Probably but it won't be as good as the phased locked control they have.
You will still need to build some custom interface electronics.
This is all the help I can give.
1 Like
If you post pictures of how the motor looks like and if you post how many coils and magnets this motor has the EE here in the forum can make suggestions for a DIY build driver.
Another option might be to use a TMC2208/TMC2209-driver.
This is a highly advanced driver for almost quite rotating a stepper-motor.
The TMC2209 does 1/256 microstepping. And creates an output current approximating a real sinus wave-form and this is what makes this driver rotate the stepper-motor almost in silence
Here is a video that explains it with measurings
I would use a Teensy 4.0 instead of an Arduino because a Teensy 4.0 can produce much higher stepper-frequencies than an Arduino with easy to write code
Of course you can do special tricks with direct port-access etc. to create higher frequencies with an arduino
for let's say 50 rpm is 50/60 = 0.83 rps (rotations per second)
a standard stepper-motor has 200 fullsteps per rotation with 1/256 microstepping this is
200*256 = 51200 steps per rotation at 0.833 rps this is
200*256 * 0.833 = 42645 steps per second.
The TMC-drivers always use 1/256-mcirostepping internally even if you choose to drive 1/8 or 1/16 stepping mode
Though I don't know if it makes a difference if you drive 1/8 or 1/256-microstepping in regards to the noise-level
best regards Stefan
This is the main board, the motor is mounted onto the motherboard, and the driving circuit is on it.
The second pic is the motor coil with the plastic thing removed.
This is the reverse side of the platter. This is the other part of the motor, it is part of the platter (though it can be removed, it's simply screwed on). When you press the start button the coils magnetize itself in a rotating magnetic field to cause it to turn. I didn't think it could turn backwards, but it can, it's just that the turntable isn't supposed to spin the wrong way but if something breaks on the motherboard, it can.
In fact one failure mode is that it has "runaway platter" meaning it will spin faster and faster until it spun as fast as it can possibly spin, and pressing any of the buttons do nothing, it just spins FAST as soon as it is turned on.
I have another SL1200 that is functional, I had to adjust the bearing spike because it wasn't tracking well, but the adjustment fixed it. The other turntable had worse tracking issue because of a busted bearing, and I had it drilled out and replaced with a standard MR52ZZ bearing and now it works fine, if only the motor will spin correctly. That tonearm is worth about 200 dollars anyways.
Here is a picture I found that explains the operation of the thing. It has a hall effect sensor to sense the position of the platter.
Do you suppose there's a standard inverter driver I can use to get it to spin independently of the board?
Me personal I know not enough about BLDC motors and how to drive them to answer this question.
I use BLDC-motors on RC-airplanes.
So to get in contact with such an expert I would change the title of your thread to
something like
"what ready to buy ESC could drive a record-turntable 12-coil BLDC-motor at 33 / 45 rpm ?"
To attract that experts that know the details about it.
This titel nails to the point all important details.
I have seen multiple projects where people created a DIY ESC for driving BLDC-motors.
For fast rotating BLDC-motors. Where fast means 3000 to 15000 rpm.
Switching the currents slower / = rotating the magnetic field-orientation slower
should make it easier on one side but maybe this requires to create sinus-waves.
best regards Stefan
1 Like
So all available serve drivers are for fast speeds? There are no prepackaged servo motor driver out there?
I don't know.
You have a rarely used application. Estimate how many direct BLDC driven turntables are in use around the globe and compare this number with how many RC-cars, RC-planes, electric scooters are used around the globe.
RC-cars /planes do have smaller motors running at HIGHEST RPMs
e-scooters have much bigger motors
What is very common are ESCs for motors that look like this
They are made for electric RC-planes or RC-cars which run at 3000 up to 20000 rpm
As these motors are much smaller than yours the inductivity will deviate very much
from the inductivity of your turntable-motor.
I don't have enough knowledge about these details. But Usermanuals for these ESCs state that you can adjust different parameters to optimise the motors performance.
It might be that deviating too much from typical RC DC-brushless motors will cause very poor perfomance of such an ESC if you try to drive your turntable BLDC.
This is the reason why I suggest that you change the
title
of your thread to words that state the important technical specifications which would be
"what ready to buy ESC could drive a record-turntable 12-coil BLDC-motor at 33 / 45 rpm ?"
Another option would be to look up how you can build such a BLDC-driver your self based on MOS-FETs (Metal Oxid Semiconductor Field Effect Transistors)
I have seen such DIY-projects even for the very fast spinning RC BLDC-motors
best regards Stefan
For driving BLDC-motors There are two different concepts
sensorless BLDC-drivers = no sensor at all
versus
WITH hall-sensor BLDC-drivers
I have taken the effort to search for BLDC-controllers and found this one.
Which is a
WITH hall-sensor BLDC-driver
I am NOT experienced enough to judge if this controller would work with your turntable-BLDC.
From all these information that I have posted you should have understand by now that "BLDC" is loooong not enough to just pick some randomly chosen BLDC-driver to make your turntable BLDC rotate smoothly and at very constant RPM.
500W is overkill. This motor is maybe 14 watts or so, it isn't high powered at all.
So there's a smaller market for turntable motors than RC cars? I don't believe that. Turntables are making a comeback, and in the old days that's what everyone had, and Technics made direct drive turntable for many years using their controller. RC car is a hobby whereas everyone (at least in the old days) had a turntable or record player.
