My homemade scope mounted acquisition box

[symmetal]

Hi,

I'd mentioned this on another thread and it generated some interest so here are some more details.

Previously, all the electrical/electronic units were sat on a tray mounted to the concrete pier with a loom of cables snaking around the scope. After seeing reports of mini pcs attached to rigs I thought of getting everything into one box small enough to mount on the scope as something to do during all the cloudy days. I bought a cheap mini pc as they don't need to be high spec for this job and chose a Z83V  which has an Intel Atom, Windows 10 home 64 bit, 2GB ram and 32GB SSD for £93. I previously ran the CCD from a 17Ah lead acid battery while the rest was powered by a switch mode PSU to avoid power supply/equipment noise affecting the images.

Everything in one box meant powering the CCD off the switch mode too so thought supply filtering would be beneficial. I ended up filtering every output, probably overkill, but would make use of my PCB making equipment which I hadn't used for over 20 years. The PCB software I last used was a DOS program modified to run on Win 95 which cost a lot at the time. Looking for free or cheap PCB CAD software I settled on KiCAD which is free open source and pretty powerful.

The box contains Power distribution on PCB, XLRs for the main connections, mini PC, USB hub, 2 dew controllers and a Lakeside Astro focus controller. My first mockup construction used the Startech 4 port 'rugged' USB hub but the ins and outs on the same side made cabling awkward so I used the 7 port D-Link which had sat on the tray for over a year working without a problem. It had a 5V input so I had to put a DC-DC converter on the PCB along with one to give 7.4V for a DSLR. The USB hub is recessed in the box so that the connectors are not exposed to the open air and the little heat from the PC should keep everything dry. The USB hole cutouts on the box also give support to the USB plugs so they don't wiggle around. The box is 240 x 160 x 90 mm and mounting it to the side meant counterweights on the other side. A dovetail mounted crossways supports the box on another dovetail at one end and a stack of weights at the other end. Box plus weights is 4kg so total weight increases from 9 to 13kg which is well within the imaging weight for the AZ-EQ6.

Cornish dry stone wall covered in vegetation gives good wind protection.

Hole in top to insert stick to switch Lakeside focuser off and on as required. 

Waterproof 2.1mm DC connector for DSLR

USB 3 port for planetary imaging and adding flash drive to transfer video files. HDMI and RJ45 for a monitor and fast network if needed.

Roll off shed and neat section of garden.

Dew controllers mounted under Lakeside controller and above PC. Hole in box to access screwdriver slot for adjustment.

Hmmm. How do I change the fuses.

The 'XP' module is the 12-5V 2.4A converter for the USB hub and the green module in the centre is an adjustable DC - DC converter made my Texas Instruments set to 7.4V for a Canon DSLR. The other 4 metal modules are Schaffner FN406 LC filters (3 at 3A and 1 at 5A (for the mount)).

All glowing nicely as sun sets.

I've only tested it doing 1 and 5 minute darks on the Atik One to check noise and there is no difference between separate battery and box power with dew at 50% so max DC switching and scope tracking. 1 min, Mean 340, Median 340, Std Dev 102. 5 min, Mean 343, Median 342, Std Dev 161.

Thanks for looking,

Alan

[symmetal]

I forgot to mention PC performance. It's running EQAscom, SG Pro, PHD2 and CDC as well as Teamviewer and it's running about 70% PSU. Memory is about 1.1GB out of 2GB and SSD is about 18GB out of 32GB. I save images to a 128GB SD card and for CCD imaging it copes easily. The only time the processor reaches 100% is when SGPro does a star analysis of the captured image. Doing some test planetary imaging with an ASI 224 MC was also no problem using FireCapture. It did 300 x 300 dpi and 200fps capture for 30s easily. There is a delay at the end of capture while Firecapture transfers the video files from ram to SD card but it's just a few seconds. Running at longer durations or higher resolutions (at reduced frame rates of course) it will run out of ram after about a minute but I don't see that being a problem. At 200fps 10-15 seconds at a time is all you need. USB3 capture puts little load on the CPU which went from about 65 to 70% during capture. You just have to minimise the Firecapture preview window during capture if the image is big as it can't cope with the screen image updates at capture speed. 

I've yet to try it on real subjects as I only finished it last week and there's been cloud since last month. 

The PC is fixed to an aluminium base plate inside the box with another plate mounted above to hold the Dew controllers. I forgot about the Wi-Fi signal from the PC. It's certainly down from when it's outside the box but still indicates max strength to a Wi-Fi access point in the shed next to it. Cat5a cables go from the shed to the house.

Alan

[BigBeard]

Proper job!

[Starlight 1]

Very nice and look well made.

[bottletopburly]

Very neat indeed ,well done 

[steppenwolf]

Very smart indeed - well done!

[symmetal]

Thank you all for the compliments. 

A couple of bonuses that showed up when operating in the dark is that the indicator leds on the dew controllers illuminate the inside of the box nicely so the screwdriver slots for adjustment are back illuminated and the Lakeside controller on/off switch is easily visible looking in the access hole. The holes I cut in the box lid to view the dew leds aren't needed. 

Also the PC blue 'on' led wasn't visible as it's shining through a dark perspex panel on the opposite side to the on/off switch and isn't very bright. I was checking the PC status by monitoring the current taken on the 12V rail. The PC takes about 300mA when it's idling. The PC auto powers on when power is applied and is shut down by teamviewer. The on/off access hole is just in case I have to manually switch it. I didn't want to remove the 12V until I was sure the PC had shut down properly. But in the dark looking into the holes cut for the hdmi and ethernet  the blue led is visible around the connectors so another win. 

I was going to cut a rectangular hole to view the Lakeside readout but once it's set up it isn't really needed. Focus position is available in SGPro. 

Alan

[Juicy6]

Nice project!!! Do you want to share the PCB layout for others to copy and for us to etch circuit board? And a schematic of components placement?

Christer, Sweden

[symmetal]

No problem Juicy6. I'll post the information later today.

[symmetal]

Hi Juicy 6. Here two views of the PCB viewed from the component side. The board is 21.0 x 7.6 cm. If you click on the images you get a larger image which is more readable.

All layers. Viewed from component side. It's just a single sided board with no wire links needed.

Edit - Just noticed labeling on Dew Control. It says 0V & 5V. It should say 0V & 12V. 

Component placement and pads.

I can give you gerber plots or the KiCAD files if you use KiCAD so you can arrange the components to suit your own project. I had to mount FL3 & 4 high up as the PC position blocked them from being lower. The fuses being at the bottom means having to lift the board out to change them which just means removing the six screws holding it in. The wires can remain attached as you can rotate the board as you lift it out. If you left the plastic covers off the fuses you could probably lever most of them them out with a screwdriver without removing the board.

I included the CPC and Farnell part numbers as references if you need more details. Farnell probably sells all of them but sometimes parts are cheaper from their CPC branch.

Let me know if you need more info.

Alan

[Juicy6]

Great. Thank you for sharing this. Why invent wheel again?

Christer

[smudgeball]

What a fantastic project !

I don't recall anything like this on the market? (I know QHY are doing something like this)

I'm seriously impressed.

Well Done

Regards

 

Neil