CONTROL BY ARDUINO AND SKYPIKIT OF A LX200 GPS MOUNT€¦ · LX200 GPS telescope which has stopped working well. With this modification, there is no more electronics inside the mount

CONTROL BY ARDUINO AND SKYPIKIT OF A LX200 GPS MOUNT

Revision 20.02.15

CONTROL by ARDUINO and SKYPIKIT of a LX200 GPS MOUNT

Project description 2

This project is mainly used to replace the electronics of a LX200 GPS telescope which has stopped working well. With this modification, there is no more electronics inside the mount. All circuits are in an external control box including the ARDUINO and the PLEIADES circuits described in another document. We try to keep existing functions as much as possible. We use the same motors and gear systems. We even reuse part of the existing wiring. However, boards must be added to allow the control signals from the external control box to be routed to the right ascension and declination motors and encoders. This is done with boards that replace the front panel of the base of the mount and a small green board that installs in the fork and that facilitates the connection of cables to the declination motor. The telescope thus modified is no longer compatible with the MEADE LX200 protocol at all. It now uses the SKYPIKIT protocol. It can be controlled directly with the COELIX software and the SKYPIKIT FEX application. An ASCOM Skypikit driver will be available later.

This telescope can easily be used for visual observation in autonomous mode with the simple handbox. It can be used for autoguided astrophotography, using for example PHD2 Guiding. It can also be controlled remotely over the Internet using an application like TeamViewer.

FUNCTIONS AVAILABLE WITH SKYPIKIT FEX - Tracking control at sidereal, solar and lunar speeds; - Autoguiding with an autoguiding camera with adjustable

corrections between 15% and 200% of the sidereal speed;

- Continuous displacements (SLEW) at adjustable speeds from 30% of the sidereal speed up to 1° / second;

- Steps displacements (STEPS) adjustable from 1’to 5°; - GOTO and SYNC functions with COELIX APEX software. See the document on PLEIADES boards for more details.


The original mount (before modifications) 3

Declination

Front Panel

Base


The original circuits removed 4

Circuits removed: the front panel, the two motor controllers, opto-detectors in R.A. We are trying to keep some of the existing cables to assign them to the same or other functions.


Elements of the new system 5

Telescope base and fork

External box with PLEIADES and ARDUINO circuits

Simple handbox for control in autonomous mode


Cabling diagram 6

There are no longer electronics inside the mount


New boards that go inside the telescope mount 7

Front view

Inside view

NEW BOARDS INSIDE THE MOUNT


Front panel and base board (schematics) 8


Front panel and base board (cable connections inside the telescope base) 9

The original mount contained several cables that connected the front panel to the circuits located in the arms of the fork. The only one of those cables that is reused is the 6-wire cable that went to the declination motor controller. We also reuse all the right ascension cables: either for the motor, the encoder and the Hall effect detector.



The connector P3 on the left contains the 6 wires cable which go to the declination motor connection board in the right arm of the fork. The other connectors are for the right ascension motor.



6 conductors Meade cable going to the fork

R.A. motor

R.A. encoder

Hall effect in R.A.

Respect the sequence of colors when making the connections


Connection board to the declination motor (schematics) 12


Connection board to the declination motor (cable connections inside the fork) 13

6 conductors Meade cable coming from the base

Declination motor

Declination encoder

Respect the sequence of colors when making the connections


Connection board to the declination motor (motor cable connections) 14

Note the three cables used for the declination motorization: - The two-wire cable connected to the motor

winding. - The four-wire cable connected to the motor

encoder; - The three-wire cable of the Hall effect

detector that is not used.


EXTERNAL CONTROL BOX 15

EXTERNAL CONTROL BOX


External control box (front view) 16

12 volt DC power input Center positive 2.5-5.5mm jack

ON-OFF switch

Tracking setting in autonomous mode

DB9 R.A. and decl. cables

USB-Bluetooth switch

Simple handbox socket

Bluetooth status indicator: flashes if not paired;

on if paired.

Autoguiding camera socket


External control box (interior view) 17

R.A. controller Decl. controller ARDUINO

See the document on the PLEIADES set of boards for the description of the boards contained in the control box.


Tracking setting in autonomous mode (without computer) 18

On its back, the ALCYONE-3 board contains a connector for the simple handbox, a Bluetooth module and the USB-BT switch. It also contains LEDs and a connection to a push button to set the tracking speed in autonomous mode. The ARDUINO program controls the operation of the TRACK button. We press the button until the LEDs indicate the desired state: - All LEDs off = tracking OFF - LED 1 on = sidereal tracking - LED 2 on = solar tracking - LED 3 on = lunar tracking When control is via USB or Bluetooth, manual control becomes inactive. You will then see the tracking status on the computer or tablet screen.

TRACK button connections

Simple handbox socket

Bluetooth module

USB-BT switch


DB9 cable connections (pins identification) 19

Female receptacle on the front panel of the mount

Male connector at the end of the DB9 cable


DB9 cable connections (wire assignments and colors) 20

# wire Wire color Function

1 Black M2

2 Grey M1

3 Yellow enc. Gnd

4 Violet enc. B

5 Orange enc. A

6 Red M2

7 Brown M1

8 Green enc. Gnd

9 Blue enc. 5V

These colors are valid only if you have the cable model 710-10011-00200 of CNC Tech (Digi-Key # 1175-1147-ND). Otherwise, check with a multimeter and make a color table.

The following wires are connected together: M2: 1 (black) with 6 (red), M1: 2 (gray) with 7 (brown), Gnd: 3 (yellow) with 8 (green).


DB9 cable connections (connections to the MEROPE-3 board) 21

9 5

3-8

4

2-7

1-6


Diagram of the power supply circuit of the external box 22

8A Connects to the PS1 connector on the ALCYONE-3 board

Jack connector 2.5-5.5mm Center positive

fuse

Fusible 8A


Calculation of the control settings for the LX200 GPS motors 23

CALCULATION OF THE CONTROL SETTINGS


Calculation of the control settings for the LX200 GPS motors 24

Settings calculations with the Skypikit Motor Tester Tuner application. See the document on this application for explanations.


Settings for controlling the right ascension DC motor 25

Insertion of parameters in the Skypikit FEX control application. The KP, KI settings were also found with the Skypikit Motor Tester Tuner application. The negative final approach of -2000 directs the telescope west in the same direction as the tracking. The Invert DIR signal must be set to YES so that tracking is done the right way for a telescope in the northern hemisphere.


Settings for controlling the declination DC motor 26


SKYPIKIT FEX control panel 27

Panel obtained with the settings for controlling the LX200 GPS. We put "Side of Pier" at Fork since it is a fork mount. FUNCTIONS AVAILABLE WITH SKYPIKIT FEX - Tracking control at sidereal, solar

and lunar speeds; - Autoguiding with an autoguiding

camera with adjustable corrections between 15% and 200% of the sidereal speed;

- Continuous displacements (SLEW) at adjustable speeds from 30% of the sidereal speed up to 1 ° / second or more;

- Steps displacements (STEPS) adjustable from 1 ’to 5 °;

- GOTO and SYNC functions with COELIX software.


END 28

END

Documents

CONTROL BY ARDUINO AND SKYPIKIT OF A LX200 GPS MOUNT€¦ · LX200 GPS telescope which has stopped working well. With this modification, there is no more electronics inside the mount