Any interest in developing an open source fuel economy gauge/computer?

[MetroMPG]

Are there any people here who would be interested in developing an open source FE gauge/computer?

We see lots of inquiries about the SuperMID, which works by monitoring the vehicle speed sensor and a fuel injector signal. Unfortunately, Yoshi's a busy guy, so he hasn't been building too many. And the value of the US dollar relative to the Yen is making the MID more and more expensive.

The SuperMID in basjoos' AeroCivic

I don't know much about this stuff, but it seems to me the open source Arduino computing device ($35) would be an ideal platform. The cool thing about it is that it could also be connected to a laptop/palm if desired.

Arduino electronics prototyping platform

I know skewbe @ GS developed a quick 'n' dirty FE gauge that uses a laptop sound card & audio input to monitor injector cycles, but an Arduino based system seems like it would make more sense to more people.

Doing something like this is outside my experience. I could probably figure it out, but I've got enough projects as it is.

So I'm just putting it out there to see if anyone else would want to spearhead things.

Thoughts?

[elhigh]

What, you mean like a Megasquirt? That's way out of my league. I know where the ON button is, and I can bang my forepaws on the keyboard to make words.

Ask me plumbing, house wiring, or carpentry. All those little wires I leave to someone else.

[MetroMPG]

Forepaws ...

No, it wouldn't have to control the fuel injection, just tap into an injector wire to monitor the pulses. It would theoretically just need two inputs, and some basic (literally, I think) programming to do the calculations.

[SVOboy]

Yes, this just need be a display, not a tool for modification or even anything too fancy like that.

[MetroMPG]

It doesn't technically even need an LCD display. If someone wanted to, they could download the data onto an old laptop, or use a laptop to view the data live.

That's the neat thing about open source - more options.

[trebuchet03]

I've always wanted to get into micro controllers

I know you can buy, from SAE, the book on the OBDII protocols and how to interface - probably something necessary if you want to plug into the diagnostics port and not tap a bunch of misc. wires.

Ladyada makes an arduino clone - the boarduino - http://www.ladyada.net/make/boarduino/ and is sold as an assembly yourself kit for ~$17



Just food for thought. I don't have time now, but if something gets going - I'll throw myself into the project (throwing myself deep into projects is both an asset and a weakness of my personality )

[Daox]

I'm with Treb. I'd love to get into it as I have interest in electronics and experience with programming. However, like you, time is a huge limitation. However, I'd be willing to do what I could to help out.

[MetroMPG]

Treb: good link. You can buy the Arduino as a DIY kit to assemble as well, but I'm not sure what the price is.

Daox - that about sums up my position = interest + some programming ability.

Let's see if anyone else dives in. If not, I was thinking of getting myself an ar/boarduino anyway, just to play with.

EDIT: forgot to comment on the OBD2 issue - the nice thing about the MID is it's universal to any vehicle with fuel injection. I figure people who have an OBD2 vehicle would just get themselves a ScanGauge anyway (unless this turned out to be significantly less money for equivalent functionality).

[Coyote X]

I would recommend using an atmel avr and use the codevision c compiler. This setup is very common and a lot of people use them all the time. Embedded C programming and the Atmel AVR is the book I recommend reading on it.

I have been thinking about making one for a while. The way I figured would be to monitor the injector signal and the vss sensor. Have the controller calibrated by driving and adjusting the speed constant to get it to match the speedo. Then for the gas fill the tank then drive around for a while while the controller adds up the total injector open time. Then it can calculate the flow rate of the injectors when the tank is refilled.

From there it is just a matter of calculating and displaying it on an lcd.

The reason I say use codevision is that 75% of what is needed for this is already included in the libraries it includes. The lcd interface library is on there and it is simply a matter of telling it what to display. The only thing that would need some real consideration is to build a circuit that can work with pretty much any injector signal and any vss signal. Having a few different circuits would make installing it much harder and nowhere near as user friendly.

[MetroMPG]

Any idea how much the atmel platform would cost?

Reason I ask is because I think cost is going to be a big concern for the type of person who's driving a pre-OBD2 vehicle.

Or for the type of person with an OBD2 car, but can't afford an SG.

EDIT: I like your calibration idea.

[Coyote X]

Since a very basic atmel chip would be enough for this I would say the controller would be less than 3 bucks. A 2x16lcd is under $20. So I would say the whole setup with the vss and injector circuits should be less than $50.

A basic interface to calibrate the speed and fuel might need 2 buttons. With a 2x16 display you could have 4 numbers displayed. So I would say instant MPG, last minute avg MPG, Trip MPG 1 and Trip MPG 2. The buttons could be used to reset the trip numbers in normal use. Maybe use a jumper on the board to put it into programming mode. Be a very simple addition but could make it a lot easier for normal use.

There would be no point in putting a tank mpg on there since one of the trip meters could be used for that or not depending on what the person using it wants to do.

[MetroMPG]

Also: I could calibrate mine quickly against the SG and then pass the settings on to anyone else with a mk4/5 car.

What would be the difference between avg MPG and Trip 1/2?

Another good parameter the MID has: % engine on vs. engine off by distance.

What else does it have, Ben?

The ability to view FE in different measurements would be good too. It's one of the things that held back the SMID's popularity on this side of the pond. L/100 km, km/L, mpg (US), mpg (Imp).

