# Tachometer



## TX_Dj (Jul 25, 2008)

Hall effect tachometers are pretty much the norm anymore, as far as modern electronic tachs go. Yes, several people have used them and their various methods of generating an input signal.


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## judebert (Apr 16, 2008)

I'm trying to use it, but I'm not having much luck. I haven't had the chance to figure out if I've wired it wrong or if I just haven't found the tachometer signal input yet.


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## DONEAL (Sep 10, 2008)

Thanks judebert, TX Dj, 
I was interested in an " out of the box" system, I've read several post about how to DIY, but, just don't trust myself in doing it. I have already installed the motor so attaching anything ( magnets) to the clutch disk would involve removeing and re-instaling the motor. The meter tach sender and collar that evparts has is a bit pricey. So far, their the only company that offers the combo kit. 
If anyone knows of a kit, please let me know,
Thanks
DONEAL


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## TX_Dj (Jul 25, 2008)

The collar you are talking about fits to the tailshaft. If you have to attach it to the main shaft, you will need to alter it, as the main shaft (i think) is a different diameter.


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## Jimdear2 (Oct 12, 2008)

I'm not an electronics man, just someone who does a lot of "fiddlin around"

JUDEBERT,

Are you trying to hook a factory in dash tach into a hall sender system?

If so what Year Make Model car. I have limited access to many OEM wiring diagrams, I just might be able to find the tach input for you. Although if this is a fairly new vehicle with computer controled everything, you may not be able to use a hall sender to drive the in dash tach, some are pulse driven some are voltage driven and there are other schemes as well. 

Also if you are using a hall sender, even if your in dash tach is pulse driven you have to know how many pulses the tach expects to count off one rpm. You might have to add/subtract magnets to get the right count for your tach.

Finally I beleive the hall sender kit might need a resistor (I have been told 2K ohms for my sender set up) placed between 12+ lead and the sensor lead. I think they call this a Pull up resistor.

DONEAL,

If your motor has a tail shaft, I would try going to radio shack or some local electronics or experimenter hobby store to see if they have a inexpensive 12 volt hall sender to experiment with. Then go get some small magnets and try attaching one or two of them (if you use two they have to be on opposite sides of the shaft) to the shaft with double sided tape then a wrap of string tape. Do a mock up wiring job on the tach and the hall sender using the equipments instructions. With the motor turning over (be safe, trans in neutral and/or wheels off the ground) slowly bring the hall sender close to the magnets while watching the tach. If the tach moves then your on your way. Note how close the sender needs too be to the magnets to get a signal. Go ahead and mount the sender and tach. All that is left is to set the tach to the pulse count needed for each rpm counted. I beleive it is 2 pulses (magnets) for the 4 cylinder, 3 pulses for the 6 cylinder setting and 4 pulses for the V8 setting s found on most aftermarket tachs.

This setup might also need the pull up resistor I mention above.

Good luck,
JIm


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## mopargarage (Jul 2, 2008)

Here is a blog post of my experiences with this issue. Maybe it will help.
http://electricmopar.blogspot.com/2008/10/tachometer.html


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## Jimdear2 (Oct 12, 2008)

To those following this thread, I did a bit of research (Google on hall sender pull up resistor) and came up with the following information. 

In order for the hall sender to produce the square wave pulses needed for a tachometer, a pull up resistor has to be installed between the Positive lead of the hall sender and the Signal Output lead of the sensor.

As I previously stated, the hall sender I will be using requires a 2K Pull Up resistor to generate a signal. Others I read about in the research called for 10K resistors. I guess it might be a good idea to contact the maker/distributor of the sender and ask what they recommend.

As soon as I can make space over the winter I'll bring the motor into the house and do a mock up on the motor, sender and tach using a 12 volt battery to see if it will work. If any one else gets to it first please post your results.

To mopargarage 
The lack of this pull up resistor may be why the first try didn't work. I know for a fact there is a square wave, 0 to 12 volts coming out of those Chrysler ignition control units. I appears your sender was causing the electronics in the unit to cycle the switching transistor to create that square wave. 

Jim


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## judebert (Apr 16, 2008)

Jimdear2, thanks for the advice so far. 

My car is a 1988 Honda Civic Wagon, RT4WD model. The tach is the old unit built-in to the dash assembly. It took 2 pulses per rotation, and that's what I (should) be providing. The collar is hooked up to the tail shaft of my ADC 4001-A.

My plan for my next opportunity is to make sure I've got the tach sensor wires well understood. I'll jack up the car, hook the tach sensor's red and black wires to power and ground, and measure voltage between the green wire and ground while I spin the wheels. If that doesn't work, I'll try green and power.

Then I'll start fooling around with the actual wiring. I figure I probably have to tap into the same ground as the tach, and I'm going to try tapping the same power. We'll see how it goes. If you've got the OEM diagrams, I'd appreciate it if you saved me the fumbling.


