Automotive tachometer for electric turbo

Projects General Guidance
1

Hey guys!

I'm very new to arduino and have limited experience (Built a lifesize robot with the Ardumoto shield) so please bear with me. I've done a ton of googling and don't understand what it takes to read RPM's from a car tach. I understand that they use frequencies and one of the ways of reading it is converting the frequencies in to volts; But is that necessary? I read somewhere that Arduino is capable of handling 16Mhz which could mean that reading my engine's max RPM of 9,000 should be feasable assuming:

9000 RPM = 9,000 revs per minute = 150hz. 1 Megahert = 1,000,000 hertz so arduino should have no problem reading 150hz.

My question is; How do I connect this to arduino? (Not looking for a hand out.. An in depth explanation would be lovely!) I don't need to display the RPM's as the overall goal of the project is to make a brushless motor spin when X RPM is hit. (Similar to a shift light).

Please assist!

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electric turbos dont work

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Greensprings:
electric turbos dont work

Thank you for your opinion. I'll determine that through testing... In the mean time; You can sign up for the following forum and track my work as I'm assuming you are making an assumption on the motor I'll be using to spin a compressor wheel: (non-Ebay) Electric Turbocharger (Supercharger?) | Page 10 | DSMtuners.com

as a side note; another company has created electric turbo's that work and have been tested and proven.

If you have any evidence that electric turbo's wont work no matter what electric motor you're using then please supply evidence. Simply saying something will not work without proof or fact is one of the main reasons projects and new ideas don't get attempted.

I don't mean to sound stingy but you honestly don't know what kind of research and money I've put in this project already. You don't know what motor I'm using; what compressor wheel I'm using, what housing I'm using, what kind of batteries I'm using, or what kind of ESC I'm using. You simply do not have sufficient evidence to state my idea doesn't work.

On top of all of this, your answer did not help me in any way, shape or form as it has nothing to do with my original question..

4

I am firmly of the opinion that electric turbos can work.

Okay, back to the tachometers. Any car built before about 1985 will have 'points' ignition. The points are just a switch that opens and closes. This can be connected to the tachometer to get the engine speed. The issue is that the points are connected to the high voltage coil and there's all sorts of nasty interference coming down that wire. Interfacing this to electronics like an Arduino requires a few components to condition the signal.

Any car built after about 1995 will probably have an ECU. This usually runs on 5v internally and it will have a 'tachometer' output that can be interfaced directly to an Arduino and you are in business. This is still measuring the frequency of the pulses. Any car built after about 2005 will have an onboard data bus which, with some interface components, can give you the digital data from the ECU.

This seems like it should be a problem that has already been solved by others. I would not expect to program an Arduino to do this. There must be RPM switches available commercially. Now if you have to put in some more logic - eg a 'map' of RPM versus temperature, dependent on throttle angle, then an Arduino might be a good idea, but I'd still be looking for an aftermarket ECU which can do this. I know Triject makes some good ones.

5

Every injector fires once every revolution. Take a look here for some relevant information. - Scotty

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MorganS:
I am firmly of the opinion that electric turbos can work.

Indeed. Electric turbo's got a real bad name when people started selling PC fans mounted on PCV piping and called them electric turbos. From my research I gathered that you would need an electric motor that can spin at a high enough speed as well as provide enough power. I'll be using a 10KW motor which is approximately 13ish HP which should be able to create decent amounts of pressure on a 2.0L engine below 4.5kRPM. The reason for this is that I wanted this to provide power in the lower end of the power band. Anything over 4.5k RPM's requires massive amounts of power to generate adequate boost (25KW+). I've been working on this for the last couple of months and have learned a ton!

MorganS:
Okay, back to the tachometers. Any car built before about 1985 will have 'points' ignition. The points are just a switch that opens and closes. This can be connected to the tachometer to get the engine speed. The issue is that the points are connected to the high voltage coil and there's all sorts of nasty interference coming down that wire. Interfacing this to electronics like an Arduino requires a few components to condition the signal.

The good news is that I want the electric turbo to power 2.0L or below cars from 1990's up.

MorganS:
Any car built after about 1995 will probably have an ECU. This usually runs on 5v internally and it will have a 'tachometer' output that can be interfaced directly to an Arduino and you are in business. This is still measuring the frequency of the pulses. Any car built after about 2005 will have an onboard data bus which, with some interface components, can give you the digital data from the ECU.

Excellent to hear! So for these cars, would I just plug in the tach wire in to one of the pins in the Arduino board and use the FreqCount Library?

MorganS:
This seems like it should be a problem that has already been solved by others. I would not expect to program an Arduino to do this. There must be RPM switches available commercially. Now if you have to put in some more logic - eg a 'map' of RPM versus temperature, dependent on throttle angle, then an Arduino might be a good idea, but I'd still be looking for an aftermarket ECU which can do this. I know Triject makes some good ones.

That is exactly what I need to do. I'm also going to be connecting the TPS in to the arduino board. The logic will essentially be provide X power at Y RPM at Z throttle percentage. I will be developing an application where the user can provide the data they want. Another reason for why logic needs to be put in is because you don't want 18PSI going in your motor when you press the gas at 1,000RPM. It would need to be controlled some how.

scottyjr:
Every injector fires once every revolution. Take a look here for some relevant information. - Scotty

Thank you Scotty! I'll do some reading on the matter!

EDIT: I've found a library that will work for me as well as tell me which input pin I should be using on my Leonardo board. The site is below:

https://www.pjrc.com/teensy/td_libs_FreqMeasure.html

FreqMeasure is used for signals between 0.1 Hz to 1 kHz which is perfect for my applications

7

Let me add a bit of information that may or may not help. My previous pickup was a 1982 chevy Diesel V8. I added an after market tachometer that used the signal from one phase of the alternator to generate the tachometer reading.

My previous car was a 1983 Mercedes Diesel. It used a magnetic pickup to watch a spot on the crank pulley to give both the tachometer signal and the timing for the electronic fuel injection.

I do not know how the tachometer reading is derived from my 2013 VW TDI.

Perhaps one of the above methods of tachometer control will be useable for the OP.

Paul