Car LED tail/brake light project

[TuscanT]

stay on topic guys. im sure you can go in depth about left hand and ride side driving on another tread.

 

[Andy1845c]

Is your goal simply to have 2 levels of brighness? To glow at half power when the headlights are on and go to max brighness when you brake? Is a side light just like a parking light, or running light? Do you need to incorperate turn signals too, or are they seperate?

You say you have hacked a existing LED tail light modual with built in resisitors. I assume then, with the built in resistors you can hook it up to your cars battery and it will light at full brighness and not burn out? Is this correct?

The most popular way to dim LEDs is with PWM. (search here or google to learn more about it)
If the lights work like I think they do, I don't see why you couldn't use somthing like a 555 timer to PWM the leds when power is applied to the wire for the side lights, and then just hook the brake light wire directly to the moduals and override the PWM side when the brake is applied.
You could also use a resistor insted of the PWM and the 555, but it would waste power.

Maybe someone else has a better idea too

 

[Darth Bagel]

actually you can.

the leds i am using is a cluster of LED from the 2002 onwards range rover tail light. they are aranged in a pentigon shape using a total of 19 LEDs. with resistors already in place. The leds are arranged in strings of 3 and 4 leds with the middle being a row of 5. iv retrofited the unit into my tail lights. they work and light up fine as a brake light. but not as a tail/brake as i want. i just need to find a suitable circuit to make, if anyone can suggest a schematic that i can use that would be great.

Resistors already in place? Strings of 3 and 4 LEDs? Sounds like you're trying to build something that's nothing like the schematic you posted.

 

[mramos1]

google for tail brake light led circuits

Here is one of 177,000 hits on the search.

https://www.redcircuits.com/Page85.htm like your with NPNs.

 

[TuscanT]

google for tail brake light led circuits

Here is one of 177,000 hits on the search.

https://www.redcircuits.com/Page85.htm like your with NPNs.

you obviously havent looked at my orignal post. didnt you think that is the first obvious thing anyone would do to seach google? Do refrain from patronising resposes if you cant be of any constructive help.
That is the orignal schematic i posted. and it is not suited for the application that i am using it for.


Andy1845c

your spot on correct with what im after.

i just simply want to have 2 levels of brightness. 1 for the led to work at half power (or brightness) with the headlights on. and at full power when the brake pedel is pressed. i dont need to incorperate turn signals as i have sorted that out already with LEDs and the correct loads in place for the relay system. The LED cluster unit i have can be safely hooked up directly to the 12v batt brake bulb circuit without burning out.

ill have a look into PWM as you mentioned tho. Thanks

 

[Boncuk]

The reason goes back MUCH further than public buses, it's not a financial reason. No one has still explained why other countries drive on the right though?.

Hi Nigel,

when Sweden changed from LH traffic to RH traffic GB was also asked to change to have european countries with the same traffic (rules). The argument for refusal however was just the reason as already posted. The problem is not the side of the road, it is the side of the steering wheel.

You will notice that cars moving in GB with the steering wheel on the left side tend to cause a traffic jam, just because the driver can't look ahead very well for overtaking. The same applies if english cars move in Germany or elsewhere in Europe.

Regards

Hans


P.S. A perfect solution would be to have the driver and the steering wheel in the middle of the car - the driver being protected from side impact by two good looking girls.

 

[audioguru]

How can a guy drive when he is in between two good looking girls?

 

[mramos1]

you obviously havent looked at my orignal post. didnt you think that is the first obvious thing anyone would do to seach google? Do refrain from patronising resposes if you cant be of any constructive help.
That is the orignal schematic i posted. and it is not suited for the application that i am using it for.

There are 177,000 sites, the one I sent a link for, I thought, had NPN transistors, and yours had PNPs. So it is not the same circuit, but probably is the same website as in was in the first three (all I bother to look at as well). And if it was PNPs in mine, my mistake. We all make them.

