Hall effect sensor signal to VR convertor

Thread Starter

ThatOtherGuy

Joined May 30, 2016
18
Hi all, I posted previously and I think my description may have been poor and misleading as to what I was after so I thought I'd repost and try be more accurate.
I have an automotive wheel speed sensor that that was not intended to be used with the control unit in the vehicle that is a hall effect sensor that produces a square wave signal that alternates high and low 50%, it measures 0.6v when low and 1.3v when high.
I want to add some form of interface between the hall effect sensor and the control module to make this signal look like the signal that was produced by the original inductive sensor that produced an A/C sine wave signal that measures around 5v peak to peak at 150Hz and needs to read up to around 900Hz, obviously the amplitude increases with increased rpm but I don't think this will be necessary. Below is a representation of what the signals look like at 150Hz. i hope I've done a better job of explaining this time.wss signal.png
 

LowQCab

Joined Nov 6, 2012
2,512
There is nothing "bad" about putting a hard-edged Square-Wave into a VR-Sensor-Circuit,
But, You do need to Ground the Negative-Input to the VR-Sensor-Circuit,
and only use the "Positive-Input",
( actually, You can use either Input on a "Wheel-Speed-Sensor-Input" ).
It will probably work just fine with a direct connection,
but if it doesn't, add a 1uf Capacitor in between the Hall-Sensor and The VR-Input.

You could also look into retro-fitting the old-VR-sensor into the new Axle-Housing.

For Wheel-Speed-Sensing, a Hall-Sensor is not intrinsically "better" than a VR-Sensor,
although there is probably somewhat less of a chance of
some kind of Electrical-Noise corrupting the Signal.
The VR-Sensor-Input-Circuitry is specifically designed to withstand, and nullify, any Electrical-Noise.
.
.
.
 

Thread Starter

ThatOtherGuy

Joined May 30, 2016
18
There is nothing "bad" about putting a hard-edged Square-Wave into a VR-Sensor-Circuit,
But, You do need to Ground the Negative-Input to the VR-Sensor-Circuit,
and only use the "Positive-Input",
( actually, You can use either Input on a "Wheel-Speed-Sensor-Input" ).
It will probably work just fine with a direct connection,
but if it doesn't, add a 1uf Capacitor in between the Hall-Sensor and The VR-Input.

You could also look into retro-fitting the old-VR-sensor into the new Axle-Housing.

For Wheel-Speed-Sensing, a Hall-Sensor is not intrinsically "better" than a VR-Sensor,
although there is probably somewhat less of a chance of
some kind of Electrical-Noise corrupting the Signal.
The VR-Sensor-Input-Circuitry is specifically designed to withstand, and nullify, any Electrical-Noise.
.
.
.
Thanks for your input, I have considered swapping the sensors however I'd like to avoid it if possible as the vr sensor is much larger and requires a pulse wheel to be added which is incorporated in to the wheel bearing on the later axle.
I haven't tried connecting the new sensor directly but someone else has and said it didn't work. I don't understand why but possibly due to it being a lesser voltage and being dc and not an ac signal I suspect.
What are your thoughts on using an amplifier of some sort then smoothing out the signal with a capacitor. I dont completely understand all this but watching videos specifically this one below seems to be like what I need to achieve just not sure how to select the specific components. Any help would be greatly appreciated.
 

LowQCab

Joined Nov 6, 2012
2,512
The Video, without even watching it, shows how to do this in a very narrow frequency range.
The Wheel-Speed-Sensor operates over a very wide Frequency-range.
It is a much more complex problem to round-off the corners exactly the same at all Frequencies.

Why have You not just tried doing it the way that I have described ?
The VR-Sensor-Input-Circuitry is virtually bullet-proof, You'd have to try really hard to damage it.

"" someone else has and said it didn't work ""
Do You know exactly what that "someone-else" did, or did not do ?
The internet has no shortages of idiots and fools.
.
.
.
 

Thread Starter

ThatOtherGuy

Joined May 30, 2016
18
The Video, without even watching it, shows how to do this in a very narrow frequency range.
The Wheel-Speed-Sensor operates over a very wide Frequency-range.
It is a much more complex problem to round-off the corners exactly the same at all Frequencies.

Why have You not just tried doing it the way that I have described ?
The VR-Sensor-Input-Circuitry is virtually bullet-proof, You'd have to try really hard to damage it.

"" someone else has and said it didn't work ""
Do You know exactly what that "someone-else" did, or did not do ?
The internet has no shortages of idiots and fools.
.
.
.
Thank you for the advice, the more I think about it you are dead right, this other person who tried connecting the hall sensor direct said he just connected it and it didn't work but I'm thinking he has just connected the 2 wires not realising that the hall sensor needed a reference voltage and the negative side to go to earth.
I was hoping to have it sorted before I actually fitted the axle to the vehicle but I think I just have to bite the bullet and put it in and connect it as you described and see how it goes. thanks again.
 

LesJones

Joined Jan 8, 2017
3,817
Even before there are any pulses from the VT sensor the ABS computer does a resistance check of each sensor. This is done when the ignition is switched on as part of the system check. I had a VR sensor that failed open circuit and it caused the ABS fault light to come on straight away. I agree with LowQCab that doing the mechanical modifications to fit the original VR sensors is the best solution.

Les.
 

LowQCab

Joined Nov 6, 2012
2,512
Or, if you're building a Hot-Rod,
just buy a MegaSquirt3-Pro,
( or even get 2, and then connect them via "CAN-Buss" ),
which has plenty of VR, and Digital-Inputs for You to choose from, and assign as needed.
.
.
.
 

Thread Starter

ThatOtherGuy

Joined May 30, 2016
18
I'm having a bit of a play to see if the square wave signal will work just by connecting the hall sensor from the new axle to the ABS module as in the below diagram and have used a separate power supply as the ABS module will detect a short to ground. The problem is when power is applied to the circuit a multimeter registers an open circuit across the wire to the ABS module and therefore it registers an open circuit. Anyone any ideas on how to overcome this.WSS circuit.png
 

LesJones

Joined Jan 8, 2017
3,817
See post #6. You could try adding a capacitor in series between the Hall sensor output and the ABS module input to block any DC component. (I suggest trying capacitors in the range 10 nF to 1 uF. Look at the input to the ABS module with a scope and choose the value that gives a waveform closest to the original VR sensor waveform.) Also add a resistor between the ABS module and ground that is about equal in value to the original VR ABS sensors. (The resistance of the VR sensor that failed on my 2004 Avensis was about 1.6K) This is to try to simulate the old ABS sensor during the power up self test. This would probably stop is conforming to safety regulations as it is no longer testing the sensor.

Les.
 

graybeard

Joined Apr 10, 2012
52
I use a cap in a product I sell that needs to be able to read either Hall effect or VR automotive speed sensor signals. I chose the cap value based on the input resistance and the range of frequencies I expect to see from the sensors.
 
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