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Looking at building an LED flashing unit, no idea where to start.

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PaulW

New Member
Hi all

Just wondering if anyone minds helping me work out how to design or make a circuit capable of switching 2 x 12v outputs (which power LED brake lights on a motorbike) in a specific order?

Sorry if I don't explain this well, but basically...

When the brakes are applied (+12V signal)

Time Left Right
50ms 0 1
50ms 1 0
50ms 0 1
50ms 1 0
50ms 0 1
50ms 1 0
50ms 0 1
50ms 1 0
50ms 0 1
50ms 1 0

then the following repeats constant cycle
5s 1 1

200ms 0 0
200ms 1 1
200ms 0 0
200ms 1 1
200ms 0 0
200ms 1 1
200ms 0 0

So basically, the quick alternating "WigWam" style effect only occurs at the start of the cycle (each light illuminates for 50ms each 5 times)
then both lights come on for 5 seconds
Then both lights cycle off and on 3 times at 200ms before going back to static on for 5 seconds

Sort of like how I've got it animating in this image



Does anyone know how this may be done? Or have any solutions where to begin?

The source power is 12v (peaking 14v), and output to each light unit is 12v at around 1.5A (I'm still yet to get the actual details on the lights)

Already looked at a few circuit designs online, but can't find anything which can do the above...

Thanks for any help :)
 

marcbarker

New Member
Hey this is a neat one!, totally illegal of course! :D

Is it for slowing down from 240 km/hr?

Parts list:
PIC microcontroller (to do sequencing)
78L05 (to power the PIC)
P-ch MOSFETS x 2 (to power the lights)
and a few other little bits and pieces

Build whole thing inside a matchbox sized module.

Do wanna market this as a product? How much would it sell for?
 

PaulW

New Member
Illegal but visible :) Won't be marketing it no, its for my own little project! I like tinkering with most things, but this is probably slightly beyond my current skill levels (give me a spanner and an engine I'm fine, but we all have to learn new things sometime right??)

Well the list you just posted up is more than I worked out... Guessing the PIC would need programming then..?? (have very limited knowledge of these). the rest does make some sense...

Feel like a lemon trying to figure all this out so far!
 

BrownOut

Banned
This would be a very simple thing to do. You just need a multi-vibrator which switches form alternating to simultaneous flashing. I hesitate to try to design the circuit however, because when I do that for folks who don't have a strong electronics background, they typically can't understand or build the circuit correctly.
 

marcbarker

New Member
I'm happy to design the whole thing start to finish, right down to the last nut and bolt. But to make it worthwhile for both of us there ought to be a return on it. Maybe you could post the design on a Biker's Forum as a product and we sell them? ;)

Otherwise, I'm happy to give rough ideas in the hope that they can be developed further :)
 

BrownOut

Banned
Why would you sell a product that you believe to be illegal? BTW, if I knew there was a market for this, I'd make a bunch and take them to my local flea market. Since I'm out of work, I have lots to time on my hands.
 

kpatz

New Member
Definitely use a microcontroller. If you try doing it with flip-flops etc. you're talking about a lot more chips. Even the cheapest 6-8 pin PIC will do the trick. Program it to do the sequence you want, have the PIC control a pair of MOSFETs that turn the lights on and off, and power it from the original brake light circuit.

Piece o'cake (well, at least for someone who knows some electronics and can program a PIC).

By the way, are these brake lights LED? Because a regular bulb isn't going to be able to flash on and off at a 50ms rate.
 
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marcbarker

New Member
Why would you sell a product that you believe to be illegal?
This is my personal opinion: It's only illegal to fit and use it, but not sell and buy it (unless doing so encouraged laws to be broken). In practice the user takes full responsibilty and the seller disclaims any liability for the use/non-use of the product, just like undersized number plates, racing tyres and bike-2-car rocket launchersAre there any state laws against motorcycle accessories such as the Sickshooter 45 Caliber Gun Foot Pegs?
 
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PaulW

New Member
Yes the brake lights are LED's, so its not an issue in regards to the 50Hz flash cycle. Started reading up on PIC programming after tea, looks simple enough so that shouldn't be a problem. I guess its just how to get everything together, circuit and such which I'm unsure of...

Just not sure (and can't really find anything online for looking...) on what PIC to use (as said, simple 6-8 pin one? Most examples online are all 16pin+...

10MHz resonator for the clock be sufficient?? Also I can see how the 78L05 is used (sort of) seems simple enough...

Also just wondering the best way to get the 12v line to the P-ch MOSFET (can't find anything) I can see how the outputs from the IC are processed, but just can't find any info on how to actually hook up a mosfet and use it...

Cheers :)
 
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