Roll off Roof safety switch

[Padraig]

Hi

I have a motorised roof and was thinking of adding a safety switch to the mount (Az-Eq6) which sits on a pier, as the telescope needs to slew 90’ before roof closes. So far I’m thinking of a snap safety limit switch attached to pier some way. Wondering has anyone come up with novel design/ pic’s ?

[maxchess]

I have the same problem. I motorised my roof with an electric car door opener and it came with an infrared  beam and sensor that will cut off the door from closing if there is an obstruction, but I doesn't work well. Lots of false stops or no stops.  My thoughts are to use an Arduino or Raspberry Pi to control multiple cheap distance sensors like the SR04  and also bumper switches .  I think both of these would be installed on the leading edge of the roof. In the event of a trigger I can send an impulse to the "Stop" connector on the door motor.  I use INDI EKOS to control my gear and the scheduler allows you to write a simple script to trigger the door to close after the mount is parked (Slewed 90 deg).   So in theory  I could kick of a schedule to run a series of imaging jobs then park the scope and close the roof while I sleep. However I am not sure I am brave enough to try it or that I would get any sleep worrying about a collision.

[Padraig]

Not a great fan of bumper switches as the collision already happened, I think ? I use Nina, but I think v1.11 can set up to close roof after a predefined home position. 
Probably ending up using something like this: https://ie.rs-online.com/web/p/products/9026865/

A bit crude …but the lesser evil than nothing. 

[Padraig]

By the way, 

thinking along this guys idea

 

[DaveS]

I went with one of These terrifyingly expensive roof automation set ups. Add a Cloudwatcher and if the weather deteriorates during a run it will park the 'scope and shut the roof.  There are sensors to tell the system that your 'scope is parked, and when the roof is open or closed.

The difference between the Talon and a bodged together garage door thingy is that this is designed and built for the job. Plus Rupert at Astrograph provides superlative after sales support.

[Padraig]

2 Reed switches on the axis …good idea, could wire them in series as the fail safe. 👍

[Padraic M]

This is something I've given some thought to for when I get around to building my micro observatory but I haven't implemented as yet. But I have built a lot of other types of sensors, and I find that you are sometimes just as likely to get a false reading from a sensor as you are to detect an actual real life event. This means that you'll end up trying to balance the risk of closing the roof on top of your scope vs the risk of leaving the roof open through a rain shower.

NINA can definitely park to a custom position (I've done that by defining a horizontal position and parking to it and it works fine). It depends on your mount type but if my HEQ5 can do it, your AZ-EQ6 will definitely do it. This can be done in pre-1.11 NINA by defining the park position in EQMOD and setting the NINA option to park scope at end of sequence. I think that 1.11 NINA with the new scheduler can do more sophisticated things but I haven't spent much time with it.

I have only had two failures with NINA parking at the end of a sequence and they were both my own fault - once because I turned off the option while testing a new sequence and forgot to turn it on again (resulted in a mount collision in the early hours); and the other one when the camera power cable got stuck around the stupid hand controller holder that has now been consigned to the bin. I think that trusting NINA to do its job properly without sensors is a relatively low-risk option. But, I agree, it's low risk/high consequences.

If I was to do anything, I might look at a way to prove that the scope has parked successfully before closing the roof, rather than trying to stop the roof en route. Regardless, what will you do if the sensor flags an error? Issuing an alert is the best outcome, as just stopping the roof leaves the scope exposed. There's a safety control and alerting system whose name I just can't think of at the moment called something like 'happy nights' or 'sleep well' or something appropriate 🙂 maybe someone else can remember.

[Padraig]

Ooooh, if I was to do all again,  a micro observatory would be the way I’d go. 
I do agree with your thinking that 99.9% of the time, it’ll be an equipment failure before automation. Just from my own experience working in a very large industrial plant. 

At the moment I watch the weather, close roof over in the morning. 
But that won’t stop the birds 💩  

My thinking at the moment would be to hard wire a sensor(s) for home position and not letting roof move at all, no worse than where I’m at now.  
Food for thought, about going with no sensor , and not cluttering up pier with more cables.  
 

