All Sky Camera/Weather Station build

[angryowl]

Covering the dome with something during the day to protect from UV would be an ideal solution if only I didn't want daytime imaging as well. I think with the camera's resolution and it being colour and the lens sharpness, it can give some great views of clouds. Plus I've motorised the lens aperture control from the get go which would only really be used during daytime. I don't plan on imaging 24 hours a day, mainly during the day when there's nice cloud formations and the lens cover will definitely be over the lens when the Sun is shining, even with aperture control as I'm too sceptic to trust that f22 with this lens results in no sensor damage. 

I love the term 'aging resistance' in the product description.

 

[Gina]

I decided to order that dome - delivery Nov. 16-25.  Be interesting to try it.  OTOH I do like the reduced reflections with just the lens.  And the ZWO cameras don't mind the sun in the FOV.  Probably won't be using this rig for daytime imaging when the sun is out though as it needs an exposure around 0.3ms (as shown here) with gain at minimum and the hardware/software I want to use only goes down to 1ms viz. Raspberry Pi 3 with INDI driver.

[Gina]

There's a 3" version of that dome a couple of quid less.  Different attachment though and not as convenient I would think :-

JMX 3 Inch Acrylic Indoor / Outdoor Cctv Replacement Clear Camera Dome Cover Security Camera Housing

[angryowl]

Starting to take shape now...

The ideal spacing between the dome and enclosure is 10mm. This can easily be achieved by using a printed spacer and two gaskets or silicone seals.

Next I'll print a holder for the main camera which will be glued with double sided sticky pads to the bottom of the enclosure.

 

 

[Gina]

The 4" dome I ordered from ebay arrived in the post today.  4'' Indoor/Outdoor CCTV Clear Acrylic Monitoring Camera Dome Cover Replacement

Looks very clear and free from distortions but would still have reflections from bright lights and the moon when out so I'm continuing with my present motorised cover version with no dome.

[angryowl]

Looking forward to seeing how your cover turns out Gina. Lucky you, received a dome free of distortions the first time, I had to return mine for a replacement as the first one had some rather large imperfections in the acrylic which showed up in images when testing.

[angryowl]

Printed the front element of the wind vane. 

Inside of it there are a number of square nuts which thread onto the rod for counterbalance as the fin is rather heavy even though it was printed with 17% infill I think. The O-ring is there to prevent water getting inside and the nuts rusting. There will also be a smaller O-ring on the rod after the cap that screws in.

I think I'll cover the exposed areas of the rod with some clear PVC hose I have.

[Gina]

I used very thin acrylic sheet for my wind vane.  Very light.

Once I get my ASC finished I might have another look at my weather station.

[angryowl]

3 minutes ago, Gina said:

I used very thin acrylic sheet for my wind vane.  Very light.

Yes, the lighter the better for a wind vane I suppose. Acrylic is also very strong so I'd say good choice. I think mine is about 38 grams or at least that's what Cura reported. 

[NickK]

On 06/08/2017 at 21:47, angryowl said:

 

One thing I noticed was that whilst testing, the steppers were getting REALLY hot, to the point I was afraid the PLA holders would start to melt. I am running them off a separate 12V 1A power supply but I don't think that's the culprit. Anyway this is only when they move so maybe it's not such a big problem as throughout a day/night the cover motor would only stay on for a couple of seconds, and so would the aperture and focus, well focus motor maybe a bit more use but not really concerned at the moment.

You need a current chopper controller.

The arduino and even the arduino servo shield aren't/can't deliver chopper style control.

I tried the shield, I tried writing a software chopper driver but in the end the rate of current control is too low.

I have a stepper rated at 3.8V 680mA and I use 12V on it with a DRV8825 (IIRC that was the number) and it sits there with no heat - you can calibrate the maximum current delivery using the variable resistor on one of the pins and at that point it will deliver 12V that firmly overcomes back EMF but limit the current so it will never burn out. The DRV also supports 1/32 micro stepping

IIRC the DRV will go up to 30V with a heatsinks so can cope with pretty much anything  It also have thermal other cutout protection.

 

[Gina]

On 06/08/2017 at 21:47, angryowl said:

One thing I noticed was that whilst testing, the steppers were getting REALLY hot, to the point I was afraid the PLA holders would start to melt. I am running them off a separate 12V 1A power supply but I don't think that's the culprit. Anyway this is only when they move so maybe it's not such a big problem as throughout a day/night the cover motor would only stay on for a couple of seconds, and so would the aperture and focus, well focus motor maybe a bit more use but not really concerned at the moment.

You're not trying to run 5v motors from 12v are you?

[angryowl]

On 05/11/2017 at 14:59, Gina said:

You're not trying to run 5v motors from 12v are you?

Haha, indeed I am. Don't know how it's happened but I had that one test then to confirm the steppers are working and then not thought about the heating issue further. The steppers are the the 5V 28BYJ-48 and ULN2003  drivers. The drivers can run on anything up to 15V I think but that would of course work on 12V steppers.

[angryowl]

On 05/11/2017 at 11:13, NickK said:

You need a current chopper controller.

The arduino and even the arduino servo shield aren't/can't deliver chopper style control.

I tried the shield, I tried writing a software chopper driver but in the end the rate of current control is too low.

