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DDS turntable power supply: how to power the motor

hi-fi132

pfm Member
I'm thinking of building a turntable power supply based on readily available AD9833 breakout modules. The AD9833 is a DDS waveform synthesiser that is easy to control with a microcontroller such as the Arduino. I was planning to use 2 of them, 1 per phase.

The motor to be driven will be either the 12V or 24V Premotec 9904 series ac synchronous motor as used in countless belt drive decks. The AD9833 modules output about 600MV peak to peak. Is n ordinary chip amp the optimal solution to boost the output to drive the motor or is there a better way? If I went with an amplifier, can somebody advise how I would calculate the power requirements to work out the optimal solution where price, performance and power are all considerations?

I have looked at other projects including the Sincos and Meldano but I want to build something that better suits my requirements than either. Software is however my forte, not hardware. Any advice, and links to other designs greatly appreciated.
 
A chip amp should work just fine yes. The main decision then is 12V or 24V motor... Whilst the motor will not need more than a few Watts the RMS voltages mean that for 24V motor a 100W amp would be appropriate whilst for the 12V motor a 25W amp would do it. As not much actual current is needed the power supplies do not need to be rated for anything like that which you would use if actually driving 25 or 100W into a speaker and can be "cheap and weedy" . I would tend to sway towards the 24V motor for reasons of lower current involved and higher resistance load etc. IIRC ST Microelectronics do a 100W chip amp.
 
A chip amp should work just fine yes. The main decision then is 12V or 24V motor... Whilst the motor will not need more than a few Watts the RMS voltages mean that for 24V motor a 100W amp would be appropriate whilst for the 12V motor a 25W amp would do it. As not much actual current is needed the power supplies do not need to be rated for anything like that which you would use if actually driving 25 or 100W into a speaker and can be "cheap and weedy" . I would tend to sway towards the 24V motor for reasons of lower current involved and higher resistance load etc. IIRC ST Microelectronics do a 100W chip amp.

Thanks for your input. Can you give me an idea of what I would need, or how I would calculate the PSU requirements to run a 100W chip amp in this scenario and do you feel that a linear PSU would be a benefit over an SMPS?
 
Thanks for your input. Can you give me an idea of what I would need, or how I would calculate the PSU requirements to run a 100W chip amp in this scenario and do you feel that a linear PSU would be a benefit over an SMPS?

Any old power supply that can give +50V and -50V will do fine. Quality doesn't matter. The smallest mains transformer you can get should be adequate and as as low as 2200uF smoothing caps will be fine. You would be using a 100W IC to get sufficient voltage swing for the 24V motor but will only be using maybe 3-8W or so from the amplifier. It will be like driving a 100 Ohm speaker!
A 35 - 0 - 35V or 2 x 35V transformer is what you need and the smallest rating that will be really commonly available will be 160VA, which will be enough to power 10 TT motors!
 
Google meldano motor controller, all you need on one pcb, USB controlled, rpm to 0.001rpm, phase to 0.01 degree, voltage via trim pot. Records total run time and has adjustable start and stop ramping.
 


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