I'm thinking about designing a electronic speed control for my Thorens turntable. Power supply similar like Project speed control.
I'm in 50 hz country. So the power supply should first lover the line voltage to 16V. 16V 50 hz is 33 rpm.
But I have no idea what components could rise the frequency to achieve 45 rpm.
I'm in 50 hz country. So the power supply should first lover the line voltage to 16V. 16V 50 hz is 33 rpm.
But I have no idea what components could rise the frequency to achieve 45 rpm.
I played with the idea on BDLC motors like the ones used in RC cars/drones plenty of motor sizes and controllers available.
Happy new year
Happy new year
It is different if the motor is AC induction or DC. If DC motor, only need to adjust the voltage until the speed desired is found.
But in AC motors of the induction type (skirrel cage) you need to increase simultaneously frequency and voltage to maintain proper motor torque.
But in AC motors of the induction type (skirrel cage) you need to increase simultaneously frequency and voltage to maintain proper motor torque.
Yes but BDLC motors are technically 3 phase ac motors that run from a battery or power supply hence the controllers working with modified sine waves (3).
There are a couple of different ones but they have normally magnetic rotors but there are also coreless ones, then there are the in runners and the out runners basically in runners like the name says have internal rotating rotors (used in RC car/boats) and the out runners have fixed rotors and the casing is the rotating part (used in RC plains and drones).
Here is a link that explains it in detail:
https://uk.mathworks.com/campaigns/offers/next/introduction-to-brushless-dc-motor-control.html
Just remembered that direct drive TT motors are technically BDLC ones
Here is a link that explains it in detail:
https://uk.mathworks.com/campaigns/offers/next/introduction-to-brushless-dc-motor-control.html
Just remembered that direct drive TT motors are technically BDLC ones
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Yes. Floppy disk drivers was the same.
You can use a microcontroller or a discrete solution. I don't understand micros so I will not talk about it.
If discrete solution, you need to create an oscillator whose frequency is proportional to the number of RPM the motor must run. Thus you divide this frequency by 3 and get the 3 phases 120° electrical apart. Independently you need to create another oscillator at 3~5Khz that will be the carrier. You need to create a PWM with this carrier, proportional to the motor current and thus AND both signals and amplify it in power to drive 6 MOSFET or IGBT units in a three phase bridge.
Usualy the carrier is chosen in this range to not overheat the core and get good square waves. I saw it in the larger 3 phase motor control for industrial machines. I repaired hundreths of them.
You can use a microcontroller or a discrete solution. I don't understand micros so I will not talk about it.
If discrete solution, you need to create an oscillator whose frequency is proportional to the number of RPM the motor must run. Thus you divide this frequency by 3 and get the 3 phases 120° electrical apart. Independently you need to create another oscillator at 3~5Khz that will be the carrier. You need to create a PWM with this carrier, proportional to the motor current and thus AND both signals and amplify it in power to drive 6 MOSFET or IGBT units in a three phase bridge.
Usualy the carrier is chosen in this range to not overheat the core and get good square waves. I saw it in the larger 3 phase motor control for industrial machines. I repaired hundreths of them.
https://www.diyaudio.com/community/...e-generator-for-turntable-motor-drive.298018/
You can use the SG4 (with an amplifier) to drive a 2 phase AC synch motor or a 3 phase BLDC motor.
Just running it with an RC esc with a servo tester for control. Very rough but works. Looking at Pyramids speed controller to see if it can be adapted for a hobby motor. Great fun so far!
https://www.diyaudio.com/community/...e-from-stuff-lying-around.393510/post-7219730
Just saw your reply. Your project is amazing!!! Might have to build one and see if can be modded for an RC brushless motor.
I do prefer DD turntables so much so that I even bought an hoverboard to test one of the motors that turned out to be a big failure because the motor (BDLC) has small neodymium magnets that causes steeps like a stepper motor.
You live and you learn...
A BLDC motor is the wrong motor to use in a TT, you need to PMSM motor. BLDC motors have a trapezoidal back EMF which causes high torque ripple. PMSM motors have sinusoidal BEMF and when controlled properly have very low torque ripple. Doing this from scratch I would use a microcontroller someathing like an STM32 and use FOC. STM have all the libraries and hardware to do this out of the box.
The motor in the Technics SP10mk2 has sinusoidal BEMF so is PMSM not BLDC.
Line frequency motor tt used a gearing system to change speed as the motor speed remains constant with line frequency.
You would have to make a 50 hz driver capable of running the motor and then switch it to 70 ish hz to get 45 rpm with the same gearing.
Fortunately I restored my LAB500 turntable which is direct drive quartz locked.
You would have to make a 50 hz driver capable of running the motor and then switch it to 70 ish hz to get 45 rpm with the same gearing.
Fortunately I restored my LAB500 turntable which is direct drive quartz locked.
One of these -
https://www.ebay.co.uk/itm/38514884...7Dcrfbh3suPlJ1hbHn24sYUA==|tkp:Bk9SR6DRoJ2uYQ
used with an Arduino Nano will generate 2 phases of AC.
Allows ramp up & down of speed.
The hard programming is done in the chip.
A good opportunity to learn a new skill.
https://www.ebay.co.uk/itm/38514884...7Dcrfbh3suPlJ1hbHn24sYUA==|tkp:Bk9SR6DRoJ2uYQ
used with an Arduino Nano will generate 2 phases of AC.
Allows ramp up & down of speed.
The hard programming is done in the chip.
A good opportunity to learn a new skill.