Author Topic: LED Rear Light Project  (Read 37196 times)

martin999

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LED Rear Light Project
« on: December 28, 2009, 01:21:56 AM »
Following on from my unsuccessful Brake Mod installation using a so called 'direct replacement' LED bulb, I have decided to do what I have been thinking about for a while now and make my own!

Hopefully this thread, as it progresses, will give others a little insight into possibilities of replacing a standard bulb with an LED array for use with the BikeVis Brake Mod..... and hopefully I'll get some advice as well!!

Of course, I could go out and buy myself a complete replacement LED tail light, but they are quite expensive and the only ones I have seen so far have a clear lens and I want to keep the red lens of the stock tail light.  Oh, and making my own is much more fun!

There are two major design considerations, 1) number and type of LEDs, and 2) regulation of the array.

1) Number and type of LEDs.

This, without doubt, is the single biggest problem and the reason why this little project has been so on and off since I started to think about it.  I could go down the trial and error route with lots of different LEDs, but this is a one off and I'm the kind of person that wants to get it right first time!  The starting point would be the 12V 5/21W bulb currently used.  The problem is that the light output of incandescent bulbs is measured in lumen, whereas LEDs are measured in candela and there is no direct correlation between the two.  I did find an on-line calculator that did a conversion using the mcd and viewing angle of the LED, but this still doesn't help much because the red lens filters out all but the red light from the bulb and the luminous flux value of the bulb is for the white light across the whole of the spectrum.  Hopefully I have that right, but in any case it means that there is no way of specifying a number and brightness of LEDs to replicate the original bulb!!

I am pretty sure that I have now decided on the following.  The array will be as follows....

         o  o  o  o  o  o  o  o
     o  o  o  o  o  o  o  o  o  o
     o  o  o  o  o  o  o  o  o  o
     o  o  o  o  o  o  o  o  o  o
         o  o  o  o  o  o  o  o 

o will be the tail light which will be on all the time.  They will be 22 Osram LS E67B-S2V1-1-1 Red LEDs
   Typical spec's are 562 mcd / 120o viewing angle / 1.70 lm / Vf = 2.2 V / If = 50 mA

o will only activate when the brake is applied.  They will be 24 Osram LS E6SF-V2BA-1-1 Super-Red LEDs
   Typical spec's are 1572 mcd / 120o viewing angle / 4.65 lm / Vf = 2.15 V / If = 50 mA

The brake LEDs will also be run through a BikeVis Brake Mod that will be modified so that they will remain off until the brake is applied.

I still have no idea if these will be bright enough, (or even too bright!) but they are as close to a best guess that I can make!  The other concerning issue is the red lens.  Hopefully the red lens will let through all the red light from these LEDs, but if the red of the lens is different to the red of the LEDs then I could loose a lot of light through the lens!!

I will also need to incorporate some white LEDs directed down to illuminate the number plate.

2) Regulation of the array.

From my experience with my 'replacement' LED bulb, I have found out that regulation is going to be important if I want the intensity of the array to remain constant with varying loads on the bike.  The two options would be to regulate the current or regulate the supply voltage.  Having looked in to both options, although regulating the current is the preferred method of driving LED arrays, it can be quite complicated to impliment.  So I have decided to go for the easy option and regulate the supply voltage.  I plan to use 2 low drop out linear regulators to regulate the supply to each of the arrays to 10V.  This way I should be getting 10V when the bike supply fluctuates with varying loads and the LEDs should not change in intensity. (That's the theory anyway!).  So, with a 10 volt supply, I will be looking at running parallel strings of 4 series LEDs, and hopefully the regulator will be quick enough for the flashing function of the Brake Mod.

Next stage is to buy the components, so I'll keep you posted as I move forward with it.

Fluke

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Re: LED Rear Light Project
« Reply #1 on: December 28, 2009, 04:33:29 PM »
Very interesting read Martin, thanks.

This sounds like a fun project and I agree a constant voltage supply is going to be the easiest as constant current will require some much more complex electronics in comparison. The advantage of a constant current supply though would be the elimination of inefficient resistors used for your LEDs...  (something that is not at all practical in higher power LEDs). I'm guessing you will be ok though with a large array of lower powered units.

Keep us posted how it goes...  your a braver man than me :-)

Regards and have a happy new year

RCE

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Re: LED Rear Light Project
« Reply #2 on: December 29, 2009, 12:16:04 PM »
Couple of points, using LEDs inside the standard tail lamp unit will invalidate the E mark.... issue then is if you get rear ended they have a get out of jail free card if the vehicle inspector finds them.


Unit failure, think about splitting both circuits so that if one section fails you still have some rear light.


