DIY 12v Multi Power Supply


After I slowly started to expand and automate more and more components on my telescope it became clear that cable management was become a bit of nightmare.

The photo on the left still shows it all fairly organised but this was with out my other project, the motorised filterwheel and motorised focuser. On top of that I am also working on a cooler box for my DSLR camera.
The box for the motorised filterwheel and focuser requires a 12v input plus a USB connection. The cooler box will also require a 12v input and maybe a USB connection in the future. So if we add it all up on what needs to come up:

  1. 2 cables for the RA & DEC motors that come from my EQAstro box.
  2. Power + USB for my DSLR Camera.
  3. USB for my finder scope.
  4. Power + USB for my motorised filterwheel and focuser.
  5. Power for the dew heaters of my main scope.
  6. Power for my dew heater ofmy guide/finder scope.

Adding this all up come to 4 12v power leads, 3 USB cables & 2 cable for RA & DEC control. That comes to 9 cables in total that I need to bring up through the mount to the scope. All these cables need to move freely to ensure the mount can move in all the directions required.

This made me decide to see what I can do to reduce the number of cables. At the end I came up with a design which would reduce to number of cables to two. One 12v power cable and one USB3 cable. It will be slim box that will sit on top of my scope between my main scope and finder/guide scope. 

To box will be fixed to the 2 scope brackets which hold my ED80 in place. On top of the box I the finder/guide scope will be directly mounted. 

This meant that the box has to be ridged & strong enough for it to hold the finder/guide scope without causing any flex when the mount is moving.

On top of all of this I want to try to do this all for a low budget as of the shelve solutions are available but these cost £150+. 

So what does the box need:

  1. It needs a 12v power supply strong enough to power all the items. Adding the power up of all my equipment I need a power supply of 12v & 10 amp (this might be different for you so I recommend you go through your electrical equipment you want to run of this box and add up the max Amp of all items. This will tell you the max Amp required for your power supply). I come to 10 amp as follows:
    1. Two Dew Heater require 1 amp each.
    2. AstroEQ box requires 3 amp.
    3. USB connections (I choose a 4 port USB3 hub) need 1 amp.
    4. Arduino Focuser and Filterwheel need 2 amp.
    5. DSLR camera need 1 amp.
  2. For the dew heaters I need 1 mono RCA Jack as I have dual dew heater control unit i purchased from Dew Control and replaced the Sigarette socket with a Mono RCA plug.
  3. My DSLR camera 7.4v DC Jack socket.
  4. A minimum of 3 USB Connectors
  5. I decided to move my AstroEQ up to the scope instead of it sitting on my pillar. So for this I will need a 12v DC Jack socket.
  6. I also want to have each set of items (e.g. Dew Controller, USB connections, AstroEQ socket) protected by a fuse.
  7. Last, I want to be able to switch each individual set of items via an electrical relay that I can remote operate from my Computer.


To create this box my equipment list will look as follow.

  1. Sturdy plastic box. I choose a the Hammond 1599KSGY.
  2. 4 port USB3 hub. I choose the aLLeri Ultra Slim USB3 4 Port Hub.
  3. The USB3 requires 5v so I needed a 12v to 5v converter. For this I choose this converter.
  4. 1 RCA Mono Jack.
  5. 3 DC Jacket sockets (one for the main power supply, one for the AstroEQ and one for my Canon DSLR). I got these from ebay
  6. 1 USB A to B lead adapter for connecting the Arduino board to the USB hub. I got this USB cable converter.
  7. 1 LED switch to power on/off the box, I got this one from ebay.
  8. 4 way relay switch board from switching on/off the AstroEQ, Dew Heaters, Canon DSLR, DSLR Cooler Box. I got this one from ebay.
  9. The ability to split a 12v input to the different items with the items being fuse protected. I spoke with the manufacturer of this item to ensure that it can take 12v 10 amp as input and use circuits (fuses) between 1 and 3 amp. They confirmed it will work. This is the 12v fused splitter.
  10. Finally I needed the power supply. The power supply will be sitting outside of the box and got one of these.
  11. Last I needed some connectors and wire that can handle 10 amp. These I got from our favorite local electronics DIY shop, Maplins.

Building the box

Building the box and putting it all together was at the end not to difficult just as long as you measure twice and cut once.


I started with removing all the screw mounts in the box. Then did laid out the major components in the box and cutting the space where the USB hub will sit. The USB hub and Arduino will be raised from the bottom of the box.

I also soldered the wires to the connectors for Filterwheel & Focuser motors. 
I use Black Heat Shrink Tube Wire Wrap Electrical Insulation Sleeving to ensure the soldered ends are not exposed and can not cause any short c

You can see the result on the left.

Here you see how I have lifter the USB hub and Arduino from the floor. In the final version I used these spacers from ebay.

Next I drilled the 2 holes for the the focusser & filterwheel connector

These sockets are 16mm in diameter each.

I also cut the hole for the main switch and screwed in the 4 way relay board. You see I used metal screws in the photo right but the final version had plastic screws.

Now I started the final layout and put it all in place.

What you do not see on the photo on the right is the 12v to 5v converter. This has been placed under the allreli USB3 hub.

Under the USB connector between the Arduino and USB Hub you see a Voltage regulator. This is to convert the 12v to 7.4v for my Canon DSLR D1000.
I made this using this diagram.


Here a view from the side where you see to sockets (from left to right Filterwheel & Focuser, Canon 7.4V, AstroEQ, Dew Heater RCA Socket and last the main 12v input socket. Above the 12v socket you see a small cutout. This is for the USB3 cable that connects to the USB hub.

The Arduino & ascom code

The full code for the Arduino UNO and associated ASCOM C# drivers can be found in my GIT hub repository.

The code is using the templates developed by ASCOM standards found here:
My code used 3 ASCOM Templates:

  • Focuser - This is to control the Focuser Motor
  • Filterwheel - This is to control the Filterwheel Motor
  • Switch - This is to control the 4 way relay.

My drivers use the LocalServer implementation to enable me to control all drivers through a single COM port.
Make sure you read up on the LocalServer principle:


The FINAL Result

Final setup all put together and switched on. You can see how the USB3 cable is guided out of the box.

Guidescope mounted on top of the box.

Powerbox and Guidescope mounted on the main scope with all cabling in place. Now only 2 cables come down the mount (one 12 power cable and one USB3 cable.