Help wanted, circuit for regular pulse variable phase shift.

cork_ie

Joined Oct 8, 2011
428
Hi Folks,I posted this some time ago when the ban on automotive questions was in force. Although I deemed it test gear and not a mod I never got to pursue the project.
I need some help. I have checked the archives and can only find time interval pulse delay circuits.

I have two wheels driven together at 2:1 ratio. Wheel 1 spins at twice the speed of wheel 2.

Wheel 1 is toothed and generates regular pulses with a missing tooth to indicate position. Sensor is either a magnetic coil or Hall effect type.

Wheel 2 turns at half the speed of wheel 1 - rate of rotation is approx 10 times/sec to 60 times/sec. It has a marker tooth which generates a pulse by switching a Hall effect sensor.

I need to advance & delay the pulse from wheel 2 by -10 Deg of angular rotation to + 10 Deg of angular rotation. The angular shift to remain steady irrespective of speed of rotation.

What I am actually trying to do is make a simulator for a stretched timing chain in an engine. By varying the phase angle of the camshaft pulse I would be able to determine whether it is the chain or the chain tensioner that is in trouble.

I know that an oscilloscope would allow me to see what is happening, but without a good waveform to start with it, it would be next to impossible to make a confirmed diagnosis. This way I can adjust the "apparent valve timing" ie what the ECU sees, electronically and increase or decrease the angular offset until such time as a diagnostic trouble code is set. That way I can exactly determine the true mid point.
I was hoping I would be able to achieve a - 10 deg delay by shifting the pulse from wheel 1 and the + by shifting the pulse on wheel 2 - effectively two circuits, only one operating at any given time.

I would prefer to avoid using a software based solution but if I have no option I will accept all suggestions.
Thanks in anticipation

Dodgydave

Joined Jun 22, 2012
11,235
How many pulses a second is the fast wheel 1, 20 to 120 per second? (20 to 120Hz)

So wheel 2 is half this at 10 to 60 pulses a second? (10 to 60Hz)

How long is the pulse width, and what voltage ?

Last edited:

Joined Mar 10, 2018
4,057
One could consider using DDS technology, maybe a PLL to phase lock
the DDS to the source then use its internal phase accumulator and phase
register to set / modulate phase. But some code involved to handle the registers,
the rest simple HW.

Regards, Dana.

cork_ie

Joined Oct 8, 2011
428
How many pulses a second is the fast wheel 1, 20 to 120 per second? (20 to 120Hz)

So wheel 2 is half this at 10 to 60 pulses a second? (10 to 60Hz)

How long is the pulse width, and what voltage ?
The crank(wheel 1) pulse rate is generally higher due to the number of "teeth" which varies from about 40 to 80 per 360 Deg of rotation
the rpm range I am interested in is 180-1200 RPM = 3 to 200 per second x no of teeth = 120 to 16,000 pulses per second.

Cam sensor Wheel two , which is far simpler and is invariably a Hall sensor is 1 to 4 teeth and turns at half crank speed i.e. 1.5 to 100 turns per second pulse range is 1.5 to 400 per second. I want to intercept this pulse and advance or delay it. +/- 10deg of crankshaft rotation 5Deg of cam rotation. Delaying the signal by 350 Deg if needed is OK

Because the crank signal is so variable I wish to avoid using it as a reference, if at all possible.
The ideal is to use the cam signal as the reference pass it through my "Black box" and insert a delay by a variable percentage ( potentiometer or otherwise) and then output the same signal to the ECU.
The time between pulses, as calculated above, varies from 2.5 milliseconds to 667 ms. The delay would be 0-2.7% of that (10Deg) of that . Pulse width is < 1deg = 0.27% 6.75 us to 1.8ms.
The important thing is that the delay is a phase shift and independent of frequency.