[JrZook]

So after working out the VSS setup I decided to go a bit further with the signal then just feeding it to the ECU and have started designing an accurate digi speedo and odometer to suit any size tire and diff ratio on the sierra's. Since the VSS gives 4 pulses per revolution and the gear ratios of both the speedo drive gear and diff ratio are known Ive managed to bust out some code on a microcontroller and calculate both the current vehicle speed as well as distance traveled very accuratly.

The inputs required are:

Speedo Drive Ratio
Diff ratio
Tire Circumference in mm

Outputs:

Speed in KPH (from 10 - 160KPH) accurate to +- 2KPH, highly dependant on tire circumference measurement.

Trip meter distance 0-1000kms, resolution of 10 meters ie 000.00km readout. Accuracy of ~ 5 meters per km again higly dependant on tire circumference.

The update time of both these outputs has been set to 1/2 sec so far which seems to give a nice readout.

At the moment the outputs are written to a 20x4 line LCD but will most likely be displayed on 3 -7segment displays for the speed and a small LCD screen for the odometer once re-designed.

Anyway will try and get some pics up soon of what I have so far. Tested it against a GPS and it seems to be working quite well

Dan

[squirezook]

This is way cool Dan I can see em lined up to grab one of these.
Glad to see you are putting your skills to some major creativity.

[morpheus]

boody good work.. lol.. gonna be a pimped digital dash sierra..

[want33s]

Cool Dan, you know where to send the first production unit....

[MrRocky]

i think someone needs a girlfriend, you seem to have waay to much spare time on your hands

[morpheus]

i have found it hard to balance a girlfriend with the love of 4X4'ing. mine is all like, why you watching those stupid 4WD videos again?? and oh my god why would you want to do that in a car.

so then i show her a vid of a cruiser in the sand gettin kinda stuck with a massive rooster tail off the back and say to her, "wouldn't you like to be in that" and she's all like NO... lol

[Polar_Bear]

dont worry dude, i get the same response when i show them my porn collection

[morpheus]

HAHA... nice..

[Fatzook]

sign me up

[royce]

If you can add in a pair of buttons or a rotary switch so you can trim the trip reading youve got yourself a rally trip computer you could sell heaps of right there!!!!!

possibly with 2 separate meters that can be reset individually

[Rusho]

I'll definately take one

[31zook]

is there anyway of having two settings? so i get around on 31's through the week but on the weekend i use 33's, could there be a function so it hold's two tire diameters? and how much?

[JrZook]

royce wrote:

If you can add in a pair of buttons or a rotary switch so you can trim the trip reading youve got yourself a rally trip computer you could sell heaps of right there!!!!!

possibly with 2 separate meters that can be reset individually

Yep this is doable.

31zook wrote:

is there anyway of having two settings? so i get around on 31's through the week but on the weekend i use 33's, could there be a function so it hold's two tire diameters?

This can be done as well. Suggestions like these are more than welcome. Trying to spec out something that will be affordable as well as help most of ya out. Whats the cost of a speedo re-calibration these days?

Ok I need a list of most common diff ratios and most common tire sizes. Was thinking of putting a very small switch block on the board once I get to that stage so the user can flick the switches to suit their tire and diff ratio combo.

Tire Sizes:

Stock-205/70R15
235/75R15
30"
31"
33"

Diff Ratios:

std WT 3.7:1
std NT 3.9:1
4.11:1
4.6:1
5.12:1

Now if there are any different speedo drive ratios I would need to know them as well. Im working with the stock ratio of 2.85:1.

Fatzook wrote:

sign me up

Pete u get my Pm RE: VSS?

Dan

Dan

[31zook]

I bought mine from marks adapters for $480 when i was engineering my zook on 31s, it came in the form of a box with ratios in it which adjusted the final cable rotation speed...

i think your spot on with the tyre sizes, and ratios

[royce]

on the calibration side of things, would a better way be to tell it the number of pulses per tyre revolution and the circumference of the tyre?

that way it could be made to work on anything with any trigger config, IE 4 magnets inside the real wheel hub on my mini with 20" high tyres

[JrZook]

royce wrote:

on the calibration side of things, would a better way be to tell it the number of pulses per tyre revolution and the circumference of the tyre?

that way it could be made to work on anything with any trigger config, IE 4 magnets inside the real wheel hub on my mini with 20" high tyres

Yes correct Royce! In my code I use the tire diameter to calculate the circumference and have a variable for the number of pulses per tire rotation through the diff and speedo gearing. If u wanted to put 4 magnets on your wheel hub it would work by setting your speedo drive ratio to 1.0 and diff ratio to 1.0. The most accurate way is to set your tires to the max pressure you would ever run and measure the rolling circumference via chalk markings on your driveway. This can still be an option. For example my new 30*9.5 bfg mudds measure roughly 29.8 inch at 32psi and 28.8 inch at 23psi (I measured the rolling circumference and converted back to diameter). Using the code calibrated for a true 30" tire displaying 100KPH, the 29.8 would be actually doing 99.3KPH and the 28.8 would be doing 96 KPH. So thats 4% out on actual speed for a tire diameter difference of 1.2".


