Driver ASCOM for dome, focusers and switch

Now I have developed all the others drivers for object controlled by Raspberry application. They are: dome, focuser1, focuser2, focuser3 and switch. All driver was checked with conformance checker and conformance document was generated.

Also in this case communication between driver and Raspberry is done via TCP/IP, using other ports. 

For these reason the Rapberry application was update, now its version is 1.2.0.0. In the resource is presente the new version.

You can find all new drivers and conformance documents in the resource.

Dome driver supports these features:

• Slaved 

• Home finding 

• park 

• Open/close shutter 

Focuser drivers support these features:

• Absolute position

• Maxposition and step configurable in Raspberry application

Switch driver supports these features:

• Ready only analogue value with temperature in the dome

• Read/write boolean value for flat field light

• Read/write boolean value for telescope decondence fan

Driver ASCOM for telescope

 Because of Raspberry controller is able to manage different devices more Ascom driver are needed, one for each device. Now the first driver is developed using Microsoft Visual Studio, thanks to development tools supplied by Ascom Platform. Conformance checker was used to verify and validate it. Conformance document was generated.

Communication between driver and Raspberry is done via TCP/IP, Each driver uses its own port. Raspberry implement a UDP broadcast communication used to make know its IP address to the driver, in this way IP address can be discovered during the driver setup.

 These are the supported features:

• Alignment: Polar
• Sync and async target and coordinate Slewing
• Target and coordinate Sync
• Tracking: Sireal with the possibility set right ascension and declination rate
• Move axis support
• Topocentric equatorial system
• Parking on local meridian at declination 0
• Pulse guide support
• Aperture area and diameter and focal length are from Raspberry controller where can be configured.
• Observatory site location is from Raspberry controller where can be configured.

In the resource you can find driver setup and conformance document

Application Raspberry

 First software version for Raspberry is ready. 

Using Codesys 3.5SP16 and Softmotion 4.8.0.0 an application was developed able to manage in the correct way all devices. This first version is marked 1.0.0.0.

In this version all the user activities are done through web page visible using a browser connected to the controller IP address (http://192.168.3.100:8080/webvisu.htm). Address is assigned to controller by DHCP so can be different.

In the resource: Codesys application for Raspberry you can find the zip file with this software

Home page shows software information and allow the observatory position set up

Telescope page allow the axis control. You can sync or move axis on a position or with drift velocity. It is possibile set the maximum speed and acceleration but for each movement you can have different speed from 0 to maximum.

Dome page shows:

·         States of push buttons and commands for dome motors.

·         Dome position as encoder pulse and azimut.

·         Azimut position for home (home input sensor) and park.

·         Shutters condition and timers

·         Temperature in the dome

Focuses page shows for each focuser:

• Current and target position
• Working and motor enable condition
• Backlash setting.

Application is deployed on more task with different priority and interval time.

• Ethercat task run in highest priority (0) every 4 milliseconds. It generates the position setpoint for both motor and send the Ethercat frame.
• Main task run in medium priority (16) every 20 milliseconds. It manages: State machine for software startup, all digital I/Os directly managed by Raspberry and dome.
• Slow task run in low priority (20) every 10 milliseconds. It manages all I2C devices: digital out for focuses, analog input for temperature reading and FRam read/write.
•  Visu task in lowest priority (31). It manages the visualization of web pages.

 Features

In the FRam are saved two different kind of information:

• Configuration data. Data related to the specific use in your own observatory: observatory location, motor speed and acceleration for axis, dome encoder, focuser Backlash. These data are showed in orange in the page. A button allows the change saving in FRam.
• Application data. Data relating to the current position of motors, dome, shutters, focusers. These data are saving automatically every second and restored at next power up. At power current telescope right ascension is computed so it should be possible do a goto command without a sync.

 

Telescope declination axis can be:

• Synched to a specific position.
• Moved with a smooth velocity profile to a target position.
• continuously moved at low speed (drift) in order to follow object with proper motion (e.g., comet)

Telescope right ascension axis has the same possibility of declination plus the possibility to activate the tracking. Right ascension is correctly computed both with tracking on and off.

