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                            ONSTEP UNIVERSAL MOUNT CONTROLLER - EQ5 This is an original and very pretty programming project by Howard Dutton, stellarjourney.com As is a very complete and customizable system i decided to make my own hardware design using Corel Draw X6 and my 3020 CNC. Enclosure of choice was a black anodized aluminum project box, work with aluminum is much hard than ABS plastic but the quality is the best, aluminum enclosure works as electromagnetic shield and heatsink sametime. The basics Onstep works as an extended LX-200 control protocol, it becomes with an Android app and a built-in Wi-Fi web server with configuration and information pages. It has an ASCOM windows driver for the unit and another ASCOM windows driver for the focuser. OnStep can be controlled simultaneously from the USB COM port, WiFi Webserver and Android app, that means, every moving or command take effect on all conected software. For this setup a Mega 2560 from RobotDyn is used, as this board meet my requeriments in size and quality, it has 2 cristal oscilators; one for the COM port and another one for the MCU, this means that the system dont need a RTC (real time clock) to maintain the tracking precise. The WiFi module used is an ESP-07s, industrial grade, it has an electromagnetic shield and a connector to extend the antenna out of the enclosure, for obvious reasons. The system can be used in ecuatorial mounts or alt-azimutal mounts making the right changes on the firmware, you will find the firmware used for the EQ5 at the end of this page. Stepper drivers and motors Many stepper drivers can be used but the right way is a good combination between the driver model, the stepper motors and the power source, 12V in this case For this configuraton TMC2100 drivers are used for RA/DEC and A4988 for the focus motor. TMC2100 drivers are configured to 16 micro-stepping SpreadCycle mode with 256 micro-step interpolation, the stepper mottors are 2 Nema 42, 400 steps, 0,9A with a holding torque of 3,6Kg.cm. The reduction factor for the pulleys is 2,5-1, so the final values are this ones: Micro-Steps per Degree:               6400 Micro-Steps per Worm Rotation:  16000 (600 seconds to complete a full worm rotation) Resolution (interpolated at 256 micro-steps): 0,0023 arc-secs Minimum move: 0,037 arc-secs (interpolated resolution x 16) PEC Sense OnStep PEC can be permanent and stored onto MCU eeprom, and start it via software but aditionally we can call the recorded PEC to re-start automatically when the worm completes an exact full rotation. PEC Sense is optional to use and consits on a simple 2 pin micro-switch installed on the mount worm gear and conected to Onstep PEC Sense imput, when the circuit is shorted PEC restarts. The EQ5 worm gear takes 600s to complete a full worm rotation, OnStep EQ5 firmware is configured to record 600s, for other mounts can be more, up to 3384s. If microswitch installed, the green led lights up when the worm gear completes a full rotation, and then, if configured, recorded PEC restarts. The right moment to start recording PEC is just in the moment when the green led light up. This option if installed is very useful because we can move the mount manually but PEC will restart allways at the correct moment. Refraction rate compensation This feature adjusts tracking rate to compensate atmospheric refraction depending on the altitude where the telescope is pointing to. By default off, can be turned on/off throught Webserver or Android app. I didnt test it but may be much helpful, seems to be in development but some users may had sucess with it, more info on main author discussions forum https://github.com/hjd1964/OnStep Limit Switch This optional feature is enabled on the firmware but take no effect unless you close the circuit between limit pin outs. Implemented for security purposes, you can install 2 micro-switch on both sides of your AR axis to prevent the mount hit the tripod or post. Optional but not fully needed, OnStep limits are hardware/software configurable. Focuser This feature is enabled on firmware, you can control a compatible focusser system based on a stepper mottor or make your own focuser, to use this feature you need to know your stepper focus mottor specs such step angle and current, the driver max continuous current is 1A. To config driver step size there are 3 micro-switchs near to the A4988 driver on the PCB, by default is configured to full step, other focuser settings can be configured on the firmware or ASCOM Driver.  