I have gone the supplemental LED route (based on the bullet), and reckon they look and work well. Unfortunately since building them the snow and ice has meant I haven't tried them on the road. Intention is to get some video shot of them to see how effective they are. For the time being here is some video of them shot outside my garage http://www.youtube.com/watch?v=AkGS2Iff4g0

zeuter

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Re: LED Rear Light Project
« Reply #3 on: December 29, 2009, 03:55:50 PM »
Hi Martin,
 
Quote
So, with a 10 volt supply, I will be looking at running parallel strings of 4 series LEDs, and hopefully the regulator will be quick enough for the flashing function of the Brake Mod.

Just put the brake modulator after the voltage regulator, it'll run quite happily at 10 volts.  Good luck with the project.
 
 

martin999

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Re: LED Rear Light Project
« Reply #4 on: December 31, 2009, 12:14:11 PM »
Couple of points, using LEDs inside the standard tail lamp unit will invalidate the E mark.... issue then is if you get rear ended they have a get out of jail free card if the vehicle inspector finds them.

Unit failure, think about splitting both circuits so that if one section fails you still have some rear light.

I have gone the supplemental LED route (based on the bullet), and reckon they look and work well. Unfortunately since building them the snow and ice has meant I haven't tried them on the road. Intention is to get some video shot of them to see how effective they are. For the time being here is some video of them shot outside my garage http://www.youtube.com/watch?v=AkGS2Iff4g0

Thanks for the input RCE.  I take your point about the e mark on the rear light, but TBH there are a few insurance 'get outs' on many bikes that have been modified.  I'm no expert, but following your train of thought does it mean that the extra brake lights you have (which look really good BTW!) are illegal as they are not e marked?

Some built in redundancy may be worth doing and I'll consider it as the build progresses.  Keeping in mind though that it is replacing a single dual filament bulb.  The LEDs should be much more reliable anyway and I always check the operation of all the lights before I ride.  I would have thought the chances of bulb failure whilst riding would be higher than failure of the LEDs.

Hi Martin,

Just put the brake modulator after the voltage regulator, it'll run quite happily at 10 volts.  Good luck with the project.
Thanks John, great advice, I'll certainly do that.  Presumably the input from the brake switch can be left as 12V?

zeuter

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Re: LED Rear Light Project
« Reply #5 on: December 31, 2009, 12:37:12 PM »
Yep, no problem Martin, the brake switch input can be at +12VDC.  (MAX +15VDC)

RCE

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Re: LED Rear Light Project
« Reply #6 on: January 01, 2010, 10:13:11 AM »
Thanks for the input RCE.  I take your point about the e mark on the rear light, but TBH there are a few insurance 'get outs' on many bikes that have been modified.  I'm no expert, but following your train of thought does it mean that the extra brake lights you have (which look really good BTW!) are illegal as they are not e marked?

Some built in redundancy may be worth doing and I'll consider it as the build progresses.  Keeping in mind though that it is replacing a single dual filament bulb.  The LEDs should be much more reliable anyway and I always check the operation of all the lights before I ride.  I would have thought the chances of bulb failure whilst riding would be higher than failure of the LEDs.


Supplemental lighting should be OK even if not E marked, as long as you are aware of the possible issues that is the main thing, as the lens is E marked you should pass mot and police inspection without issue as long as they assume it was manufactured with LEDs. The LED bulb replacements are easier to spot by the mot/police so chances are you will be OK.


The bulb is a single point of failure, and is the reason I initially tried various LED tail light bulbs. I had a number of problems with the LED bulbs, including not as much light output, electrical failures of the LED bulbs, and mechanical failures (eg falling apart due to vibration). In the end I found the normal bulb more reliable, and can be replaced easily at the road side as most petrol stations sell replacements.


The above are the reasons I decided to go the supplemental route (glad you like them), if the bulb fails I still have some rear light until I can get to a petrol station. If the LED fails I still have the tail light.


Be very interested in seeing the results of your build.


Oh and why don't bike manufacturers build all bikes with twin rear bulbs for just this reason, would make a lot of sense as far as safety is concerned.



martin999

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Re: LED Rear Light Project
« Reply #7 on: January 23, 2010, 09:48:22 PM »
A little tease for you.... it's almost complete, but I haven't taken any pictures yet!

The build when pretty well really.  In the end I used 24 of the lower intensity LEDs around the outside for the tail, and 24 of the higher intensity LEDs in the centre for the brake light.  There are also 3 white 'side looking' LEDs pointing down for the number plate illumination.

All of the LEDs were SMDs soldered on to the track side of Vero board.  The current limiting resistors were through hole components on the rear of the board.

