LED Project #2 – Introduction
After many
months of R&D and buying different parts, I believe I can call LED Project
#2 finished. I have entailed all the details below, and if there are any
questions please feel free to instant message me or email me. Before you
do, *please* read everything in this document, as your question may have
been previously answered.
Preface
After the
installation of LED Project #2, your instrument cluster will be converted into
a dynamic indication of your speed and engine RPMs. As you accelerate,
LEDs will light up to indicate your current speed and engine RPM. The
faster you go, the more LEDs will illuminate. You also have the option of
turning all the LEDs on if you like, for example, to bring your car to a show
and leave the cluster illuminated for others to see.
The project
also includes an adjustable shift light so you can have an indication of the
optimum shift point.
Just a
couple of legalities first. You WILL void your warranty,
at least for the instrument cluster. You WILL be taking
parts of your car apart, prying into them, and putting them back
together. But in the end, every time you start up your car, and you see
those red LEDs illuminate as you rev your engine, it will be well worth
it. So read on!
Theory
So, how
does this whole thing work? Since the
concept is the same whether you are talking about RPM or Speed, we'll focus on
the RPMs for now. The entire process is based on a concept known as
"signal conditioning". This means we are taking one type of
signal and converting it to another type that is more useful to us.
The signal
for the RPMs comes from a sensor mounted on the engine block. By its
fancy name, it is called a "Hall-effect reluctance sensor" or other
words to that effect. How it actually works is beyond the scope of this
document, but what we want is to understand the signal that is produced.
As the
engine turns, this sensor interprets the engine output and generates the
following signal:
Note the
swing between the positive and the negative voltage. This swing is
essential to the operation of the circuit you will be making. As the
engine turns faster, the graph looks the same, but there are simply more swings
for a given time period.
Taking this
pulse signal, we run it through an converter that will count the number of
pulse swings in a given time period, and generate a voltage that is directly
proportional to the number of swings detected. For example, look at the
information below:
# of
swings
Voltage produced
10
.5 Volts
20
1.0 Volts
30
1.5 Volts
40
2.0 Volts
50
2.5 Volts
And so
on. So the signal coming from the RPM sensor has been converted from a
swing type signal to a linear type signal like below:
Now that we
have a given voltage produced from a certain RPM, we will illuminate a
series of LEDs based off this voltage. I will try to explain this as best
as I can. Let's take a specific RPM, say 1500 RPMs. Based off the
graph above, you can see the voltage produced at this RPM is 1.5 Volts.
The way the circuit is calibrated will determine how many LEDs light up for
this particular voltage. The calibration procedure will be covered later
on, so understand that for now, the circuit is broken up into 10 LED
blocks. By adjusting part of the circuit, we can control how many LEDs
turn on at 1.5 volts. Look at the graph below - the black vertical line
indicates 1.5 volts.
You can see
that at 200 ohms, all 10 LEDs will be illuminated. At 400 ohms, only 7
LEDs will be illuminated. At 600 ohms, 3 LEDs, and at 800 ohms, only 2
LEDs. So you can see how by adjusting circuit settings, you can change
how many LEDs light up. This is the
basis of the calibration procedure.
Now that we
have the circuit designed, all we have to do is build/install it. There
are some additional features worked into the project, such as turning the
system off, or going full scale. Those features will be covered
later on in this document.
REMEMBER: Depending on your skill level, familiarity with tools, and
available work area, the install should take around 3 hours. The prep time (ie; watching the DVD, reading
the procedures) and the calibration time (adjusting the circuit) are not
included in this time. Make sure you
can dedicate a couple of hours to this task, because you will not be able to
use your car.
DISCLAIMER:
I cannot and will not be held responsible for any errors in the
procedure, injuries sustained, or damage that occurs to your vehicle. I provide this kit as tested, and I have
done the best I can to ensure you install the kit properly. If there are any questions or problems,
first re-read the install to make sure you have followed the directions
properly. If you are still in need of
assistance, you may contact me at:
Mike Classe
704-719-0136
http://www.fallastarmedia.com/ledproj.htm
or on www.vwvortex.com as UserID: FaelinGL