Help in creating a battery pack charged by bicycle dynamo

[barughy]

Hello all,
I'm a complete novice in regards to anything electrical (I know how to wire a plug and thats about it) so I need you help if possible.

I'm looking to charge a battery pack using a 'Brompton AXA Traction Right Hand Dynamo'

This is what i'm hoping to acheive (let me know if its possible or not)

1. That I can charge to battery pack (what size? What type of batteries? etc.)

2. I would like to make a light sensitive switch that would allow my headlamp (LED) to draw power from the battery at night automatically (help in how to do this and what I need to complete the circuit)

3. If possible I would like to also allow my I-pod to connect to the battery pack for charging during daylight hours (again is this possible? and can you please guide me through the process?)


That's pretty much it. I really dont know where to start and the information on the internet involves a hugely steep learning curve. I need to do this as part of a project so buying ready-made equipment isn't an option. DIY only.

Any help would be huge.

 

[SABorn]

Well for starters you need to help us help you, by finding some data on variuos parts you have, like what voltage do the dynamo put out at what rpm of the wheel (approx rpm), any idea on what current the dynamo will supply.

What is the voltage and current needs for the led headlight.

You ask about battery packs? but without the above information we can not give an answer.

Light sensor is the easy part, and a LDR and a opamp or comparator would do that, but we need to know the data on the led headlight so we know the current supply needs and the voltage.

Best you do some of the leg work, and then we can help fill in the gaps.

Just remember the greater the current load that is drawn from the dynamo, the greater the friction drag applied to the bike wheel, and hence the more energy required to pedal the bike.
The more power you extract from the dynamo will be like putting the bikes brakes on more and require you to pedal harder to over come the added friction.

Pete.

 

[barughy]

Hi Pete, thanks for replying. here is the dynamo I've just bought;

**broken link removed**
Power source: 6V, 3W
I dont know what the RPM requirments are because It's being delieved by post, but reviews have said that walking speed is enough to power their lights.

The LED light that I have is powered by two AA batteries. I would like to dispose of the batteries and have it powered by the dynamo instead. It may be easier to buy a new light or make one myself, so I'm open to suggestions.

As for drag and friction, that's not really a problam. I have to build this as part of an apprenticeship presentation interview. So as long as it works I should be ok.

 

[barughy]

Thanks for replying Pete,

My dynamo is in the post but online reviews say it generates enough power for lights even at walking speed.
Here's the link: **broken link removed**

Power source: 6V, 3W - I believe that the current is DC, but not 100% until it arrives.

The light I've purchased is this: Eurolight Blue 3 Led Bar Light with Static and 3 Flashing Modes: Amazon.co.uk: Sports & Leisure

I would like to wire it so that they run off the storage battery that is charged by the dynamo during daylight hours, with the light sensitive switch determining when it turns itself on. Hopefully all the circuitry for that can go into the space used for the batteries.

As for friction and drag, it's not such a big issue. I have to complete this project as part of an application to an engineering apprenticeship, so as long as it works i should be ok.