Speedometer Calibration / DeMetrification

[CTScott]

If you are wondering what the heck DeMetrification is, it is my new term for modifying a device intended to display in Metric units to display in English units.

Last month I finally figured out how to reprogram the odometer on our instrument cluster to allow for easier swapping of clusters (http://www.yarisworld.com/forums/showthread.php?t=41461).

The most common reason for wanting to swap clusters it to gain the OEM tachometer (for those in the US with 2009 or older manual transmission, non-S package Yaris, which did not have the tach). The problem is that S package MT liftbacks were not very common, so few clusters from them are available on eBay or from junkyards. On the other hand, all MT Canadian liftbacks had tachometer equipped clusters, so Kmh clusters are very easy to find for reasonable prices (typically under $100).

The problem, for those south of the border, with running a Canadian Kmh cluster is that (besides the large-number primary speed display being in Kmh) the odometer increments in kilometers.

After driving around for a couple day with an oscilloscope attached to the speed sensor input to the cluster, I was able to develop a device which measures the pulse width of the signal and replicates that signal, with the pulse width proportionally adjusted to allow the cluster to display in MPH as well as increment the odometer in miles. I also added a feature, which allows the user to make a fine adjustment to calibrate the speedometer to a GPS to account for variations in tire diameter, etc.

The device has four wires that connect to the right side connector on the speedometer (power, ground, speed signal in, and speedometer out). Normally the speed signal goes into the cluster and then out of the cluster (unmodified) to the ECM. In my initial testing I found that feeding the modified signal to the ECM on my automatic transmission Yaris caused some really odd shift point changes (since the ECM controls the AT). To eliminate this I simply disconnected the ECM output wire from the cluster and connected it to the input to the cluster (so that it sees the unmodified signal).

Note that once connected and calibrated, this device would not be mounted to the dash, but would simply be tucked under the instrument cluster.

Here is video of it in action. I apologize for the shakiness from my headrest mount.
http://youtu.be/KkUOgEvTYAY

[BEEF]

any way you could post some pictures for us guys that can't see youtube at work? (yea, that part about my job really sucks)

amazing what you have figured out with the yaris.

you're awesome

[WeeYari]

On the other hand, all MT Canadian liftbacks had tachometer equipped clusters

...and AT as well

There are absolutely no Yaris in Canada that did not have a tach.

[CTScott]

any way you could post some pictures for us guys that can't see youtube at work? (yea, that part about my job really sucks)

amazing what you have figured out with the yaris.

you're awesome


Here are a couple of snaps from the video. Basically, with a flick of a switch the needle moves from showing kmh to MPH on the large numbers:

48678

48679

[BEEF]

that's an awesome little thing there. I assume you are going to be selling these?

[CTScott]

that's an awesome little thing there. I assume you are going to be selling these?

I can definitely build some up for those interested. The ideal way to do it is to buy the cluster, and ship it to me for odo correction as well.

[suckerface]

The only downside to that would be that if we drive the cars while you have it, the mileage would be off (granted, not by much).

How much would you charge for the service on top of shipping? (I'm likely to do this ;0) )

[CrankyOldMan]

Wow, I had imagined doing something like this for my microcontroller class project this semester. Well, the speedo correction for tire sizes, anyway.

CTScott scores again!

[CTScott]

Wow, I had imagined doing something like this for my microcontroller class project this semester. Well, the speedo correction for tire sizes, anyway.

CTScott scores again!

That would be a more fun project than the one I had to do 20+ years ago using a Motorola HC6811 microcontroller. My professor owned a lumber mill and our project was to simulate a control system (with PID control of the heating) for his lumber kiln using a toaster oven. We spent many late evenings in the lab writing code, drinking beer, and precisely cooking frozen pizza.

What family of micros do they have you working with?

[poorsh2]

I have the cluster, tell me where to send it

[jayeh]

...and AT as well

There are absolutely no Yaris in Canada that did not have a tach.

Why is that exactly? :iono:

I've noticed the same thing on AT corollas. I was kind of a bit shocked when I saw old american corollas and tercels with MT's and no tach too! :eek:

[jpmck03]

Here are a couple of snaps from the video. Basically, with a flick of a switch the needle moves from showing kmh to MPH on the large numbers:

48678

The right hand side of that demetrified speedo is going to be awfully lonely!

Anywho, amazing work, again CTScott!

[CrankyOldMan]

That would be a more fun project than the one I had to do 20+ years ago using a Motorola HC6811 microcontroller. My professor owned a lumber mill and our project was to simulate a control system (with PID control of the heating) for his lumber kiln using a toaster oven. We spent many late evenings in the lab writing code, drinking beer, and precisely cooking frozen pizza.
The project used to be an open-ended "you choose it, you build it" paradigm, but some students were getting in WAY over their heads and not passing the course, while others were making something far too simple and walking away with an A. The solution last year? "Here's a list of common hand-held electronic device functions. Choose three. Go." The net result was things like audio playback with accelerometer response and short audio recording, etc. The solution this year? "Build an Arduino-based RC hovercraft for < $100. Go."

What family of micros do they have you working with?

We start off with a Spartan3E FPGA, then move up to ATMEL Atmega644 and/or Arduino Uno. I'm trying to also use a PICAXE M2 in our controller, since they're cheap, low-power and super small (DIP-8 with 6 I/O pins!). What did you use for this little beasty?

[CTScott]

I have the cluster, tell me where to send it

We should just coordinate a day where you can come down and we'll install it.

[CTScott]

The project used to be an open-ended "you choose it, you build it" paradigm, but some students were getting in WAY over their heads and not passing the course, while others were making something far too simple and walking away with an A. The solution last year? "Here's a list of common hand-held electronic device functions. Choose three. Go." The net result was things like audio playback with accelerometer response and short audio recording, etc. The solution this year? "Build an Arduino-based RC hovercraft for < $100. Go."

[QUOTE}What family of micros do they have you working with?

We start off with a Spartan3E FPGA, then move up to ATMEL Atmega644 and/or Arduino Uno. I'm trying to also use a PICAXE M2 in our controller, since they're cheap, low-power and super small (DIP-8 with 6 I/O pins!). What did you use for this little beasty?[/QUOTE]

I used a PIC 18F series, as I needed the extra processing power. I exclusively work with PICs, since that is also what I use for work projects.

[07stlYaris]

Holy crap...I haven't heard 68HC11 uttered in over 15 years. My senior project was an open loop EFI for a lawnmower. It worked extremely well but would have doubled the cost of the mower. Neat stuff Scott.
P.S. Still working on the S/C from the Milennia for my Yaris.

[poorsh2]

Maybe another install day, as ong as it is on a sunday I am good to go

[CTScott]

Holy crap...I haven't heard 68HC11 uttered in over 15 years. My senior project was an open loop EFI for a lawnmower. It worked extremely well but would have doubled the cost of the mower. Neat stuff Scott.
P.S. Still working on the S/C from the Milennia for my Yaris.

I haven't touched a 6811 in about 10 years now. The robots I used to work with had a 68000 as the primary processor with a slew of 6811s as subsystem processors.

Did you actually purchase the S/C?