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electric power assist steering


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I actually just mapped out the Signal PCB for a simple inline magnetic speed sensor.  You put it inline with the speedo cable, and it sends a signal to this PCB. This PCB then changes its signal to an electrical pulse that the unit can read. Its actually pretty easy. Not sure how it would work with the unit your attempting to use.

 

Another option is a signal unit right off the ignition. I can source a universal PCB sending unit that is made to do this from Japan.

 

Good friend of mine has a steering unit. He loves it, says its awesome….  Only issue I've come across is with his PCB going out. Its only been isolated to him, so not sure what it is. Been super sporadic and with no precursors... Not sure if he's having a electrical surge in his wiring, or if its something in the unit itself. I'm in the process of trying to get this issue resolved. Going to send back to customizer in Japan, and have him diagnose it, repair, or replace.

Edited by azcarbum
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I had a sporatic loss of assist in my system which drove me crazy. One day I realized it was happening when I had the directional on but only when the light was actually on. Seems I tapped the power signal to the directional circuit and the fluctuation in voltage when the light was on was enough to shut off the power steering motor. Moved the power signal and all is good!

 

Joe

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Thank you for the offer azcarbum. I will keep this in mind if I get stuck. I will be running an electronic speedo so the first option you suggested is out. Would the second option you suggested be self adjusting and also work if the car was going in reverse? From what I have figured out so far I need to run an active wheel speed sensor verses the old passive wheel speed sensor. I have now acquired the under dash wiring from a Scion FR-S. I separated the wiring that went into the steering brain box. There is only one small white and one small black wire that fed to a plug that was taped up in the wire harness which was not ever plugged into anything. Then there is a heavy gauge power and ground and then one green with a white tracer with silver dashes. This has to be from the wheel speed sensor. I stopped at a Subaru and a Scion dealership neither of which were any help what so ever. There is a shop down the street from me that specializes in automotive wiring. They are my next stop and should have been my first. They have helped me figure some things out in the past. Once I cut what I want from the wire harness for the rest of the steering column controls I will be paying them a visit.  I am going to use the Scion controls and ignition switch. The light switch has a plug with ten wires. wiper switch has six wires. The ignition switch has two plugs. One with two wires one with seven. They will be able to tell me what all of these are plus will be able to get me a wire schematic from the Scion  FR-S. Something neither service manager wanted to be bothered with.    

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In a kind of unrelated topic if anyone is thinking of adding LED lighting to their vehicle be careful. The scion I got the dash wiring from had a engine fire from what was listed. When I received the harness it was cut from a few inches in the engine compartment and included everything under the dash. It had an after market LED Control Module plugged into the lighting harness under the dash. The wiring is fine going into the control module but a few inches on the other side of it the wires are completely melted. These were under the dash and looks like it may have been what started the fire. Just my observation and wanted to share. 

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I finally found what I was looking for. I am using a LT-1 T56 which from what I found is a 4KHZ square wave pulse. This is an active vehicle speed sensor which can read zero mph and also recognizes reverse. I am going to try to keep this simple and use that signal and see what happens. I will also be using a speedometer that works from this sensor so that will also let me know this sensor is working.

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Just when I think I might have a semi original idea on my hands I find I'm at least 4 weeks late to the party. Ah well, I'm not able to attempt anything crazy on my Z yet anyway, so I'll just continue to live vicariously though you guys.  :rolleyes:

 

Was seeking a bit of clarification.

 

"I am using a LT-1 T56 which from what I found is a 4KHZ square wave pulse."

 

So, your saying is you've got a T56 transmission that has a VSS in it that puts out a 4kHz square wave? I'm assuming you where getting this signal while letting trans's secondary shaft spin?

 

Also, for anyone wondering, quadrature hall sensors are a thing. They're just two sensors built into the nose of a single housing. You index the sensor so that one sensor is "behind" the other. This way, when a trigger tooth flies by, one detects it before the other. This allows for direction detection when interpreting both signals.

 

Convenient primer with diagram: http://www.sensoronix.com/00pdf/newsletters/Miniaturized%20Hall%20Effect%20Quadrature%20Sensor!.pdf

 

Good luck on the install!

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I think you mean 40000 PPM (Pulse Per Mile). The frequency at which the pulses occur will be directly proportional to the rate at which the tone wheel (reluctor wheel) is rotating. In other words, the frequency of the pulses is dependent on vehicle speed.

 

There is usually a control box involved, in many new cars this would be along the lines of the BCM and/or the PCM, to send a proper signal to the EPS. From what I have been able to find is that the signals that go to the actual EPS unit are usually a square wave PWM signal to vary the amount of assist, and in some cases is inversely proportional to what a VSS signal would be.

 

This is where spending some time with a Oscilloscope and/or logic analyzer will help decipher the signals needed.

 

This is one of my main projects for this summer, but using different components.

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Six_Shooter  from what I have read all newer vehicles have what is called active vehicle speed sensors which when looked at with a scope shows a square wave pattern. Also there is a voltage increase related to vehicle speed from these vss sensors. Older vehicles used what was considered a passive wheel speed sensor that do not produce voltage output. Both work off reluctor wheels but give off different types of readings. I am going to use the signal from the t56 and see how I like it. I have a plan to make a set up that will work off the front wheels if I do not like how the steering assist works when my tires are spinning. I have a spare 280z sitting in my garage for mock up purposes which comes in very handy.

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Both old and new sensors produce a voltage, otherwise there would be no signal. With the exception of sensors that modify (a reference) voltage, which are usually resistance based.

 

This is easily measured with a DMM, but the waveform can be seen with a O-scope. The type of signal depends on the type of sensor. Most sensors themselves produce a sinusoidal signal, unless there is some conditioning of the signal, which has nothing to do with the age of the vehicle, since you can find sensors in new vehicles that produce a sinusoidal output.

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