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[on:]

Hey guys!

I am in the process in converting my car to an electric drive train. Removing the stock engine / transmission have rendered my digital instrument cluster, as well as electronic power steering, useless. The two primary signals that feed the car's computer are the vehicle speed sensor (VSS) signal and the crank signal. From these signals, the computer calculates the vehicles speed (off of VSS) and the engine's RPM (off of crank signal). The computer also sends both the VSS and engine RPM signal to the electronic steering pump's control box so that power steering works. However, I am not sure how the power steering control box handles the signals - this is why I need to figure out how the signals interact before making a final circuit.

I want to use an arduino, either a mega or an UNO R3, to make both signals at the same time. I know a mechanical relay would not be capable of running the necessary frequencies (0 - 100khz-ish), so how would I do this? Transistors?
The engine RPM signal runs off of 0-5v square wave signal, while the VSS runs off of a 0-12v signal.
I should also add that the signals will not run at the same frequencies, the VSS may be running at 50khz while the crank signal may be running at 5 khz.

Thanks for the help guys :-)

[Reply #1 on:]

That's quite a ambitious project you've taken on. I can only give a possible answer (but not validated) to:

The computer also sends both the VSS and engine RPM signal to the electronic steering pump's control box so that power steering works. However, I am not sure how the power steering control box handles the signals - this is why I need to figure out how the signals interact before making a final circuit.

I believe the higher speed a vehicle is going the less power steering force it requires to prevent over sensitive steering control at higher speeds. So I suspect the signal was used to vary or bypass the hydraulic pressure applied to the power steering assist actuator.

Lefty

[Reply #2 on:]

That's quite a ambitious project you've taken on. I can only give a possible answer (but not validated) to:

The computer also sends both the VSS and engine RPM signal to the electronic steering pump's control box so that power steering works. However, I am not sure how the power steering control box handles the signals - this is why I need to figure out how the signals interact before making a final circuit.

I believe the higher speed a vehicle is going the less power steering force it requires to prevent over sensitive steering control at higher speeds. So I suspect the signal was used to vary or bypass the hydraulic pressure applied to the power steering assist actuator.

Lefty

You're likely correct. I think the computer may search for an RPM signal (~1500 RPM, idle) at zero mph, and in turn give full power steering. After that point, I think it would moderate the power steering based on the mph reading. As you go faster (increase mph), less power steering.

[Reply #3 on:]

I want to use an arduino, either a mega or an UNO R3, to make both signals at the same time. I know a mechanical relay would not be capable of running the necessary frequencies (0 - 100khz-ish), so how would I do this? Transistors?

Better use MOSFETs, they're more efficient in switching, faster, too. Provides more power if you need it, aswell.

Good luck on the project! Quite ambitious, but FUN! Post some pictures!

[Reply #4 on:]

I want to use an arduino, either a mega or an UNO R3, to make both signals at the same time. I know a mechanical relay would not be capable of running the necessary frequencies (0 - 100khz-ish), so how would I do this? Transistors?

Better use MOSFETs, they're more efficient in switching, faster, too. Provides more power if you need it, aswell.

Good luck on the project! Quite ambitious, but FUN! Post some pictures!

Would a mosfet like this work ? http://www.radioshack.com/product/index.jsp?productId=2062618
What would I do with each of the pins? I need a fritzing diagram!

As for the project, take a look here http://www.s2ki.com/s2000/topic/975497-wait-that-isnt-an-f20c/

[Reply #5 on:]

bump help

[Reply #6 on:]

The RPM signal should not be a lot of current and the Arduino output itself (maybe with a resistor too) will likely suffice.

As for the 0-12V "VSS" - Is it PWM, or some varying frequency or what?  You're going to fool your panel's speedo that it's getting 0-12V or some PWM-related signal?  That's probably not a high-current deal there either.

Anyway, leave that IRF510 at Radio Shack.

[Reply #7 on:]

I want to use an arduino, either a mega or an UNO R3, to make both signals at the same time. I know a mechanical relay would not be capable of running the necessary frequencies (0 - 100khz-ish), so how would I do this? Transistors?

Better use MOSFETs, they're more efficient in switching, faster, too. Provides more power if you need it, aswell.

Good luck on the project! Quite ambitious, but FUN! Post some pictures!

Would a mosfet like this work ? http://www.radioshack.com/product/index.jsp?productId=2062618
What would I do with each of the pins? I need a fritzing diagram!

As for the project, take a look here http://www.s2ki.com/s2000/topic/975497-wait-that-isnt-an-f20c/

The MOSFETs would be used for voltage isolation, protects the Arduino pin, too. In case of a higher voltage pulsing that is required to the system, the MOSFET would help.

On the fritzing diagram attached, your output to the system would be on the middle pin, and the battery pack could also be 12V.

[Reply #8 on:]

Schematic?

[Reply #9 on:]

Schematic?

[Reply #10 on:]

You can't do "source follower" with a MOSFET.

[Reply #11 on:]

Thanks for the help guys!

I don't think the signal will be PWM, it should just be 0-12v with changes in frequency.
If "source follow" doesnt work on a mosfet, does that mean that the circuit provided wouldn't work?

[Reply #12 on:]

If "source follow" doesnt work on a mosfet, does that mean that the circuit provided wouldn't work?

Correct.

[Reply #13 on:]

If "source follow" doesnt work on a mosfet, does that mean that the circuit provided wouldn't work?

Correct.

Hmm
How would you do it then, assuming the arduino cant output a 12v for the 0-12v pulse

[Reply #14 on:]

So "VSS" ends up being the speedometer input.
What is the speedometer?  Is it essentially a frequency meter? 
[The speedometer in your vehicle's "modern" instrument cluster here is much differ than the situation in a '65 Mustang.]
So, if it is a freq meter (like), making indications based on some varying freq having a 0-12VDC amplitude, then all you should need is an NPN transistor configured for "common emitter", as depicted in Fig. 1 -- https://en.wikipedia.org/wiki/Common_emitter
Further, that'll require a resistor between the Arduino output and the base (2k-5kΩ), the collector resistor could be 1K or so, and "V+" is your 12V.