© Peter Ogden, 2007
LED High Level 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
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.
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.
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
Now I'm looking at the other tail light assemblies... I wonder???...
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.
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.
This is the optional "attention getter" circuit.