Automatic dimming bicycle light help! – University Major Project. - Page 1
Forum section: electronics / projects

author: AdamMortlock
author_rank: Newbie
timestamp: November 21, 2013, 10:48:06 am
content: 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:http://www.kickstarter.com/projects/1670187625/seesense-the-intelligent-bike-light-with-road-sensthis is a light that is a more complex version of what I am trying to do (I think)Thanks for your time,Adam.

author: Jon86
author_rank: Frequent Contributor
timestamp: November 21, 2013, 01:01:22 pm
content: How are you trying to measure the speed of other vehicles with an accelerometer?If I understand right, this should be fairly easy to do with some Schmitt triggers, logic etc. At least give it try, and we'll help.

author: AdamMortlock
author_rank: Newbie
timestamp: November 21, 2013, 01:59:47 pm
content: Thanks for the shown interest guys! to answer your questions;Quote from: Pippy on November 21, 2013, 11:47:50 amAs a Product Design student I do not think I have to design the automatic dimming light function (but I do need to fully understand it), but if it is something that wouldn't be to hard to do I would love to give it a go! I do want to have a working concept, so if it was too difficult then I would pay someone to design and make the component (unless it was a ridiculous cost)Quote from: Jon86 on November 21, 2013, 01:01:22 pmAm not sure to be honest, I think I had the wrong idea for the accelerometer looking now.Just an update, I am thinking for power using, 4 X 700mAH 3.7V CR123A rechargable batteries, can yo guys see any problems with that?

author: Jon86
author_rank: Frequent Contributor
timestamp: November 21, 2013, 03:40:25 pm
content: An accelerometer is a chip that measures the acceleration of itself, on three axes usually. It cannot measure the speed of anything external, and it cant measure the speed of itself either. Those batteries should be okay, you can always add more if you need to.Now, have you got any ideas for your circuit? Any basic plans?

author: Legit-Design
author_rank: Frequent Contributor
timestamp: November 21, 2013, 03:50:54 pm
content: Quote from: AdamMortlock on November 21, 2013, 10:48:06 amFirst you don't need two different leds for two different brightness levels. If you actually did any research into leds and electronics you would have found out about PWM of leds.Why dont you ask them to add functionality you want into their existing product? Looks like their product is already 99% there. If they can blink a led at different brightness levels then they need to just change the functionality a little bit. Or just get their product, modify it to do what you want. Better yet buy group of people their own and hope some of them will be motivated enough to do it.

author: AdamMortlock
author_rank: Newbie
timestamp: November 21, 2013, 04:33:25 pm
content: Quote from: Legit-Design on November 21, 2013, 03:50:54 pmThanks for the input! Well I will be running the same LED's but they need to go through two different lenses to give the different beams. (full beam and Dipped beam), is that what you mean? Unless PWM can completly make up the beam shape of the LED then I am not sure it will work? this light is for cyclists the needs both wide lighting for off-road and closed lighting regulating to german road legislation for on-road/ oncoming traffic. If it comes to getting one, to modify it slightly I am fine with that also. but this learning process is good for me also.Quote from: Jon86 on November 21, 2013, 03:40:25 pmThanks for clearing that up for me, I have been given a plan from someone else in another forum, Hopefully it does the following;1. The user can do several things, They can manually change the beams themselves if they want to, if the light is switched on by the user then the light will automaticallly go into the full beam until the sensor puts it into the dipped beam, unless it needs to be in the full beam.2. If the dipped beam is started by the sensors sensing oncoming traffic/ street lighting then the dipped beam will acivate and then the full beam will go off (it has to be this way around, to ensure ther is always some lighting)3. When the traffic passes or it get's dark again the full beam will come back on and the dipped beam will go off.4. Users need to be able to overide this module so they can turn the automatic switching off (some riding needs to have full beam constantly irrespective of oncoming people)Below is the image I got.

author: IntegratedValve
author_rank: Regular Contributor
timestamp: November 21, 2013, 04:48:57 pm
content: Quote from: Pippy on November 21, 2013, 11:47:50 amIs it that you can do the design for some cash? Nice try.

author: Jon86
author_rank: Frequent Contributor
timestamp: November 21, 2013, 05:25:55 pm
content: That schematic could work, however you're not going to get a very reliable system from that.You probably want a comparator with a potentiometer so you can change the thresholds, and a schmitt trigger so you don't get your lights flickering on and off.See if you can make up a little schematic with that, and we'll give you some help if you need it.Also, how much EE knowledge do you have? What kind of things do you understand?

author: Jon86
author_rank: Frequent Contributor
timestamp: November 21, 2013, 05:29:31 pm
content: Just a little sidenote here, that crowdfunding campaign you linked to, it seems like a nice idea, but did anyone else watching that get really pissed off by the flashing light?I'm a cyclist myself, and I understand how frustrating it is when cars don't take notice of you, but I'd never use a flashing light like that because it must be incredibly irritating for motorists, especially when it flashes that bright.

author: Rufus
author_rank: Super Contributor
timestamp: November 21, 2013, 06:23:14 pm
content: Quote from: AdamMortlock on November 21, 2013, 10:48:06 amThat is probably your first problem.Hands up anyone who has been dazzled by a bicycle light and wished they had a dipped beam....

author: AndyC_772
author_rank: Super Contributor
timestamp: November 21, 2013, 07:37:15 pm
content: I wondered where that "need" came from too. I'm far more often annoyed by cyclists that don't have a decent light, or any light at all, for no better reason than they can't be bothered.To me it feels like a lot of technology being throw at a problem that could be far more easily solved by using a slightly bigger battery.That doesn't make this project a bad academic exercise, of course. If the object of the exercise is to learn something about sensors, power control, product design and so on, then the fact that it wouldn't be a good commercial product doesn't matter.Switching LEDs on and off is the least of your problems. It's completely trivial. The challenge here is sensing the unit's environment, and doing it in a way which is compact, inexpensive, draws much less power than an LED, and above all, is reliable.

