Noel replied to the topic 'I made this! INDI in an all-in-one power box, with dew heater' in the forum. 5 months ago

To ground everything I used a brass 'bus bar', its the first picture (here's more examples www.aquashopkampen.nl/product/busbar-10x8/ ). This is a common ground connection for the modules and connected to this is negative of the DC input. The DC power is grounded via the DC power supply connection.
This bus bar needs to support the maximum current load of all modules combined so give that some consideration when selecting the part. You could make your own if you have the tools and materials as some bigger modules get quite expensive.
For my project I summed the maximum rated load of all components and then rounded up - in reality it's been overkill, while running my system draws about a quarter of what it's 'designed' to do - but I feel better safe than sorry.

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Noel replied to the topic 'I made this! INDI in an all-in-one power box, with dew heater' in the forum. 5 months ago

@supernov - thanks for your kind words. Building my unit was fun and a learning exercise - there's a few things I plan to do a little differently for Mk2. If you have any questions or comments feel free to get in touch.

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Noel replied to the topic 'I made this! INDI in an all-in-one power box, with dew heater' in the forum. 5 months ago

Thanks for picking up on that, I'll modify my unit accordingly.
I've started brainstorming 'Mk 2' and will power any fans from a dedicated 5v or 3.3v line - or at least a module that can handle the current with ease.

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Noel replied to the topic 'I made this! INDI in an all-in-one power box, with dew heater' in the forum. 7 months ago

Thanks Ihoujin for your GPS mention - I forgot to mention I have a cheap USB GPS dongle (model VK-172) that is inside the box and connected to the pi via the micro USB connector and a USB OTG cable. The USB model gives location sync but lacks the pulse output to sync time - instead I use a small script at startup to read the time from the USB module and set the time from that.

I'd prefer use a module like you suggested; was implementing this straightforward?

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Noel replied to the topic 'I made this! INDI in an all-in-one power box, with dew heater' in the forum. 7 months ago

Hopefully this makes sense. Every 'functional group' is connected in parallel. This made design and troubleshooting easy.



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Noel replied to the topic 'I made this! INDI in an all-in-one power box, with dew heater' in the forum. 7 months ago

[remaining pictures]

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Noel created a new topic ' I made this! INDI in an all-in-one power box, with dew heater' in the forum. 7 months ago

I then used Inkscape (free vector drawing app, you could use any drawing app or even a pen and paper) to make a layout of where I need to cut/drill the box [see fig 3]. I printed this and taped it to the box. Drilling pilot holes for large holes made alignment accurate. A rotary tool (eg Dremel) made shaping the holes easy but a series of drilled holes shaped using a small file would do the job as well. Using a drawing app makes things super easy when you later want to design your labels as you already will have a layout of where the holes are on your computer!
tinyurl.com/y8dnudze )
To mount the modules I screwed them onto threaded nylon stand offs, applied epoxy glue to the ends of the stand offs and placed the modules in position. Once the glue had cured I unscrewed the modules and voila - custom mount points for my modules. The 12V regulator only had one screw hole so I glued a standoff under it for support.

Prior to assembly I designed some labels for it. I used Inkscape but use whatever you're comfortable with [fig 4]. I laid out my labels on a A4 layout and had them printed at a copy shop with a colour laser printer onto glossy self adhesive paper. It looks durable enough but its still paper based and may need a clear coat to make them durable. Time will tell.

With holes cut and everything test fitted, I applied the labels and began assembly.
Fig 5 - the nylon mounts glued to the base of the box. The lead is from 5V 30mm x 30mm cooling fan.
Fig 6 - label on the rear (operator) side of the box.
Fig 7 - label on the forward side of the box, heater outputs in close proximity the fronts of the lens/scope.
Fig 8 - label on the side of the box - I'd already fitted the fuse holder, switch and dials before thinking of taking a photo. Eagle eyes will see I've used 10A fuses instead of 5A as I didn't have and 5A handy at the time.
Fig 9 - inside of the side cover showing the blade terminals of the fuse panel and the dials that connect to the PWM modules.
Fig 10 - the modules used. Anti-clockwise from top left. Raspberry pi, 12V regulator, regulator for 7.4V, regulator for 5V, 4x PWM modules.
Fig 11 - a bus terminal block used as a negative DC bus. All negative leads connect into this.
Fig 12 - assembly underway. High current DC input lead, 12V module and 7.4V module fitted. RCA terminals on right with leads unattached.
Fig 13 - all modules except the pi are fitted. The high current side of the fuse panel has been interconnected.
Fig 14 - everything connected. See Fig 1 for finished item.
Fig 15 - mounted on the baseplate
Fig 16 - Cable mess begone! There are three leads bound together that connect the box to the mount - power, eqmod cable and ST4 guide cable.

Electrical Layout:
(I'm open to constructive criticism here as I've only ever studied basic electronics and do not profess to be an expert. What I came up with so far works well. )

I'll try this in text as I don't have a pretty diagram.
I'm using a 13.5V supply. This could be 12-14V, I'll refer to it as 'Source'.

