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2.5 Adaptive Speed Control
– PID
Once you have the controller board installed and providing basic 33.3 or 45 rpm
operation; the IR sensor is installed, adjusted and correctly displaying the platter RPM
to a reasonable degree of accuracy (i.e. around 33 or 45 rpm) then you are ready to
enable PID control.
The advantage of PID control is that it reads the actual platter rotation and
compensates for any wear in your components (and stylus drag). It does this by
calculating speed corrections every 50ms using a PID control algorithm. You should
be able to achieve rotation speed accuracy to at least two decimal places. Typically,
the third decimal place will fluctuate.
To enable PID control connect your Laptop to the USB port and go into 1. System
parameters menu. Step through the configuration until you reach “Are you using PID
and platter sensor” – set to Yes and quit out to the main menu. Consult section 2.5.1
to see if there are specific PID values for Kp, Ki and Kd for your turntable. If there
are, use option 3 Set PID control variables and step through the questions setting
values for Kp, Ki and Kd. Quit out to main menu and write the changes to EEPROM
using option 6.
You may find the turntable takes a little longer to reach initial speed (around 8-12
seconds) but when running the accuracy of rotation speed should be far enhanced.
2.5.1 Turntable PID values
If you can find your turntable in the list below you can probably skip the PID Tuning
sections and just enter the values for Kp, Ki and Kd either by using the serial terminal
or the PIDTuning windows application. The boards come supplied with Linn LP12
parameters set. This should get all turntables going with a basic initial set of
parameters. However, you may be able to reduce the time to stable rpm values by
adjusting the parameters below. Please read section 3.2 before attempting to work out
specific PID values for your individual turntable make/model.
Turntable Model Motor Kp Ki Kd
Linn LP12 Linn/Airpax/Philips 2
phase synchronous 0.25 0.25 0.191
Manticore Mantra Airpax/Philips 2 phase
synchronous 0.4 0.31 0.191
If you are able to improve on the parameters listed above, please email us with your
turntable details (as per above table) so we can update the table for other users.