*** hot topic *** HB Led's for automotive tail lights

[rolo95]

Okay - MSP430 GPIO is connected through a current limiting resistor to an NPN transistor, emmiter to ground, collector to the bottom of a string of diodes.

Simple bitbang software on the MSP430 with a counter, that will do a rudimentary PWM.

/R

Rochey,
hey man
RISC micro-controller with a switching transistor  opposed to a dedicated LED controller chip..
how much more components you need to run the MC, and also how stable it will be under a car voltage fluctuations
i am looking at costs here ,and also the more easy to assemble the better...

I mean , i know you are a whiz TI Microcontroller Coder , but... Ahem... Rolo is not... lol
so i dont know if you can take a peek at the LED driver chips that where already posted in here

or come up with a complete circuit and code to have 2 brightness levels on the LEDS
one for normal running level and when you press the brake pedal
also i want to have 2 pots, one for the idle level and one for the brake level
that way i can adjust the levels to an acceptable OEM escalade tail lights levels or at least close to it

thanks for your help Rochey
Rolo.

 

[PRR]

> MSP430 GPIO is connected through a current limiting resistor to an NPN transistor, emmiter to ground, collector to the bottom of a string of diodes. Simple bitbang.....

Simple?

For a rider who won't bother to spell "brake" correctly?

No, "simple" is RESISTOR.

Motocycle has 10-70 horsepower, 7,000-50,000 Watts snarling mechanical power on board, 100+ Watts of long-term electrical power and battery which would easily handle 1,000+ watts for the time it takes to brake 100-0.

> dont know how much amps the stock tail lights suck

1157 is 0.6A Run, 1.05A Brake. That 3057 is surely an 1157 with a funny (plastic) base.

> looking at 7 amps on 10 of those things

But at 2.3V. You have 12V. You can run several in series.

> 3W Cree XP-E red are 2.3V @ 700mA

Using the simple resistor and varying battery voltage, put three in series. That's nominal 6.9V. You want 0.7A, you have 12.6V. So the resistor must waste 12.6-6.9= 5.7V when passing 0.7A.... 5.7V/0.7A is 8.14 ohms.

Actually you mostly brake after ZOOM so the battery will be full, say 13.5V. 13.5V-6.9V= 6.6V, 6.6V/0.7A is 9.4 ohms.

Now get real. 10 ohm is a lot easier than 9.4 ohms. How does that work out? When battery is on FULL charge, 13.9 volts (modern dynamos don't get this high because sealed batteries would bubble) you have the max 0.7 Amps. When battery sags to 12V you have 0.51A. The difference in LED brightness from 0.7A to 0.5A is small, in fact smaller than the dimming of the incandescent lamp at these extremes.

The heat in the resistor rises faster than the square of the battery voltage. And you do NOT want the brake light system to burn-out on top of other electrical trouble. Assume worst-case 16V (my ill BSA did this, burned 1157 in minutes). Minus the 6.9V in LEDs, gives 9.1V which in 10 ohms is 8.2 Watts. This will not be a 24/7 or 10,000 hour stress, we can use a 10 Watt resistor with excellent safety.

There may be 10 ohm 10 watt resistors at the local Radio Shed, buck each, far in the back, in secret drawers.

How many 2.3V 0.7A LEDs does a bike need? LEDs are FAR more efficient than incandescent, we surely need less total power. However this "simple" drive scheme wastes half the input power, Even so, I am sure 3*2.3V*0.6A= 4.7 Watts of good LED beats 13 watts of hot tungsten. If not, two such LEDs+resistor strings is 1.2A nominal which is within slop for "1.05A" lamp wiring.

 

[rolo95]

Hey PRR
MANY thanks  for your detailed reply..

now... how do you make the LED's to change brightness from idle to braking
some switching scheme we will need to add right ?

Rolo.

 

[PRR]

> how do you make the LED's to change brightness from idle to braking
some switching scheme we will need to add right?

The bulb is 2-filament, 3 (or 4) contacts.

The direct approach is two LED-strings with two different resistors, "run" 5 or 10 times larger than "brake".

If that's not obvious, I won't even get into the cleverer solution.

