Car LED tail/brake light project

[TuscanT]

hey guys

im trying to build this circuit below. but im using 19 LEDs as apposed to the suggested 12 but the resistor R2 is burning up. The brake light works fine (when R2 is not connected) But the side light circuit does not work. When it is connected. the brake lights stay on continuously at full brightness on my car instead of half power.

can anyone shed any light to this please.

**broken link removed**

ripped from original site:

When SW1 is on, the cluster will illuminate at medium brightness. When brakes are operated, SW2 will be closed and the cluster will shine at maximum brightness.
These two brightness levels of the cluster are obtained by a constant current source drive formed by Q1 and Q2. The two constant current levels are set by R2 and R3 values.

* The cluster can be formed by up to 12 LEDs as shown in the circuit diagram. Common cluster types usually range from 5 to 10 LEDs.
* Using the values shown above, stand-by current was 1mA; SW1 on = 20mA, SW2 on = 60mA.
* Constant output current value can be changed by varying R2 and/or R3.
The formula is: R = 0.6/I (in Amperes).
* Please note that the brake current is obtained by paralleling R2 and R3 values.
* Use high brightness, high efficiency red LED types of suitable size and change R2 and R3 values to suit LED's Absolute Maximum Ratings.
* Any Schottky-barrier type diode can be used in place of the 1N5819: the BAT46 type will be a very good choice.


Parts:

R1______________10K 1/4W Resistor
R2______________33R 1/4W Resistor (See Notes)
R3______________15R 1/4W Resistor (See Notes)

D1___________1N5819 40V 1A Schottky-barrier Diode (See Notes)
D2--D13________LEDs High brightness, high efficiency red types (See Notes)

Q1____________BC557 Transistor
Q2____________BC327 Transistor

SW1____________SPST Tail Light Switch
SW2____________SPST Brake Light Switch

 

[blueroomelectronics]

Where did you get the schematic? I'm not an LED expert (many others here are) but it doesn't look right combining the two LED strings like that.

 

[TuscanT]

i got it from https://www.redcircuits.com/Page85.htm

the schematic on the site is designed for a car bulb using 2 neg and 1 positive as the source of power but the the schematic that iv posted relates to my car (1 neg 2 pos)

when i connected it to my car, and turned on the side light switch, all the lights on the dash came on.

 

[audioguru]

If Q1 and Q2 are connected properly and work, then R2 will have only 0.7V across it. The power that heats R2 is (0.7V x 0.7V)/33 ohms= only 15mW which is nothing.

I wouldn't use the circuit in a car because the current changes with temperature change.

 

[audioguru]

Your car's battery is connected upside down.
Do you drive it on the wrong side of the road?
English car?

 

[TuscanT]

...lol wrong side of the road

yes my car is a right-hand drive car (renault megane cabriolet)

I replaced the resistor and tried to connect it again, I checked a few times this time before connecting again. (made a slight error before) and all the lights on my dash just lit up as soon as I switch on my side lights.

The purpose this is just for me to be able to run the leds at half or 60% power when the side light is on, and then full power when the brakes are pressed.

Can anyone suggested a more suitable circuit design?

...lol wrong side of the road

 

[Hero999]

How have you connected your 19 LEDs?

What's the foward voltage of the LEDs?

At best case if it's 1.8 the total drop is 10.8V which means it'll only regulate properly when the alternator is running.

You can't connect 19 LEDs because it's an odd number.

Do you understand how this circuit works?

If not then I suggest that you make sure you understand it before you build it otherwise you're wasting your time.

 

[audioguru]

yes my car is a right-hand drive car (renault megane cabriolet)

I had two Renaults. They weren't made "backwards" and they didn't have a rag top. I drove them sitting at the driver's side, not in the passenger's seat.
I never drove a car in the UK. Driving on the wrong side of the road would be scary for me.

 

[Hero999]

What do you mean by a rag top?

Is it the same as a soft top?

A convertible with a PVC or rubber roof.

 

[audioguru]

I have seen "hard top" convertibles. They use mechanics to hide the top.
I have also seen convertibles with canvas "rag tops" that little kids destroy for fun.
I have never seen a PVC or rubber convertible top. Does it rain that much in the UK?

 

[Boncuk]

Hi Tuscan,

I have simulated your circuit and R1 determines the maximum current flow in it to a great extend. Reducing its value to 1K8, changing R2 to 15Ohm and omit D1 and R3 will give you currents of 30mA with S1 closed (60mA with R2=8.2Ohm in case the LEDs are too dim), and 220mA with S2 closed. S1 will be overridden by S2. The LEDs connected in series of six are not a very good solution. Better use 4 strings with 3 LEDs each. The output voltage is 6.08V with S1 closed and 6.49V with S2 closed. The current values are well within limits taking 20mA max current flow per LED into consideration.

Regards

Boncuk


Edit: All values are based on 12V.

 

[Nigel Goodwin]

I never drove a car in the UK. Driving on the wrong side of the road would be scary for me.

There's a sound historical reason for driving on the left of the road, I've asked before, but why do others drive on the right?.

And yes, driving on your side would be scary for me as well!.

 

[mramos1]

hey guys

im trying to build this circuit below....

Try to google search for "motorcycle LED tail light"

I have built a couple that worked well for a car and a golf cart. I recall there were a few out there and one had a link for 1000 high lumen LEDs for $14.95 US$.

EDIT: And I would never be able to drive on the right side seat in the left lane either. Would take a cab instead.

 

[audioguru]

It is like my RC model airplane. When it is frying towards me then the steering is backwards. To make it go to the right then I must steer to the left.

 

[TuscanT]

How have you connected your 19 LEDs?

What's the foward voltage of the LEDs?

At best case if it's 1.8 the total drop is 10.8V which means it'll only regulate properly when the alternator is running.

You can't connect 19 LEDs because it's an odd number.

Do you understand how this circuit works?

If not then I suggest that you make sure you understand it before you build it otherwise you're wasting your time.

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.

 

[Boncuk]

There's a sound historical reason for driving on the left of the road,

There are only five countries where road traffic is on the "right" correct side of the road.
Thailand is one of them.

The historical reasons for driving on the left side are of financal nature: Modifying the public buses takes too much money.

 

[audioguru]

Our buses are made here. They drive on the "right" side of the road and pickup passengers on the "right" side of the road.
We don't have any UK double-deck backwards buses here.
Trains and subways are also made here. I think people enter the trains on the "wrong" side but enter the subways on the "right" side.

I think Boeing airplanes have passengers enter on the "wrong" side.
I don't remember Airbus planes.

 

[Boncuk]

I think Boeing airplanes have passengers enter on the "wrong" side.
I don't remember Airbus planes.

Hi audiguru,

every airline has their passengers enter the plane on the "wrong side. It's getting time to change that!

 

[Nigel Goodwin]

There are only five countries where road traffic is on the "right" correct side of the road.
Thailand is one of them.

Someone previously posted a map of countries that drive on the left, it was surprising how big a percentage does!.

The historical reasons for driving on the left side are of financal nature: Modifying the public buses takes too much money.

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?.

 

[audioguru]

Many more people are right-handed. They can shift gears easier with their right hand, I guess.

Which side of a horse-drawn carriage did the driver sit on?
The pics I found have the driver sitting exactly in the middle!