I figure most people have more NPNs and it might help you out. Sorry to offend you, it will not happen again as I will leave your thread to you.

Looks like it turned into off-topic anyway. At least I tried to help.

 

[Andy1845c]

ill have a look into PWM as you mentioned tho. Thanks

Here is a site about 555 timers. About halfway down it shows how to wire one for asable operaton. That is the way you would use it for PWM. Its all expained on the website, but you adjust the resitor and capacitor values to change the frequency and duty cycle, that will determin how bright the LED looks to the human eye.

You won't be able to drive the LED moduals directly from the 555, as they can't supply much current (200mA max) so you will need to use a transistor also.

 

[Boncuk]

Hi TuscanT,

back to the original thread:

This circuit works with PWM. (Frequency ~ 1.8KHz) If the brake pedal is not depressed (S1 open) the duty cycle is 50%. You can increase it by changing the value of R5 to a smaller value if the LEDs are too dim.

If S1 is closed the duty cycle is 100%, meaning a connected frequency counter doesn't "see" any frequency because of supershort off-cycles.

Using a BUZ11 would be good enough for a big cluster of LEDs. Be good and give it a heat sink too.

Calculate the current limiting resistors for a supply of 14.4V, which the car electric system normally has (13.8 - 14.4V) if the generator is working. There will be a very small change in brightness used just on battery power.

Hope that helps you to complete your project.

 

[Diver300]

Hi TuscanT,

back to the original thread:

This circuit works with PWM. (Frequency ~ 1.8KHz) If the brake pedal is not depressed (S1 open) the duty cycle is 50%. You can increase it by changing the value of R5 to a smaller value if the LEDs are too dim.

It's not legal in the UK to have flashing tail lights.

https://www.opsi.gov.uk/si/si1989/Uksi_19891796_en_3.htm#(Tii)i3lampshowsteadylight

You can interpret flashing various ways, but LEDs have a response time of nanoseconds, so the light will be turning on and off.

 

[tonigau]

Here is a circuit that I made for my xv1000 some time ago, simple & reliable.

When just the Tail signal is energized the array is fed via 1 68R resitor, when both Tail & Stop or just Stop alone the 68R & 56R are in parallel = 30.7R

The 100R resistors ensure each string gets nominally equal current.

You could adapt the diode steering to your circuit but you would need to reconfigure the array strings.

 

[mneary]

We aren't offering much useful information to the OP. He has a pre-built stoplight LED module and wants it to operate from the tail light circuit at reduced brightness. The solutions offered seem to ignore this. It's probably also desired to use existing vehicle wiring (one side grounded without much freedom to modify).

To accomplish what you want, put a diode in series with each supply line so that they don't feed one another. (If it's negative ground, that would be connect the cathodes together.) In the tail light circuit, add a series resistor of a value that produces the desired (reduced) brightness.

The resistor will (my guess) probably have about 4V across it; calculate the power the resistor needs (V^2/R), and double it. Choose the next higher power rating.

Example: If your LED stoplight draws 250mA, a 4V drop would need a 16 ohm resistor. This works out to one watt; so choose a 2W or larger, 16 ohm resistor.

 

[Boncuk]

It's not legal in the UK to have flashing tail lights.

You can interpret flashing various ways, but LEDs have a response time of nanoseconds, so the light will be turning on and off.

I think you don't consider your TV a flash light, although the lines are drawn in fast sequence.


Of course will the LEDS been turned on and off, but the human eye is too slow to follow the switching. So a PWM-controlled LED isn't a flashing light.

There is no other way to interprete flashing as an obvious flashing with a distinct off and on time. The "flashing" at a speed of several KHz is recongnized as a steady light.

 

[Boncuk]

We aren't offering much useful information to the OP. He has a pre-built stoplight LED module and wants it to operate from the tail light circuit at reduced brightness. The solutions offered seem to ignore this.

He wants to operate a circuit similar to that he already has posted. A pre-built module was not mentioned.

