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Old 12-08-2002, 07:32 PM
BlueJeeper BlueJeeper is offline
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Join Date: Jul 2002
Posts: 524
Hi Frank,

Sorry it has taken me so long to reply.

You know I remember your COG writeup and can't believe it didn't cross my mind to integrate that into this system. It could be done easily as long as you could define your center of gravity in 3-dimensional space. It would be easy to display this along with the other data I wish to display.

What's cooler is that it could easily be integrated with your AiRock system. When the angle between the line passing through your COG towards the center of the earth and the plane incident with the frame has reached a predetermined tolerance, you could theoretically control the AiRock very easily to air up a corner of your suspension to make the frame closer to being perpendicular with the line through your COG. It could be designed to be seamless, although it would probably take some getting used to on the driver's end. I don't suppose AiRock would be interested? Great idea, Frank. As you can see, there are lots of neat possibilities with a system like this.

I *am* using a Parallax Basic Stamp II to interface my accellerometers. I had thought about going to their new Javelin (I think that's what it's called) chip because it uses a Java subset, but I think I'll stay with the Stamp until it no longer suits my needs. I intend to process the data dynamically through an RS-232 serial port unless I decide differently later. The data could then be stored on a laptop or PDA for later examination as well. This is all TBD until I get to that point though.

I really have little intention of making a commercial endeavour out of this. As I said before it is more just a learning exercise for myself. It's definitely just part of my hobby and I'm happy to share my work with you. If any commercial work came of it that'd be great, but that's not my goal.

I actually thought up the idea over a year and a half ago but haven't had nearly the time to work on it that I'd like. After the holidays I will have significantly more time to work on it. Most of the work I have done has just been researching how it might be done, and learning about the components I want to use. You can actually get free samples of the accellerometers from Analog Devices, and I did this about a year ago. The accellerometers come in tiny, tiny packages with no leads.

I spent a lot of time trying to work with those, but trying to solder leads onto those tiny packages takes a very quick, steady hand. If you hold a soldering iron close to them for too long the internal components will melt. The benefit was that these samples were free, but they were too hard to work with.

I was aware at the time of the evaluation boards available for these accellerometers, which have all the necessary components pre-assembled and have leads attached. However, I believe Analog devices had just finished retooling from their old, larger accellerometer to the smaller one I had been working with, and there were no eval boards yet available. So I dropped the project for a while until only several months ago, when the boards were available again. You can now get them for about $30 each straight from Analog Devices, Parallax, or a company called Crossbow which you can find online.

These evaluation boards are extremely easy to work with and can be plugged right into most of the Basic Stamp programming boards. Unfortunately I have only had time to play around a bit with the eval board since I got it. I have nothing of much use yet but that will come as I get more time to work on it in the coming weeks.

In the future, when I am able to work on the graphical interface, I will probably have the Basic Stamp send the data from the accellerometers to a PDA or laptop through the serial port. The data will be recieved for each accelerometer as its angle in radians with respect to the flat earth plane. I will then write software that will display this data graphically. Initially I will start out with 3 accellerometers; one in the cab to measure the tilt of the body and frame, and one on each axle. On the display you would see a graphical representation of how these components relate to each other in 3D space. Simply put, you will see your Jeep "flexing" as it would appear to an outside observer. You could also display your COG as well as a number of other things. I will probably write this application in C code so that I might be able to use OpenGL, but will go with the flow when I get to that point and use whatever works.

As I said this project is still in the very early stages but I think it has some potential. I am glad that you see some use for it and that has inspired me to make time to work on it in the coming days. I would be happy to answer any questions you have for me about it, and sincerely appreciate your input and ideas. I will keep you up to date on how it is going and would be happy to share my code with you once I finally get a working prototype (which should hopefully be soon). It would be fun to have a Jeepin' open source project!

You can always contact me at rickbernotas@hotmail.com. My hotmail has been acting up the past few weeks and has been dropping some sent and recieved messages, so if I don't respond in a timely manner (usually 24 hrs.) just email me again. Of course you can always get me on the forums as well, I check them daily.

Rick
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