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## Jimdear2 (Oct 12, 2008)

Doneal

Sorry, don't mean to hi-jack your thread. Since Judebert seems to have parts in place, ready to test, I'll give him my thoughts. They should apply to you question as well. I think in all cases of a hall sender and a pulse counter type tach., the pull up resistor is the cure to this problem.

Judebert,

I will check to see if our collection of wiring diagrams goes back to 1988.

In the mean time you should: (an assistant would be a big help) 
1.) Go to Radio Shack or ?? and get a selection of resistors, get a 10k an 8k and on down to 2k ohms
2.) Set up so you can easily jumper a resistor between the red and green wires 
3.) Hook red to positive
4.) Hook black to ground
5.) Hook green to the vehicle tach input wire.
6.) Make sure you didn't disable power to the instrument cluster when you did the conversion. (See note below). The tach will need power/ground as well as an rpm signal.
7.) Be very sure that you are in fact getting a signal to the tach in the cluster. Don't assume, CHECK IT!!! Use a suitable continuity tester.
8.) Get the traction motor turning safely at a fixed speed (in neutral/wheels off the ground etc.)
9.) Vary the air gap of the sender pick up and the magnet collar. Try very close, a few hundredths up to maybe a tenth of an inch.
10.) If no results, set the air gap close and with the motor turning, jumper a 10k ohm resistor between the red and green wires of the hall sender. 
11.) If no results, Try varying the air gap.
12.) If still no results, try the other resistors the same way.

NOTE) Be sure that your instrument panel is correctly powered. This may require you to use a volt meter on the printed circuit of the instrument cluster. 

Other things to try:

Assume nothing, test everything.
Hook the sender up and test as above but use a known good tachometer. Hook up pulse counter or duty cycle meter to see if there is an output. 
Get the senders manufacturers testing specs/procedure for the pick up.

Hope this helps,
Jim


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## DONEAL (Sep 10, 2008)

Thanks Jim,
Not a problem, I think this is a good thread, and alot of us have the same questions about the tachometers on ev's.
I'm still working on the hall effect sensor, trying to determine which one to purchase, there is several types. Unipolar, Bipolar and Latching. I have read where the analog sensors has to have the pull up resistors and I would asume that the others would too. Once I have put one together I will post the results for all to share.


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## atzi (Jun 26, 2008)

DONEAL said:


> Has anyone used this tachometer sender and magnet collar?
> From evparts.com
> tach sender Item #in2551 and magnet collar item# in2552


I have purchased the 2 parts from EVParts but have not yet installed them. Not sure about your vehicle, but on a 98 Saturn, the original tach which I am attempting to get working, used the crankshaft sensor signal. It was a 7 impulses per revolution which went to the PCM which used that signal to send *? *impulses per revolution to the tach.


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## DONEAL (Sep 10, 2008)

ATZI,
After reading several posts about the Hall Effect sensors and how they work, I will try to build my own. The sensor is less than a dollar and the collar can be made from a left over piece of plastic. My tachometer is just an off the shelf type. From everything I have read this should be easy to make.
My EV conversion is a 91 Chevy. S-10. It's about finished, all I have left to do is to install the batteries. Keep us posted on the tach. Sender you purchased.


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## DIYguy (Sep 18, 2008)

mopargarage said:


> Here is a blog post of my experiences with this issue. Maybe it will help.
> http://electricmopar.blogspot.com/2008/10/tachometer.html


Thanks Mopar. Nice lookin ride btw! Looks like a very practical and "DIY" approach  ....and well documented too.

Gary


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## Thaniel (May 25, 2008)

On a previous project I used a Hall effect sensor part# MLX90217LUA-ND to supply the pulses for an electronic speedometer. I had it mounted to sense some magnets I'd put on the axle shaft and then fed it to a converter box to adjust the number of pulses. It worked great.

The sensor's a whopping $8 from digikey and a couple of magnets and a method to attach shouldn't add up to much. When I get to that point I think I'll try it for the tach sensor on my EV.

Spec page for the sensor http://www.melexis.com/prodfiles/0004759_MLX90217_rev9.pdf
Application guide has interesting information on Hall effects for those that aren't familiar with them http://www.melexis.com/prodfiles/0003715_hallapps.pdf

If someone has somthing better let me know.


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## Drizzle (Jun 17, 2008)

I don't suppose anyone has any tach data for a '96 Ford Probe 2.0... That's what I'm converting, and would love to use the stock dash tach, but at the stage of learning I'm at right now, a lot of the discussion here is still above my head... So, I guess I need to start collecting info and hope by the time I'm ready to put the motor in, I've gotten some good info to apply...

I still have the ECM on my car -- anyone know if I should try to throughput with that? Or adopt a method of sending a signal straight to the tach?

Not asking anyone to do all my work for me, but if someone happens to be familiar with my car, and can nudge me in a helpful direction, I'd be grateful.

