Retrofitting old analog tachometer to another engine

Community Projects
1

I need to make an old analog tachometer work with a diesel engine that does not originally have any tach on it.

I think the easiest is to get an stepper motor and driver and use signal from the alternator (like many aftermarket tachometers do).

The stepper will just directly drive the tachometer.

But I don’t know how to convert and adjust the signal from the alternator so that the driver will understand it and output correct RPM to the stepper motor. Maybe something with Arduino? So I will need help with that or if you have any better ideas on how to do what I need. I have never done anything with Arduino but I have some experience with electronics, usually just following some guides. I do have soldering equipment and some basic components already.

https://www.instagram.com/p/BWBPwHilFn9/

2

If you could read the passing of a magnet attached to the crank pully with a Hall effect sensor it seems this would be easier. Posting here mainly to bookmark as I have a small diesel engine I would love to track its RPM too.

3

Hall effect would definetely work and make programming a bit easier. I am not 100% sure what kind of signal comes from the alternator but it would alteast require some work to figure out how to calibrate to show correct rpm.

I have looked into using Arduino and it looks like this project should be pretty easy.

E: Well not too easy, looks like stepper motors have about ~1000rpm max speed. Tach needs to turn atleast 3500rpm (assuming it’s 1:1 drive internally). So I need to either use some gearing with a stepper or use a DC motor with some way to control the RPM precisely.

4

I have seen where others have used the stepper to only move the neddle of a tach in a relationship manner where the stepper doesn’t spin the drive as a standard cable driven tach, but rather moves up and down in response to RPM. I think a Google search will uncover such an application, as I have seen this done.

5

That’s actually great idea, why did I not think of that! For normal users this will work but I want to retain the vintage not-so-precise function of the tach, so I don’t think it’s an option for me. Here you can see what I mean, the needle is sort of bouncy https://youtu.be/SEyZWB4gsTM

Here is the kind of tach I thinking of getting

http://i.ebayimg.com/images/g/3EQAAOSwa … s-l400.jpg

6

I am so sad that I can not help you because my knowledge is limited!

But I would like to suggest you some forum which maybe give you help.

Have question about circuit, go to https://www.allaboutcircuits.com/

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About robot or project ,go to https://www.instructables.com/

About arduino,go to https://forum.arduino.cc/

About signal,system,control ,go to http://archives.math.utk.edu/

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