Motor vehicles are not good places for DIY. There's standards for vehicle lighting, and testing is important.

You can buy a pre-made solution inexpensively.

Google "3057 LED bulb"

http://www.catoctinoffroad.com/ProductDetails.asp?ProductCode=RECON_264207WH&gclid=CI618YiylqoCFVDCKgodXUppww
http://motors.shop.ebay.com/catoctinor/m.html?_trksid=p4340.l2562

http://www.amazon.com/Pilot-LI-3057-Brake-Tail-Lamp/dp/B000NWPTV0
http://www.amazon.com/Signal-Corner-Parking-Marker-Backup/dp/B002SCXEG0
http://www.amazon.com/Resistor-Hyper-Blinking-Warning-Signal/dp/B002CJQIGW

http://www.gorecon.com/product.php?pk=218
http://www.gorecon.com/categories.php?p_cat=57

 

[rolo95]

> how do you make the LED's to change brightness from idle to braking
some switching scheme we will need to add right?

The bulb is 2-filament, 3 (or 4) contacts.

The direct approach is two LED-strings with two different resistors, "run" 5 or 10 times larger than "brake".

If that's not obvious, I won't even get into the cleverer solution.

Motor vehicles are not good places for DIY. There's standards for vehicle lighting, and testing is important.

You can buy a pre-made solution inexpensively.

Google "3057 LED bulb"

http://www.catoctinoffroad.com/ProductDetails.asp?ProductCode=RECON_264207WH&gclid=CI618YiylqoCFVDCKgodXUppww
http://motors.shop.ebay.com/catoctinor/m.html?_trksid=p4340.l2562

http://www.amazon.com/Pilot-LI-3057-Brake-Tail-Lamp/dp/B000NWPTV0
http://www.amazon.com/Signal-Corner-Parking-Marker-Backup/dp/B002SCXEG0
http://www.amazon.com/Resistor-Hyper-Blinking-Warning-Signal/dp/B002CJQIGW

http://www.gorecon.com/product.php?pk=218
http://www.gorecon.com/categories.php?p_cat=57

Yeah shoot the cleverer solution

i cannot design but i am good at soldering
so, i can build the switching circuit on  a perfboard or some
and work from there...
if someone can draw a schematic

dont like those single 3057 led bulbs
i was looking on  something like these
http://www.carid.com/2011-nissan-sentra-taillights/cg-led-tail-lights-259427.html

thing is that i have seen a couple of those aftermarket tailights and the leds are not bright enough
as i think they use low brightness cheap led's
easiest path would be to modify one of those atermarket tail lights with quality leds and maybe adding the LED controller board to it
Rolo.

 

[rolo95]

Ok,
i have found dimmers already made that use PWM

they care 14.95 each... so i think with a pair i am good
almost at the bottom there is the
LDK-8A: 12 Volt DC Single Color LED Dimmer
http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fhobby.htm%23Dimmer

Thanks for the ones who replied
Rolo.

 

[abechap024]

Those Premade lamps look like the cleverer solution to me

 

[rolo95]

Yeah
i just wanted the custom look of rows of led's like those escalades...
but ohh man... that dont come cheap..  :

 

[Rochey]

Rolo,
I know little about those LED chips.

RISC micro-controller with a switching transistor  opposed to a dedicated LED controller chip..
how much more components you need to run the MC, and also how stable it will be under a car voltage fluctuations
i am looking at costs here ,and also the more easy to assemble the better...

You'd need a constant current source for the LED's to deal with any voltage fluctution for the LED's. Then, either control the brightness with PWM, or if it's only two different brightnesses, maybe change the constant current source.

Who knows man... I'm not an LED guy.

/R

 

[rolo95]

well, i have come up with something...
not yet have the drawing
but it will use a relay
with the NC side wired to a resistance to limit the current of the LED's for the low brightness mode
and the "BRAKING" leads will power the coil of the relay so when it activates the NO will engage with a lower resistor
and thus increasing the brightness of the LED's

plain simple with not chips or PWM control...
i know the led's will look a bit dimmer when the car is off , so i need to calculate the resistor values
at around 13.8 V that is the voltage of the alternator when the engine is running...
what you guys think.
Rolo.