[sti robot]

mocked up stuff with the lcd tonight...click for bigger pictures

[Mack]

lookin good, i like the progress!

[sti robot]

Ok, didn't get much time to fiddle with stuff last night (or post), but things are looking good.

The LCD is fairly easy to hook up and relatively easy to send commands to. It has a splash screen that is configurable. So, if you wanted it to say "Hello, Dave" you could. It took me a bit to figure out what mapping it was using to display the box character, but once I got that it was fairly easy. The back light is program adjustable (this means that if I really wanted to get fancy I could hook up a circuit to the headlight on/off switch and automagically adjust the backlight accordingly.) It almost matches the interior red color. Its about 97% there, about like an omori gauge. The LCD is also a little bit larger than the clock.

The board programs nice and hooks up to a mac easily. When I do a final setup I'm going to have to solder in nice interconnects and such instead of using spare wire. Also, one needs to unplug the tx connection to the lcd when programming the board to prevent frying the lcd controller, so a pluggable connection would be beneficial.

I didn't get a chance to mess with the accelerometer at all. I figure I'll get to it after I read up on it sufficiently. Part of me wants to rush and have something duct taped to the dash for saturday's autox and part of me wants to take is slow and not mess things up.

[Mack]

pm'd you.

[sti robot]

Just to clarify and keep me form getting banned.

I am not a vendor. I cannot sell you anything. I don't want to get in trouble.

I may be able to build one-run units (like 5 of them or so) out of parts you buy and I assemble. I am not at this point yet and we'll cross this bridge when we come to it.

[sti robot]

After reading about the accelerometers I think I may have bought the wrong one. Or rather, bought one I didn't need to buy. I got a digital/analog one that does 1.2g. I think a better choice would've been an analog 5g...would have saved $10 and had a better range of measurement. The analog works just fine with the board I got because it comes with a nice ADC in about 5 slots and will break the voltage signal into things from 0 to 1024 (digital numbers) or 0 to 5 volts. The accelerometer outputs either 3 or 5v max and is fully documented as to what means what measurement.

Using the digital signal on the accelerometer requires using PWM (pulse width modulation). This means I get a waveform (square wave) from the accelerometer and changes in the pulse width of that wave contain the data. So 0g is at a set frequency and as the width increases you go one way and as it decreases you go the other way. The unfortunate part is that you have to do some time calculations to get the number of pulses for per time to get the correct measurement.

[sti robot]

someone mentioned data logging:
http://www.sparkfun.com/commerce/pro...roducts_id=752

I think you can just serial tx to this thing and get ascii text in a file on a SD card. This could be cool, but its $60.

I guess it could eventually be a full on gps/accelerometer track datalogger with a radio beacon and crap , but then i'd probably split it into different screens or something at that point.

To be totally honest, they sell a kit for GPS logging that is pretty nifty/easy to set up.
http://www.sparkfun.com/commerce/pro...oducts_id=8237
http://www.sparkfun.com/commerce/pro...oducts_id=8242
http://www.sparkfun.com/commerce/pro...roducts_id=671

[sti robot]

More spam from me.

I got the accelerometer working. I'm currently using the pulse width modulation method. The reasoning is that all I need is 1 full pulse sample to get a reading. With the analog method you get a sampling and average over that to get a reading.

I'm still trying to figure out how to convert the pulse to the correct scale and i'm learning a bit about the lack of data representation stuff in this IDE.

[sti robot]

More thoughts:

1) self leveling - set 0g as whatever the reading is when you turn the device on. So if there is a little tilt wherever you install it it'll still make sense.

2) I'm doing analog. Its a) easier b) you can find more sensors in different sensitivities that are analog and c) i figured out how to easily map the values programatically

[sti robot]

ooh a video...

That's me tilting the accelerometer (the earth provides us with a 1g reference )

http://randomcrap.us/otherjustin/accelerometer_demo.mov (1.2Mb in size)

On my todo list:
-verify calibrations
-verify maths
-fiddle with update rate
-find an easy way(s) to mount the lcd in car
-self level/zero via software on startup
-add LEDS for forward and reverse acceleration??
-write program to parse raw serial output to a computer