Cheers,
Drizzle


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## Thaniel (May 25, 2008)

Drizzle said:


> I don't suppose anyone has any tach data for a '96 Ford Probe 2.0... That's what I'm converting, and would love to use the stock dash tach, but at the stage of learning I'm at right now, a lot of the discussion here is still above my head... So, I guess I need to start collecting info and hope by the time I'm ready to put the motor in, I've gotten some good info to apply...
> 
> I still have the ECM on my car -- anyone know if I should try to throughput with that? Or adopt a method of sending a signal straight to the tach?
> 
> ...


The ECM won't help you. Pull it sell it, Pitch it. whatever. The ECM was being fed a tach signal from the ICE motor. Most likely the same signal was going to the instrument cluster. Either way you just need to send a similar signal to your dash. I expect most cars use a similar pulse set up. Example. I put an V8 camaro engine into my BMW and used the same tach output (adjusted for the change in cyl) and it worked fine.

Humm..now you've got me thinking. Most ECU sensors run off 5V. However the inst cluster runs of 12v. I'm going to look at some diagrams.

Thaniel


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## tj4fa (May 25, 2008)

I pulled out my ECM and wiring and have a bunch of things on my instrument panel that miss that 5v signal. 

-Brake light stays on
-Rear Anti-lock Brake light stays on
-My Temp gauge goes really cold
-My fuel gauge goes from 3/4 full to well over-Full when I turn the key on 

There is some DIY tach stuff (pictures) at the link below I posted a few days ago that might help. It should be basically the same on most vehicles, you just have to find the stock tach signal wire and provide it the pulses to operate.

Oh and it's cheaper than buying those expensive sensors.

http://www.diyelectriccar.com/forums/showthread.php?t=25855&highlight=tachometer


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## Thaniel (May 25, 2008)

tj4fa said:


> I pulled out my ECM and wiring and have a bunch of things on my instrument panel that miss that 5v signal.
> 
> -Brake light stays on
> -Rear Anti-lock Brake light stays on
> ...


Unless your car is a newer vehicle running the CAN system (which I'd not want to play with) The Temp signal comes from the engine and not the ECU. The ABS is probably missing the speed signal that may have been supplied from the ECU but can be supplied from another source or the connection cut when the ECU removed. Brake light? Wierd. From the ABS or did the Master cyl level sensor wires get disconnected? Fuel gauge makes no sense to me. OBDII cars have a fuel gauge TO the ecu (not from). Perhaps it is grounded somewhere now the ECU is gone.

Oops Just realized this is way off topic. Oh well just trying to be helpful with some ideas.

Back on topic. I don't think a $10 hall-effect sensor is a "expensive sensor". I used a reed switch on my speedometer for awhile (got it free). Reed switches are mechancal (have moving parts) and do eventually wear out. They are also much more sensitive to air gap (at least min was). I used a reed switch for my speedo pickup originally but replaced it after it started acting up with a hall effect sensor (used the same exact magnets. Just swapped sensors). When I sold the car after 18,000 miles the speedometer was still working great. 

Thaniel.


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## skeeterb (Feb 6, 2009)

I have a 1990 Pontiac Grand Am with 129000 miles on it that I am thinking about converting. The Quad 4 engine is dead so I think it might make a good donor car. It has a Tachometer on it even though it is an automatic transmission. This thread has me wondering if I could use my Tach when I convert. The instrument cluster is pretty simple with just the gauges for coolant temp, oil pressure, charge system status and fuel gauge with a few idiot lights like brake, service engine soon, temp warning, and alternator warning.


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## DONEAL (Sep 10, 2008)

Skeeterb
There are at least a couple of ways to hook up a tach. I haven’t had any luck yet to get one to work. I purchased a Hall Effect sensor; pull up resistor and some magnets. I purchased a new after market tach. and just can’t get it to work. On your 1990 Pontiac Grand Am the signal that the ICE sends to the tach. May come from the flywheel, or distributor and then to the ECM (on board computer). I have read post where other builders have had luck getting the tach.'s to work. 
I will continue to work on mine and will post the results once I get it to work.
When you pull the ICE, mark all your wires going to the old ICE. and don't forget the grounds. One loose or mising ground can cause hours of headache.


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## skeeterb (Feb 6, 2009)

DONEAL said:


> Skeeterb
> There are at least a couple of ways to hook up a tach. I haven’t had any luck yet to get one to work. I purchased a Hall Effect sensor; pull up resistor and some magnets. I purchased a new after market tach. and just can’t get it to work. On your 1990 Pontiac Grand Am the signal that the ICE sends to the tach. May come from the flywheel, or distributor and then to the ECM (on board computer). I have read post where other builders have had luck getting the tach.'s to work.
> I will continue to work on mine and will post the results once I get it to work.
> When you pull the ICE, mark all your wires going to the old ICE. and don't forget the grounds. One loose or missing ground can cause hours of headache.


The quad four engine doesn't have a distributor. Under the cover marked Quad four is 4 coil packs. The coil packs are probably controlled by the ECM sending the pulses at the correct time to ignite the mixture. I've go a picture I can send to you if you want to see what the engine looks like.


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