There is no "general purpose" servo motor kit, the range of applications is far too wide. It's like saying is there a standard "engine kit" for motor vehicles. You need to at least look for kits aimed at audio turntables.
In terms of DD, there was a DIY turntable kit on the market ("Phainn" sold on ebay) but no longer available. There is an nice kit available from OEM Antrieb – Langer but you need €3500 and be an OEM with a quantity order.
There are some belt-drive kits on the market.
An interesting and informative DIY thread I discovered is
However you go, the DIY route is unlikely to be cheaper then buying a new turntable if you want to achieve typical hifi spec of 0.01% wow and flutter. If you want a cheap solution then any DC gear motor would do and feed it PWM to get about 33 RPM. With an optical or magnetic sensor to close the feedback loop, it could be fairly accurate.
People always seem to be surprised that the one obscure thing they are after doesn't exist.
I'll bet the market for DIY RC car parts was always higher than DIY turntable parts, even when turntables were a thing. Literally no one I know has a turntable. It's a niche within a niche. And DIY turntables are a niche in a niche in a niche.
1 Like
You seen how much records are selling for these days? I'm serious, people are willing to pay 50-100 dollars for records now.
In fact Technics started making the SL1200 turntable again, the SL1200 mark 6. I'm just surprised that they don't have any of their control IC's available, unless they are doing a limited run and using existing stocks.
I find it hard to believe that Panasonic would have a set of custom chips that they make only for turntables (technics is owned by Panasonic).
They make a million different direct drive consumer electronic devices from front loading washers all the way to inverter ac units. Surely the same controller is used in other Panasonic devices.
Question is figuring out which is which.
It is easy to make a driver for a brushless motor, all you need is an H-bridge for each coil. DIY example for a five-coil stepper. If the coils are connected together in a ring arrangement, you need only one half-bridge per lead.
To make it work as in the original, you need to know the sequence in which the individual coils are powered up as the turntable rotates.
I imagine that for a turntable, this sequence is very carefully tuned to minimize platter vibration and maximize rotational frequency stability. What does the service manual say about that?
1 Like
I'm going to have to read it but I'm sure it's well known. There's only so many sequences to energize it to get it to even spin. I think the challenge is to govern that speed, so it doesn't spin faster and faster. It has a hall sensor to aid in that and provide feedback I guess. I'm not an EE but if nobody figured it out by now, it must be impossible.
Platter is already fairly heavy so it can tolerate some variation.
Not at all. The speed is set by the time interval to switch between coil states.
Yes BUT what you have is NOT a normal servo. They are using the term "servo" generically to indicate that it has a speed sensor with speed-feedback control.
A normal servo is an "angle motor" that rotates about 180 degrees so it's perfect for steering an RC car. A normal servo motor is geared-down It has a built-in driver and a potentiometer for positional feedback. It's super-easy to use (assuming you have a microcontroller). You just supply power and then feed-in pulse with a certain duty-cycle to set the angle, and it goes as fast as it can to that angle and then holds it as long as the pulse-train remains the same.
There are "continuous rotation servos", but they are simply servos with the potentiometer removed ,and as far as I know, they are only for "hobby use" when someone wants an easy-to use geared-down motor with a built-in driver.
It may not be required but it would probably be super-helpful.
You need to know the voltage to the coil and of course the 'scope won't help unless you have a working turntable to measure.
That should be "easy", but the clock in "basic Arduino" isn't a crystal and it's not as accurate a crystal.
...My old lower-end Technics has a neon strobe wired to the AC line. (It doesn't have any "electronics"... Just a resistor. (1) and it flashes at 100 or 120Hz (one light-pulse per half-cycle).
There are 4 sets of "dots" on the edge of the turntable, with one pair used with 60Hz power and the other pair for 50Hz. In most countries, the power-line frequency is super-accurate so it works great. (2)
(1) I've never opened-up the turntable but it has that classic orange neon glow and I've seen that circuit many times. The same thing is often used as a power-indicator in a power strip. (It's easer than using an LED when you have high voltage).
(2) mechanical AC clocks use a synchronous motor or there are digital clocks sync'd to the power line and they keep time better than crystal-controlled clock or watch.
Electric analog clocks can be "perfect" as long as you don't loose power because (in developed countries) if the generator runs a tiny-bit fast, they'll slow-it down, and over the period of a year or more the number of AC cycles can be exact. (The clock in your cell phone or computer is even better because it's synchronized to a remote atomic clock.)
The tiny frequency variations won't be noticeable (not even measurable with "standard equipment") and there are turntables built with AC synchronous motors. They are used in turntables with belt drive (or drive-wheel) because they rotate too fast for direct drive, and the speed is not adjustable. A turntable with a synchronous motor doesn't need any electronic circuitry.
14W should be enough to spin a record, but to me it "seems low" for the high-torque SL1200. If you know the coil voltage, you can measure the coil resistance and then calculate the required maximum current (and wattage). Everything AC powered should be marked with the required voltage and wattage, and most of the watts go to the motor.
It's not impossible but to build something that would work as good as their PLL speed control from scratch just isn't practical.
1 Like
So basically it's better to pay too much for out of production components than to build a replacement? Or even just throw out all the drives and stick another drive on it?
It's a shame that we're throwing away perfectly good turntable because of one lousy chip (and not even an advanced one at that).
Planned obsolescence at its finest.
I do have another functional turntable but I'm afraid to do anything else to it fearing that I could render it nonfunctional.
If it was my turntable and even though I probably could build a replacement and my own time is free (don't need to pay myself) I would still buy the ICs.
1 Like