Record player / turnable Motor with Ardurino - a good idea?

Other Hardware Motors, Mechanics, Power and CNC
1

Hi guys!

I'm a skilled electronics but - absolutely no plan with motors, ardurino and programming (made PCB layout and was project manager prototyping).
Not at all I have an crazy idea and hope, you can help me.

I want a precice motor regulation on a belt driven high end turnable (in attachment an rendering of my turnable base project, not ready yet).

Want to use a brushed 12V Maxon motor (very quite, ironless rotor) as driving unit. My idea: get the rpm from the turnable by a hall sensor at the 30cm platter (33/45 rpm) and regulate with this data the 12V motor (900-1200 rpm appr.). A small LCD or LED display at the motor station should show the measured value at the platter. At the motor station should be a start/stop button, a switch 33/45 and the display - thats all. The rpm should be regulated digital by software, there should be also a softstart function.

So my questions:

  • is this a good idea?
  • is it possible?
  • is Adorino Uno + Motor shield a good choice?
  • is a hall sensor at the platter a good solution?
  • Can anyone help me in the project? (Will be rewarded after realisation)

Greetings Dago from Switzerland

P.S. sorry about my horrible english; I'm a bit out of practice.

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2
  • is this a good idea?

Only you can answer that. I don't know your definition of good.

  • is it possible?

Yes.

  • is a hall sensor at the platter a good solution?

Again, define good. I would use dark or reflective marks on the edge of the disc and an IR reflective sensor. More pulses per revolution give finer RPM measurement to feed to a PID control loop. Google "arduino PID motor speed control".

  • Can anyone help me in the project? (Will be rewarded after realisation)

That is what the forum is here for. Read the how to use this forum-please read sticky for some advice on how to get the most from the forum.

3

"I would use dark or reflective marks on the edge of the disc and an IR reflective sensor. More pulses per revolution give finer RPM measurement to feed to a PID control loop."

I have a 40mm Diameter base only for using a sensor actually...

4

Just looked with your google search term. Looks interesting. Thank you.

5

Dagolard:
Hi guys!

I'm a skilled electronics but - absolutely no plan with motors, ardurino and programming (made PCB layout and was project manager prototyping).
Not at all I have an crazy idea and hope, you can help me.

I want a precice motor regulation on a belt driven high end turnable (in attachment an rendering of my turnable base project, not ready yet).

Want to use a brushed 12V Maxon motor (very quite, ironless rotor) as driving unit. My idea: get the rpm from the turnable by a hall sensor at the 30cm platter (33/45 rpm) and regulate with this data the 12V motor (900-1200 rpm appr.). A small LCD or LED display at the motor station should show the measured value at the platter. At the motor station should be a start/stop button, a switch 33/45 and the display - thats all. The rpm should be regulated digital by software, there should be also a softstart function.

So my questions:

  • is this a good idea?
  • is it possible?

Yes, many turntables use DC motors under microprocessor control.

  • is Adorino Uno + Motor shield a good choice?

First choose the motor, then choose the motor driver depending on the motor.

  • is a hall sensor at the platter a good solution?

No, you need much better control than that. Something on the motor shaft will be much more
sensitive as its turning more often - your control loop will need to update very frequently to be effective,
perhaps 1000 times a second, in order to have authoratative control in the face of varying load / friction.

The accuracy of control will depend almost entirely on how accurately you can sense the motor speed.

There is a subtlety though, sensing the motor only will not correct for stretch/slip of the drive belt. However
sensing the platter speed is a much harder problem - a more accurate encoder on the platter would allow
for correcting for drive belt, but mechanically may be tricky, and is probably v. expensive.

A different approach commonly used is to use a lot of inertia in the platter and drive a synchonous motor
from a fixed frequency ac waveform. This avoids using a control loop, so is simpler, and typically can work
well as adding inertia to the turntable is very effective and cheap.

