The ARTA Turntable Project (Summer 2016)

Info: ready to use interface modules can be obtained in our shop at http://www.m1n1.de/shop/

From time to time I get involved in some kind of special projects,where I can provide my expertise in PCB design, layout and production. In this case I was asked to support the design of a USB interface for a motor control.
I tried to keep it simple and reliable using minimal number of components which are easy to obtain and versatile in its application.
Together with Dr. Heinrich Weber (ARTA) and Wim Huyghe (PIC Software) we developed the little driver module below.
It is capable of driving two indepentant channels (Full Bridge) for either a Stepper Motor, or using only one PWM controlled channel for a DC motor.
In parallel the PIC accepts the signals of an encoder mounted on the DC motor, for high accuracy positioning of the Table.

DIY ARTA Automatic Loudspeaker Turntable Drive from dougie on Vimeo.

 Here is a LINK to the Video, how to build your own Trntable

In this project we will use a DC motor with encoder and Wim was so kind providing the software for the PIC. As the Motor is not able to draw more current from the driver IC (an Allegro A4970 FullBridge Driver) even when blocked, I decided against a current limiter function, for making the PCB design easy and reliable.
The rest is quite straight forward: a 5V regulator and some capacitors for smoothening the power supply even the motor draws some more current.
The PIC provides an USB slave interface out of the Box and connections to the motor are made using standard terminals.
 

Wiring up the module is quite simple.You need 2 connections for the DC Motor, 4 for the incremental encoder and 2 for the 12V supply.
 

Function

Pololu 12V Motor

Phidgets 12V Motor

PCB Connector Pin

Motor DC Power (-)

black

(own choice)

3

Motor DC Power (+)

red

(own choice)

4

Hall Sensor 5V DC

blue

red

5

Hall Sensor GND

green

black

6

Hall Sensor Out A

yellow

white

7

Hall Sensor Out B

white

brown

8

Module Supply +12V

1

Module Supply GND

2

The positioning accuracy is really quite nice and should enable automated measurments on a very high quality level. Please see a chart of the measured deviation below.

Below you can see some pictures of the device in operation, measuring a spaker in an anechoic chamber..Because the control software is seamlessly integrated in ARTA,it makes measurements a charme, which would be quite time consuming otherwise.