Smooth Analog Stepper Motor Control

[Bob Scott]

 

[blueroomelectronics]

It's like the CMOS version of Roman Blacks popular stepper design.
https://www.romanblack.com/lini.htm
**broken link removed**

 

[blueroomelectronics]

I wonder what your circut waveform looks like? Have you built and tested it?

 

[on1aag]

Hi Bob,

I think you'll never gonna get that oscillator working at 16 kHz.

on1aag.

 

[audioguru]

The needle in a phono cartridge tracks the groove on a vinyl record.
Why does your tone arm need a motor to move it? Is its low friction bearing seized?

I haven't used my Shure cartridge for about 20 years. I think its needle has a weight in the groove of about 2 grams.

 

[blueroomelectronics]

Guess the OP wants one of these things.
I doubt it's a stepper though, probably a long worm gear and a synchronous motor.
**broken link removed**

 

[Nigel Goodwin]

Guess the OP wants one of these things.
I doubt it's a stepper though, probably a long worm gear and a synchronous motor.

Certainly not a stepper (could you imagine a worse choice?), and certainly not a syncronous motor either - it's a simple DC motor feeding a long worm gear, as part of a servo system. The arm has a small amount of horizontal movement, so tracks across the record as normal - at the rear of the arm is a slotted opto-coupler, and as the arm tracks it blocks the slot - this triggers the DC motor which moves the pivot point of the arm to catch back up again. A CD tracks in a very similar way, but with no mechanical contacts or sensors.