A prototype is a preliminary model of something. Projects that offer physical products need to show backers documentation of a working prototype. This gallery features photos, videos, and other visual documentation that will give backers a sense of what’s been accomplished so far and what’s left to do. Though the development process can vary for each project, these are the stages we typically see:
Proof of Concept
Explorations that test ideas and functionality.
Demonstrates the functionality of the final product, but looks different.
Looks like the final product, but is not functional.
Appearance and function match the final product, but is made with different manufacturing methods.
Appearance, function, and manufacturing methods match the final product.
I started out with the simple goal of wanting to automate a few things around the home starting with my vertical garden using a Raspberry Pi.
With that goal in mind I decided to make a 16 bay relay board so I could control as many devices as possible from a single point. It was then I found how much space this would take up, and how long it would take to wire up and it became impractical.
So the next logical step was to look into making my own PCB. I noticed that virtually all the devices I wanted to control ran on 12V, I also noticed how many spare ATX power supplies I had lying around and the gears in my head started turning.
Why not combine an ATX power supply and a Raspberry Pi?
So the Pi Power Board was born !!
It has 12V DC jacks on one side, an “off the shelf” 16 Channel relay in the middle, and an ATX power supply up the front powering the lot.
As time went on I developed more and more features and decided the best place for all this to live would be in a standard PC case, so I made it mountable.
I have spent the past few months growing the idea and features and now have a full circuit diagram and board layout fully designed by a professional PCB creator.
The challenge now is that I need to pay for the PCB services, such as time for PCB designer and my first prototype and board batch run.
I am now looking for anyone who would like to share in this by assisting with funding and would welcome any feedback, especially from people with more experience than me.
So how far am I along?
The circuit diagram and PCB board are complete. Shortly I will be ordering my first prototype and will begin testing. I am almost there but need little help getting it to completion. The cost of the prototype and first few boards are going to stretch my finances too far, but with your help we will get this into our homes soon.
For a technical review please watch this, or skip over and read all about the features
Features of the Powerboard
By working with ATX standard it has made the device fit into an existing market of parts.
You will see below how I take advantage of as many features as possible to create a board that is highly versatile while being affordable
First off you will need a Raspberry Pi to run this, but I will assume that you are already familiar with the Pi and are just looking to expand it
The ATX power Supply
The ATX power supply is perfect choice for this design it has 12V, 5V and 3.3V. Also with its control and signal wires we can fully control it from the Pi.
When power is connected to the ATX, and the rear switch is turned on, it will immediately send power to the 5V standby wire (Purple). We will be using this to power the Pi, and give a GPIO access to a transistor that will control the main power wire (Green). With the power wire shorted to earth the PSU will spring to life, outputting the 12V we need. At the same time the power good (Grey) will link up with another GPIO and can be used to monitor if the PSU is running as it should
Support for mounting into a PC case
The design right from the start was to mount everything into a standard PC case, preferably a Mini ATX computer Case, but any size PC case will do.
With that in mind I have placed mounting holes that match standard PC case holes, allowing mounting into a standard PC case, along with the ATX power supply making it a self contained device. I have also allowed extra holes so a Pi or another PCBs can be mounted on top also. Just stack your Pi on top of the power board and it will be fully mounted and self contained
Jumper Pins to control PC lights and buttons
I have added Jumper Pins to power the HDD and Power LED on the case. 5V standby would be connected to the HDD LED, and 5V would be connected to the Power LED.
That way you could see from the outside the current power state
I also have pins for power switch to enable a quick way to power down the device. One end of the pin will be connected to 3V, the other to a GPIO. The Pi will be watching that GPIO and when it sees it HIGH it can initiate a shutdown, of course this will be controlled by the code, see code samples for more info.
The reset Plug can be connected to the Pi’s reset pins, Pins are not soldered on at the factory, you will need to solder them on yourself. The Pi comes with a reset option so why not use it, it also will make it easier to hard reset your Pi if there is a fault you can’t recover from.
