Can an accelerometer be used in this or would the GPS module be able to do the same thing? I would give you measurements, but the 11 button mainboard is a different size from the 18-button. Also, different IC's in the two.
The GPS module I worked with will give you one datapoint per second, so you would have the speed at 2 points A and B and the average acceleration between them every second.
It can give the 3 components (x, y, z) or the total, or total on XY as far as I can remember.
Anything quicker than one per second will have to be done with an accelerometer module, but for the price I would stay with the GPS technology.
Regarding the 18btn vs. 11btn. I got 18, and I think there are 2 kinds of E36 drivers, those that have 18 btn and those that want 18 btn so why don't we design the whole thing based on the 18 btn size?
there's a GPS module for gumstix, as well as other things. They came out with alot more since I used it on my other projects. THere's a built in A/D converter and full I2C / serial in/outs. THere's also a seperate microcontroller board to use as well. But the key is, GUMSTIX runs on linux / windows CE. So its alot powerful and alot easier to use, and like its name, its really small, like a stick of gum. Let me know if you need any help, I've had a lot of experience working with these types of things.
Last edited by suntex01; 01-24-2009 at 06:40 PM.
Guys, great feedback thus far; please keep it coming while I figure out the display interface.
Where this project goes and how far depends on it!
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
Suntex: your experience is crucial.. and welcomed. I have been reading about gumstix and I have 2 big issues with it.
A) You buy the tiny thing and then you buy a 60 pin header to wire all the inputs into it? Is there a robust off-the-shelf connector from there into 20awg cables?
B) Power supply. These things will need some 12V to 3.3V regulator with robust RF noise suppresion. This means we will have some dangling power board next to some dangling gumstix? otherwise we have to put everything on another holding board of the exact size of the stock board, which is an added expense.
C) mechanical. We are talking about using this for 0-60 tests and dangling things are no good. The custom-drawn board will have the same size of the old one and will have the old connectors welded on it and screws. To achieve this mechanical stability with the gumstix i'm afraid we will need yet another "holding" board. Any thoughts??
I agree. The custom etched board will much more accomodate the size, structure, and form of what we want to accomplish without added construction on holders or a whole new casing for the added boards or units. Also with the custom etched board we can still use the existing connections to the factory wiring with added outputs for carpc connectivity. This will make it much more mobile and with the ability to transfer from one car to another if need be for any reason, just unplug and move.
For the first iteration, I will use a high-end PIC18xxxx series microcontroller. It's got plenty of horsepower for what I want to accomplish with this project.
I'm a huge fan of Linux and RTOS's but IMHO save those for the CarPC itself. This controller is really just an I/O board that reads and writes data from sensors, keypad, and to the existing OBC LCD.
As for a stable power supply, I'm looking into incorporating a high-current, switching 5V supply so RF noise will not be an issue.
Accelerometer ICs are available at a cost of a few dollars per piece, so that's not a problem. I can interface one of those with a couple pins on the microcontroller. Also, GPS may be overkill for the initial release; I will do more research and get back to you.
As for I/O, I already have some ICs in mind for high-current (500mA) outputs that I have used in the past. Again, these are low cost and very reliable.
Once I get the display part figured out, I will build a rough design of the circuit and post it here.
Then we can refine peripherals and eventually settle on a board design! Exciting prospects indeed!
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
I am on the bandwagon. This sounds addictive. HEHE
Dunno if you guys need it, but I have a 7 button OBC I can donate for this project.
Thanks for the offer, but we're looking to target the 18-button OBC at this time, due to its flexible internal design.
I'd love to support more OBC's (11-button and 7-button) in the future, but we have to start somewhere...
Of the 3 types, the 18-button appears to be the most "hackable" due to the fact that the display drivers are on a separate PC board.
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
Well, in the past I made my own cable so I don't know if there's a robust off the shelf connector. You can try and see if digikey sells it.
I think we can probably find a car adapter for the 12V to 3.3~5V conversion. Plus, it probably won't be dangling, gumstix is designed to be mounted / screw together.
The website / wiki had many examples of people using gumstix to built UAVs / micro UAVs and I personally didn't have any problems with this issue. Digikey carries alot of enclosures and these things are pretty small they should fit in something the size of today's smaller gps. So I don't think you would have anything just dangling around.
