ASC Build - Another Eye On The Sky

[kbrown]

So here's my take on an all sky camera that I've been wanting to build for a long time. I've finally made a start. It's going to be a Raspberry Pi 3B + Raspberry Pi HQ camera based system with a DIY nichrome wire dew heater. Everything will be powered from a PoE splitter which gives me max 5V / 2.4A.

Here's what I've got so far:

RPi 3 and the PoE splitter + a 50g bag of rechargeable silica gel.

 

Camera and lens are attached to the box with an adapter I 3D printed. Around this is a 3D printed bracket that holds the thin nichrome wire dew heater. It's about 20cm long 0.2mm thick and draws about 400mA at 5V. Seems to warm up nicely but not too hot to melt the plastic.

 

I'm using one of these pipe shelf brackets to attach it to my garage wall. It also serves the purpose of the cable entry to the box. The box itself is IP65 rated and I've tried to seal everything up as good as I could with neoprene gaskets and silicone. Also what's not shown in the pictures is one of these pressure compensation valves (IP68) I added to the bottom of the box:

 

More to come soon...

 

[kbrown]

Out of curiosity I thought I'd check what the effect of the dew heater would look like on a thermal camera.

Here's before turning it on:

 

And here's after about 10-15 minutes of full power:

 

6-7 degrees above ambient. Hoping this will be enough

[kbrown]

Decided to add a DS18B20 temperature sensor inside the dome so I can control the dew heater better as I'm also adding a outside temperature / humidity / pressure sensor:

Temperature sensor inside the dome

 

Designed and printed a sensor screen for the temperature / humidity / pressure sensor. Probably an overkill but at least it looks kinda cool

 

It'll be sitting on the bottom of the box like this.

[kbrown]

Well it's not the prettiest thing I've ever made inside but it does work

 

I'm able to read the BMP280 and AHT20 sensors via the i2c interface and the DS18B20 sensor via the 1-Wire interface. I also added an STP55NF06 mosfet in series with the dew heater so I could control it's power with PWM0 (GPIO18). All there's left to do is to write proper software for this. Happy so far

 

Edited August 28, 2023 by kbrown

[kbrown]

Had to jump through a number of hoops but I now have the first working version of the INDI driver for this:

 

I couldn't find libraries / examples on how to read the sensors connected to the GPIO via C++ so I wrote a python script that uses various python libraries in order to read them. The script dumps all the sensor data into a json file periodically. I've set this to run as a systemd service so it's always running. My INDI driver then reads the json file and updates the UI properties etc. Then in order to control the dew heater with PWM I had to install pigpio and run it as a daemon. The INDI driver connects to it and issues the desired PWM duty cycle commands. Bit clunky but it works

 

For the actual all sky camera I'm running this: https://github.com/aaronwmorris/indi-allsky

 

Edited September 2, 2023 by kbrown

[kbrown]

Nearly there. Decided to add an external 500GB NVMe storage with a USB adapter to both increase the storage capacity and reduce the I/O on the SD card. I've setup indi-allsky to use this drive for its database and image / timelapse storage. It's not the speediest thing with the USB 2,0 connection of the RPi3 but neither is the SD card.  I had it running for a couple of days on my desk and it all seemed to work okay. Added bonus is that the drive generates a little more heat so maybe the need for the dew heater inside the dome is minimal.

Just need to sort out a few more niggles with the LAN connection to the garage and then I can install this to the final location. Happy days

Edited September 7, 2023 by kbrown

[kbrown]

Houston. We have first light:

Temperature reading is not working yet for the image. Not sure why but doesn't matter really as my indi driver does read it correctly...

Here's how it's sitting on the edge of the garage roof:

 

[kbrown]

After a bit of tinkering with the config and python scripting, I managed to get all the sensor data embedded into the images:

Got better white balance too for both day and night images which was a bit more complicated than I would have liked

The biggest challenge with my setup is the limited ram of the RPi3 (1GB). If I turn on certain functions like detection map or logo overlay, then it'll struggle with memory and start swapping and all goes a bit haywire. I have ordered a 4GB RPi4 but I'm not sure if I will actually use it for this as it would run quite a bit hotter and there's no ventilation in the enclosure. The RPi3 together with the NVMe adapter are already keeping the dome temperature like 10C above the ambient. Yesterday was very hot day and the RPi3 CPU temperatures were close to 85C so it might have already been throttling down the speed to keep things cool...

Edited September 11, 2023 by kbrown

[kbrown]

Just managed to configure indi-allsky to upload its data to my website. Not sure how useful this is to anyone apart me but why not

http://knowhere.myqnapcloud.com/WordPress/the-eye-on-the-sky/

[kbrown]

Been learning and tinkering with InfluxDB time series database and Grafana data visualisation tool. Have both of them running on my NAS in docker containers. Bit of Python and php scripting and I've got a fancy weather dashboard on my website updating every 5-10 minutes:

http://knowhere.myqnapcloud.com/WordPress/weather-dashboard/

[lunator]

A very neat project. 🙂

Cheers

Ian

[kbrown]

First encounters with the not so nice British weather revealed a few problems. Moisture was getting inside the dome and no amount of heat could get rid of it.

 

There was a few places I could identify. First one is visible in the photo above. The neoprene gasket between the box and the dome wasn't working properly as the underside of the dome isn't perfectly flat. Some water might have gone through the screw holes too.

Also I don't think this box was ever meant to be mounted this way as the screws that hold the lid down are in a deep recess that just invites water in.

To remedy these issues I did a few things. I "glued" the neoprene gasket to the underside of the dome (but not to the box) with some silicone. I added rubber washers to the screws holding the box lid down:

 

I also added rubber plugs onto the screw recesses. Finally I replaced the dome screws with flanged stainless steel ones to both prevent rust and to increase the surface area pressing down on the rubber washers.

Hoping this will do the trick

 

Edited September 28, 2023 by kbrown

[Mandy D]

Fill the screw recesses with petroleum jelly. That will keep water out and is easy to remove.

[StevieDvd]

If you need to change the enclosure for any reason there are ones like this on Amazon which have non-metal screws that don't intrude into the enclosure and have drain through for the screws.

I did get a little dew (no heating inside) in mine which was due to a loose cable hole/seal. Planning to replace it properly with a split gland but for now used a ton of hot glue gun to seal it which seems to have done the trick.