Thursday, 2 August 2012

Here but not here

Just thought I would send out a quick note that I am currently away, out of country, for an extended period on a work project.  No time for my favourite hobby nor much time to add anything to the blog.  To those who continue to check in and follow me, be assured that when I return I will resume the project and bring it to termination.  So check in every now and then for new posts and in the meantime thanks for your patience.

I sure hope I remember how I built this thing when I get back !!

Have a great summer.

Friday, 6 July 2012

First Dry Run - Ariston RD11 and Bi-Onda Controller

Since I am getting ready for my extended trip for work, I don't have a lot of time to devote to the Bio-Onda controller project.  Even worse is that I am having to pack everything away, which is making my wife very happy of course, but me sad.  Before I packed everything I did want to do a full dry run, that is to connect the controller to the Ariston RD-11 turntable and see everything turning in beautiful harmony as driven by the controller.

But before I could that, I did need to do a little bit of work on the Ariston's motor.  I heard a definite cyclic clicking noise coming from the motor and a bit more motor noise than would be considered normal.  Remember I had bought this turntable from a guy on a local internet classified, I have not done and servicing or reconditioning of the table yet. Suffice it to say for the moment that I did put some time into caring for the motor, after all it has a good 30 or more years of service under it's belt, definitely time for a little TLC!  I will not describe what I did with the motor in this posting, I will reserve that for another post later on.  I did get the motor working fine, much quieter.  So stay tuned for that info at a later date.

I did remount the motor and put the turntable together with the Bi-Onda controller driving the motor fully.  It worked great, sped the platter up no problem, spun nicely.  I tried out the 33.3 rpm and 45 rpm, the acceleration of the motor/platter looked good with the 'basic' values I had programmed before.  Speed was good.  I was especially curious to see how it ran at 45 rpm and was very happy with that.  I did notice that the speed, as per my default setting was a bit slow, but increasing the sine frequency by about 0.3 Hz brought it nicely up to 45 rpm, on the nose.  Me happy.  I did not spin any vinyl though, the table mounts an SME 3009 Improved and I have not set it up yet.  A full turntable reconditioning is slated for this unit, hope to make that into another series.

So far so good.  That was all the time I had for testing, I had to start putting all the equipment neatly and safely away until my return.  Geese, just when it was getting so close and running so well, now I will have to wait to finish it.  Sorry I could not include any pictures, was just too pressed for time.


Wednesday, 27 June 2012

Forced Break

Well, just as everything was coming together and I was close to the end of this project I am now having to delay it.  It looks like I will be away and tied up with work for a few months and so will have to delay this project.  Bummer.

If I can work on anything while I am gone, then great otherwise continuation of the project will have to wait for my return.

I hope that I can still post something to the blog every now and then, maybe on some other topics other than the motor controller.

Tuesday, 12 June 2012

Feature Review

Since the first version of the software is now complete I was thinking this might be a good occasion to summarize the features and functions of the Bi-Onda TT motor controller as they are now implemented.  I must admit I had an idea for a new feature last night but I will keep this on the back burner for now.  Gotta stop somewhere.

So let's take a look at the feature list.

  • Dual DDS sine wave generation.
  • Adjustable frequencies with a resolution up to 0.01 Hz.
  • Micro controller DDS generation, 16MHz quartz clock, interrupt driven
  • Chebyshev low pass filters
  • Power Op-amp amplification up to +-15V with transformer boost to 120+VAC
  • Adjustable output levels
  • LCD 16x2 character backlit display
  • 33.3 & 45 RPM speed generation
  • EEPROM storage of calibration settings
  • Remote expansion header to allow incorporation of all, or some, operating buttons into the turntable, parallel to the buttons on the Bi-Onda.

Operating Modes
User selectable operating modes:
  • Continuous always-on mode with single or dual sine wave out as mains source
  • Switchable on-off mode with dual sine wave, phase shifted for direct drive of motor coils

Run Mode
  • Calibrated sine output for 33.3 and 45 RPM operation
  • Speed selection
  • Speed adjust with selectable resolution: 1.0Hz, 0.1Hz, 0.01Hz (during play and in CAL mode)
  • Incr Decr speed buttons
  • Motor acceleration startup (spin-up)
Calibration Modes
  • 33.3 RPM Calibration
  • 45 RPM Calibration
  • Phase Shift adjustment (1.4 degree steps)
  • Operating Mode selection
  • Acceleration Mode (on or off)
  • Acceleration Parameter Adjust (start frequency, frequency step, step delay)

This should pretty much cover most needs as a power source upgrade or for custom turntables.  The one thing left to do is determine the total power handling capacity based on the components (op-amps, transformers, etc.) currently in use and possible alternatives to drive motors with lower voltage requirements or motors with higher wattage ratings.

Thursday, 7 June 2012

Firmware Finito
(that means finished !)

Now that the hardware is behaving as it should, I decided to get back to the firmware and see about giving it some necessary cleanup.  There were features to add and unnecessary/debug code to clean out.

The main feature I needed to add, and the one that I was hesitant to tackle, was the acceleration feature.  I knew I needed to add an option to spin up the motor gradually rather than the full-on power up I have been using.  The main idea of course is to compensate for the inertia of the platter and belt system, the heavier the platter, the more important this feature is.  In fact, on my Ariston RD11 they designed the motor pulley with a slip clutch to deal with the inertia problem (you will find this on many Thorens turntables as well).