 

[Padraic M]

I'm thinking along the lines of a 1m-cubed flower planter with a hinged roof and some linear actuators to open/close it. In my very small garden I have high trees to one side so blocking off one side with the roof isn't an issue for me. I'll leave North free for polar alignment, and have a reasonable view to the South, SE and directly overhead for imaging. Inside I could just use a tripod on a solid base rather than sinking a pillar in concrete. 

I still have the same question as you - 'Can I close the roof?'. 

Interesting point about the birds - I suspect that birds won't perch on the scope until they get used to it being there. I leave things set up only while I can be sure of the weather so it's only ever up for a few days at a time, and the birds don't go near it. But if they do, a safer, easier option might be to automate a simple scope end-cap/flat panel?

[Padraig]

I watching Joe’s astrophoto, at the moment,  he’s building a setup with sliding gate motor and utilising an arduino. I reach out to him and he says he’s putting together a video. 
should be interesting. 

I went with hoist motor which I had to remove internal brake because it was too severe …that’s a +1 for gate motor. 
Don’t think he has a problem with roof height. 

 

[maxchess]

I went with a Shartec Garage door opener. It uses a chain drive in an enclosed rail. Can be operated by wiring buttons or remote control. Has auto load calibration so it applies just the right amount of force to open or close the roof. Also on closing has built in collision routine if impact does occur when it will stop and roll back. (designed to avoid crushing children).  It has been working well for two years. I have linked it to my Telescope control software INDI EKOS.  So in theory after the scheduler has parked the mount it will shut the roof. I have run it with me watching. I also have a webcam in the observatory, so in winter I can check the mount is parked and then use the software to close the roof and kill all power. Just haven't quite trusted it to do it unaided. I think the key is multiple sensors. So Reed switches on the mount + Distance sensors on the roof + Buffer switches (will stop roof a few inches before a collision) . I will get round to it as my next project, for now I can check the mount is really parked and close the roof from my bed on a tablet which is good enough for a cold February. Also good wheels on the roof is important.

 

Edited August 31, 2021 by maxchess
missed a bit

[Padraig]

Hi maxchess

Are you running a raspberry pi  to connect between hardware  ? Not that familiar with Ekos , I went the traditional route.

Maybe you could put up a pictures of how you mounted the reed switches, it’ll be great to see. 

Sounds like you have a all angles covered.  
 

[maxchess]

Until recently I was running off an Rpi with everything attached. However needed more power for Firecapture so replaced with Ubuntu on an old desktop.

I highly recommend Indi Ekos but it requires some Linux knowledge.

At present Indi Ekos does the checking that the mount is parked before kicking off the script to close the roof and I have that working. However as stated above I am a bit nervous about letting it go unattended. The three sensor design  (Reed+distance sensor + bumper) would be an additional fail safe wired directly to the STOP terminal on the roof motor.

I would implement it as a two stage process. First use the Reed switch to independently check if the mount is parked. (So an extra check on the software) If it is, let the roof close but Stop the roof if a collision occurs.

Although leaving the roof open is not ideal it’s better than a collision. Could also get Arduino to send an alert could be txt, email, or even a very loud horn.)

It is very simple to f do using an Arduino, it’s multiple switches and  you test to see states and if bad just switch “Stop” to on, but I have not implemented it yet.

there are standard ready written routines for most of this.

Of course you could just leave the roof open and have a rain detector raise an alarm. I have also installed shower curtains so if necessary I can leave the roof open and just the mount and scope get wet. I think most kit would be ok in the occasional shower??

Edited September 1, 2021 by maxchess
Missed a bit

[Padraig]

Well, I don’t have shower curtain but all auxiliary equipment is housed in a timber press. I “inherited” a   electrical panel which I’ve mounted on wall and yet to move pc , power , hub,  etc… into. Nothing should be exposed. 
Also, floating an the idea of using miniature inductive switches instead of Reed & magnet. 

[Padraig]

You could always check home position in real time 😀

credit : Lazy Geek

just tried it ,  a bit of fun 👍

Edited September 1, 2021 by Padraig

[Ian Thrax]

Two reed switches in series work for me, but they go to lunatico dragonfly which wont allow the roof relay to operate if the scope isn't in the park position, so wouldnt know where to start with RPI.