I made this! An all-in-one power box, dew heater and INDI controller.

BigNoel (Noel) · #1 19-03-2018, 09:48 PM

What is it? [see fig 1]
A small box designed to be connected to the baseplate supporting telescope on an EQ mount with the purpose of providing:
- power to the mount
- power to either a DSLR or cooled imaging CCD
- four dew heaters with variable control
- EQ mount and imaging control via INDI/Ekos system running on Raspberry Pi single board computer.
- Wireless connectivity to INDI system.

Why did I?
I don't have an observatory, I image either in the backyard or at a dark site, both have mains power available.
I wanted a way to minimise cabling around the mount and to simplify the setup.
I was in need of a dew heater and was already using a raspberry pi attached to the mount, and was running power cables to the mount, the camera and pi computer.
I figure I could put the pi in a box, with some PWM controllers to function as dew heaters plus some voltage regulators to power the camera.

I set about this first version as a learning exercise and proof of concept. I'll no doubt encounter problems I had never though of and will refine things in a later re-design.

Why should you?
Chances are this exact design isn't going to suit your needs 100%, which is why I haven't done a painstaking step-by-step write up. Instead I want to demonstrate how you might be able to come up with a neat solution that is perfect for your setup and give you some ideas on how to go about making it. If you want to know more detail of anything I've done or mentioned, please ask.

My current rig is a side-by-side setup with a DSLR camera + lens and a ZWO camera + lens as guide scope. I had space on the end of my baseplate to mount this box.

I have intentions to upgrade to a larger refractor or so one day and will redesign this box to have a longer shallower linear shape to attach to scope rings, or from a bracket extended from under the scope.

Your rig and requirements might be different and I hope this gives you some ideas and motivation to create your own.

I set about listing some requirements:
- Dew heaters made by using PWM led/motor controller modules. The use of these modules is widely discussed. Be sure to get something that operates in the voltage you want to and can handle the power output needed. I'm using 12V 2A modules. If you have big scopes you might want something like a 3A or 4A output.
- Voltage regulator to output 12V (in case I'm lucky enough to get an ASI1600MM-C or similar).
- Voltage regulator to output 7.4V to my Canon EOS DSLR. This is using a dummy battery to run from an external DC supply.
- Voltage regulator to output 5V to power the raspberry pi.
- Be able to pass through voltage to the EQ6 mount. My EQ6-R is tolerant of 11-16V so I wont use a regulator for this (my power input will be either 12V or 13.5V volt).
- I wanted to be like one of 'the cool kids' and have a row of blade fuses like those trendy RigRunner modules.

You may not be using INDI/Ekos so may not have the need to run a 'pi on your mount, alternatively you might opt to use one of those Intel Compute Sticks if you wanted to run a Windows based platform on your mount.

I brushed up my google-fu and sourced a variety of things. As many of the store links I used have expired, I've added some links to the same products from various other sellers on ebay/aliexpress for your reference. I'll leave it up to you to find a suitable source for your components. Fortunately we live in a world of 'makers' thanks to Arduino and Raspberry Pi projects, inexpensive modules to do a variety of functions can be easily found.

- PWM Modules for Dew heaters (
https://tinyurl.com/y8dnudze) - 12V 4A buck boost regulator (https://tinyurl.com/y74hwm5w)
- Voltage regulators for 7.4V and 5V output (https://tinyurl.com/y8mz8kdu) - inputs 3-40V, outputs 1.23-30V
- Blade fuse holder (https://tinyurl.com/ydf2efbh)

Dew heater outputs use RCA terminals (like many commercial dew heater controllers) (online or your local electronics store).
12V and 7.4V DC power outputs use regular 5.5mm x 2.1mm DC jacks (online or your local electronics store). *see hindsights & lessons learned.
Not necessary, but I matched the EQ-6 power connection using the same GX12-2 socket (you'll find these on ebay)

The box I ended up using to house this is a Jiffy 197x113x63 plastic project box (https://tinyurl.com/y8nncfzk)

To mount it to the base plate, I use an inverted camera quick release plate (https://tinyurl.com/y9t23xsg) The plate is mounted to the top of my base plate using its 1/4-20 screw. The clamp section is attached to the bottom of the project box using a 1/4-20 screw.

Before buying the box I worked out a layout so I had some idea of what size box to use. I used TinkerCAD (https://www.tinkercad.com/) (free, online 3D modeling app) to come up with a design layout. You sketch this on paper if you prefer or make a model using cardboard. Once I'd created basic shapes of the modules, TinkerCAD let me drag them about in 3D and work out where I wanted dials, outputs etc [see fig 2]. Don't underestimate the space needed for cabling. The first box I bought would fit the modules but was too tight to connect everything. The box I'm using now is very snug.

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!

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.

[continued...]

BigNoel (Noel) · #2 19-03-2018, 09:50 PM

[from previous]

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 - https://sourceforge.net/u/brownrb/profile/ ), but that will wait for another cloudy night.

Finally - INDI/Ekos is brilliant. Read more about it here: http://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.

[Posted to CN, IIS and INDI forums].