Instructables

Rechargeable Bike Light with automatic switch of energy source

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First of all, excuse my non-native English and my lack of professional electrical engineering skills. I see this as a hobby and have no claim to be perfect. However, if you have some ideas on how to improve the setting don’t hesitate to write a comment ;-)

I haven’t seen any similar Instructable yet, which is why I quickly created one =)

My former bikelight was a pretty standard halogen light which was directly connected to the dynamo (generator) of the bike. Major problems I had with it were:
- Insufficient brightness
- Characteristics of the light beam caused by the reflector
- Light was not available when standing or at very low speed (disadvantageous at traffic-lights, junctions etc.)

My goals for the new bike light were:
- Rechargability via dynamo
- No need to exchange batteries
- Higher brightness
- Better distribution of the light beam
- Availability of light at all times (standing vs cycling)
- Low-cost

edit:
- quite similar project : Rechargeable Bike light set with bottle battery
- all pictures shot in battery mode (on dynamo it's approx. 1/4 brighter)

 
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Step 1: Parts and Prerequisites

Picture of Parts and Prerequisites

Prerequisites
- Bike
- Dynamo (mine is 6V / 3W)
- Mount from old bikelight
- Small metal-box (Altoids etc.)
- Arduino Uno / duemilanove (only to program Attiny85)
- Heatshrink tubing / Lighter
- Wires (I use wires from old IDE/P-ATA cables and mark their polarity with permanent marker)
- Hotglue-gun
- Glue
- Electrical tape
- Cable straps

Specific parts
(all prices approximated, some example links provided)
- 5V Linear Voltage regulator $0,51 / 0,37€
- 5W LED Driver 3-18V input $2,60 / 1,89€
- Li-ion charge controller input voltage 4.5-5.5V $1,87 / 1,36€
- 2x Small R/C helicopter battery 240mah $3,44 / 2,50€
- Cree XR-E Q5 (or any high-power LED) $5,60 / 4,07€
- Bridge Rectifier $0,38 / 0,27€
- Attiny85 Microcontroller $2,49 / 1,81€
- Socket for Attiny chip (called DIP8) $1,88 / 1,37 €
- Lens or Reflector for LED $ 0,52 / 0,38€
- Capacitor (I used a 10 µF one, higher capacity is better ) $0,27 / 0,20€
- Transistor (I used 2N2369A, better use one for high currents) $0,27 / 0,20€
- Switch $0,27 / 0,20€

Sum ~ $20 / 15€

ktronik8 months ago

HI Great work, but I feel that your un-loaded voltage from the hub will be too high at good speed and will cook your main voltage reg (LM7805) over time.... you need to use a voltage limiter somewhere, and would pay to use a bigger smoothing cap, 4700uf is fine....

hope this helps....K

MYawar8 months ago

Thanks a lot! I have a similar configuration on my bike

Bumsfallera (author) 8 months ago
Thanks a lot! Really happy about the feature award too! =)
boatingman8 months ago
This is great stuff and your English skills rock.
billbillt8 months ago

i think this is very useful and a good idea..