Once I googled the acronyms and what they are and do, I can just about make sense of that!

[Lughnasadh]

I totally need one of them ^^ in my life.

What does it do?

[jameso]

Is that a flux capacitor?

[Blackhound]

Bit of a thread resurrection. I am looking for a battery pack to sit between my SP dynamo ( for Revo) and Garmin Dakota that I can also use to charge as necessary. This gets a recommendation on the YACF forum but will it charge and discharge at the same time?

In use my understanding is that I would have batteries in the Dakota and when ever the lead from the dynamo via the battery is plugged in then it will override the batteries saving them for when needed which will be when I have the light plugged in during darkness. It will also override the batteries when the battery pack (which would start off full) and I have a lead between the two. Do I have this all correct?

I also plan to use it when camping or travelling for my phone so happy to have plenty of battery.

http://www.tecknetonline.co.uk/tecknet- ... black.html

[composite]

My setup is exactly like how you describe Kevin, you are understanding correctly. The only thing is that I use a Garmin 800 so I can't comment for exactly how your GPS will behave. The battery I use is this one. http://www.7dayshop.com/products/7daysh ... ONE4S-7003 Jack uses the same one.

I'm currently working on a blog post that covers my setup, all the kit used plus the work flow and cabling with photos. Just need to take a couple more pictures and it will be done.

[Blackhound]

Thanks Neil, will order one later. Look forward to your blog post as well as may give more ideas.

[Lughnasadh]

Blackhound,

I thought I had tried this before and IIRC you can not use a Dakota 20 while it is USB charging.
It might be worth checking that before shelling out. I thought I would need a second pair of AA with a AA charger running from the dynamo.

[numplumz]

Don't worry Kevin it will work.
You get the drive connected screen on first connect, res-start then operates as normal.
https://www.flickr.com/gp/44171250@N00/Xs6m73

[Blackhound]

Thanks Jack.

Ordered one this morning as the 7DayShop one was out of stock. Hopefully have for my first week in Septembers's adventure.

On the YACF discussion one person reckoned he had given up on his dynamo and gone for packs only. His thinking was that 4/5 packs costs ~£100 and would last for many hours. He was on about using in long audaxes where there is a drop bag so he can swap them out during his event. His gps could have a back-light overnight and sufficient light as well. Might be useful for up to 4-5 days, not sure about longer unless you were certain you could recharge your packs.

[JohnClimber]

The classic chinese cree lamps can now be had with USB plugs too. Still, I've bought a Revo now!

With £8 carriage do you think these are worth a punt?
https://www.chinavasion.com/china/whole ... aterproof/

Or one of these at £8.12 and free carraige
http://www.ebay.com/itm/CREE-XML-T6-5V- ... 0878036325

Would they work nearly as well as Revo's? through a SP hub and a Sinewave Revolution

[DoctorRad]

I think this is what you need

Woah! What does this do then...?

[johnnystorm]

That doofer doesn't do much until you hit 88mph.

[evilgoat]

John climber, that usb xml light won't work as output from an sp hub is limited to 500ma. You need 1500ma to get 300 lumen from that light.

Xml leds are rated to run at high drive currents. Not suitable for dyno applications.

[johnnystorm]

Battery packs back in at B&M. Will do simultaneous charge/discharge.

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