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Need help on a circuit design and picking out components for a high output LED bicycle light! Answered

I am building a high powered LED bicycle light using two 7V 5W LEDs (P/N: VL-H01W60005 from here: http://www.superbrightleds.com/moreinfo/component-leds/vollong-5w-white-high-power-leds/898/2213/ ) and I am unsure what other components I should use. 

I was considering using a bunch of 9v batteries in a series & parallel configuration to achieve 18v and a higher amp-hour output.  Also, could I implement the use of a Joule Thief in my circuit to get more out of my power source?  Does anyone have any suggestions on a different power source as well?  Many thanks!


A Joule Thief has only a 40% to 70% efficiency; you should not consider it for your light. 9V batteries are ridiculously expensive, so use them if you have deep pockets. I would use 6 cells in series, but 5/7 of an amp is a lot of current for AA cells, maybe use C or D cells instead. 6 cells give you 9V, the LED needs 7V, so you use a current limiting resistor of 2.8 ohms, or 3 ohms would do, and at least 2 watts. If you want a low power setting, switch to a 5 to 10 ohm resistor. If you use rechargeable Ni-MH cells, put 8 in series to get 9.6V. And keep a spare set of cells in your pack, you're going to need them after few hours of riding,.

I think you will have to decide your power requirement first. This can be calculated once you decide the longest timings that you want your lights to be on.

Once this is decided you will be able to calculate the minimum power requirement for this and then you have to select the batteries according to your need & a circuit that will see that you get constant power ( proper voltage & proper current despite changing condition of battery).

This is required to get constant light output from your LEDs. That is where the switching regulator will come into picture.

You need a proper switching regulator to drive these beasts - buy one is the best option. COncentrate on your housing.



What is the benefit of a switching regulator? I honestly have little knowledge about proper circuit components. Do you have any recommendations on a specific switch regulator for this device?

Also, I am using a modified Sharpie Magnum marker as the casing for this light. The sharpie magnum marker comes in an aluminum cylinder that the LED fits perfectly in.


Switchers are close to 90% efficient at getting the energy in a battery safely converted into what your LEDs need.

I've been meaning to put a new Instructable together about building one for what you want to do. Can you wait for a week or so ?

Switchers are fairly tricky to lay out so that they work reliably. "Linear Technology" and "Maxim" offer some great products though.

Look for "boost" LED regulators


I will definitely wait for your Instructable. Thanks for the information about the proper circuit components.