A VSS typically puts out a signal rated in pulses per mile.  I'm not sure what that rate is for an AOD VSS.  I do know that the Dakota Digital SGI-5 can manipulate a VSS signal and change the output by multiplying or dividing the pulses per mile.  If that's your goal, here's a link:

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=287/mode=prod/prd126.htm

If not, I need to know more about what you're trying to accomplish.  One of my best friends has a Masters in electrical engineering and I can ask him, as he's always tinkering with stuff like this. 

So you want to be able to adjust steering effort in an electric assist steering system using the VSS to determine road speed.  Instead of adjusting it manually with a pot you'd like an IC to do it automatically.  A circuit providing varying resistance based on input pulse frequency.  How many wires go to the VSS?  Two?

Last edited by TKOPerformance (3/29/2016 1:28 PM)

Rudi wrote:

I am looking for a circuit that will receive a VSS signal from an AOD transmission and convert it to 0 to 100 K ohm out put. An audio taper of the resistance is preferred. There must be an IC that will do that but I can't seem to find one.
 Any takers?

That output needs to be 12v or 5v through the 100 ohm resistor right? Sort of like a throttle position sensor? You have a 5v reference, a sensor ground, and then the output which varies as the TPS moves (the TPS is the resistor).

I am talking about the output side of the circuit, so this is the signal that goes *to* the EPAS.
 

Last edited by Raymond_B (3/29/2016 2:20 PM)

I made a circuit that connects the base of a PNP transistor to the input from the VSS. It puts out a solid square wave based on the supply voltage and the frequency of the VSS. Connect the square wave output of the transistor to a frequency to voltage converter (LM331). You can then take that voltage and feed the input to a comparator  IC (LM393). The LM393 has 2 outputs that can be turned on and off at any preset voltage levels. If needed they can be use to turn on and off relays. Now put 3 resisters in parallel. ( For an example lets say 10K, 5K and 1K) they can be connected or disconnected via a relay. Lets say the all three resister are in parallel to start, total resistance < 1K. As speed of car increases, freq of vss increases, voltage increases, this turns off one of the comparator circuits in the (LM393) drops off the 1K resistor - total resistance now < 5K. As speed increases drop off the 5K resister to farther decrease assist. Kinda hard to splain something like this on here.

wsinsle wrote:

I made a circuit that connects the base of a PNP transistor to the input from the VSS. It puts out a solid square wave based on the supply voltage and the frequency of the VSS. Connect the square wave output of the transistor to a frequency to voltage converter (LM331). You can then take that voltage and feed the input to a comparator  IC (LM393). The LM393 has 2 outputs that can be turned on and off at any preset voltage levels. If needed they can be use to turn on and off relays. Now put 3 resisters in parallel. ( For an example lets say 10K, 5K and 1K) they can be connected or disconnected via a relay. Lets say the all three resister are in parallel to start, total resistance < 1K. As speed of car increases, freq of vss increases, voltage increases, this turns off one of the comparator circuits in the (LM393) drops off the 1K resistor - total resistance now < 5K. As speed increases drop off the 5K resister to farther decrease assist. Kinda hard to splain something like this on here.

 That theory might work but I would rather not use relays which would put out a  stepped increase in the resistance instead of a constantly tapered increase.

Good info on the signal characterization.

http://accutach.com/Documents/VSSCharacterization.pdf

TKOPerformance wrote:

Rudi wrote:

TKOPerformance wrote:

So you want to be able to adjust steering effort in an electric assist steering system using the VSS to determine road speed.  Instead of adjusting it manually with a pot you'd like an IC to do it automatically.  A circuit providing varying resistance based on input pulse frequency.  How many wires go to the VSS?  Two?

Yes , two wire VSS.
 The assist control (pot) goes into an after market control box that sends a signal to the power steering control module. The manual pot has two wires going intocontrol box.

So, a two wire VSS is a magnetic AC pulse generator, which produces a sine wave format.  That's important because some VSS are actually hall effect (three wire) which would be a totally different direction. 

So what's needed is a varistor circuit that converts a magnetic AC pulse sine wave to a varied resistance.

What's the voltage going through the circuit?  I'm assuming the manual pot is the varied resistance so the control box is seeing a given voltage at varying amperage. 

 I will have to see if I can take an actual measurement to make that determination

Rudi I'm very green when it comes to electronics but I've been thinking about a crank fired ignition which lead me to the Megasquirt  line of EMS processors.

The Microsquirt I/O expansion in particular seems like it would do what you need plus control fans, fuel pump,etc., as all the megasquirt ECU'S inputs/ outputs can be custom tailored for whatever purpose desired-

http://www.msextra.com/product-range/expansion/microsquirt-io-box/

Anyway besides electronic ignition an EPAS is another direction I'm going with and these will link with it and the output can be tuned for the desired level of assist in whatever increments you set, so not only variable assist but ultimate control of how much and when.

Don't mean to waste your time but thought this might be worth a look for you, especially if you have other electronic control needs like PWM speed controlled fans.

Thanks Bob. That seems to be what I am looking for. Right now I am trying to determine the voltages the control is.
 Any more help on this would be much appreciated.