The 180SX Pages

180sx.gif - 1196b
logo.gif - 19kb
Animated Aussie Flag

Folder Home
Tree branch Changes
Tree branch Tree branch Stereo
Tree branch Tree branch Engine
Tree branch Tree branch Seats
Tree branch Tree branch Boost Gauge
Tree branch Tree branch Lighter Socket
Tree branch Tree branch Steering Wheel
Tree branch Tree branch Subwoofer/Amp
Tree branch Tree branch BikiROM
Tree branch Tree branch Strut Brace
Tree branch Tree branch Turbo Timer
Tree branch Tree branch Blow Off Valve
Tree branch Tree branch Intercooler
Tree branch Tree branch Boost Ctrlr
Tree branch Tree end LED Brake Light
Tree branch Links
Tree end Photo Albums
Folder Physics of Racing
Folder Locost Site
Folder 200SX Site


Google
web locost7.info


Valid HTML 4.01!

Valid CSS!

© Peter Ogden, 2007

LED High Level Brake Light

Testing LED brake light I was bored one afternoon after tinkering in the garage, when I spied my spare high level brake light assembly. Looking at it closely, I noted that the translucent cover is easily removed. Prying it apart, I noted that there was a fair amount of space inside the unit. Being interested in electronics, I thought it wouldn't be too difficult to update the assembly to use high intensity LED's to replace the quite soot blackened incandescent bulbs that light the stock assembly.

The nice thing about LED's is that they use considerably less power than incandescent bulbs and don't generate anywhere near as much heat. The two standard bulbs are 18W each, which will draw up to 1.5A (a total of 3A), whereas 60 LED's will draw less than 300mA total (1/10 of the current!). Also, the life span of LED's is considerably longer than incandescent bulbs. The LED's should probably outlast the car.

I investigated purchasing some suitable high intensity LED's. I gauged that two rows of 8000 mcd 5mm diameter LED's would do the trick nicely. To my shock, the typical electronics stores (Dick Smiths, Altronics, Jaycar, etc) wanted around $2.00 each for this style of LED! As I was intending to use around 60 LED's, an alternate source would have to be found. The Internet to the rescue! I discovered an online store called LED Shoppe that offered free delivery to anywhere in the world and could supply 1000 LED's for US$25.00 (about AUD$34.00 - 3.4 cents each!). They arrived only a few days after ordering them online. They were well packed and they even threw in a free LED keychain/torch! Definitely recommended.

Now that I had the LED's, all I needed was a board to mount them on. Rather than making a custom printed circuit board (which would be ideal if I was going to make more than a couple), I bought some "veroboard" (sometimes called stripboard) which I cut down to fit neatly in the assembly.

Components of high level LED brake light The circuit could not be simpler. As this is purely brake only (not stop/tail), there is only need for one brightness level (full on). The circuit is actually made up of 10 modules, each having 6 LED's in series, with a 68 Ohm current limit resistor. Once completed, I tested the board by connecting it across a car battery. I found one module was inoperative, which after close inspection, was due to a small solder bridge. Unfortunately, this resulted in the remaining LED's in that module being overloaded, taking out the other 5 LED's. No problem, there are still plenty of LED's left! After replacing that string of LED's, it all worked fine and is quite bright - in fact, quite uncomfortable looking directly into the light.

Mounting the board into the assembly was a simple matter of glueing the board to the translucent plastic cover with "liquid nails" and leaving overnight to dry. Once dry, I refitted the translucent cover to the housing and soldered the wires to the existing plug. It was then a simple matter of plugging it in and bolting it up.

Before doing this, though, I did fire it up alongside the existing brake light and visually compared the original (incandescent) brake light to the LED modification. I temporarily powered the LED assembly from a car battery that I had recently replaced as it wasn't retaining a charge (so it wasn't in peak condition), yet the LED assembly was still slightly brighter than the incandescent assembly. Not only that, I also found that as the LED's are mounted very close to the prismatic surface of the cover, the brake light appeared to "sparkle", which should also draw the attention of the following driver. I've run that configuration for a few weeks now and it appears to be working very well.

Circuit board mounted The next step is to make the assembly even more visible, by including a small circuit to flash the array a few times before staying lit, thus drawing the attention of the following driver. I have no idea as to the legality of doing this, but as I discovered that an Australian electronics magazine (Silicon Chip) has previously run a circuit doing exactly this, I'm hoping that it should not be a problem. I intially thought of making a circuit using the ubiquitous 555 timer, but I discovered that I could make a much simpler and more flexible (and possibly even cheaper) circuit using a microcontroller (PIC). Although this might seem like overkill, these are so cheap these days and so easily programmed, they are a very cost effective alternative.

The "Attention Getter" circuit is literally a 5V regulator circuit (a couple of capacitors and a 78L05 regulator), a PIC (I used a particular PIC called a PICAXE-08), one resistor and a power MOSFET (an MTP3055E being used as a switch). Total cost of around $8.00 in parts. The PIC has a small amount of code that, at power-up, rapidly flashes the array a few times (4 or 5 times), then holds the array constantly lit until the brake is released. I used a large electrolytic capacitor (4700uF) in the regulator circuit which serves two purposes - to reduce the likelyhood of any problems with noisy power (always a problem in automotive environments) and also to keep the "attention getter" circuit powered for a time after the brake is released. This results in the circuit not going through the flash cycle again (just lights the brake constantly) if the brake is re-applied within 15 to 20 seconds. This should hopefully be less annoying in stop-go traffic, where you are continually on and off the brake.

I'm quite pleased with the results. For around a total of $20 in parts per assembly (I have enough parts left over for many more assemblies!) and a few hours of time, I have a unique high level brake light and as a bonus, I'm no longer bored!

Now I'm looking at the other tail light assemblies... I wonder???...


UPDATE:

After having a few inquiries regarding this modification, I have decided to add some further information to the page to allow others to reproduce what I have done.

LED modules LED circuit The LED circuit board is simply 10 repeated modules of 6 high intensity (8000 mcd) LED's and a 68 Ohm ¼ watt resistor. I didn't bother making a printed circuit board for a one-off, just replicated this using "veroboard".

The circuit diagram is to the right.

LED brake flasher unit This is the optional "attention getter" circuit.