CityCyclingEdinburgh Forum » Computers, GPS, 'Smart' 'Phones

Warning for gadget geeks

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  1. chdot
    Admin

    "Actually I don't have many photos of the trip. I made a charger using a circuit from the internet so that I could charge my camera phone from the front hub dynamo. This worked well for a while before cooking my phone down a long decent!"

    Posting on a Moulton Forum.

    Bike in question (touring Switzerland)

    "I am happy to report that my 1963 bicycle performed superbly with no problems whatsoever other than punctures. The F-frame really is an awesome load carrier"

    Posted 12 years ago #
  2. cb
    Member

    "I made a charger using a circuit from the internet"

    I think I've spotted where he/she went wrong.

    Posted 12 years ago #
  3. ""I made a charger using a circuit from the internet"

    I think I've spotted where he/she went wrong."

    Must have had a REALLY long cable...

    Posted 12 years ago #
  4. spytfyre
    Member

    I am tempted to make a solar charger from 4 solar powered garden lights and an old USB extension cable, put the lot inside plastic pocket folders (like for CCG geeks) and seal them up... I would never trust a dynamo.

    Posted 12 years ago #
  5. chdot
    Admin

    "I would never trust a dynamo"

    to do?

    The thing about dynamos is that their voltage isn't entirely linear - doesn't keep going up with speed.

    The voltage also depends on load - which is why, if you've ever used one, you'll know that if one bulb goes, the other is likely to soon after!

    I suspect the charger wouldn't have been a particularly high load, and whoever designed the circuit wouldn't have allowed for the fact that it was going to be used on a small wheeled bike (on very steep hills...)

    Posted 12 years ago #
  6. steveo
    Member

    Fairly simple to get around if your not interested in efficiency. An LM7805 can take up to about 37v input with a smallish heat sink and out put a good, clean, constant 5v. Any power over 5v gets expelled as heat.

    Hook that up to the dynamo along with a simple bridge rectifier made from 4 diodes and you have exactly the same 5v you get on your USB.

    They use these chips in most pc power supplies.

    Posted 12 years ago #
  7. spytfyre
    Member

    @chdot - to charge a phone or other expensive device, lights yes.

    Posted 12 years ago #

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