Power out and Fan Plug
The board will have a female molex connector and a standard fan plug. You can use either to power a fan or you might just need access to 5V and 12V
There is on board support for sensors, with 4 easily accessible GPIOs with 5V and Ground pins by their sides. There is a 10K resistor to give you a pull up signal allowing you to plug DHT Temperature and Humidity sensors straight in with no extra soldering. Of course there are pins to disable the pull up meaning you can plug any sensor you like in
At the front of the board is a breakout area that have 3 power rails supplying 3V, 5V and 12V. This will allow you to add your own circuits further customising the board. There are also jumpers to disable the power rail if you don’t want them
There is a 24 Pin box header connection to connect the Pi to the Power Board. 5V standby will be feed to pins 2 and 4 allowing the Pi to draw power from the ATX at all times. So as soon as the ATX is connected to mains, the Pi will boot and allow you control the PSU
There is another 24 Pin box header connection to be used as an out. I didn’t like the idea of having all the pins trapped and not easily accessible so I mirrored them to another 24 pin connector. The exceptions being that the Pi out 5V and 3V pins will be powered from the ATX and not the Pi, as to reduce load on the Pis power source. Its also important to note that its 5V and not 5V standby. The Pi out connection is not really intended to have another Pi connected to it, only to allow easier access to the pins for other uses, such as a sensor
16 Channel Relay Board
These 16 channel relay boards are cheap and readily available. I have made allowances for this board to be mounted and powered. It runs off 12V so there is a connector to allow powering of it. By using this off the shelf device it will reduce the production price of the Pi Power Board
The relays 12V common and normally open will be connected to the board to allow the flow of 12V to the DC jacks. The relay contact points will be connected to the board via Wago connectors like these. Just push on the pins and your wire will slide in and clamp, no screws needed..
The rear will have 16 DC Jacks that will peak though the standard shield hole on a PC case. This will allow you to close up the case and have the DC jacks accessible.
If you use DC connectors similar to the image here you can easily plug up any 12V device. The screw terminals means no soldering or heat shrink.
Activating the Relays
Relays rely on their pins to be made low, so you can’t just connect a Pi straight to the device and set a pin to high and have a relay activate. My solution was to setup a simple transistor to complete the circuit to ground. This way you can set a Pi pin to high and the relay will activate.
Some of these features might not suit every situation so I have added Jumpers to turn features on or off
There is a pin to not allow 5V standby to flow into the Pi, allowing you to power the Pi the old fashioned way, via a USB plug
Or just want the ATX to fully turn on when power is connected, then just put a jumper onto the pin and it will short Power on (Green) with Earth, turning the ATX on. You can even cut all power to the Pi out connector. Or save a GPIO by not watching the “Power Good” cable (Grey)
I didn't want to completely lock down everything so these jumpers make it more versatile
Node Red is a very quick and easy way to program your Pi, and it comes built in to Raspbian. I will supply sample code so you can get started immediately with your new board. Its web based so you can control it from your phone and its quick to learn.
Risks and challenges
This system relies on 5V Standby Power being injected into Pins 2 and 4 on the Pi. This is not the recommended way to power a Pi as it bypasses the power filter on the Pi.
However this risk is minimal due to the ATX PSU delivering a clean 5V from the Standby Wire.
I have included pin jumpers so you can disable this feature and power the Pi by alternative means
Overloading of the board by connecting up too many 12V devices
This has been addressed by splitting up the 16 Ports into 4 12V power sources. Also the PSU has a power overflow cutout feature, and will notify you via the “Power Good” wire
DC Jacks are surface mounted straight onto the PCB
Jacks have an anchor, so should take some mistreatment but could break off if pushed too hard
There are two Pi connectors
Murphy's law says that someone will plug into the wrong connector. The good news is that no harm can really be done, but I might get a complaint or two about it not working properly
It will be poking out the back of the ATX case so will leave a big hole. I should put holes to allow mounting brackets alongside the DC jacks. Then at a later date create something and screw it in place. But I will probably just have a custom shield built later
Lack of eyes
Although myself and two professions have looked over this board and added in key ways, only 3 people have seen it up to this point. It would be good to get feedback on things we may have obviously missed or even ideas for new features.