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WebServer config pages (Click to enlarge)
Web Server In AP mode the webserver configuration pages are located on 192.168.0.1 IP Adress, its accesible via web browser by the user, by default OnStep starts in AP mode, the default password is “password” The command channel is located on 192.168.0.1:9999 this is where the aplications such onstep app, SkySafari,  Stellarium,  ASCOM telescope driver, ASCOM focus driver and other softwars connects to. In Station mode Onstep connects to a configured router credentials, DHCP should be enabled in most cases to easy identifi what IP has been assigned to OnStep (checking the router local nerwork tab)                                                                     
Android app All configurations can be done via android app too, adinionally, the android app has a large database of solar system and deep space objects, custom objects can be added too manually. The interface works very quick due to the main controll is made from OnStep MCU (Mega 2560)
Android app config pages (Click to enlarge)
ASCOM Telescope and focuser drivers Provide compatibility with all telescope and focuser control software, telescope control and focus control can be controlled simultaneously throught IP Adress but via wired USB COM port only one of them can be controlled.
System mounting on EQ5 Custom motor legs has been made for this project to meet my requeriments of keep the motor axis as near as possible to the EQ5 supports, all parts has been CNC machined, this video shows the very summarized manufacturing process and assembling procedure onto the EQ5;
Conclusion and resources This project supossed to me gratefully to make it, as is a very complete, customizable, open source code and works extraordinary well, also has increased my knowledge and skills about electronics design from start to end a complete electronic project with a pretty enclosure. Thanks to Howard Dutton, the firmware developper for his nice work. Also the motors used for this project are suitable to motorize other mounts like Skywatcher NEQ6 or Losmandy Gemini G11, wich is the current project im working now. Firmware used for this setup (moded for EQ5 requeriments): 1.1f   DOWNLOAD ASCOM Telescope driver windows: v1.40  DOWNLOAD ASCOM Focuser driver windows: v1.31  DOWNLOAD Android App: v1.81  DOWNLOAD Original project developper, Howard Dutton:  http://www.stellarjourney.com/ Main project discussion, forum, support and resources: https://github.com/hjd1964/OnStep *In order to work with the firmware, Arduino IDE 1.8.4 must be installed first, then add the ESP8266 to the Arduino IDE boards manager, Mega 2560 and WiFi ESP8266 firmwares must be uploaded separatelly. Once firmware file are unziped open “OnStep.ino”, a list of tabs will be added automatically, all firmware changes should be done on the “Config.Classic.h” tab, save project, select “Mega 2560” board and upload the sketch via OnStep micro USB COM port. *The ESP8266 WiFi firmare is located on “src/addons/WiFi-Bluetooth” patch, open “WiFi-Bluetooth.ino” and rest of tabs will be added automatically, there is no need to work on WiFi firmware, credentials can be changed from the Webserver but is useful for developpers. System specs Current comsumption: Max 1A at 12VDC, 12V is the recomended voltage imput, stepper drivers current output has been fine adjusted to balance stepper motor torque, source voltage, driver heating and GoTo rate, wich is by default 400X (1,6º/s”), GoTo max rate can be increased up to 500X in safe mode, wich is the mode where there is no risk to motor stahl even with the mount counterweights wrong balanced. But still 400X rate is a very well balanced rate unless you wanted to follow a falling star on the sky ;) The low driver heating is dispelled throught the aluminum enclosure, keep the driver heating low increase the efficiency a lot because the driver MOSFET electrical resistance increases with heating. Micro-Steps per Degree:               6400 Micro-Steps per Worm Rotation:  16000 (600 seconds to complete a full worm rotation) Resolution (interpolated at 256 micro-steps): 0,0023 arc-secs Minimum move: 0,037 arc-secs (interpolated resolution x 16) Pulleys reduction factor: 1-2,5 If you want to implement this system to your mount mail to instein.eu@gmail.com
April 2018 By instein.eu  instein.eu@gmail.com
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