not a clue to what im doing

[stevenfrye]

hi all, let me get this out of the ive read the begineers radioshack books and thats about it. ive a problem, i have almost been run over twice on my motorcyle since allot of the time i just let off on throttle to slow down. i need help on building a accelerometer based something to flash the brake light to let people know what im doing. ill be reposting whatever help i get onto the motorcycle forum to let other riders do this too, dont want cash or anything just to help myself and others out.

 

[keith1200rs]

Buy a book on how to ride a motorcycle. The UK book 'motorcycle roadcraft' covers such situations as well as many other ways to help you stay alive on a motorcycle.

Keith

 

[stevenfrye]

Buy a book on how to ride a motorcycle. The UK book 'motorcycle roadcraft' covers such situations as well as many other ways to help you stay alive on a motorcycle.

Keith

WELL guy I know how to ride quite well l in fact have been most of my life. First off I live in California not in the UK where people generally give a Damn about whose on the road with them. Now to repeat myself to which I am loath to do. How can I build an accelerometer based light trigger to flash the brake light when I'm not using the brakes and slowing in deceleration and to shut off when I lay into the throttle again. My riding or mechanical skill are not in question here my electronics skill, let us stick to that I would rather not have to speak to you like your an impertinent child.

 

[keith1200rs]

WELL guy I know how to ride quite well l in fact have been most of my life.

It doesn't really sound like it.

One thing mentioned in the book (chapter 6 in the edition I have) is the importance of touching your brakes so your brake lights come on so people behind know what is happening even if you don't need the brakes to actually slow down. Same goes for when you are stationary at a junction. Electronic gadgets are no substitute for riding skill (and yes, I have been riding bikes for a very long time as well).

An accelerometer could be used to do what you want but I think it would need to be in conjunction with a microcontroller to prevent it coming on when you don't want it to. However, debugging the software will be tricky as it will need to be on a moving motorcycle. A simple analogue system may work, although you would need to add adjustable time delays before it actuates and after it has come on (555 timers could probably suffice). You might also want to check the legality of what you are planning to do.

Keith

 

[betwixt]

I agree with Keith and I've clocked up around 100,000 miles on two wheels myself.

From a technical point of view, I wouldn't use an accelerometer, I would interrupt a light beam through the back wheel (that way it still works when you pull wheelies :grin and check if the rotational speed is increasing or decreasing. It would be cheaper and less complicated and most importantly, it wouldn't give false readings when you turn corners.

Brian.

 

[keith1200rs]

Another option would be a microswitch on the throttle with a delay so it doesn't put the brake light on when changing gear. However, I still think it is a complicated alternative to touching the back brake when decelerating.

Keith

 

[kripacharya]

..... it wouldn't give false readings when you turn corners.....

I was curious why you would get "false" readings ?
Wouldn't the acceleration round a corner be at right angles to the original movement, and hence not appear on the (say) X-axis output, but only on the Y-axis ?

 

[stevenfrye]

Sorry I got a bit snippy. On my bike I do allot of what we call twistys and a considerable amount of track practice. When your flipping your bike side to side at a considerable amount of speed dragging on the brakes isn't all that advisable, plus using the brake activates the anti dive function built into the front forks. I thought about somethings simple as spring ans weight loaded device but I don't want inadvertent bump activation.

 

[betwixt]

The accelerometer would return XY values according the force vector acting on it. In the case of a motorcycle it isn't generally a good idea to apply the brakes when cornering so there wouldn't be much point in sensing side-to-side forces. Using only the forward direction, a vector away from straight ahead would return an inappropriate although not technically wrong reading and make the lights operate. In use, it would probably light the brake lights whever a corner was turned which isn't what is needed. I would imagine for this application, only a single axis reading would be necesary anyway so simply sensing the speed should be enough.

Brian.