Gina

Ditto...

Don't think I know that one.

Trying to recall which software I used for drawing circuit and block diagrams. Thought it was LibreOffice Draw but can't seem to get it to do what I want.

Not good! At least you didn't pay much for it...

The LEDs just provide local diagnostics of any problem. I agree that I will have remote indication of some things and that I can close the roof remotely assuming everything is working correctly but my imaging runs usually go through the night and I go to bed to leave everything operating automatically. Rain detection means I can image even if there's a possibility of rain. Many times in the past I have been unable to image because of a remote possibility of rain later in the night. To make things clearer, there are two scenarios. One is that everything is working and I can open and close the roof locally or remotely and automatically close if rain is detected. The other is that the roof doesn't move when it's supposed to and something has failed. This is when the diagnostic LEDs come into the picture. To add these four LEDs takes very little effort when the unit is built but diagnosing faults later would require taking the lid off the unit and testing with a DMM while trying to operate the controls. Too many times I have found I need three or four hands to fault-find.

If I can arrange a digital ammeter for the roof controller I can dispense with LEDs to indicate motor current. I can make use of these for showing the motor is connected to a power supply. I don't need the LED to show that rain has been sensed as mentioned above. Consequently, my plan for LED diagnostic indicators is as follows :- Green - Roof closed - safe from rain etc. White - Roof open to the sky Blue - Motor supply set for closing Yellow - Motor set for opening (Red - not used) Green and White LEDs can be connected to limit switches with series resistor whilst the Blue and Yellow LEDs can be connected from motor terminals to ground (again with series resistor). No LEDs would be connected to the Arduino. LEDs could be run at 10mA so with 12-14v and LED voltage drop of around 3v, a 1K resistor will be suitable. With just 100mW dissipation, quarter Watt resistors will be fine. The motor current will still be sensed to feed to the remote control and the indoor INDI display.

Nothing done in the observatory today, mainly due to the weather but also because I needed a break from the physical effort. Far from a wasted day though, apart from the rain sensor tests, a day of rest is needed now and then plus some electricals sorted out.

Had a search for those digital ammeters but no joy. I thought to myself "oh well never mind I'll just buy some more as they're only a couple of pounds each" but I can only find combination voltmeter and ammeter units and a few voltmeters. I may find the digital ammeters in time and can do without meantime. I can get a combo V/A meter for the battery voltage and one of the current supplies.

One thing that would be possible with remote control is that I could schedule the roof to close when my scheduled imaging run has finished. (As well as Parking the mount if using a large telescope.)

The difference between a very fine drizzle and a heavy dew... Could be a difficult one!

That I don't yet know. If it does I may need to add a dew heater though not too much. There is electronics inside the detector which will provide slight heating - 8mA at 12-14v = 100mW approx.

It has occurred to me that an indication of rain having caused the roof to close is not needed. If the roof has closed and I haven't closed it then it must have been rain that caused it to close!

Whether some sort of funnel would be a good idea for the rain detector, I'm not sure. With a fairly strong wind the funnel would shield the rain detector from rain until some ran down the funnel. A wide funnel would slow down raindrops running down the funnel surface.The rain has eased off to a very fine drizzle and the rain detector heater has dried off the sensor. There is still a good breeze. Seems that this rain detector will detect moderate or heavy rain quickly but a fine drizzle could last ten minutes or more before being detected. Maybe two rain detectors could be used - one with a funnel and one without. At least a sudden downpour should close the roof.

I think I shall put the electronics for my imaging rig in a waterproof casing. The camera would not be affected much by a drop of rain though the connections will want protecting. Filter wheel is virtually sealed and lenses/telescopes wouldn't suffer from just a little rain. I can arrange that some things be covered to keep rain off. All this means a light rain shower shouldn't be a serious problem and heavier rain seems to be detected.

Just started again and detected it within a minute or two. Can't be absolutely sure how long as I wasn't watching the PSU at the time - watching Bargain Hunt 😁 That first shower didn't wet the ground - just a few drops, so maybe wouldn't have done any harm. This one is a lot heavier and the observatory roof is well and truly wet!

No need for imitation rain - I have the "Real McCoy"!!

Had a shower of moderate rain for the last ten minutes and the rain detector has shown nothing!! I guess our rain is too clean today. Rain has stopped now. More and heavier showers are forecast for this afternoon.

Whilst redesigning my power distribution unit I might as well add a couple of extras I've thought of. When not using the observatory for some time I disconnect the 13.8v PSU from the battery and turn it off. I have several digital ammeters and voltmeters in stock and would like to check the battery voltage and also might as well have ammeters for each of mount, imaging rig and roof control unit. If I have an ammeter for the roof controller, I shall not need an LED for the motor current on the control unit. ATM I have one ammeter which shows total current to mount and imaging rig - makes more sense to separate them.

In addition to the roof controller, I shall need another output from my main power distribution box. I could just run the roof power from the mount output but I really want the supply to the mount and roof control separately fused. So ideally I shall want to design and build a new power distribution box. This is not difficult - just yet another thing to do. I believe in doing things properly and not skimping - particularly on safety features.

I don't really want to use an Arduino Mega so I'm going to look at what I can do with a Nano. The Nano has 12 digital I/O pins and 8 nominally Analog input pins, 6 of which can be reassigned as digital I/O. The LEDs that indicate the state of limit switches can be operated by the limit switches themselves. This would save current from the Arduino. The limit switches have independent NO and NC contacts so one pair of contacts can be used as input to the Arduino and the other to power the LED. LEDs for "Roof Closed due to Rain Detected" and "Fault" will have to be controlled by the Arduino. The Yellow "Motor Powered" could be run from the motor power lines and would be useful to show that the motor was powered ie. there is voltage applied to the motor. To allow for the reversible motor voltage, the LED could be run from a full-wave rectifier. Alternatively, two LEDs could be used, each between one motor wire and Gnd (with series resistor, of course). To be continued... (Tomorrow)

I think I now have enough information and made sufficient decisions to design the electronic circuitry. Below is a quote from a few days ago which contains most of the information but whilst the lock-down latches and window bolts will be retained there will be no sensing of this condition, I shall rely on my common sense to disengage the clutch when locking down and maybe set a switch to relay this condition to the indoor client system. I also plan to have LED indicators on the control panel to confirm that everything is working or if there's a problem. These would be :- Green - Roof closed - confirms limit switch state White - Roof open- confirms limit switch state Blue - Roof closed from rain detected Yellow - Motor told to run Red - Fault eg. excessive motor current

Distilled water will not trigger the rain detector - this is a known fact. The water needs to contain salts to be conductive. We will get rain eventually that is a fact.

Photos of limit switches in operation - two for roof closed and one for roof open.

For anyone not knowing what I'm talking about, it comes from a maxim we had at work "The easy we delegate, the difficult we do straight away, the impossible takes a little longer".

This job is NOT going to beat me!!! Just a case of the impossible taking a little longer!