The reason why I recomment this is because I've interfaced accelerometers, electronic compasses and other things to this without alot of trouble. And there are gps / wifi module designed to gumstix. So it provides a greater flexibility and a lot more options.
I think its going to be too big of a task to try and retrofit the obc, maybe you should try and tap into the OBC lines and make something that's would have OBC and this custom module together.
Hey this is why I called my project "Open" -- if you want/can make the gumstix work, by all means do it!
I'm going to go with what's most familar for me, which is an inexpensive discreet microcontroller with a good C compiler. That suits my needs.
If you want to run Linux in your OBC, that's fine.
If someone else wants to power theirs with a Basic Stamp, that's fine too.
Heck, someone could just wire the display board and buttons to a PC via the parallel port and do a 'virtual' OBC in software.
Hopefully this project will "open" the OBC up to more tinkering, once we get the pinout/protocol decoded for the display part.
Last edited by m2pc; 01-26-2009 at 06:54 PM.
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
Add some canbus and go to town!
accelerometers of a few buck? can you post a link?
I used to love the altimeter function of my last GPS project, so I would still encourage you to draw the room for a gps module, even if nothing gets welded on it....
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
Nice...
Cool. I crunched some numbers. The analog devices MEMS device quotes a 2mg error, which for an E36 at 3100lbs translates to an error of about 9HP at 60mph.
The nice thing is that you can change the capacitor value which defines bandwith. Larger capacitor is less error averaged over a longer time but implies less readings per second, however 10 readings a second should be no problem.
On the other hand the GPS has an error of about 1cm/s^2, which translates to about half an HP for the same conditions. The big drawback is that you are limited to one reading per second.
I hope the board has enough space to draw both things in it!!!
Can't wait to get it done.
I think we can easily fit both a GPS and accelerometer on this board. We've got plenty of space available.
I found a really tiny GPS module (1cm x 1cm) for only $39:
http://www.sparkfun.com/commerce/pro...oducts_id=8825
Only problem is there's no antenna onboard, so we'd need to fit an external one.
Or here's a very fast (5Hz) updating unit with integrated antenna:
http://www.sparkfun.com/commerce/pro...oducts_id=8266
Only drawback is the cost: $99
Mefis, which GPS module(s) have you used in the past? Links?
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
That second one is nice... would require direct wiring to the battery for memory. But that should not be a problem. Would be nice to find those features in a bit cheaper unit.
Agreed. Speaking of memory, add this to the feature list:
- Battery backed RTC (real-time clock)
One of the most annoying things to me is having to keep resetting the OBC date/time whenever I disconnect the battery. Here's an example of a tiny 8-pin IC we can use:
http://foxlx.acmesystems.it/?id=105
It's only $2.57 in qty 1.
We'd just need to provide space on the board for a small CR2032 coin cell battery to keep the clock running when power is disconnected.
Of course having a GPS module onboard would give us a very accurate timebase without the need to set the clock, since the GPS signal includes the date/time. We'd just have to provide the option for the user to set their timezone or GMT offset.
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
I have not personally handled the 18-Button OBC, but is there room for a riser board for possibly attaching the extra features including the CR2032?
Yes, there's a good 1/2 to 3/4" of space inside the back of the OBC between the PC board and the back shell.
This is to accomodate the X1070/1071 connector heights so they sit flush with the rear casing, and to allow the TO-220 power transistors that control the backlight lamps to get some breathing room. Switching to LED backlight will eliminate these and give us even more space.
1999 ///M3 TiAg | Heated Power Vaders | DDM Projector36 5000K 55W HIDs | DDM 3000K 35W HID Fogs
DDM Smoked Corners | DDM Weighted Shift Knob | K&N CAI | Mishimoto AL Rad w/Zionsville AL Shroud
Stewart HiPo Water Pump | Samco Hose Kit | 16" SPAL Puller Fan | Viper 5701LE Security
E36 OBC is now open! Join the effort: BF.C Thread | openOBC Wiki
And with the leds it should be a little more power efficient I am guessing.
Not that that is a real concern, but less power, same results is good to me.
Bookmarks