Automatic dimming bicycle light help! – University Major Project.

Hi guys,

Warning! I am no Electrical wiz!

I am a (BA) Product Design student studying at the University of Derby. I am currently going through my major project research module, I have evaluated the market and found a need for an automatic light switching device between two different LED’s (mimicking a car full beam/ dipped beam light setup) I want this product to automatically do this through the sensing of its surroundings.

I have done research into Photodiodes, Accelerometers and Reverse-Biased LED’s, I want to be able to make this product change through either the monitoring of the light using a reversed biased LED (to know when a car’s lights are coming towards it, or going into street lit areas) or the use of an Accelerometer to monitor movement in the surrounding area for objects moving faster or slower than the cyclist, but not stood still. I will be running this product from a set of rechargeable batteries (early on in the project so not sure specifically on types Li-on most likely, something giving around 2300mAH)

As I say I really have little experience in this (If any), I hope someone could give me help/ advice in what is realistic in a solution for this project, I understand I have not given much to go off. Obviously the smaller and lighter the solution the better.

I will check back on here very regularly (every couple of hours) and look forward to see what you all know! Please if I am going completely up the wrong street with the technology I have already looked into or this is an unrealistic project please tell me!

For a bit of inspiration: https://www.kickstarter.com/projects/1670187625/seesense-the-intelligent-bike-light-with-road-sens this is a light that is a more complex version of what I am trying to do (I think)

Thanks for your time,

Adam.
:smile:

I designed something similar a few years ago but it never reached the prototyping stage. It used a PIC12F683, you are welcome to the source code if you want it.

My design worked the other way around, the light was turned on by a momentary push-button and while the bike was in motion it ran the light at full brightness in the assumption that a dynamo/generator was keeping the battery topped up and full brightness was best while cycling anyway. If the bike stopped, after a delay (traffic junctions etc) it started to dim the lights in stages using PWM until eventually shutting down altogether. The theory was that it was impossible to leave the bike for more than a few minutes with the lights left on so it preserved the battery while at the same time it gave best brightness when it was needed. Also, when stationary there was a danger that the lack of air flow around the LED would allow it to overheat if left for too long so gradually reducing the LED power protected it.

Brian.

Hello!

I did also my own brew of the same system.
As for getting power from the dynamo, I also made a FET rectifier rather than a
diode bridge. The advantage is that there is no loss at all (at least a very low loss compared
to diodes).

Dora.

betwixt said:

I designed something similar a few years ago but it never reached the prototyping stage. It used a PIC12F683, you are welcome to the source code if you want it.

My design worked the other way around, the light was turned on by a momentary push-button and while the bike was in motion it ran the light at full brightness in the assumption that a dynamo/generator was keeping the battery topped up and full brightness was best while cycling anyway. If the bike stopped, after a delay (traffic junctions etc) it started to dim the lights in stages using PWM until eventually shutting down altogether. The theory was that it was impossible to leave the bike for more than a few minutes with the lights left on so it preserved the battery while at the same time it gave best brightness when it was needed. Also, when stationary there was a danger that the lack of air flow around the LED would allow it to overheat if left for too long so gradually reducing the LED power protected it.

Brian.

Click to expand...

Hi Brian,

Sounds interesting! If that source code would be of some help to me, (am not sure, am too new' at the minute) I would be happy to look at it!