 

Dome can rotate both manually and automatically (slaved). Shutters can be open and close both manually and automatically. There are six buttons for dome/shutters management:

1. Dome right
2. Dome left.
3. Sliding open
4. Sliding close
5. Tilting open
6. Tilting close,

When they are pushed alone, they activated manually the function as their name. When push is removed motion is stopped.

Pushing dome buttons together dome enter in “slaved” state so is following automatically the telescope azimuth.

A “double click” on dome right button activates the automatic positioning on home position.

A “double click” on dome left button activate the automatic positioning on park position.

Pushing sliding buttons together it is activated the automatic shutters opening.

Pushing tilting buttons together it is activated the automatic shutters closing.

 

Focuser step motors are activated when the target position is different than the current position. Motors are driven with fixed frequency 100hz in start-stop way. It is possible define a forward or backward backlash compensation.

Hardware ready software in progress

I have mounted Raspberry board, I/Os boards and rele board an plastic supports. These was arranged with DIN rail hangs so they are finnaly mounted on two DIN rail.

Now DIN rail are placed on a wood support in order to have an easy equipment for testing. In the final deployment they will be placed in the observatory frame. 

A temporary panel with push buttons is attached the the system. These are for symulation of buttons and sensors in obervatory. In this way is easy develop and test the application. 

Now is only matter of software. 

The developping of the application is alreay started, I hope to be ready in one week.

Step motor board

Hello to all,

 In the time from last post I have designed an realized the board for step motor driving.

Three step motors need to be driver by the controller in order to act as focuser. For step motor adapting an L298 bridge is chosen. From the market is possible found chip board with this component and radiator.

 Every board need 5 digital output for driving: Enable, IN1 (A phase +), IN2 (A phase -), IN3 (B phase +), IN4 (B phase -). It is not mandatory have the possibility to move all focus at the same time so phase signal can be common for all motor having maintaining one enable signal for each motor. In this way 3 enable signal plus 4 phase signal are needed.

No more digital output are available directly on raspberry board so the solution for increase its number is the use of a little board with the component PCF8574. It is a remote 8-Bit I/O Expander for I2C Bus

Because of step motor power signal can generate noise in the low power CPU signal is a good solution make outputs optoisolated.

 

This is the board schematic available also as external file 

This Board is designed so to be mounted up the I/O board. Mounting is shifted so to allow the plug and unplug of the connettors from I/O board and Raspberry and from I/O board and relè board

 

IO Baord

Raspberry has 17 GPIO pins able to be programmed as input or output so these can be used as digital I/Os. They manage segnals with few Volts with the same electric potential of Raspberry, it is not a good idea have a long wiring with these signals, the risk is for the incoming noise and electric spike, they could hung up the Raspberry CPU.

For this purpose an expansion board need to be developed where 8 digital signal 24Vcc are optoisolated and adapted to the Raspberry GPIOs voltage and 8 Raspberry digital outputs drives relès. Relés make outputs optoisolated so driven signals can go far way from Raspberry.

For each digital input a this circuit is implemented

For digital output we bought a board from the market suitable for interfacing with Raspberry. Unfortunately this board reveses the commands from Raspberry, this not acceptable because during the Raspberry boot up for a litte time all reles are on. For this reason on the board an 8 inverter ports (74LS240) is applied in order to have the correct driving condition.

An analog input is needed in order to get the current observatory temperature. We bought an I2C analog to digital converter ADS1015. This is able to get 4 single ended signal or 2 differential signal. We select the second option in order to connect one PT100 termoresistor, this assure e low noise signal. This is the only not optioisalted signal so ti can’t go much far away from controller. A trimmable resistance che adjust the current flowing in the PT100 so to have precise measure.

An I2C FRam memory is mounted allowing the controller to save information need to be retained when power down. It has 32Kbyte more than enough.

In the resource the full board schematic is available

Don't forget something

As Alex Osborn said: "ideas evaporate faster than water". I think is better fix all the steps and project decisions in a document so it is possible review them in a long time.

Now in the resource gadget on this page you can find a link to that document. Now it is incomplete but I want update it along this project so at the end it can be use for reproduce and fix it .