Note: holy shit that's a diameter change 30.4mm just by changing tire pressures!!! Where the frig did qld DOT get there '15mm increase in tire diameter is illegal and dangerous' when you can exceed that by changing tire pressure?

Anyway for a comparison sake lets assume the original speedo was dead accurate for the stocko 205/70 tires at 100KPH. Putting a true 30" tire on the actual speed at 100KPH would be 114KPH! So yea thats 14% out and a fine from mr plod.

Dan

[Zachius]

I love this idea! I am guessing that you doing this via a programmable chip?

I have had some experience in assembly and C for programming a robot (in a uni course) that I suspect would be somewhat similar.

[JrZook]

Ok managed to snap up some pics of the prototype that I made up to test the code and functions of the unit.
So this is what Ive come up with so far.

The prototype uses 2 buttons, one for menu selection and another for adjusting parameters as well as reseting the trip meter.

The Menus:


Run screen displaying current speed and distance travelled


Tire circumference input screen, units in cm


Diff ratio *100 ie 3.70 ratio input 370


Speedo drive ratio *100 ie 2.85 ratio input 285


Pulses per sensor rotation. Example VSS outputs 4 pulses per rev

And heres one of the unit in action on my test bench. Sierra speedo with VSS installed.


As you can see the speed and the trip meter are wayy off on the standard speedo unit. The digital one has been setup as above for 30" tires on my WT.

Dan

[Rusho]

Absolutely awesome...when do you think they will be available? What cost do you think these beautys will be approx?

[bazook]

how bout using one of these up the top
http://www.jaycar.com.au/productView.asp?ID=QP5570
and then doing the other screen as odometer and temp volts rpm's that would be cool

[bazook]

oh whoops its not backlit though

[JrZook]

bazook wrote:

how bout using one of these up the top
http://www.jaycar.com.au/productView.asp?ID=QP5570
and then doing the other screen as odometer and temp volts rpm's that would be cool

Yes the plan is to use 3-7segment led displays for the speed and a 8 character by 1 line back lit LCD for the trip meter. For now I'm using this LCD for de-bugging purposes.

Dan

[bazook]

cool ill be in for one

[11_evl]

have you got experience with the microtech hand set controller. all the functions of that would be cool

[BlueSuzy]

If this was made with all the adjustability for diff ratios as lcd etc. As seen here. I will buy one definately.

I am always changing my car. So different tyre sizes etc.

[JrZook]

11_evl wrote:

have you got experience with the microtech hand set controller. all the functions of that would be cool

No I haven't. But im currently building a custom EFI controller from scratch tho . What sort of functions do you speak of?

Dan

Ps you ever sort out that SR20 auto box i think it was? Pm was a while ago.

[JrZook]

BlueSuzy wrote:

If this was made with all the adjustability for diff ratios as lcd etc. As seen here. I will buy one definately.

I am always changing my car. So different tyre sizes etc.

Well what you see on that lcd is its functionality so far. All those parameters are adjustable. Will see how I go with the size of the code and try to add in a switch and a second set of parameters so like you suggested with a flick of a switch your back to running your daily tyres or diff ratios etc.

Dan

[atari4x4]

this is simply awesome, good to see someone putting their knowledge/skills to good use...

this & the VSS thingo are seem so simple in theory but to sit down & do it is a whole different ball game 13/10 from me

[royce]

I would think if you could make it so that you removed the speedo altogether and made a vss type sensor to screw into teh transfer then ran this as a speedo with a non adjustable odometer as well you could claim it to be an ADR compliant speedo for engineering

[Damo]

royce wrote:

I would think if you could make it so that you removed the speedo altogether and made a vss type sensor to screw into teh transfer then ran this as a speedo with a non adjustable odometer as well you could claim it to be an ADR compliant speedo for engineering

JrZook & I were talking about that initially, but since he got the VSS thing happening he's getting the speedo side worked out first. Feeding the electronic speedo from a VSS type transfer mounted sensor would be really straightforward.