author: AdamMortlock
author_rank: Newbie
timestamp: November 21, 2013, 10:50:12 pm
content: Thanks guys!Quote from: Jon86 on November 21, 2013, 05:25:55 pmOK, thanks for the help, my EE knowledge is non-existent, but like I say I have 3 -5 months to get knowledge and create a good working one, which with the help of you guys, me testing different things and the help of the electrical engineering tutors at University it should be plenty of time. Yes! that flashing was a bit annoying in the video, I imaging it would be especially annoying on the front light!Quote from: AndyC_772 on November 21, 2013, 07:37:15 pmyour right! you do not get dazzled by cyclists very often, that is because now they have German regulated lenses that have a horizontal cut-off to stop the light going into the oncoming traffics eyes, the problem is that this kind of light is no good for off-road (as you need light everywhere) so cyclists often have to get two lights, one for off-road and one for getting to the trails and back, and then swap it between bicycles for weekly commuting. Why not get it all-in-one? and even better if it has innovative functions! then you only have to worry about charging one light, swapping one light and only have one light to worry about keeping on you so it doesn't get stolen. Hopefully this makes senseThanks guys !Adam.

author: kizzap
author_rank: Unknown
timestamp: November 21, 2013, 11:54:39 pm
content: Don't quote me, but isn't it illegal to use the high beams in built up areas? (where most cyclists are going to be riding)

author: JohnnyGringo
author_rank: Regular Contributor
timestamp: November 22, 2013, 12:26:28 am
content: Quote from: AdamMortlock on November 21, 2013, 10:48:06 amAs I'm sure you learned from your Physics 101 classthat speed is relative to your choice of reference frames. Google "future light cone" for some basic information.A cheap GPS module (as recently discussed in this forum) can establish the cyclist's inertial frame.For detecting the speed of objects in the surrounding area, you will need to establish their reference frame as well. A simple range finderwww.amazon.com/gp/product/B0066X9V5Kmight work.With a arduino, you'd need to transform one of the frames with some simple vector algebra.The rest of the problem I'll leave as an exercise for the reader.

author: RobB
author_rank: Contributor
timestamp: November 22, 2013, 11:57:01 pm
content: Just to tie together some of the ideas offered so far.The Arduino is an exellent means of achieving what you desire. There is an almost endless supply inovative applications and many pre made modules like IMU's, relay boards motor drivers, GPS etc and most importantly a large helpful user base.I made a dimmable cycle light a few years ago using PWM from a microcontroller on a 20W halogen MR16 bulb. This was before the availability of powerful LEDs. I am not sure of the luminosity of MR16 ligfhts but I will say they certainly gained the attention and respect from car drivers. So I would suggest a similar of better luminosty in what ever luminare you use.Some observations on what works and what does not. Firstly the beam width. I found the optimal beam for fast road riding was using a lamp with a 20 degree dispertion angle. This concentrates the light beam to be ideal for a cycle. You could also add some smaller side emiting lights to give better visibility of the cycle to vehicles on side roads.Like some others have said the concept of an actual dipping beam on a bicycle is not really relevant as a cycle does not travel fast enough to require a hi beam per se, but the concept of a dimmable light intensity is useful as you can vary the light output to suit the ambient light and conserve battery consumption.As you are aware battery capacity is important so you don't want to be burning up that power with conventional biploar transistors. Best to use very low resistance FETs field effect transistors.As this is a design exercise and not an electronics major, an alternative simple way to control the light might bebrushednot the more common brushless motor speed controller as used on RC models. This again would be easily controlled from an Arduino or even a 556 dual timer IC.Using the Arduino you will have plenty of capability to add extra functionality like turn direction indicators programmed to self cancel after the corner has been negotiated. Incoprorate a speedo and trip meter and all sorts of other functions. The other party trick of the Arduino is the various form factors. Obviously the standard board will not be suitable for finished unit but you can get variants like the Nano model which is sort of IC shaped and sized as well as the option to make a custom PCB for just the Arduino processor chip and support parts.A better battery chemistry would be LiFePo4 commonly called lithium iron, LiPo's are trickier to charge and handle safely while the LiFe batteries are much safer and have similar capacity to mass ratio just a lower discharge current rating, typically 1 to 5C which in the case of a 3000mAH cell would be up to 15 amps at 5C. In reality you will never need any more than 2-3 amps for the LEDs.Definitely fit a fuse physically close the the batteryfor safety reasons.Finally for the oncoming light detection you will need to restrict any stray side lighting with, for example a long black tube with the sensor mounted at the far end.Best of luck with the project and career.cheersRob

author: miceuz
author_rank: Frequent Contributor
timestamp: November 23, 2013, 12:57:13 am
content: If you want to go dirt cheap, this is a switch for you:It accomplishes the same effect as an accelerometer. It is cheap as dirt in components, but might be not that cheap as in manufacturing.Here's more info:http://wemakethings.net/2013/02/03/auto-off-bike-light/

author: JohnnyGringo
author_rank: Regular Contributor
timestamp: November 23, 2013, 04:00:10 pm
content: Quote from: JohnnyGringo on November 22, 2013, 12:26:28 amI'm surprised that nobody picked up on my pun"future light cone" -- moving flashlight ? I though that deserved as least one *groan*.