New tach thread

GEM Forum
1

Better start a new thread. I was hijacking the other.

Trying to develop an add-on tach kit for Gems.

May work on others as My Tomberlin E4 has the same motor sensing and plugs.

Would be much easier to make a hard wired kit.

This is my first attempt at wiring harness.

Could loan/rent if any interest.

Already made a counter. Which counts motor pulse per wheel circumference. To determine gear ratio.

Or sell if it doesn’t take too many hours to build.

What would the crowd bear?
About $40 in parts so far.

2

So far so good.

Did the math for my divide by “N” counter, to calibrate for 4 pole magnet.

My 2400 rpm motor shows 4600 at 25mph. (~22 actual)

Either my math is wrong or I’ve got an 8 pole magnet. :frowning:

As I don’t know how many pulses per turn or my gear ratio, I’m out of luck for now.

I’ll try to research online, but it’s not like the Gem with a large following.

May have to wait for my new gem.

3

Without taking anything apart, I believe my gear ratio is 10.35 and PPR is 8.

The only know quantity was my 18" rolling radius and the controller function “6” factory set to 73.

Guessing at a gear ratio of 10 would have set F6 at 35, about 1/2 actual.

Running the numbers with 10.35 ratio and 8-PPR Gives me 72.5.

This lines up perfectly with factory setting and also gives me the reason my tach reads double when programmed to 4-PPR.

All I can do now is wait for my Gem next week, or send it to someone to test.:slight_smile:

I do have parts to make another.

4

You can use a bicycle speedometer for a counter 7 bucks on Ebay

5

Looks more professional.
I wonder if it will calibrate to high enough PPR?

6

I was thinking wheel counter. The magnet assy. is about 3/8 x 1/2 and the sensor is about an inch long. amazing bit of technology for 7 bucks.

7

The tach project is going well.

Not yet ready for prime time.

FSIP lead me to believe that the 12v motor sensor supply from the controller could supply an extra 100ma for an added accessory.

This turns out to marginal at best. Supply is current limited internally, and voltage drops with added load.

Although it worked for first test, it wouldn’t be fool proof.
Also 12v from controller is on even when key is off.

The fix may be to power tach/counter from the 12v converter and build an isolated pulse buffer, for feeding the pulses to tach.

Other option would be to find a self powered tach or lower power lcd version.

Something like Rodney suggested.:clap2:

8

I think you’re on to something.
Specs say it can be set to tire diameter from 0 to 9999MM (@ one pulse per rev.)

If someone could check my math.:confused:

I have a car with 18" tall tires. (460MM) X pi = 1445mm circumference.

Speedo would then be set to 1445 if sensor was on wheel.

Just checked my motor/gear box. It has 40 pulses per tire rotation. 10/1 gear and 4 magnets.

Seems that would be the same number of pulses per mile as if my tires were 1/40 size.

1445mm/40=36.125

So setting speedo to 36mm and connecting to motor sensor should read MPH.

9

If this looks like something that is needed, I’ll buy one and make an interface.

It should then connect with two wires, like my pulse counter.

http://www.electricforum.com/cars/buy-sell-parts-accessories/9717-pulse-counter.html

10

[quote=Inwo;27687]So far so good.

Did the math for my divide by “N” counter, to calibrate for 4 pole magnet.

My 2400 rpm motor shows 4600 at 25mph. (~22 actual)

.[/quote]

And as it turns out, it is correct.:slight_smile:

Can you check my math Rodney?

18" high tires
25mph
10.35 gears
motor ~ 4600 rpm

I’ve been looking for my mistake for two days. Could not believe oem would run the motor that fast.

11

4834 by my spread sheet @ 25MPH

They can handle 5000 and change.

Polaris went back to the 10.35 box in 2014 because outlaws were burning them up over revving on 12.44’s

12

[quote=OLD HOUSEBOATER;27771]4834 by my spread sheet @ 25MPH

They can handle 500 and change.

Polaris went back to the 10.35 box in 2014 because outlaws were burning them up over revving on 12.44’s[/quote]

Thank you,

You mean 5000rpm?

I’m surprised.:confused:

13

Yeah 5000 RPM

14

Couldn’t wait for the goop to dry.

Connected with test leads and backed it in and out of the garage tonight.

This one has a 9v battery clip to make it easy to test.

If you want to install permanently, connect to switched 12vdc.

It is pre-programmed to read rpm from a 4-ppr (magnet) motor.
Completely isolated input to 5k volts.

Only loads the sensor output with 1000 ohms ~ 5ma.

As far as I can see its ready for a beta tester.

If these burn out as fast as Rodney’s amp meter, I’ll have to go back to the drawing board.:slight_smile:

15

I’m going to box this up with my Volt/Amp meter. The GEM Speedometer is fine.

My volt meter gives me actual volts in real time. The Amp meter helps me keep a lighter foot. Volt and Amp readings give me horse power. I put my foot in it the other night and pulled up 16 and a half horsepower. The Tach will satisfy the gadget hunger for this month.

Rodney

16

After some false starts, my original design transfers from the T3 in my Tomberlin to the T4 in my 2010 Gem truck perfectly.:clap2:

It was a 2 minute install. Plug-in, no wiring needed.

Better yet, the Gem is wired to turn off with key, making it plug and play.

Rodney has issues with it working on T1 controller that may or may not be resolved.

Motor runs ~5000rpm @ 25mph. :slight_smile:

17

Still will continue to work with Rodney building it into gauge cluster.
As a stand alone tach/speedometer it’s ready to roll.

If someone prefers a 2" round, I believe the same interface will work. (tach only)

Will build and program to order.

18

With the T! the tach works but then the BDI won’t register MPH Do you think the 12 volts vs 5 volts on the tach supply explains it?

If it includes speedometer function you will need to know tire size and gear ratio

19

I will have to get more data.
There is no reason I can think of why it won’t work with T1.

I wish you could have seen me connecting mine.:eek:

All the things not to do.
Unplugged sensor and measured 12v while hot.

Plugged in tach plug adaptors, hot.:slight_smile:

There must be something wrong with your controller, yet I will not dare let anyone try it on a T1 until issue gets resolved.:confused:

My old gem was T1 and had none of the issues described.
Sensor neg. was connected to pin 16. I wonder if that causes ground issues?

20

[quote=OLD HOUSEBOATER;28030]With the T! the tach works but then the BDI won’t register MPH Do you think the 12 volts vs 5 volts on the tach supply explains it?

If it includes speedometer function you will need to know tire size and gear ratio[/quote]

Picture shows speedometer and tach together.

Yes, will need your calculations to program for speedometer.

Maybe I can find a spare T1 for testing here. Not likely to find another guinea pig.:smiley:
I bet if you told fspi that your control won’t allow a simple vom probe, they would concur.