MIMA status update

[Mike Dabrowski 2000]

Hi Guys
I have been busy with other projects, but have managed to do some testing of the MIMA_C in my car. (no test pilot volunteer yet)
As soon as the MAP , TPS, and Battery amps signals were all connected to the MIMA board, I began to have unreliable A/D conversions and could see with the scope that the problem was due to high frequency noise spikes between the individual module grounds. The signals all need to be read by the MIMA A/D converter, so they needed to be brought to a common ground in the MIMA . Several simple ferrite bead and differential input schemes were tried, but none truly isolated the signals, or removed the noise. I finally decided to go all the way, and have designed a full precision optically isolated input for the three signals that should solve this problem, and let me get back to the software and final board layout issues.

http://pages.cthome.net/genesisone/index.htm

Thanks for your patience.

[Armin]

Mike,

sorry to hear about the roadblock you ran into! But it seems to me you are on the right track to overcome it, already!

I remember when we first talked about it that there are various signals referenced to different grounds. Optical isolation is the surest way to resolve the problem. I don't think filtering will get you there, since what you see are most likely ground-loop currents. Isolation is the only thing that will stop them for sure!

I'm sorry I don't have more time to contribute to the project. I think you are doing a great service to the Insight comnmunity!

Thanks for all your work and keep it up!

[Mike Dabrowski 2000]

Good news!
The Opto couplers did the trick. I now get clean stable signals on all analog inputs.
I will put some scope traces before and after and photos of the prototype board @
http://pages.cthome.net/genesisone/index.htm
Now I can proceed with board layout, parts purchacing, and throttle based control software.

[Mike Dabrowski 2000]

Further update
To help with the throttle based control, I have made up a test conector that lets me connect the Micro in the MIMA_C with a Labview based Data Acquisition card in my notebook computer. I am capturing the ThrottlePosition, MAP, Joystick,Battery amps, CMDPWR, and both MAMODE 1 and 2 signals in real time on a graph while driving.(don't need a test pilot) The data is stored to an excel spreadsheet file that I can view later in detail with labview. I will do some test runs tomorrow, and post some of the graphs on my web site. It should help me define normal IMA action and MIMA based action, of all my signals, and therefor be a great tool for determining the best approach for the throttle control. It will also let you guys see the interactions of the signals.

[b1shmu63]

I like your testing approach! This will give us some really solid data to work with. I'm really impressed with the circuitry for the opto couplers as well.

Kip

[Mike Dabrowski 2000]

Hi Kip
Afraid I can't take too much credit for the Opto circuit. The design came right off of the HP data sheet for the parts.
I should have some data by this evening, as it is time for another 100 mile round trip to visit the Indians

[Mike Dabrowski 2000]

The first labviewdatalogs are at:
http://pages.cthome.net/genesisone/test_results.htm

[Mike Dabrowski 2000]

The boards have arrived message

http://www.insightcentral.net/forum/vie ... 3&start=75

[Mike Dabrowski 2000]

Hi Guys
I have built up the first MIMA_C board.
I could not help reflecting on how much building the board was like building a heathkit, and really think that some of you will want to build it your self.
The ground plane, and small pads will make good soldering skills and a clean very fine tipped soldering iron a must for building the board.
It took me well over 2 hours to build the first one, and the price of the assembled and tested board will need to reflect that, which is another reason to offer you the option of building your own. I will build up the other boards, and see how fast I can build them with the experience of several boards under my belt.
http://pages.cthome.net/genesisone/index.htm

This is an exciting time.

[Kevin Dougherty]

Mike,
That MIMA board is a thing of beauty, I especially like the surface mount LEDs' arranged on the penny. Will that configuration be available?