  • Can anyone help me in the project? (Will be rewarded after realisation)

Greetings Dago from Switzerland

P.S. sorry about my horrible english; I'm a bit out of practice.

6

May be, I misunderstood anything...

I use a transmission motor : platter of 1:30 (approx.). At the platter actually I plan to use a IR Reflection sensor + a strobe platter with 120 segments. That means, per motorturn I have 4 high/low signals...

I think, that should be enaugh for a good speed regulation - or I'm wrong?

Edit actual ordered setting:
Motor Maxon DCX, 12V / 10W; Motor Driver L928P (up to 2A), Ardurino Uno R3 (Shield + Ardurino Developement boards).

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7

Latency is an issue with control-loops. With your 120 segments you can only update the control loop every 15ms (at 33 1/3 rpm). This means you have a latency of at least 15ms in the feedback, which will reduce the effective loop bandwidth. Latency in inputs is a direct enemy of loop stability, meaning the loop gain has to be reduced, and thus regulation becomes laxer over the short-term (flutter).

This is why many turntable designs use a heavy platter as a means of stabilizing speed on the shorter timescales.

8

MarkT:
This is why many turntable designs use a heavy platter as a means of stabilizing speed on the shorter timescales.

So I have a good chance ;D . The platter weights of my turnable are 5.2kg (clear acryl) and 6.2kg (black POM).

Not at all I will check the number of segments. If the sensor recognition works well, I try to use 240 and 360 marks. Never tried this before, so I have to make some experiments. Not at all - the rubber belt and the heavy platter should do their job.

9

With that much mass you probably just need a synchronous motor.

10

If I wanted to use this one, I had other problems :smiley:

I choosed this kind of motor "because of reasons". :wink:

11

Dagolard:
So I have a good chance ;D . The platter weights of my turnable are 5.2kg (clear acryl) and 6.2kg (black POM).

Not at all I will check the number of segments. If the sensor recognition works well, I try to use 240 and 360 marks. Never tried this before, so I have to make some experiments. Not at all - the rubber belt and the heavy platter should do their job.

This is NOT a good design. Your turning acrylic will generate loads of static electricity which will effect all of your electronics, if it doesn't kill it. Any plastic of any type that is moved will generate static electricity.

Paul

12

I've been told you can spray it with Static Guard (in fabric softener area of grocery store) to dissipate static build up.
I'm working on 3D printing a box to mount a card in and will spray the interior for the same reason.

13

Paul_KD7HB:
This is NOT a good design. Your turning acrylic will generate loads of static electricity which will effect all of your electronics, if it doesn't kill it. Any plastic of any type that is moved will generate static electricity.

Paul

No. It's a question of Acrylic type and Design. As ESD responsible person in my company I have some experience with that problem. We use ESD acrylic windows at our machinery. Additional there are special ESD Coatings, i.e. APL400h by Electrolube.

14

Dagolard:
No. It's a question of Acrylic type and Design. As ESD responsible person in my company I have some experience with that problem. We use ESD acrylic windows at our machinery. Additional there are special ESD Coatings, i.e. APL400h by Electrolube.

Thank you for the update. I know there are ESD safe plastic formulations, but did not know acrylic to be formulated that way.

Paul

15

Paul_KD7HB:
This is NOT a good design. Your turning acrylic will generate loads of static electricity which will effect all of your electronics, if it doesn't kill it. Any plastic of any type that is moved will generate static electricity.

Paul

Static is generated by friction, not movement as such.

Electronics is pretty safe from mild static in the final form, its only uninstalled components that are sensitive because they are handled without the rest of the circuitry connected.

Note every good insulator has static charge scattered about its surface (especially in dry weather), whether moving or not. A sensitive electroscope will detect this. However insulators cannot deliver much charge at once, whereas a human body can (if its walked across a nylon carpet).

The stylus running along a record groove generates loads of static however due to the large friction pressures at the contact points - a carbon fibre anti-static brush is very useful.