It's probably also desired to use existing vehicle wiring (one side grounded without much freedom to modify).

It is just a guess.

To accomplish what you want, put a diode in series with each supply line so that they don't feed one another. (If it's negative ground, that would be connect the cathodes together.) In the tail light circuit, add a series resistor of a value that produces the desired (reduced) brightness.

You forgot to mention that he wants reduced brightness at normal operation and full brightness as soon as he hits the brake pedal.

 

[mneary]

It's been a confusing thread. Hopefully all of us are still driving on the correct side of the road for our region.

He's using the LED module from a 2000+ range rover. (Dec. 2 post)

The reduced brightness that I propose would come from the 16(my guess) ohm resistor in series with the 'tail light' leg. The full brightness would come from the brake light leg which contains no resistor.

'Tail light' is the term that we use in America for the pair of rear facing red lamps which operate when the headlights are on.

 

[Boncuk]

Hi mneary,

I always drive on the right side of the raod. Thailand has L/H traffic, but using the right side of the road gives me a short cut of 20yards driving home. Nobody cares - and not even the police seems to know the "right" side of the road.

Considering the threat I would select another way to operate the LED clusters. I'd use a constant current source with two different currents, the low current adjustable to individual needs and operated by the brake panel.

Concerning the brake lights there is a big disadvantage about them anyway. You never know by the lights if the driver in front of you just brakes to adapt his speed to traffic flow or he is doing an emergency braking. I already made a suggestion to the German government to change the rear lights to indicate the state of braking action. The solution was like this: Use the built in tail lights with an extra bulb or twin filament additionally to the brake lights. Soft braking: one normal light (each side), hard braking - two lights, emergency braking - two lights and additional directional light all fashing in fast sequence. That way many accidents could be avoided.

It would just take a brake cylinder with three different electric outputs depending on brake pressure. (Cheating by just touching the brake pedal (contact closes by slightly pressing the brake pedal with no braking action) to force others to brake - in order to outmaneuver them would be impossible - illegal car races amongst Mercedes and BMW drivers).

I made that suggestion about seven years ago and the government replied I should not interfere with new suggestions because european discussions about that problem were already in progress with a very poor solution (Use the brake light and additional directional light).

Nothing has changed since.

Boncuk

 

[Diver300]

I think you don't consider your TV a flash light, although the lines are drawn in fast sequence.


Of course will the LEDS been turned on and off, but the human eye is too slow to follow the switching. So a PWM-controlled LED isn't a flashing light.

There is no other way to interprete flashing as an obvious flashing with a distinct off and on time. The "flashing" at a speed of several KHz is recongnized as a steady light.

If car lights were modulated at several kHz, the modulation wouldn't be visible. However a lot of cars modulate at 100 Hz and they are distinctly visible, and annoying.

 

[Boncuk]

If car lights were modulated at several kHz, the modulation wouldn't be visible. However a lot of cars modulate at 100 Hz and they are distinctly visible, and annoying.

Absolutely true. Reminds me on the cheap graphic accelerator cards for PC's. The monitor flickered at a rate of 40 to 50Hz, very annoying and tiring too!

I used the flickering of the 50-Hz frequency to calibrate my optical rpm-meter for model engines.

 

[TuscanT]

To accomplish what you want, put a diode in series with each supply line so that they don't feed one another. (If it's negative ground, that would be connect the cathodes together.) In the tail light circuit, add a series resistor of a value that produces the desired (reduced) brightness.

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[/FONT]Thanks Mneary and other for your constructive responses.

in regards to your reply

what sort of value resistors would i need to make the leds operate at 60% power and 100% power? (50% doesn’t light up the leds evenly) Also what kind of diode?
Im not sure how much mA the LEDs draw because it is a sealed cluster unit. The only thing i know about them is that they operate fine using my car's 12v supply that usually powers a 15w bulb.

Im quite new to building electrical circuits so those whom are experienced help is appreciated .