The way the acceleration needed to work is that when the user started up the turntable, the Bi-Onda controller would have to start spinning at a much lower frequency than 60Hz and slowly, or quickly, ramp up to the final frequency set by the user for their turntable.  I concentrated on acceleration and felt that deceleration was not as big an issue and decided to omit a deceleration routine.

My problem was trying to figure out how I would shoehorn this feature into the existing software without having to re-write the existing code or change the overall structure.  While writing a post on a blog for assistance, the ideas became clear to me and I was able to figure out a relatively simple way to implement it that would only require modification of one function subroutine and would work with any action that started up the turntable (calibration modes, 33 and 45 rpm etc.).  That also reminds me that another reason to implement acceleration is the feature that allows the controller to increase the motor speed to reach 45 RPM, this higher drive frequency can cause difficulty in these motors to start turning from 0 to the high frequency of the 45 RPM mode.  Accelerating from a lower speed usually works well in dealing with this issue.

I made the acceleration feature flexible to anyone's needs.  In calibration mode you are able to turn acceleration on or off and you can set your own parameters for: starting frequency, frequency step in Hz and the delay time between steps.  These are all stored in eeprom and only need to be set once.  So you can pretty much set up your own acceleration ramp (linear).

So now I will need to build an enclosure for this unit and put it in operation.


Sunday, 3 June 2012

Dang! It's Working!

The basic electrical tests and scoping show that the new PCB layout is working fine.  Time to hook it up to an AC motor for the real deal.  First of all I wanted to take a look at the stock configuration of my Ariston RD11 turntable, so here is a picture of the 'underbelly' and we can see the phasing cap (yellow) that feeds the second coil of the AC motor.  I took the oscilloscope to the motor to see what the two phases looked like as per stock.
Close up of phase capacitor
Ariston RD11 showing AC motor

Here in the picture you can see that the phase shift is fairly decent by the cap but the waveforms themselves are not the best looking sine waves ever seen.  This is off the 120VAC line voltage.  You can see that the capacitor does affect the quality of the waveforms to some degree, both being affected.

AC at motor coils without TT controller
Time to remove the motor and connect it to the Bi-Onda controller.  I first calibrated both sine waves at the tranformer outputs to 119VAC rms as measured on my multimeter.  I then connected each channel to a coil as per the Ariston configuration: AC direct coil to sine A and the cap shifted second coil to sine B outputs.  When I started up the controller and ran the motor, beauty, turning perfectly.  The motor runs nicely.  I then scoped the outputs to the motor like I did before and here is the photo, the waveforms are very nice and clean sine waves.  Me happy.

AC at motor driven by the BiOnda Controller - clean!

I did check the output and it looks like the voltage dropped about 9VAC with the motor connected and running.  Since the power supply is unregulated, I expected some voltage drop and am happy with that and a small drop should not affect the overall performance.  Now this of course is a no load condition, no platter is being turned so I will have to check it again when the TT is assembled and running the platter.  One very nice thing that I did notice, is an improved torque.  With the motor in stock condition off of the AC I noted how easily I could stop the motor from turning by gripping it with a particular amount of pinch of the spindle.  When driven by the motor controller I noticed that it was still possible, but I had to exert more pressure, thus increased torque.  Nice, not sure I was going to have more torque, but looks like I do.

I also tried changing the sine frequency to alter the RPMs and the motor responded nicely.  I did notice however in 45RPM mode the motor had a problem in starting it's rotation.  As soon as I gave it a bit of a spin it would run nicely.  This likely means that I should add an acceleration routine to the controller software to help the motor spin up, especially for the 45 RPM mode.  I also noted that the motor was spinning backwards, no big problem, just reverse the hookup of sine A & B outputs, but I will look into the software too, could be I incorrectly calculated the direction of phase shift of sine B, which would easily be corrected by changing the subtraction to addition or vice versa, which ever is currently in the code.  Will test that in the next couple of days.

I did play with the phase change too and was able to sense a slight change in the motor's vibrations as I went far off the 90 degree mark in either direction. In the end it felt like a phase shift of 91.4 degrees seemed to provide the least amount of vibration in my hand. 

Next, will have to improve the heatsink, I have been holding off on getting a good one together but I did notice the small aluminum plate I was using getting a bit too warm, so will have to find an appropriate one.  Then I just need to hook it up fully and spin some vinyl.  I do want to do some restoration and upgrading of the Ariston at this point too, so I may do this before putting the unit back into full operation.

Thanks for tuning in, keep checking back!
If you have any questions, feel free to leave it in the comments.

Monday, 28 May 2012

Ver. 2 PCB on test bed.
Update on Testing

Just a brief update on the tests with PCB Ver. 2 for those following.  I have fully connected the op-amps and output transformers and the waveforms look excellent.

They are very clean, stable and no signs of noise or ripple.  So far thumbs up. You can see the new layout in the photo above. 

Scope shot of dual sine waves at 60Hz
It is still using the hand wired button panel, not expecting too much trouble from the PCB for that. Here is the first posting of a picture of my oscilloscope output of the two sine waves.  This is during a run at 60Hz with 90 degree phase shift.  All in all, looks ok.  The waveforms have been scoped at the output of the boost transformers, so this is what would be feeding the motor.

I will now have to proceed to rewiring my turntable for dual power, for each coil, and drive the turntable motor.  May take a few days, I have to clear some space on my makeshift bench.

So far no tweaking of any components was necessary, so values look acceptable, at least before load and current testing starts.