Electronic Speedo sender, My solution Options

[Steve]

I got a degree in electronics 20 years ago and pretty much forgot everything.
Do you by chance know the components and schematic required to drop it from 16 to 8?

thanks,

Steve

[sechszylinder]

hilow steve,

you could simply use a 74ls74 d-flip-flip . You have to convert the voltage level coming from the sensor
to TTL-Level. The output of the flip-flop must be converted to 0-12v level to drive the speedo. Here you
can use a 2n2222.
Another idea is to use a small microcontroller, so you can something more than only half the puls rate. ...

benno

[ss6]

Been watching this thread with a little curiosity, since I posted a how-to a few weeks ago on rigging a 911 speedo with a homebuilt sender.

A GM/VDO sender will cost at least $75, you'll have fab an adapter to attach it to the tranny right angle drive, and now it looks like you may have to build a circuit to divide the pulse train in half. To each his own, but why is this more desirable than a $30 sender and hacksawing some scrap iron?

[sleepdoc]

Hi ss6,

Some solutions are completely functional and cheap.
Some solutions are beautiful, engineered, funtional, and expensive.
Some solutions appeal because they are elegant.

Many of the mods we do to our teens are of the first variety
like the BMW320 front calipers.

Some for the fortunate are of the second type like James' beautiful
RennShift.

This mod is just plain elegant, using off the shelf parts in a mix and
match way to get rid of a long revolving cable and an old and cranky
mechanical speedo. (I have to rap mine just so to get it started).
It also offers the advantage of allowing the adjustment of the new
speedo for different wheel size with a signal adjuster like this.
http://www.abbott-tach.com/era.htm .And with this ratio adapter
a later model porsche electronic speedo will work correctly.

Desireable ? It is in the mind of the desiree. There is no question
that your solution is functional and is a very impressive piece of
engineering and I followed your thread closely, but I was already
trying to find a sensor that would fit on the 901 speedometer
output, and Wasa914 verifying that the gm sender physically
attaches to the 901 makes me want to opt for the drill, cut solder,
etc instead of the cut grind bend bolt etc.

You da man! with the custom sensor and the metal fins.I was wowed
at your solution and would have implemented it if this other idea had not
surfaced.

I appreciate both you and Wasa914 posting your stuff, what an incredible resource this is.

best Mark

[Steve]

WOW $145.00 for the ERA controller.
It looks like a perfect solution for electronic speedo's but why so expensive??
This web site is a wealth of information and I appreciate all the help and diferent ways of doing it.
I just won an Electronic 911 speedometer off of ebay.
I still have my TI TTL cook book from college.
I will look up the 74LS74 in my book.
I will also visit my local radio shack and check out my options.
I also love the ingenious way of bending scrap metal and using a sensor.
I remember something similiar to this in the early 80's for cruise control.
Except they had a conductive strip that wrapped around the axle.
This strip had metal pieces sticking out similiar to SS6's solution.
It would be interesting if you could use one of the cruise control kits and kill two birds with one stone.
So many choices so little time and money.

regards,

Steve

[ss6]

You don't need the ERA controller if you're willing to open up the speedo and tweak the pot inside.

[Steve]

You don't need the ERA controller if you're willing to open up the speedo and tweak the pot inside.

If you use the GM sender with the 16 pulses can you tweek the 911 speedo to work with it since the 911 speedo is expecting 8 pulses??

regards,

Steve

[ss6]

Steve,

I don't know if the 911 Speedo has enough adjustment range to accommodate 2:1+ "tweakability", kinda doubt it without changing some its timing circuit components.

Suggest searching the Pelican 911 bbs for speedo calibration, those guys have been up and down that topic at least once.