A to D converter for anti lock braking wheel speed sensors

[Chris Wilson]

I am running out of small Siemens made analogue to digital converters for converting the sine wave of magnetic anti lock automotive braking wheel speed sensors to a square wave digital signal. They no longer make these and I am looking at building a small batch. I use them when changing to a programmable after market ECU in performance road cars and race cars, s most of these ECU's expect a digital signal inputting.

Can anyone give simple suggestions for building something, ideally four channel in one package? Here's a link to one of the Siemens devices I looked at with a scope:

http://www.mkivsupra.net/vbb/showthread.php?316889-Traction-Control-and-ABS-analogue-to-digital-converters&highlight=analogue+digital

Thanks!

[mongo]

I would hate to make a mistake in this project but is there any reason a simple Schmitt trigger wouldn't fit your needs?

It would seem that a ADC would be overkill when really what you need is the comparator function.

[retrolefty]

I would hate to make a mistake in this project but is there any reason a simple Schmitt trigger wouldn't fit your needs?

It would seem that a ADC would be overkill when really what you need is the comparator function.

 This is correct. 

[max_torque]

Early (Pre ~2003) vehicles used VR sensors, that output a sine wave whose amplitude is proportional to the tooth passing velocity.  To read these, you need to use pretty much any VR amplifer IC that has a large input impedance (as most do).  Most of those IC,s low pass filter the input to get an average signal then look for zero crossing to create the digital edges. Google for "VR sensor amplifier" or "VR Sensor conditioner" etc


(modern cars use 7-14mA current digital sensors that also encode diagnostic and rotational direction information)

[Andreas]

Yes that is the point.
you need a adaptive trigger level + hysteresis.

the sensor voltage changes between several 100 mV and up to 100V for the speed range 1 MPH to 150 MPH with different tolerances of air gap.

ICs (single channel) are e.g. LM1815 or CY30

with best regards

Andreas

[langwadt]

I am running out of small Siemens made analogue to digital converters for converting the sine wave of magnetic anti lock automotive braking wheel speed sensors to a square wave digital signal. They no longer make these and I am looking at building a small batch. I use them when changing to a programmable after market ECU in performance road cars and race cars, s most of these ECU's expect a digital signal inputting.

Can anyone give simple suggestions for building something, ideally four channel in one package? Here's a link to one of the Siemens devices I looked at with a scope:

http://www.mkivsupra.net/vbb/showthread.php?316889-Traction-Control-and-ABS-analogue-to-digital-converters&highlight=analogue+digital

Thanks!

one config I've seen work well with everything from cranks sensors to abs sensor is based on a 74hct14

one inverter is used to make an oscillator, the output of that is lowpass filtered and used to bias the rest of
the inverters each via a large resistor, input signal is capacitive coupled and the inverter inputs have a series
resistor to limit current with high input voltages