I have a stepper rated at 3.8V 680mA and I use 12V on it with a DRV8825 (IIRC that was the number) and it sits there with no heat - you can calibrate the maximum current delivery using the variable resistor on one of the pins and at that point it will deliver 12V that firmly overcomes back EMF but limit the current so it will never burn out. The DRV also supports 1/32 micro stepping

IIRC the DRV will go up to 30V with a heatsinks so can cope with pretty much anything  It also have thermal other cutout protection.

 

Just realised I was driving 5V steppers from 12V input. I'll probably change the 12V adapter I set aside for the steppers with a 5V one rather that purchasing new stepper drivers as it would be more economical. But thanks Nick and Gina for pointing this out otherwise I surely would have had issues down the road.

I'll be looking into chopper drivers for one of my other projects, an ASCOM focuser for my scope so this will come in handy.

[Gina]

I use these little geared stepper motors in two ways from 12-13.8v.  Yes, the 12v version from ULN2003 drivers and also the 5v ones modified to break the connection between the commons and the A4988 driver modules.  This allows finer control as the A4988 does microstepping.  To convert the stepper motor from unipolar to bipolar operation see the ADDENDUM at the end of my blog Setting up a Raspberry Pi for Astro Imaging and Hardware Control

[Gina]

For anyone interested in using the little 28BYJ-48 geared stepper motor for fine control I offer this modification.  The diagram below shows the coil connections for the 28BYJ-48 stepper motor.  The centre-taps on the coils are joined on the connecting block behind the blue cover.  This prevents the motor being used in bipolar mode with microstepping drivers such as the A4988, which requires electrically separated coils.  The modification involves cutting the PCB track that connects these centre-taps as mentioned above and not using the red wire.  The whole of each coil/winding is used rather than half, which doubles the voltage required to drive it and since the microstepping drivers limit the current it is perfectly safe to run the 5v version from 12v or more (eg. 13.8v).

 

[Gina]

The 4" acrylic dome has arrived from China.  It looks identical to the cheaper one from ebay except that it has the maker's mark on the rim - JMX-04H.

[sloz1664]

So Gina, which one are you going to use.

Decisions, Decisions, Decisions 

Seriously I am toying with building one of these or an Arduino sky quality meter.

Steve

[Gina]

ATM I'm not planning to use either dome - I'm trying a dome-less ASC with a motorised cover to cover the lens when the ASC is not in use.  If I get problems from birds, insects or other grot on the lens I might go back to a dome.  The trouble with domes is that they get internal reflections, particularly from bright lights or the moon.

[angryowl]

Drilled the bottom of the enclosure for the two 10mm mounting rods and two holes for ventilation (square one fan pushes air out and smaller round one for intake) with some metal mesh over them for keeping out insects. I'll be using 13mm hollow rods to to pull the cables for the anemometer, wind vane, rain gauge and Stevenson screen. I've mounted the ones for the anemometer, Stevenson screen and rain gauge but since the wind vane is using two cables I'll need to find a place to mount two more. The fourth 13mm rod seen in the images is for the Ethernet cable going into the USB Ethernet adaptor.

And the adaptor is in a holder which is mounted on the 13mm rod 

Also printed the camera holder. The camera slips in and is held by two screws going through the top. This has enough clearance on the bottom to allow for the two M10 nuts and washers to thread onto the main mounting rods.

A holder for the hard drive. This will have double-sided sticky tape on the back and will be mounted on a wall. The HDD is held in place with two M3 bolts and the smaller bolts are there to slip into the holes on the HDD on the other side. 

The PCB where most of the electronics will be is also going to be mounted vertically and with double-sided sticky tape.

And finally something to keep the main ventilation fan in place above the square hole on the bottom of the enclosure.

 

[angryowl]

Printed a nifty adaptor for the WiFi antenna which simply screws into one of the 6mm threaded holes on the bottom of the enclosure.

[angryowl]

Done printing the ASA spacer that goes between the dome and enclosure lid. Bad print as it started coming off the build plate half way through which caused some issues but I plan on using two rubber gaskets then drown it in silicone sealant. This way the dome will only need to be removed when the ASA part wears out or the dome deteriorates, access for maintenance will be provided by simply lifting the entire lid off with the dome attached. 

 

Also finished printing holders for all of the parts inside the enclosure. 

The next steps are soldering the electronics on the PCB and wiring up the Arduino and all of the other connections then print the rain gauge and it can all be mounted in place.

Then further down the line resume work on my Arduino main sketch and application in Visual Basic which'll be used for pulling data in, processing, displaying and allowing manual control.

[angryowl]

Oh and of course let's not forget about calibrating the anemometer and wind vane BEFORE lifting it all up 

[angryowl]

What a better way to start the day than with the smell of burning electronics...

Whilst I was bread boarding the connections for the camera 12V input, fan and TEC this morning, I noticed a burning smell and a bit of smoke coming out of the underside of the camera. It turns out I had directed 12V through the fan outputs whilst trying to turn the fan on via the Arduino.

Imagine my relief and joy when I connected the camera and took some quick shots only for them to come out flawlessly. 

Lesson to learn from this is I am not a morning person and I should avoid starting work on delicate electronics so early in the morning 

[Gina]

I know what you mean!!

[Gina]

I was very interest in the MLX90316 rotary position sensor that you are using for the wind vane sensor   Nice and simple compared with my system   Where did you buy yours, please?