A journey through automating a dome without breaking the bank

[RolandKol]

Very Nice SteamPunk style Dome!
Enjoyed to read from A to Z  

Especially to see how the motor suspension solution works

Thanks a lot for sharing!

P.S.
Will you automate the roll off roof also?

[JSeaman]

I wasn't going for steam punk but I guess that fits!

I was going to automate the roller door but really would like an excuse to go outside at least once on an evening so will leave it for now. When Summer hits (?!) I'll be taking the door off to re-make this and fibreglass it properly so may have a play then.

[tooth_dr]

Fantastic read. Well done. 

[skybadger]

Thanks for that. Interested in your approach to setting up Alexa ?

 

[JSeaman]

I have two smart plugs, one powers on by default and switches on the vast majority of the kit. The other one is switched off by default for the QHY10 (I only want power to that after USB is switched on and connected to the PC). I can then tell 'her' to turn things off when I'm ready. I also use it to power my PC on and off but I shut down programatically so don't need it at the end of the session. I had to use a wifi extender to get coverage up the garden but otherwise it works very well (and there is a USB port on the plug which is permanently powered and I use this to power my LEDs around the edge all the time)

[skybadger]

Thanks for that.

 I have an Alexa and have created a script in node-red , just looking for shared experiences there. 

 

[sloz1664]

Great imagination and methodology on achieving your Semi-automated Dome

Next step... the Shutter ?

Steve

[JamesF]

Brilliant!  Lots of lateral thinking there, and an excellent solution in the end.  I love the use of the car timing belts to turn the dome.  Seeing the video of the dome rotating was great   Well done.

James

[Gina]

Very interesting indeed - a great read and a great solution - love it

[JSeaman]

I was tempted to get a bit more involved with Alexa but settlted myself into some code for running the imaging instead

The shutter may follow, it seems to be a popular demand!

Thanks for all the feedback

[sloz1664]

Just seen the video. The dome is turning at a fair lick and could cause damage to the drive belt teeth or de-bond the belt due to the inertia when the dome starts and stops. I use a motor controller and have slowed my dome down to 60 secs per revolution to combat this issue.

Steve 

[JSeaman]

Yes, if you read the comments this was on a car battery at +12V. It is now running off a power supply at 9V/8A and is much softer on the belt

[JSeaman]

 

With the long Summer nights are in full flow, I decided to update the observatory a little. The conductive fabric was crude and the geometry of the scope position (imaging and guide) didn’t work well to reliably trigger. I decided it was time to use time. I tried to keep things simple looking at triggering a 555 timer board periodically with relays but that ended up being more complicated than accepting an Arduino into my life.

I ordered a £20 starter kit which is an incredibly useful package containing all the sensors and bits and bobs to make your first project. I have a software degree so coding it was a doddle but the electronics is where I had to work a bit harder. By the point of completion, the functionality is:

 

1.       I have a configurable timer (in 1 minute increments) and a configurable output (in 10mS increments) to drive some outputs i.e. the dome

2.       There is an LCD display which shows me how long it is until the next move and various other things

3.       There are three push buttons which can be used to manually drive the dome or navigate a menu system with various settings

4.       Two TP122 transistors drive the relays which ultimately make the dome rotate

5.       A simple protocol is supported for USB comms to the board but not required in normal operation, this allows different levels of tracing (output text) for debug purposes

6.       EEPROM is used to store/load settings (the pulse frequency and duration amongst other things)

 

I have removed the proximity sensors, springs and fabric sheet and made my own little breadboard. I then moved to veroboard for a prototype before the final design as shown in the pictures

Spinning the dome one full RPM took about 34 seconds. Based on 86,400 seconds per day this is 1 second of dome rotation for every 42 minutes of time or roughly a 250mS pulse every 10 minutes. I sanity checked this based on how long I know it takes for a typical star to move across the end of the garden and it looked close enough to sidereal to try. Last night I got a clear hour and proved it to be correct.

I need to make the LCD turn off after a minute off no buttons being pressed as it is quite bright! Other than that it seems to work very well so I think I’ll call that a solution.

 

Arduino pin outs

                SCL – No connect

                SDA – No connect

                AREF – No connect

                GND – One side of the push buttons and the transistor emitter

                Pin 13 – Push button (menu)

                Pin 12 – LCD Register Select

                Pin 11 – LCD enable

                Pin 10 – TIP122 base through a 1k resistor

                Pin 9 – TIP122 base through a 1k resistor

                Pin 8 – LCD Data

                Pin 7 – LCD Data

                Pin 6 – LCD Data

                Pin 5 – LCD Data

                Pin 4 – Speaker (so I can do an old fashioned beep beep startup!)

                Pin 3 – Push button (anticlockwise)

                Pin 2 – Push button (clockwise)

                Pin 1 – Serial comms

                Pin 0 – Serial comms

 

LCD Pin Out

 

                VSS – Ground

                VDD - +5V

                V0 – 10K Potentiometer to 5V

                RS – Pin 12

                RW – Ground (always writing)

                E – Pin 11

                D0 – No connect

                D1 – No connect

                D2 – No connect

                D3 – No connect

                D4 – Arduino Pin 8

                D5 – Arduino Pin 7

                D6 – Arduino Pin 6

                D7 – Arduino Pin 5

                A - +5V

                K – Ground

 

Pot

 

                10KOhm potentiometer was used to provide adjustment to the LCD backlight

                                Pin 1 goes to ground

                                Pin 2 goes to the LCD (V0 pint)

                                Pin 3 goes to +5V rail

 

                Adjusting the brightness is necessary, especially when switching between 5V and 12V power sources

 

Transistors/Relays

 

                A TIP122 transistor is used to trigger a standard Bosch 5 pin automotive 12V relay. Per the previous posts, this is used to drive the motor forwards/backwards

 

                The TIP122 allows the power hungry 12V 5 pin relay to be switched by the output of an Arduino pin

                Pin 1 (Base) goes to the Arduino pin via a 1K resistor

                Pin 2 (Collector) goes to the relay ground side of the switching pins (85/86)

                Pin 3 (Emitter) goes to ground

 

                Essentially, when the Arduino pin is set high, the base of the transistor pulls a small current and switches a ground connection to trigger the relay. To avoid a spike when switching, 1N4002 diodes are placed across the relay’s switching pins.

 

My only problem now is that my QHYL5-IIC has stopped talking and the QHY8L seems to be a bit intermittent too. Maybe it's time to go for an Atik ...

 

[JSeaman]

After several time based revisions, I have just finished what I hope to be the final solution to the dome rotation problem!

I've taken two Sharp GP2Y0A02YK0F IR sensors and mounted them on extensions either side of the telescope. With a complete Arduino re-write and a move to 5V relays instead of 12V I now have a fairly neat system. Whatever orientation the telescope is in, and whatever speed it travels, as soon as the IR sensor detects the dome, it kicks the motor up and rotates.

All that's left to do is try it but sadly the weather's not being kind for the next few days. I'm sure there will be some teething problems but it feels like this is the right solution.