Dynamo overvoltage protection- Mtbr.com
Results 1 to 6 of 6
  1. #1
    mtbr member
    Reputation: piesoup's Avatar
    Join Date
    Feb 2009
    Posts
    455

    Dynamo overvoltage protection

    Hi everyone

    I have a project, where I want to get USB 5V out of a dynamo.
    Its a standard 6v/3W dynamo.
    I can make the switch mode regulator circuit, there are loads out there. And I can rectify the AC from the hub to DC. But, if there is no load on the circuit and I ride over 25mph, the dynamo can produce over 100v. The 5V regulators I've seen, has a Vin MAX of 60V.

    I would like to limit the voltage after (or before) the rectifier, but keeping the circuit as efficient as possible, as its my spindly legs that's powering it!
    I have seen a few circuits with 2 zener diodes in parallel to Vin. Seems simple enough, but they don't look all that efficient. The other reason I'm asking on here is that the posts are often over 6 years old. Has the tech caught up and is there a more efficient method? Preferably something that doesn't get hot.

    If not, can I get some help in selecting the correct zener for the job. I know ktronic has done a lot of work on dynamo lights, hiopefully he'll see this!

    Links to the zener protection I have seen

    http://www.ad5x.com/images/Articles/Vprotect.pdf
    https://people.nscl.msu.edu/~daniel/sreg.htm

    Thanks muchly!

  2. #2
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    324
    If there is a more efficient way, I haven't stumbled upon it. The commercially available overvoltage limiters use zenners as I understand it - eg shimano overvoltage protection.

    From a conceptual point of view, to limit voltage wouldn't you need to either open circuit the dynamo (ie before the rectifier) or add a load.

    Is there any reason a switch wouldn't work - ie disconnect the dynamo when no load ?

  3. #3
    mtbr member
    Reputation: piesoup's Avatar
    Join Date
    Feb 2009
    Posts
    455
    Quote Originally Posted by find_bruce View Post

    Is there any reason a switch wouldn't work - ie disconnect the dynamo when no load ?
    Then it isn't really failsafe protection is it? Want something automatic I think.
    Good to know zeners are still the component of choice, nice and easy! Cheers, I'll have a look at that link you sent, never really thought of looking at OEM.
    Cheers

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    324
    Don't think the Shimano one will permit enough voltage for your purposes - I believe it limits to less than 9V

  5. #5
    mtbr member
    Reputation: piesoup's Avatar
    Join Date
    Feb 2009
    Posts
    455
    Yeah, I saw that too.
    I've found a good alternative. Use an AC zener on the AC side and couple a thermoswitch directly to the zener. Zener starts conducting, heats up, the switch opens the circuit. No more voltage flows and the zener cools down.
    This wont be a problem as there will only be an over voltage if there is no load.

  6. #6
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    324
    Neat solution - got a link to the parts you are using ?

Similar Threads

  1. Dynamo Hub ...
    By xJZ in forum Lights and Night Riding
    Replies: 12
    Last Post: 09-30-2013, 03:25 PM
  2. Frame protection and fork protection tape
    By Roadking1962 in forum Pivot Cycles
    Replies: 20
    Last Post: 09-10-2013, 07:53 PM
  3. Dynamo light + dynamo GPS (or phone) charging. Bye-bye batteries?
    By robdeanhove in forum Lights DIY - Do It Yourself
    Replies: 8
    Last Post: 11-04-2012, 02:38 AM
  4. Replies: 12
    Last Post: 05-01-2012, 08:28 AM
  5. Dynamo hub
    By more10 in forum Lights DIY - Do It Yourself
    Replies: 5
    Last Post: 11-26-2011, 12:06 AM

Members who have read this thread: 0

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.