Observatory automation project - need advice

Using Arduino Project Guidance
1

So I have a little backyard observatory with a rotating dome that I purchased used in the fall. It came with motor to open the shutter and 2 motors that rotate the dome so that the dome slit is the same direction as my telescope. My primary interest is astrophotography and I'm able to control all of my image acquisition steps by remote controlling a laptop that's inside the dome and connected to telescope mount/imaging camera/guide camera/etc, all from inside the house. However the dome does not track with the telescope, so I have to go out every hour and turn the motors on to rotate the dome in one direction or another so I'm not taking pictures of the inside of the dome. I'd like to try and fully automate this process so I can rotate the dome from inside the house, open/close the shutter, and turn on/off equipment inside the dome. Perhaps one day track the domes position and have it sync with the telescope, but for now manual control from inside the house is a good start. I will be attaching a webcam to the scope so I will know if things are lined up from inside.

I've never owned an Arduino before, but I'm pretty tech savy and enjoy tinkering, but I realize I don't know what I don't know and I could use your help to make sure I don't fry anything.

I have an Uno on the way and an 8 channel relay. The wiring looks straight forward between the arduino and relay. Relays will be dedicated for the following:

Energize dome power supply for shutter and rotation motors (this is just a transformer that makes 12v DC available for the motors)
Open the shutter (timed operation, separate relay with a magnetic sensor cut the power when it's completely open/closed, this came with the dome) 12v DC
Close the shutter 12v DC
Rotate the dome clockwise 12v DC
Rotate the dome counter-clockwise 12vDC
Power up camera (AC power)
Power up mount (AC power)
Power up EL panel (AC power)

I don't have an electrical engineering background and my astronomy equipment is very expensive, is there anything I need to add to this system to protect it from any kind of electrical surges? This is my biggest concern, please be honest.

I found some sample code to turn the relays on and off for timed duration's, but I need manual control over actions like powering the camera on or off and rotating the dome for 2 seconds or 5 seconds or 60 seconds. What's the best way to go about this? Do I need to create some kind of GUI or is there a way I can send commands in real time to the arduino? It will be connected via USB to a laptop at all times.

I hope you all can help me make this project a success. I'm sure I'm leaving out a lot of information, please let me if there is any info that would help.

2

First, you need to make sure that you have AC relays are for AC and DC relays for DC. They are not interchangeable.

If the Arduino is going to be plugged in to the laptop, how are you going to transmit the required signals to the relays? A long cable?

What are the motor's specs? current rating?

How are you powering up the camera etc? Light switch? Control panel?

We need more info on the existing system. A schematic would be great, but a hand drawn diagram would suffice.

BTW, post some pics of the setup, curious as to what you got!

3

this is a very simple fix. the telescope rotates. put two whiskers on it. when a whisker breaks the opto-interrupter, the dome rotates until it clears. the dome takes lots of little steps and always leaves the telescope near the center of the opening.

if you put a reflective dot on the telescope and an IR emitter/receiver (simple chip)
you will get nothing until the reflector is in the view.
every time it is in view, the motor would turn on and move, the dome would move this out of view.

I would offer that a PWM on teh motor would allow it to move slowly and not jump. or, you could feed it to the arduino and do some software.

this would be a very simple project, great for a first project.

4

I do not like relays for the noise on the power line.

if you give us some more information about the drive motor and any existing drive control, we can help walk you thru this.

5

Thanks guys! I worked on a few things to answer your questions, so here it goes

codlink:
First, you need to make sure that you have AC relays are for AC and DC relays for DC. They are not interchangeable.

Understood, hopefully my diagram below will make this clear.

codlink:
If the Arduino is going to be plugged in to the laptop, how are you going to transmit the required signals to the relays? A long cable?

Correct, the laptop that is permanently inside the dome will be connect to the Arduino via a short USB cable.

codlink:
What are the motor's specs? current rating?

Motors had no markings or stickers unfortunately, but I do have a kill-a-watt meter and measure the draw from each device during operation (all at 120v AC)

Shutter Open/Close: .9 amps
Rotation: 1.7 amps
Laptop: .4 amps
Mount: Max .7 at max speed in both directions, .15 when guiding (most common)
Focuser: .07 when focusing
Camera: .4 startup (thermo-electric cooling active), when cooled tempurature reached .25
EL Panel: Unknown, maybe .1 amp

Typically only 1 or 2 devices will be under load at any given time. The total load at any given time should be less than 2.5 amps at the UPS system.

codlink:
How are you powering up the camera etc? Light switch? Control panel?

There is no switch on the camera, it powers up when it's plugged into the outlet.

codlink:
We need more info on the existing system. A schematic would be great, but a hand drawn diagram would suffice.

I made the schematic of the new system below. The existing system has manual switches that close each circuit for shutter and dome control, so it's pretty much the same as the below with manual switches in place of the relays. All the stuff on the right side I just manually plug in and power up.

codlink:
BTW, post some pics of the setup, curious as to what you got!

Sure! Didn't take any pics last night, but here are some that were on my phone. I included a couple of my astrophotos as well: Dome automation - Album on Imgur

6

dave-in-nj:
this is a very simple fix. the telescope rotates. put two whiskers on it. when a whisker breaks the opto-interrupter, the dome rotates until it clears. the dome takes lots of little steps and always leaves the telescope near the center of the opening.

if you put a reflective dot on the telescope and an IR emitter/receiver (simple chip)
you will get nothing until the reflector is in the view.
every time it is in view, the motor would turn on and move, the dome would move this out of view.

I would offer that a PWM on teh motor would allow it to move slowly and not jump. or, you could feed it to the arduino and do some software.

this would be a very simple project, great for a first project.

Those are very interesting ideas! It would greatly simplify things, I wouldn't have to sync up with the telescope coordinates given off by the software which was going to be challenging. Wind may be a concern with the whiskers, it can get pretty gusty, though anything over 20mph I probably won't be imaging as atmospheric turbulence would ruin the pictures anyway. I'm wary of putting any electronics on the rotating portion of the dome that require wires going to the lower half of the dome, as the dome rotates they would be ripped out. The shutter is able to operate only at a precise position as there are a couple of contact plates that line up and supply power to the shutter motor.

The IR emitter may cause issues with taking pictures, one of the cameras is sensitive to IR light (its modified for full spectrum, though I usually have a filter to get rid of most IR light)

Thanks! Look forward to hearing more!