[GenKreton]

I've done PLC's/PIC's, LCD's, and I do a lot of general coding for Linux projects; I think I can contribute a lot, but it may have to wait 6 weeks. Anyways, what I need help understanding is how to access the data - that is get the measurements on the wide range of vehicles we want it for. I do not know cars yet!

Can we gather the information directly from gauges already installed? Which are best to read from? Will they all be sending the same conditioned signal - that is, the same voltage range scaled the same amount? If not then we need some rudimentary way of calibrating it, which would be easy for mileage but harder for fuel.

[zjrog]

I would be quite interested in a Pre-OBD2 setup. If you could make it interface with a Linux PC so much the better.

[LostCause]

I'd go with a common processor over a prefabbed/complex circuit. If the computer is built from components that can be had from boston to timbuktu, from now until 2015 then we can help everyone help themselves...

Yoshi had the right idea and I think the easiest route would be to learn from his lead. Common microchip, homemade PC board, cheap 20 line display, etc.



Look at the simplicity of the design compared to the arduino. No pre-etched board and just a bunch of components that can be bought at once from Digikey, Mouser, etc.

Originally Posted by GenKreton

Anyways, what I need help understanding is how to access the data - that is get the measurements on the wide range of vehicles we want it for. I do not know cars yet!

I'm pretty sure Yoshi pulled the signal from one of the injector wires coming out of the ECU and tapped into the electronic VSS signal at the speedo.

- LostCause

[GenKreton]

Originally Posted by LostCause

I'm pretty sure PIC's need an external box for programming and PC boards need some specialized equipment to etch. The code could be put available online for everyone, programmed PIC's could be sold for a tiny profit by someone with the equipment for those without, and etched PC boards could do the same.

Essentially, there would be a few specialized parts that someone with enough desire could still acquire cheaply on their own if community supply lines shut down. Everything else could be condensed as a shopping list from Digikey, Mouser, etc.

Depending on the PIC and school, there is a good chance one of us at a university has access to the development kits for the controller so we can develop and test before committing to buying them. Generally development kits are not so cheap in my experiences.

[trebuchet03]

Originally Posted by LostCause

I'd go with a PIC processor over a prefabbed circuit. What happens five years from now when the arduino is no longer available?

Buy an ATmega168 (common) and burn the boot loader

The only thing that makes the arduino nice is that it's an easy to use platform that doesn't require external hardware. For the same reasons you say the superMID design is nice are the same reasons why I wouldn't try to replicate DIY. I'd much rather prototype on a nicely etched and silkscreened board that I can just plug into rather than deal with a homemade PC board and a bunch of components Now, if I were making something to sell - I think I would agree with you (and I'd spend the extra time) because having an on board programmer isn't really that necessary

That's just me, as someone with limited experience with microcontrollers - which is very likely the case for someone that is going to replicate any efforts.

[Coyote X]

I think for the input signals the easiest thing would be run a 10k resistor to a 5v zener. Then maybe use a transistor to isolate the microcontroller if needed. That should get a signal the controller is able to handle.

The VSS is just a voltage pulse every so often. Usually so many pulses per mile. So to measure it, just set an interrupt and use a bit of math to calculate speed by averaging the last few pulses for a steady number.

The injector would need a pair of interrupts. One rising edge and one falling edge. That can give a good way to measure pulse width of the injectors.

Once the basic math is figured out converting to whatever unit is needed would be a simple matter I figure. The avg mpg I was thinking of was 'Last minute avg MPG' That seems useful to make sure you aren't getting high peaks in the instant mpg reading but killing your avg by doing it wrong.

Really once the vss and injectors are going into the controller anything you can do with those numbers would be pretty easy to implement. Writing it in a higher level language like C and not assembly makes stuff like that just a few minutes worth of work.

There are some really simple atmel programming setups. So a programming circuit could be as simple as a single IC and a few wires. I figure there will be a lot of people not willing to build their own and will want to buy one. Having a easy to build system would be nice for whoever wants to make and sell them assembled. Another advantage of the atmega setup is that even if the chip is discontinued it would be a 5 minute job to port the code to a new one assuming there isn't one that is directly compatible.

[LostCause]

Originally Posted by GenKreton

Depending on the PIC and school...

Originally Posted by trebuchet03

Buy an ATmega168 (common) and burn the boot loader...

Aww, you guys quoted before I had a change of heart and edited my post.

I'm just concerned over availability and cost. By building the circuit with basic components that are widespread and cheap, then what is developed here will always be available. I just like the idea of ordering everything at once from Digikey or Mouser rather than having to go through specialized sources (arduino, someone on this forum, etc.). There are less logistics to deal with that way.

Originally Posted by Coyote X

There are some really simple atmel programming setups. So a programming circuit could be as simple as a single IC and a few wires. I figure there will be a lot of people not willing to build their own and will want to buy one. Having a easy to build system would be nice for whoever wants to make and sell them assembled. Another advantage of the atmega setup is that even if the chip is discontinued it would be a 5 minute job to port the code to a new one assuming there isn't one that is directly compatible.

Ahh, this is the method I am trying to describe! Simple, available to all, and easily adaptable if a component is no longer supported. If it isn't too much trouble, it would be cool to see the development (i.e. steps taken in detail) laid out so we can follow the logic.

- LostCause

[SVOboy]

The superMID also has lap capability, which