I dont know what he uses,but the guy from speed changer told me the one he uses is tiny.It is small enough to screw directly onto the back of the speedo with no other support,so it has to be pretty small and light.There may be some factory ones like this if someone has access to some,mabye a junk yard.

 

The factory electronic speedos do not use a motor that rotates, they function just like electric oil pressure or water temp gauge.

 

I was thinking of modify my speedo to use a small known stepper motor much like what you would find in a newer vehicle. The speedo in my truck has a sweep of 120-130 degrees and doesnt match any newer vehicle. So it would basically be a custom electronic speedo and a custom driver to read the vss which in turn would adjust the stepper to give the correct mph. I'm now thinking this would be a fail for most people since you would have to modify there original gauges. I'm now thinking instead of modifying the speedo just control a small electric motor to reproduce the rpm to replicate a spinning speedo cable. This is now sounding like the Speedchanger more then anything else. But the more i think about it the more i think its very possible and would be much closer to the $100 mark or less for a diy version.

 

Let us know what you find out.

 

I've looked into this a bit....to make something to turn the speedo cable.

Stepper motors: can be loud, draw lots of current, most are not made for high rpm.
dc motor: rpm will very depending on load

To do this correctly, you need the ''right'' stepper motor (able to operate in the rpm range needed, NOT overheat) and controller, or a DC motor with some sort speed sensing ability.

Most cable drive speedo's are 1000 revolutions per mile, so, at 60 MPH, the cable is turning at 1000 RPM. The factory output from a calibrated GM PCM is 4000 pulse/mile, dc square wave. So at 60 MPH, the frequency from the PCM is 4000/60= 66.67 HZ (Most of the LSx PCM's also have a 128,000 pulse/mile output, that could be used for better resolution)

1. The motor/stepper driver needs to be able to control a motor from a range of 0 RPM to 2000 RPM smoothly. (up to 120 MPH)

2. Input Frequency range: 2hz to 134Hz (this gives you a range of up to 120 MPH)

3. STOP value, Most GM PCM's have a programmed value, that is the amount of time between speed sensor pulses to be considered a ''stationary'' vehicle. This prevents the speedo cable from slowly creeping at a stop due to noise in the circuit I would guess.


The Cable X device has DIP switches to calibrate it. If someone came up with one that is just designed to take in a 4000 pulse/mile INPUT and a 1000 RPM/mile OUTPUT, I think the design could be made a lot more simple.

-Brendan.

 

Pretty easy to go to digikey and look up DC motors and controllers.

http://search.digikey.com/scripts/Dk...dll?Cat=983982

This controller is $109.

http://search.digikey.com/scripts/Dk...e=296-25445-ND

http://media.digikey.com/pdf/Data%20...Fs/MDL-BDC.pdf

The recommended motor (MABUCHI RS555PH-3255) is only $3

http://www.surplustraders.net/a/0546.shtml

From what Busta says looks like the motor has correct voltage and speed range, looks pretty small too. But the controller linked above looks massively more complicated than it needs to be.

Someone figure it out for us.

 

Thanks for the info guys. Damn! That motor controller kills it though. I need to find something cheaper if this is going to be beneficial. I don't have the motor in my truck yet, so I probably wont get to this for a few weeks. I'll certainly be researching parts tell then.

Someone was kind enough to have gone through the trouble of inputting the vss into arduino for a really cool mpg calculator. You can find the project here. Now all that's really needed is the motor and controller setup that will be quiet, reliable and cheap.


I'll certainly keep everyone updated as I make progress.

 

http://www.microcomponents.ch/produc...ec/switec.html

These are oem type stepper motors, they will move the needle, but not the odometer.

 

This is good, this thread has everyone at least thinking about this speedo drive problem.I am sure there is a way to do this if we can find the right stuff to use.I wish I had more knowledge about the electronics.Some of you electrical gurus use your talent and help find a solution for this.

 

On a mechanical speedometer if the needle moves, the odometer also moves. We need a motor that spins the mechanical part of the speedometer for it to function properly.

 

bumping this thread.

I've been trying to figure this out also for a T56, I'm putting a ls1 into my rx7 and I want to retain the stock speedometer, so far I think doing this is very DIY-able

I'm still not 100% sure how the VSS Sensor works, but if I understand it right I should be able to pump 5v directly from an Arduino to the VSS Sensor and then back up to a digital input where it will read the square wave and set it as a PulseIn input.
then from there have the arduino do the pre set calculations using the 4000 pulses per mile and convert that to a 0-255 (depending on the motor rpm) PWM output to a beefy transistor which will control the speed of a regular 12v DC Motor.

I was thinking of using a smaller motor and attaching it directly to the back of the gauge cluster to overcome any load from the cable.

 

I am working on the solution. I have found a motor that works well from .5 volts to 15 volts and drives my speedo from >5 mph to 160mph. The motor is about the size of a "d" battery. I am looking into a motor controller, have a couple of choices. This should be under $150.00 Will keep you posted.......

 

Seems so simple. Just convert the VSS signal to a variable output going to a small DC motor attached to the mechanical speedo where the cable used to connect. I waited for a while on a guy in Michigan that claimed to have solved the problem but never was able to offer a finished product for sale.

Whoever solves this will make a lot of cash if they can advertise properly.

Personally, I really wanted this type of solution but could not find a supplier or figure it out myself. Ended up buying a full set of electronic gauges and will install them in the same location as the factory gauges.

 

For under a $150.00 put me down for one of the first ones. If you are looking for guys to test them let me know i all so Owen a Mechanic shop and do swaps in my shop for people now so i can help you sale some.

Send me a PM when you have some for sale are if you need some one to test one.

 

Will do, I have it narrowed down to two controllers, waiting on a response from the manufacture. I am able to mock it up on my Ford speedo, just need a GM to check fitment.

 

Sound Great, @ < 150 Count me in, let me know and I can ship you buick speedo head for test fitting if you wish, just started the conversion so i will be down for a couple months

 

That is the question I was asking me-self, then I decided to pick a dash from a junkyard (it was given to me for free with other purchases) and then I proceeded to gut it.
I plan on using it behind the face of my 69 C-10, I have not tried it yet as this only happened yesterday.
I am using a 90ish Astro van, and hope the VSS signal is the same, if not I have seen I can modify it.
The reason I went for an Astro is that some newer ones seemed to have the electronics integrated on the back board, not really sure as I did not tear them open, but the astro's unit is readily separable with clearly marked input connectors.
I had already desecrated the dash to install a Tach anyway.
I do not know if this is what you were talking about, but I think it'd be awesome to save 250 bucks and put them to a better use.
Rat Chevelle

 

Suscrbed........ I have only found the Tailshaft conversion kits for VSS signal & Cable drive but all are around $450 .

 

Motor is working out very well. made improvements on the coupler. Its near silent at 85mph, and still very quiet at 165mph. the controller parts are ordered, it will be about a week or so to test the prototype. the motor is smaller than the "d" battery, more like the size of a "c" battery. Designing it fit any speedo, just working on the mounting bracket to make it universal.

 

Awesome news. Put me down for 1.