Hi!
I have been through a number of threads here about motor controllers for turntables. But several of these threads are quite old and new products have come on the market. What are your`e thoughts about the following solutions:
Solution 1: Pi Pico generates a sine curve for each of the motors windings. The sine curves are amplified with an affordable class D amplifier that drives the motor. One channel for each winding. If so: Do I need a transformer between amplifier and motor? And what specifications must this transformer have? The motor on td 166 is 16v ac.
Solution 2:
Use a PWM generator to synthesize a sine and switch the signal to and from the two windings? I do not quite see how to do this. This may require that the PWM signal is generated with varying duty period throughout a cycle. Is this😕 possible? In addition, should a low-pass filter be installed? If so, where in the chain should it be placed, and how is such a filter calculated?
Which of these solutions will be easiest to succeed with? Are there other similar solutions that may be possible for someone with limited experience?
As you can see, I'm totally new to this, so sorry for the stupid questions.
Cheers!
I have been through a number of threads here about motor controllers for turntables. But several of these threads are quite old and new products have come on the market. What are your`e thoughts about the following solutions:
Solution 1: Pi Pico generates a sine curve for each of the motors windings. The sine curves are amplified with an affordable class D amplifier that drives the motor. One channel for each winding. If so: Do I need a transformer between amplifier and motor? And what specifications must this transformer have? The motor on td 166 is 16v ac.
Solution 2:
Use a PWM generator to synthesize a sine and switch the signal to and from the two windings? I do not quite see how to do this. This may require that the PWM signal is generated with varying duty period throughout a cycle. Is this😕 possible? In addition, should a low-pass filter be installed? If so, where in the chain should it be placed, and how is such a filter calculated?
Which of these solutions will be easiest to succeed with? Are there other similar solutions that may be possible for someone with limited experience?
As you can see, I'm totally new to this, so sorry for the stupid questions.
Cheers!
Solution 1: no DAC in the Pico, so you'd have to add one, then you'd need amplifiers and transformers to boost the voltage - a lot of components.
Solution 2: yes, this is how motor control is done, PWM synthesis of a waveform, the motor's inductance smooths out the current for you, easy...
However you may need to worry about any signals in the audio frequency range leaking out to the surroundings (electrically or mechanically). Ultrasonic PWM frequencies are normally used to avoid this.
Most turntable motors are mains voltage, which causes complexity issues as you need a mains rated IPM or similar to switch the actual mains.
I rewound a 2-phase Dual TT motor for 12V use, then a simple MOSFET bridge for each winding was all I needed, could all be on one PCB then.
Thread here: Rewinding turntable motor for low voltage
Solution 2: yes, this is how motor control is done, PWM synthesis of a waveform, the motor's inductance smooths out the current for you, easy...
However you may need to worry about any signals in the audio frequency range leaking out to the surroundings (electrically or mechanically). Ultrasonic PWM frequencies are normally used to avoid this.
Most turntable motors are mains voltage, which causes complexity issues as you need a mains rated IPM or similar to switch the actual mains.
I rewound a 2-phase Dual TT motor for 12V use, then a simple MOSFET bridge for each winding was all I needed, could all be on one PCB then.
Thread here: Rewinding turntable motor for low voltage
Thanks for the great answers. There is no conventional D / A in PI pico, but this guy uses PWM to play recorded files Raspberry Pi Pico Audio output - YouTube. But I see that there may not be an easy path.
Very interesting the solution you outline for the Dual player. My Thorens has a 230v -16v ac / ac power supply and the motor is made for 16v voltage, so I should be able to leave it untouched.
Again. Thanks
Very interesting the solution you outline for the Dual player. My Thorens has a 230v -16v ac / ac power supply and the motor is made for 16v voltage, so I should be able to leave it untouched.
Again. Thanks