I worked out the current limiting resistors for each string using R = (Vs - (n*Vf))/If where Vs = supply voltage (10V in my case) n = the number of LEDs in the string, Vf and If from the data sheet for the LEDs.

When initially testing I found that Vf from the data sheets wasn't that accurate and I was over running the brake array and under running the tail and number plate arrays!!

Using a variable PSU and limiting the current to If I could measure Vf accurately and was able to change the current limiting resistors to suit.  Now each string runs at recommended If +/- a couple of mA.

Considering the tail LEDs should be 1.7lm each and the brake LEDs 4.65lm each, there isn't a huge discernible difference between them.  Not that it is much of a problem as there is still a nice big difference when the brake LEDs kick in! (especially when using the brake modulator)

With a bit of rough comparative 'testing by eye' with some work colleagues it looks like my array is a little brighter than the standard 5/21w bulb, but not overly bright, so it looks like I just about got it right with the choice of LEDs  8)

The LDO regulator also works well with no observed change with a constantly varying supply of 11 - 14V.

The modified brake modulator also works a treat holding the brake LEDs off until the brakes are applied.  It also has the option to reinstate the 30% when the brakes aren't applied, so I will have a little play to see what it looks like if I connect both tail and brake arrays to the modulator therefore using a single array at 30% for tail and 100% for brake.

Next stage is to run all arrays constantly for a burn-in test to make sure nothing untoward happens.

Once I am completely happy, I will coat the board with conformal coating and get it on the bike..... with the weather looking up, I NEED to do this ASAP  :D

zeuter

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Re: LED Rear Light Project
« Reply #8 on: January 24, 2010, 11:16:16 AM »
OK Martin,  stop teasing, show us the pics!!!


PS,  Glad you're happy with the modified Brake Modulator.


Regards, John

Fluke

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Re: LED Rear Light Project
« Reply #9 on: January 24, 2010, 04:36:08 PM »
Sounds great Martin... looking forward to photos also :)

martin999

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Re: LED Rear Light Project
« Reply #10 on: January 25, 2010, 07:53:27 PM »
Here's the update with pics!

Front side of board (sorry about the focus, obviously a bit too close for my camera!)


Rear side of board with current limiting resistors


Tail lights and number plate illumination running at 10V from PSU


As above but with brake light on


Mounted in tail light housing.  Run from PSU at 13.5V through regulator that you can see to the left.   Thought I might get away without a heatsink for the reg, but looks like I will have to use one.  You can also see the white illumination for the number plate.


As above with brake light on


Quick shot of the rear of the unit showing the mounting plate I made that goes where the original bulb holder was


Had it running for a couple of hours with the temporary heatsink and all looks good.  Will run it a bit longer before opening it back up and coating the board with conformal coating.

zeuter

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Re: LED Rear Light Project
« Reply #11 on: January 25, 2010, 11:03:09 PM »
Wow!  Great job Martin.  8)   I've just had a rear light bulb blow on my Fireblade and no spare!  Now, do I buy a new bulb, or ...............


Where did I put that veroboard, it must be kicking around somewhere :)

Fluke

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Re: LED Rear Light Project
« Reply #12 on: January 26, 2010, 08:22:22 AM »
Really fantastic build Martin (you have 100* more patience than me)...  how to you think it compares to stock bulb for brightness ?. Have you tried the Modulator on the brake LEDs ?
 
Regards

martin999

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Re: LED Rear Light Project
« Reply #13 on: January 26, 2010, 01:22:57 PM »
Wow!  Great job Martin.  8)   I've just had a rear light bulb blow on my Fireblade and no spare!  Now, do I buy a new bulb, or ...............

Where did I put that veroboard, it must be kicking around somewhere :)

Cheers John!  TBH even if it doesn't work out, it's been a fun little project to do!

Really fantastic build Martin (you have 100* more patience than me)...  how to you think it compares to stock bulb for brightness ?. Have you tried the Modulator on the brake LEDs ?

Thanks Dan, The brightness is a slightly up from the stock bulb, but not too much.  I always had in mind that some bikes have 2 x 5/21W bulbs in the tail, in theory giving out twice as much light as my single bulb, so I slight increase should be fine.

The brake mod works well.  I had a play using both arrays together through the mod using the 30% 'normal' operation and TBH it probably looks asteticaly a little nicer because all of the LEDs are on all the time, but the brake signal is no where near as noticeable as with the two separate arrays, so I will be sticking with plan A :)

martin999

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Re: LED Rear Light Project
« Reply #14 on: January 26, 2010, 09:35:00 PM »
Couldn't resist taking a little video with the brake modulator in circuit!  :)



The flash rate looks a little uneven, but it must be to do with the frame rate of my camera as it is perfectly even in real life!