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Basic-Tutorial

Jean-Etienne LAMIAUD
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eqtrack-basic-tof.JPG (23559 bytes)

Tutorial

Software

You will need to install the GP Utils tools (http://gputils.sourceforge.net/) to build the executable files ; and GP Sim (http://gpsim.sourceforge.net/) to run the unit tests (apply the GP Sim PWM timing patch ID 1623165 if not merged into the main stream).

To build the executable files, open a Terminal window :

  • change directory to the "prod" folder in your copy of the EQ Track Basic source code tree : cd <source code path>/prod where <source code path> is the file system path where you have placed the EQ Track Basic source code tree.
  • launch the build of the two executable files
    • make equa_4_1.hex
    • make keypad.hex

To build all the executable files and run all the unit tests :

  • change directory to the "prod" folder as above.
  • launch the complete build
    • make

The executable files are the files named equa_4_1.hex and keypad.hex in the "prod" folder.

Hardware

Decomposition

EQ Track hardware is composed of two parts :

  • The main controller, which was built around a PIC16F876A ; any compatible recent Microchip PIC can be used. The main controller is connected to :
    • The 12 V DC power supply (VCC and Ground),
    • The two stepper motors (2 x 4 phases + Ground), either unipolar or bipolar,
    • The keypad, through a 3 wire interface (5 V, Ground, Data).
  • The keypad, which was built around a PIC16F628, any compatible recent Microchip PIC can be used. The keypad is only connected to the main controller, and uses 4 buttons and 3 switches to control the system.

Here is the controller built by a friend ; quite different from my own "small black box" controller.

Programming

The software hex files shall be programmed into the microcontrollers :

  • equa_4_1.hex into the main controller PIC16F876A or compatible,
  • keypad.hex into the keypad PIC16F628 or compatible.

Many PIC programmers can be used for that purpose.

The main controller board has a PROG connector for In Site Programming.

Connections

Power supply

The power supply cord shall be connected to the RED and BLACK connectors of the main controller ; of course, RED connects (through a fuse) to +12 V and BLACK to the ground.

A fuse shall be placed between the +12 V conductor and RED, to protect the hardware from mishandling (inversion of polarity for example).

Motors

The stepper motors connection to the main controller depends on the kind or motor (cf. article "2 phases stepper motors" for details) :

  • Unipolar : the phases windings are connected to a center tap ground. The right ascension motor windings shall be connected to the pins 1 to 4 of the main controller MOTORS connector, and the center tap grounds to the common ground pin 9 ; the declination motor windings shall be connected to the pins 5 to 8 and 9 for the common ground. The order of the steps is 1, 3, 2, 4 in right ascension, and 5, 7, 6, 8 in declination. The order of the windings shall be determined from the motor documentation, or by testing.

  • Bipolar : there are only two windings, the order of the phases is controlled by the sense of the current in the winding. The right ascension motor first winding shall be connected to the pins 1 and 2 of the main controller MOTORS connector, the second winding to the pins 3 and 4 ; and the declination motor to pins 5 and 6 for the first winding and 7 and 8 for the second winding. The pin 9 is not used.

In either case, the rotation sense can be reversed by swapping pins 1 and 2 (or 3 and 4) in right ascension, 5 and 6 (or 7 and 8) in declination.

Keypad

The keypad connects to the main controller through 3 wires, from the keypad CONN1 connector to the main controller UART connector :

  • CONN1 pin 1 to UART 1 (Ground)
  • CONN1 pin 2 to UART 4 (5 V)
  • CONN1 pin 3 to UART 3 (Data)
Settings

Adjust the main controller R3 resistor so that the LED starts flashing amber when the power supply voltage drops below 11.5 Volts.

Once everything is built and connected, you can start using EQ Track basic. The User manual page explains how to use the keypad.

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Related

Wiki: Basic
Wiki: GoTo-Tutorial-Electronic

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