Very cheap dynamo light upgrade

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Stradageek
Posts: 1657
Joined: 17 Jan 2011, 1:07pm

Very cheap dynamo light upgrade

Post by Stradageek »

I know there are many elegant solutions around but I wanted a minimalist way of a) stopping my old bottle dynamo driven lights blowing bulbs on fast descents and b) to increase the brightness of the rear lights

For £1.98 I bought 10 IN4001 diodes and 10 5.7V/1W Zener diodes. I added some old 200 Ohm resistors and two red LEDs from some defunct battery rear lights at no cost.

The Zeners made a back to back 6V clipping circuit and the LED/resistor/diode (half wave rectified) replaced the rear light bulb.

I now have a brighter rear light and a bright but safe front light all in the original vintage housings. Total cost of new components 30p per bike.

And, most important, it was fun to do
Brucey
Posts: 44521
Joined: 4 Jan 2012, 6:25pm

Re: Very cheap dynamo light upgrade

Post by Brucey »

nice work! Next step is a DIY LED upgrade for the front light, obviously.... :wink:

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
rjb
Posts: 7200
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Very cheap dynamo light upgrade

Post by rjb »

Nice,
Lots more ideas here - http://pilom.com/BicycleElectronics/DynamoCircuits.htm
and a good source of leds is from GU10 bulbs where the electronics fail but the actual leds are fine.
viewtopic.php?f=5&t=116628

you may even be able to use a MR16 led bulb if there is room to squeeze one in. :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
SA_SA_SA
Posts: 2360
Joined: 31 Oct 2009, 1:46pm

Re: Very cheap dynamo light upgrade

Post by SA_SA_SA »

Why not use a full wave rectifier for less flicker?

NB I would use an 'approved'* dynamo LED rear lamp in parallel for legal piece of mind (eg an electrically frugal one: spanninga's usually only use 30mA).



*Stvzo (with RKF3 if possible) or BS6102/3(rare :( )
------------You may not use this post in Cycle or other magazine ------ 8)
Stradageek
Posts: 1657
Joined: 17 Jan 2011, 1:07pm

Re: Very cheap dynamo light upgrade

Post by Stradageek »

I wondered about the flicker level but decided that as it only appeared at very low speed that a) it didn't matter much and b) might be considered a bonus - as I slow and the LED dims the flickering might make it more noticeable

Like the idea of using old GU10's too. I've pulled a few apart to show people that when they die it's not the LED just the cheap over-driven bias circuit, now I have a use for debris
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