Watch the board in action

Raspberry Pi

Raspberry Pi

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  

ATX PSU 24Pin

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

MiLittleMinder - Micro ATX 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

Pins to control PC lights and buttons

Power Plugs ATX Case MiLittleMinder

LEDS  

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

Power Switch  

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.

Reset Switch

MiLittleMinder - Pi Reset Pins

 

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  

Pi Power Board Power out

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

Sensor Support

Sensor Pins

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

Breakout

Power Rail Options

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

Pi Connector  

40 Pin Ribbon Cable

 

Pi In 

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

Pi Out 

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 

16 Channel Relay

 

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

Easy Connectors, no screws

Terminal Block Wago 250-204 MiLittleMinder

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.

 

DC Jacks 

Pi Power Board DC Jacks

Pi Power Board Power DC Jacks

 

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 

Transistor

 

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. 

Options 

Pi Power Board Jumpers

 

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 put a jumper onto the pin and it will connect 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

Code Samples

MiLittleMinder- Node Red

 

Have you heard of Node Red ?

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.