Source(positive)
|
|-20A Fuse-|
|-5A Fuse-|-1KV 10A Diode-|-GX12-2 output on rear of panel-|| .... to mount
|
|-3A Fuse-|-1KV 10A Diode-|-Regular set to 5V output-|-small DC plug-|-Raspberry Pi DC jack input-||
|
|-5A Fuse-|-1KV 10A Diode-|-12V Regulator-|-DC jack 5.5mm x 2.1mm-|| ... for 12V output for a cooled ZWO camera
| |-Regular set to 7.4V output-|-DC jack 5.5mm x 2.1mm-|| ... for 7.4V output for Canon DSLR
|
|-2A Fuse-|-1KV 10A Diode-|-1.8-15V 2A PWM controller-|-RCA Socket-|| ... for dew heater, max 30W output.
|
|-2A Fuse-|-1KV 10A Diode-|-1.8-15V 2A PWM controller-|-RCA Socket-|| ... for dew heater, max 30W output.
|
|-2A Fuse-|-1KV 10A Diode-|-1.8-15V 2A PWM controller-|-RCA Socket-|| ... for dew heater, max 30W output.
|
|-2A Fuse-|-1KV 10A Diode-|-1.8-15V 2A PWM controller-|-RCA Socket-|| ... for dew heater, max 30W output.

Each module's negative connects back to the negative bus block.

Electrical Discussion:
As part of the design I summed all of the maximum current draw ratings of each module/device. I rounded this up if needed to determine what fuse would be required. This gave me the total maximum current drawn by the whole system. At absolute full load my rig will pull 19A, that includes 4x 30W dew heaters at full power. I expect to never see it at full load, however I've designed everything to handle full load.
The current draw also determines the minimum size wiring to use, I often erred on the side of caution and used thicker cable than necessary.
I used 1KV 10A diodes as a basic reverse current protection. Should a module short and draw high current a fuse will protect it. Should a module fail and produce reverse current, or should an attached device generate a reverse current in the system, the diodes will prevent that. It helps give some segregation to an otherwise very interconnected system.
If you are concerned of interaction/interferenece between your modules affecting your system you could consider using suitable voltage regulators through to further condition the power being supplied.

All modules are connected in parallel. The source supply is delivered to two high current 'buses'. The positive bus is the fuse panel, high current along one side with suitable fuses and diode at each module connection. The return current is via a high current terminal block. Consider the fuse panel to be an 8 way 12V power outlet.

-First fuse is the for the current into the whole system.
-Second is for the mount and connects through to the GX12-2 socket on the rear side.
-Third is to the 12V regulator. From here, I connect the 12V output to a DC socket on the box AND I connect another regulator in series to this module. The second regulator drops the 12V down to 7.4V for output to my DSLR. The 12V regulator won't handle both outlets used simultaneously, but I don't plan to connect my DSLR and a cooled ZWO camera at the same time.
-Fourth to Eighth fuses outlet to each of the 4 PWM modules. These can handle 1.8V to 15V input and output max 2A.

*Hindsights & leasons learned:
-Using the same size jacks for a 12V output and 7.4V output and putting them next to each other might be a quick way to cook my Canon DSLR. I've pugged the 12V jack using some rubber insulation to prevent a light night mis-connection. As I made my own power cables for these I should have chosen dissimilar sizes to avoid an accident.
-Try to find modules that have sufficient mounting holes to support the board. The 12V 4A regulator I used only had one hole and was unstable until I supported it.
-Having accessible blade fuses looks kinda cool and is handy but the fuse panel I used took up a lot of room in the project. It was hard to find a fuse panel that didn't have teminals on the side or top. Many automotive panels aren't designed to be so openly accessible and have exposed terminals. For MK2 of this project I intend to design my own PCB power distribution board with blade fuse sockets and low profile screw terminals - but thats for another day. If you want to keep your project slim and lightweight don't use the same kind of fuse panel I did.
-Don't leave your soldering iron on for a long time, they don't like it.
-Practice makes perfect - soldering is no exception. Keep your solder tip clean. Use solder flux/rosin. Use an extraction fan - that smoke isn't good for you.
-The 5V cooling fan I'm using can be heard during operation. Sound = vibrations and thats possibly not good. I've now connected this to a 3.3V output from the pins on the raspberry Pi to slow it down.
-I needed an 'on' LED so I found a 5V power output pin on the pi and connected a suitable LED with resistor to the rear of the panel. If it's too bright I'll put this on a 3.3V output pin.

I had a lot of fun designing and making this. It took several months all up, some components were ordered from overseas and there's only so much free time. I made some mistakes along the way so it was a good learning exercise.

I'm already thinking of ideas for MK2 and hope to include an arduino based focuser and dew heater controller (using Robert Brown's designs - sourceforge.net/u/brownrb/profile/ ), but that will wait for another cloudy night.

Finally - INDI/Ekos is brilliant. Read more about it here: indilib.org/ Buy a Stellarmate if you don't have a raspberry pi and can't be bothered installing it. If you have a 'pi and are happy to install it you can buy and download an install image for it OR if you're really keen you can download and setup the the applications yourself. I did the later, it was fun and 'rewarding' but I'll never get those weekends back!

Happy to answer and questions and accept constructive criticism.

Cheers.

Noel.

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