Gina

Having moved the motor unit I found the chain had jammed and I've had to take it right off to clear it!! It's going to stay off and the chain disconnected whilst I sort out the limit switches. I need the roof as free to move by hand as possible as I'm having to move it back and forth to test the limit switches.

Anyway, the current 70mm OD pulley is working adequately and I'm not looking for extra work - I have more than plenty already!! Once I have everything working I might look at improvements.

I have a large ball bearing 50mm x 78mm x 18mm which I could use and cut down on the thickness of plastic the chain rides on.

If I had my lathe working I could turn one. OTOH printed parts are very strong. I could use PETG rather than PLA for extra strength and durability. The current one was printed in ABS.

Motor unit position adjusted.

Looking at this photo, I think a slightly bigger pulley would be better, lifting the chain a bit higher above the motor board. Another thing this photo shows is that the motor unit may not be quite at the right angle for the chain to the large pulley. Something to investigate.

Not sure I'm completely happy with the small chain pulley - may redesign it and print a new one. A bit wider and deeper flanges with a bevel perhaps. But not now, maybe later.

Yes, just had a nice cup of tea. 😀 Watching Countdown to relax.

After a lot of messing about getting the pulley aligned well enough and reconnecting the chain ends to the roof, I have succeeded in getting the chain drive working again. Now need a break.

One limit switch installed and operating but not connected yet. Nothing yet to connect it to, anyway. Small chain pulley unscrewed, brought indoors and centre hole drilled out to 8mm for an 8mm SS coach screw. That won't bend!

Never mind - plenty to do on the observatory that wants fine weather (though not too hot).

Very dark clouds have gone again... Been out to observatory and looked at positioning of limit switches. Think I have it sorted out. Now taking a break for breakfast

A watering can would contain polluted water but what I really need is real rain. Anyway, there are very dark clouds gathering so a shower may be imminent.

Rain overnight was detected by the rain detector - tick. What I don't know yet is how soon the rain was detected after it started, because I was asleep when it started.

Progress (or lack of) so far then :- Loop parts of roof anti-lift system will be screwed to the corner uprights of the fixed observatory framework. I shall keep the storm lock-down latches and window bolts so won't need the linear actuator to bolt the roof closed. Limit switches are well on the way to being sorted out. Rain detector will be tested when we get some rain. Spring to tension chain and limit force used to close roof, works well. Push buttons on the control unit will provide local control - Open, Close, Abort. May use coloured LEDs on front of control unit to indicate status - Open, Closed, Closed after rain detected, Fault, etc. I plan to include RPi in the control unit box for remote control and feedback. The bungee cord for pulling the window open seems to be loosing strength so I'm going for another solution with lever and spring. The small chain pulley needs a thicker screw into the baseboard - current one is bending from the tension in the chain.

With the limit switch brackets printed, I've attached the switches to the brackets and taken one out to the observatory to check position etc. However, they can't go where I originally thought, on the partition wall on the south side, because of the sliding door but they could go on the other (north) side. Would just mean slightly longer cables to the control unit. I'll probably leave it until tomorrow now - had enough for today.

Don't think I'll be doing much more on this job today, if any. The omens are not as good as I thought!

Had a thought about the limit switches. I may be able to use one limit switch for both directions since the actuator arm works both ways. OTOH that may have other ramifications...

The drizzle has gone - not enough to wet any surfaces, so I'll not blame the rain detector yet.

Fine drizzle - not detected!! Tried to drill holes in the observatory fixed framework for the coach bolts but came across screws and ended up ruining two drill bits. I shall just have to attach the loops with the lower two wood screws. Might drill the holes out in the loops and use 8mm coach screws for more secure fixing. Not today though - one calamity is enough for one day!!

No rain yet... Designed and now 3D printing brackets for the limit switches.

Any time now according to Clear Outside. The sky is darkening. Just checked and the heater only comes on after rain has been detected. This raises the current drawn from the supply from 8mA to 120mA so that is enough to tell that rain has been detected. I can see 120mA on my bench PSU. I could use this to operate the logic and save a wire but the relay contact is probably simpler (and safer).

I now have the rain detector on the sun room roof with a long multicore cable attached to bring connections onto living room table where I have a bench PSU and DMM to check the relay contacts. The roof has an estimated slope of around 20°. All set up ready for the forecast showers this afternoon (which will probably not materialise!!).

No, I'm not, the rain detector relay will simply connect to an Arduino input with internal 10K pull-up resistor enabled so will only be switching 0.5mA.

I know there's a relay in the unit. Only has to operate logic.