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Electronic

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Breakdown

EQ Track hardware is built around an AT90 USB Key device.

A power electronic board interfaces the device 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 (cf. EQTrack basic for the keypad description), through a 3 wire interface (5 V, Ground, Data).

And the USB plug of the AT90USBKey interfaces to a laptop for LX200 protocol over a serial port emulation, and maintenance.

Download the schematics from the files section to build the power electronic circuit card.

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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... To be completed

• Bipolar : there are only two windings, the order of the phases is controlled by the sense of the current in the winding... To be completed.

In either case, the rotation sense can be reversed by swapping pins.

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)

USB

The USB multiplexes two interfaces :

• A standard serial port profile, over which LX200 protocol can be exchanged.
• Maintenance endpoints, which allow to tune all software settings and monitor the controller (with a dedicated software).

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