Carduino

[nasphere]

This thread will be the basis for R+D of an arduino based MIMA/battery gauge.

To start off, my original design sparked when I decided to build a MIMA-L. Well being into arduino I decided it would be easy to throw a digitally controlled joystick on the circuit and use a Nintendo Wii Nunchuk to control it. After placing everything and testing, I found out about the hardware timers that are capable of driving just about frequency and PWM. So after ripping half the board apart that I had already made, I'm down to one IC, 20x4 LCD and all the other small components with dead accuracy on frequency and PWM values.

I've already tested the circuit in car and it works great except one thing: When the car wants assist, and you want regen, MAMOD2 gets pulled low and the IMA light toggles.

Pictures, schematics and source all coming soon.

[retepsnikrep]

Look forward to seeing it in and working! Good luck.

What chip are you using?

[nasphere]

Originally Posted by retepsnikrep

What chip are you using?

I'm using an ATmega328 with the Arduino environment.

The board I'm using is a 2"x3" perforated board from radioshack.

Every wire, including all the jumpers and harness wires are all copper core silver wires with PTFE insulator. Most of the harness wires are silver braided twisted pair wires to keep the interference down (It may be overkill, but that's me lol).

I think a solution to the MAMODE2 issue is if the car wants assist or engine start, it'll disable regen. This should keep from throwing the light.

I've successfully passed, and am able to change, all the car's stock signals with my system. Auto-stop restarts and all (thanks to retepsnikrep).

The interface is really amazing. Wii nunchuks have 2 buttons, a joystick, XYZ accelerometers, and connect to the host with 2 data lines. The accelerometers allow you to use orientation to enable different features. For example hold the nunchuk to the left to allow the joystick to control LED brightness or LCD color in a certain mode. I've used the accelerometers to "flick" right/left through the menus and pages as well as a few enables here and there.

To save pins on the MCU and make things simpler, I made a simple shift register PCB for the LCD screen and modified the LCD library to adapt it.

[retepsnikrep]

Is the MAMODE2 a problem?

It's either low for assist or high for regen and standby asfaik

I pass thru or modify that signal as well on mine depending on what is reqd.

Thanks for the notes and code.

[mct75]

While I don't have the grit to build up a mima system, I'd love to use a Nunchuk to emulate the clutch/brake switches. I'm aware of the I2C interface, and am an arduino fiend.

[nasphere]

Originally Posted by retepsnikrep

Is the MAMODE2 a problem?

My circuit just piggybacks onto MAMODE2 because cutting the wire is kind of a waste. So like I said before, when the car wants assist, it pulls MAMODE2 low, at the same time my MIMA wants regen, throwing the light.

Seems like an easy fix though cause I have MAMODE1 input from the car. So if the car wants assist or engine start, the MIMA could disable regen.

Also, not sure if anyone has checked this, the background charging can be initiated in standby (MAMODE1 50%). I got the basic 4 bars charge when I dropped CMDPWR to < 30% in standby.

[nasphere]

Originally Posted by mct75

While I don't have the grit to build up a mima system, I'd love to use a Nunchuk to emulate the clutch/brake switches. I'm aware of the I2C interface, and am an arduino fiend.

My MIMA is full of alot of features and is probably overly complex. A simplified version is VERY easy and very possible. I could change the code a bit to adapt a very simple form of MIMA using a joystick or wii controller if you'd like. I can also give a schematic diagram so you can build your own simple arduino controlled MIMA. Opening the rear IMA box cover is about the most difficult part, other than the slightly tedious build of the circuit board.

I found 2 more problems with my MIMA today: VSS may be needed because using regen under a certain speed triggers a P code. Not sure what this is, but it appears to be alot of bad interference during auto-stop. The LCD screen pops up all kinds of weird characters and MAMOD1 doesn't read correctly. It's in development stage so the board is ontop the BCM with twisted pair PVC wires going to/from all the signals and power. Any ideas? Is twisted pair bad without shielding?

[RobertSmalls]

This seems like an excellent project. I look forward to hearing about your results.

[3-Wheeler]

Originally Posted by nasphere

....The LCD screen pops up all kinds of weird characters and MAMOD1 doesn't read correctly. It's in development stage so the board is ontop the BCM with twisted pair PVC wires going to/from all the signals and power. Any ideas? Is twisted pair bad without shielding?....

Twisted pair is great for low-frequency without shielding.

It's when the frequencies get higher that shielding really helps.

Jim.

[nasphere]

Originally Posted by 3-Wheeler

Twisted pair is great for low-frequency without shielding.
It's when the frequencies get higher that shielding really helps.

Huh. I'm thinking the interference produced in auto stop is messing with the LCD only, or the power being tapped from the box is a bad idea, or twisted pair on the power lines is bad. It works fine when the engine is running. Could it be something to do with the DC-DC converter kicking more EMF in auto-stop?

The final harness will have the really nice 26ga twisted pair shielded wires for all the signals going to the box. I plan to put my controller either in the shifter housing or E-brake housing depending on how it acts with 5' long wires. I guess a body ground wouldn't be a bad idea, but idk if that is at the same potential as the logic ground.

I've just ordered a new o-scope, should ship may 15 or so. (may help a little more with troubleshooting than with my 1-channel)
(Pre-order) DSO Quad - 4 Channel Digital Storage Oscilloscope [TES101D2P] - $199.00 : Seeed Studio Bazaar, Boost ideas, extend the reach