MPGuino release one workspace

[dcb]

Originally Posted by ac7ss

What do you think about the lights?

I'd recommend starting a new thread to demonstrate/discuss the concept.

[ptsmith24]

Camry numbers updated (finally) on the wiki. This is the first true calibration tank (well as true as it could get because it reset 3 miles into it). But, the distance is now more accurate and I'll know about the tank fuel used at the next fillup. I won't remove the "still calibrating asterisks" until I get 3 or so consistent tanks of data. Not sure if any other 'guinoers have the 3s-fe camry, but hope that helps.

[Thalass]

Stupid question here, but is it possible to calibrate the MPGuino in metric units? L/100km (or even Km/L)

MPG doesn't really mean much to me.

[dcb]

Not in stock form,
but you can certainly calibrate the fuel usage in liters and the mileage in kilometers. Just pretend that it says liters instead of gallons and kilometers instead of miles.

Then all your usage will be in terms of K/L

Then add a function to convert k/l to l/100k and wrap all the displayed mpg values in it. I can take a stab at that if nobody else wants to.

[Thalass]

I wouldn't mind having a crack at it myself, but I don't have any code-fu belts and I haven't got a guino to test it on right now.

I was going to buy an iduino kit but with the exchange rate as it is now it'll cost me nearly double what it would have cost two months ago!

[jsheerin]

Acura Integra numbers in the wiki. They're based on one tank, but the mileage was already pretty close, so that should be good. I'll tweak the values if I find they change on subsequent fillups.

[wyatt]

Do you guys think it would be useful to have an additional column in the wiki's "table of car settings" for "final gear ratio adjustments"? A lot of us are running different transmissions/tire sizes that affect the numbers.

[wyatt]

What happened to the MPGuino wiki?

[moorecomp]

An automated spambot from a Netherlands ip keeps trashing it. The guys are working on it.

[mambrino]

This is my first actual post so Hi! to everybody.

I've been following this thread for a while now and I'm planning to build something similar to MPGuino (the main reasons, too much time and a litres/(100 Km) "european" presentation instead of MPG).

To the point... I've been thinking for three days now what's the purpose of the 5.1 V zeners in the VSS and injector inputs.

At first I thought it was a "voltage regulator" configuration. The idea is, Vin is 11-14 V, but the zener limits it to 5.1 V, a somewhat valid TTL "high" level, so the input pin reads a "1".

However, a zener MUST have a minimum inverse current to work properly, a 5.1 zener, about 50 mA. The 100k resistor limits the current to (13 V - 5 V = 8 V; 8V / 100k = 0.08 mA), a fairly lower value than the ~50 mA required. In theory, the zener would not give the 5.1 V but another value between that and 0 V.

What I'm missing? Maybe it's there for surge protection? Then how is the level conversion done?

Also, anyway, why are we not using a more "normative" input level conversion, like this ones (link below), suggested in the Arduino website?

http://www.arduino.cc/playground/upl..._4_arduino.pdf

Please, tell me! I need to sleep!

Thanks!

[dcb]

From my understanding, the zeners operate low on the "knee" at low currents, holding the voltage below 5.1 volts. It was tested and the injector'vss signals at the pin looked fine with an oscilloscope, as far as I can tell. The Zener is cheap, simple, and effective at forward and reverse voltage protection, and fairly common "normative?" practice.

If it aint broke why fix it? I tried a transistor circuit originally, didn't work the first time, and I want as many folks as possible to be able to get it working the first time. There's no reason an experienced person cannot embellish the interface or even the power supply or??? But my philosophy is simpler is better, especially with months of testing in many vehicles behind it and in lieu of a non-theoretical problem.

[mambrino]

Hi dcb, "the man itself"

It's just that (with the datasheets in hand) it's not very clear what the zener is going to do when provided with a low current. Is it going to stay at 5.1 V? 3 V? or 0 V? An ideal zener would keep the 5.1 V, but what about a real one? It seems (to me) that the datasheet is "silent" about this point.

Well, if the experience tells that it works, it's OK, so no more to say...

I wasn't pretending to criticise or offend (of course!), I just wanted to understand the circuit.

By the way, great work!

Many thanks!

Originally Posted by dcb

From my understanding, the zeners operate low on the "knee" at low currents, holding the voltage below 5.1 volts. It was tested and the injector'vss signals at the pin looked fine with an oscilloscope, as far as I can tell. The Zener is cheap, simple, and effective at forward and reverse voltage protection, and fairly common "normative?" practice.

If it aint broke why fix it? I tried a transistor circuit originally, didn't work the first time, and I want as many folks as possible to be able to get it working the first time. There's no reason an experienced person cannot embellish the interface or even the power supply or??? But my philosophy is simpler is better, especially with months of testing in many vehicles behind it and in lieu of a non-theoretical problem.

[dcb]

Here's a picture, at lower currents, the zener voltage is lower, so low current is not a concern from a protect the pin perspective. With 12 volts through 100,000 ohms we are in .1 milliamp land, which is apparently enough with the zener diodes specified and the atmega168 to make a clean signal (needs to get above 2.5 volts).

[mambrino]

Nice graph! If we take a look at the 5.1 (maybe?) curve, it's "obvious" that it gives about 5.1 at 50 mA, and about 5.0 at 10 mA, but it's less clear what happens at 1 mA. Maybe 4.5 V or 4.7 V? And at 0.1 mA, it's so close to the axis that's impossible to tell from the graph...

Anyway, as you said, "if ain't broke...". And if so many people have tested the circuit in reality, there's not much to object.

Originally Posted by dcb

Here's a picture, at lower currents, the zener voltage is (...)

[orange4boy]

Hello,

Just finished soldering my MPGuino kit from Fundamental Logic. Huston, we have lift off!

I have some reading to do to figure all this out but I'm stoked!

I also got a present in the mail from vtec-e. (a prince among men) A sweet digital vac gauge! I'll post it all soon with pics in The Golden Egg mod thread. Mostly minivan modding

So many gadgets so little time...

Thanks dcb, You rock!

[orange4boy]

Got everything set up and wired but it does not turn on in the car. USB hookup works. I get 12V and ground cont. at the board in the car but mpguino is blank

The machine comes pre loaded from spiffie yes? I don't need to flash anything if the program comes on with the USB hooked up or is that a separate program?

The instructions are not entirely clear on this for us non techies.

Thanks

[wyatt]

if you don't see anything, try pressing the center button a few times. It may just be that the contrast is off.

[dcb]

hi Orange, do you have usb and 12 volts connected? (just curious, probably wasn't designed for both at the same time)

If usb works, and 12 volts through the regulator circuit doesn't, then your onboard regulator circuit is funky. Take a voltage reading to ground on the other side of the diode, on the regulator input and on the output to help isolate the problem.

[orange4boy]

Getting .56V on the outer leads. Funny thing is that I'm getting continuity between the wrong leads from the RJ connector. Should there not be 12V getting to the regulator diode? the square one with the heat sink tab? Im getting 12v at the back of the female RJ on the opposite side to the one with continuity to the diode which points to a mistake in the instructions or a crossover phone cord. possible?

It's not the contrast for sure.

How would I rewire the RJ?

[dcb]

you should have 12 (ish) volts to the regulator, 5 volts out, and a ground. If no 12 volts then maybe a diode is installed backwards?