Steve K
Flashlight Enthusiast
Yeah, going fast is the easy bit! I did think about using a microcontroller, using a voltage divider to sense the voltage and therefore the speed. Could use a FET to turn on the extrab LEDs couldn't I? With a IC out could get real geeky and have it adjustable too!
This is great, thanks Steve. I won't be building this immediately, just want to do as much research as possible first. And I should be studying for my aircraft engineer degree, not tinkering in my workshop!
a microcontroller would make some of the control easier. Measuring the dynamo's speed would let you use knowledge of the dynamo's characteristics to match the load.
I matched my load by adjusting the number of LEDs hooked in series. I just shorted out half of the LEDs at low speeds, just to keep things simple. A more sophisticated technique would be to have the dynamo feed a buck converter, which then drives a single big LED like an XM-L. The microcontroller would measure the dynamo's speed and set the buck converter's duty cycle. Piece of cake.
I haven't worked with micro's for over 15 years, and that was with Motorola's 6811 family. A little PIC or Atmel seem like a good match for this sort of work.
A more general approach would be to use "maximum power point" or "peak power tracking" method that involves making small changes to the desired output power of the buck converter and seeing if the actual power to the load increased or decreased. When I designed a circuit for this purpose, I actually monitored the input power ripple while adding a small "dither" to the control voltage to the buck converter, and the control loop tried to minimize the ripple.
Is "aircraft engineer" similar to an aerospace engineering degree here in the US? Aerospace and/or aviation is a very interesting field of work. I spent a number of years doing electronics design for aircraft and satellites... lots of fun, but funding was very volatile.