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I want to design a Johnson/ring counter circuit for control of my sr motor. Until now I have got this information, which I have tabulated in the following waveforms I am attaching for the reference:-

enter image description here

Now, I want to be able to run the motor at low speeds of Not more than 200-300 RPM. I was hoping to control the motor via johnson/ring counter circuitry by generating control pulses to the power circuit. For the power circuit, I am using a DC split link based converter topology to energize each phase. Thus, each phase needs just one MOSFET switch to be energized. I have drawn the expected pulses duration for each phase in the above waveform template. Also, the position sensor outputs and their complements I have drawn. Low level is 0 Volts while the High level is 5 Volts for the sensor output.

All for a conduction from 0-180 (mechanical), the rest 180-360 is also the same.

So, my question is:-

From the above waveforms templates: Given the output of the position sensor of the motor(optical type slotted photo-interrupter), and the expected pulses for each of the given phase (Which have to be synchronized either with falling or rising inductance of each phase); How I might be able to generate the output control switching pulses (each of 20 degrees duration) from a sequential circuit(Johnson/ ring counter) for each of the four phase MOSFET switches to drive my motor at a particular low speed?

Any kind of help will be appreciated.

I have tried making a logic with the ring counter which should go like: 1000 => 0100 => 0010 => 0001 and then repeat.

But, it dosen't seems quite right.

So please give your inputs, suggestions or directions to help me

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  • \$\begingroup\$ +1 for the hand-drawn timing diagram. I don't know that I can help other than say that whenever Johnson / ring counter is mentioned that the CD4017 chip comes to mind. It has ten stages and you can daisy chain them to get more. To get 'n' stages you connect output 'n' to the reset pin. (The count is zero-based.) \$\endgroup\$ – Transistor Sep 30 '18 at 21:12

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