[DeTomaso] Optical turn signal control

gow2 at rc-tech.net gow2 at rc-tech.net
Sat Jan 26 11:13:53 EST 2013


> Cool stuff... do tell more...
>
> David
>
>



The control for the turn signal encoder is called the Arduino. The Arduino
is what I call "a micro controller for dummies". These type of platforms
are becoming very popular. Arduino is one of the most popular platforms
with an enormous wealth of information.

I call it a micro controller for dummies because yu don't have to
understand much about the micro controller. Configuring and programing is
basic. If you have done ANY basic level introductory program you can
follow the examples which are plentiful through Google and books. It is
just about getting the syntax right.

The Arduino has a compiler (free download). The Arduino plugs into a USB
on the computer. If you want to control say a servo, in a Micro Controller
you may have to create a signal at a specific pulse width to operate the
servo. In the Arduino, you make a note in the beginning to add a servo,
name an item a servo then tell the item to move to a position. It's that
simple. The rest is how you nest your program to do what you want.

There is an explosion of these sort of boards right now. I would say the
Arduino is one of the most popular for this sort of application. Radio
Shack is even carrying these now; along with the LCD I use, and intro
boook, etc.

Someone directed me to a new board this week which...is not really what I
need here, but is unbelievable. It is basically a computer which runs
linux in the same configuration with massive inputs and outputs. It is
called the Raspberry and is ....$35. !!!!!

http://www.alliedelec.com/lp/120626raso/

Back to the Arduino. I start with the "Uno" which is a prototyping board:

http://arduino.cc/en/Main/arduinoBoardUno

It has 14 digital input/output pins and 6 analog input output pins. I work
out the logistics with the prototyping board then move to a more solid
solution.

I have circuit boards made for the NANO which is pretty much the same
thing except it is designed to be soldered on a board:


http://arduino.cc/en/Main/arduinoBoardNano

The circuit boards I have made are designed to hook up the things I need
such as a voltage converter to take the voltage from 12v to 5,  sockets
for thermocouple chips, encoder counters, pull up/down resisters, mods
etc. It is a flexible circuit in which I am on my 3rd rendition.

The encoder itself is not hard but the timing can be tricky. The encoder
has 2 LED emitters/detectors. They are staggered 1/2 wave. The logic is to
read the separate waves. If both are high and one goes low, you know which
direction it is moving. Each move provides a count.

The tricky spot is timing. If you are doing things in the program when the
count comes across, you will miss it. A separate chip is used to take care
of the logic. It is a very simple chip which works well for this
application. It tags the Arduino on 2 pins. One pin is an interrupt. It
gives direction and count +/- 1. The interrupt is the key because at every
count it interrupts the program and updates the count so nothing is
missed. Works very well for this application.

The arduino will also manage 8 servos on the heaterbox in a constant loop.
If an input condition has changed it will turn on the servo, move it, and
turn it off.

There is a whole group of conditions going on in the turn signal process.
It will control each of the 4 turn signals and flashers via a power
mosfet. It has a few things to consider; position of the wheel, are the
flashers and turn signals on at the same time, are the lights on (the
front marker is both marker and turn signal), manual cancel, etc.

I can do creative things like make the front marker both a turn signal and
a marker. If flashers and turn signals are on, I will flash 2x, turn
signal 2x, flash 2x, etc. If I leave the turn signal on for 5 min, turn
them off. Things like that.

he left is the prototype. The right is the actual column. You are seeing
the bottom of the column:

http://www.rc-tech.net/cars2/panttransam/turn/turn3.jpg

I have been working through the learning curve on the prototype. This
involves making a lot of mistakes, figuring out what I have done and
getting it right. A soldered board is so much better when done right the
first time. As I get parts nailed down, I hope to begin putting it
together in the car Sunday with some finish wiring. So much still to do.

The mile stone for me was getting the encoder to read reliably without
error which I have done. That above all was the hardest part. The rest is
just logistics.


Gary









> On Fri, Jan 11, 2013 at 2:51 PM, <gow2 at rc-tech.net> wrote:
>
>> Here are some parts being used to build the encoder based turn signal:
>>
>> http://www.rc-tech.net/cars2/panttransam/turn/turn.jpg
>>
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