The Thorens is a synchronous AC motor that runs on 110Vac and uses a voltage dropping circuit (with mains rated capacitor) to reduce the supply from 220/240Vac to ~110Vac. Both windings run on that 110Vac but the extra capacitor in one feed forces the current to be out of phase in one of the windings and that determines the direction of rotation.Pjotr said:
The Premotec appears to be different if these last two posts are correct.
Well, they can't both be correct:- one says resistor and the other says series for a 240Vac supply.
Hi Andrew,
Of coarse one of the phases runs through a phase shifting capacitor but the motor in total runs through a voltage dropping resistor.
Have a look here and download the service manual (probably you need to register to be able to download): http://www.vinylengine.com/library/thorens/td160.shtml
There a voltage dropping resistor of 5K6 is stated but have seen TD160 with a 10K / 2W dropping resistor.
Cheers
Of coarse one of the phases runs through a phase shifting capacitor but the motor in total runs through a voltage dropping resistor.
Have a look here and download the service manual (probably you need to register to be able to download): http://www.vinylengine.com/library/thorens/td160.shtml
There a voltage dropping resistor of 5K6 is stated but have seen TD160 with a 10K / 2W dropping resistor.
Cheers
Pjotr said:
Not necessarily so if you use a DDS oscillator. Which is the obvious thing to do with a micro in this matter IMO.
I did say COULD.
The DDS would at least not chop up the mains to control the motor. Chopping the mains results in masses of noise.
A burst control could be used but care would have to be taken not to introduce DC by allowing odd cycles through.
A phase locked loop is another possibility.
nigelwright7557 said:
You did say:WOULD as it concern a micro
Bur anyway there are more ways to Rome.A PID is more complex than DDS if you want to implement it in a micro. But with a DDS generator there is no objection to output a analogue sine signal in the end if you wish and feed it to a power amp.
Cheers
Pjotr said:
You did say:WOULD as it concern a micro
A PID is more complex than DDS if you want to implement it in a micro. But with a DDS generator there is no objection to output a analogue sine signal in the end if you wish and feed it to a power amp.
Cheers
It depends on which type of PID you use.
There is a 3 stage formula that is quite easy to implement based on the last 3 error values. I found the same PID could be used from everything from fast control to controlling a multi ton drum that mixed cement !
You basically alter the gain and sampling period of the PID to match.
In fact there are millions of drills in Germany running that PID !
Pjotr said:Ehh……….., it concerns a synchronous ac motor here that takes up just a few watts, not a multi ton drum or a drill. That only needs 2 sine waves of the correct voltage and frequency in quadrature (90 degrees phase shifted).
Your method sounds like quite a lot of curcuitry.
A triac is a pretty cheap method.
My solution uses a handful of CMOS chips which are 50c each. You could probably program a uC to do the same functions for even less money.
The analogue side will add another $100 or so if you want first class performance, less if you'll accept a compromise solution. The power supply is anything from $10 up - I happen to like SLAs so that's a bit more.
The analogue side will add another $100 or so if you want first class performance, less if you'll accept a compromise solution. The power supply is anything from $10 up - I happen to like SLAs so that's a bit more.
It can be done relatively simple. Some 10 years ago I build a variable AC supply for my Thorens TD160. As I noted in post #6, I did use a power Wien-bridge oscillator: A LM3875 power amp chip wired as a Wien-bridge oscillator and a door bell transformer at the output. Amplitude stabilisation was done by a 6V / 50mA standard light bulb.
The thing was remarkable stable But when I replaced the TT belt for a new one the TT ran spot on directly from the mains, so the thing was recycled for other purposes.
Cheers
The thing was remarkable stable But when I replaced the TT belt for a new one the TT ran spot on directly from the mains, so the thing was recycled for other purposes.
Cheers
Won't work, you'll have 180 degrees phase shift.
In the development phase of my controller I used an HP3326A dual channel frequency synthesiser with internal high stability reference to synthesise the quadrature waveforms. The frequency stability is around 1ppb, step size is 0.1 mHz, phase angle selection to 0.01 degree, distortion better than -80dB. I described it at the time as the penultimate motor controller.
In the development phase of my controller I used an HP3326A dual channel frequency synthesiser with internal high stability reference to synthesise the quadrature waveforms. The frequency stability is around 1ppb, step size is 0.1 mHz, phase angle selection to 0.01 degree, distortion better than -80dB. I described it at the time as the penultimate motor controller.
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