ClusterCTRL: Stack

The ClusterCTRL: Stack (controller and passive backplane) is a simple way to both power and control cooling for a stack of 5 Raspberry Pi boards (not included).

The entire stack of Raspberry Pi can be powered by a single 12-24V PSU with a 5.5mm jack and 2.1/2.5mm pin (not included - see notes below on power) via the onboard 10A 5.1V DC-DC regulator - providing 2A per Raspberry Pi.

The main board includes a 6-pin header for monitoring each Raspberry Pi, and includes connectors for 2 independently controlled fans. The USB-A connector is intended for 5V power only to run a low-power switch or similar.

Connecting the ClusterCTRL Controller (via the Micro USB connector) you can use the "clusterctrl" tool which allows the following:

• Control power for each Raspberry Pi individually
• Ganged FAN On/Off (when "off" the individual fans are still controlled via GPIO as above)
• Measures both the voltage supplied to the Raspberry Pi and the 12-24V input voltage
• Configure power-on state (each individual Pi can be set on/off by default)
• A single Controller Pi can control many ClusterCTRL devices (Stack/Triple/Single/etc)

Controller

• Powered by 12-24V PSU.
• 20 pin header for Power (2x5V and 2xGND for each Pi).
• 6 pin header for monitoring of Raspberry Pi (1 GPIO pin per Pi).
• Onboard 10 Amp 5.1V DC-DC regulator (2 Amp allowance per Pi).
• Connectors for 2 independently controlled fans.
• Micro USB for ClusterCTRL allows controlling individual Pi power, fan, auto power on, voltages, etc.
• USB Type-A connector 5V (ONLY) power output, can be used to power a 5V switch for example.

Passive backplane

• Connects between the ClusterCTRL Stack Controller to each Raspberry Pi.
• 20+6 pin connectors for ClusterCTRL Stack Controller.
• 20 pin connector for each of the five regular-sized Raspberry Pi (B+/2/3/3+/4).
• Connects GPIO BCM18 of each Raspberry Pi to the Controllers monitor header.

Usage

As supplied the Controller can be used standalone - once power is applied to the ClusterCTRL Stack each Raspberry Pi will be powered on in 1-second intervals. The GPIO (BCM18) pin from each Raspberry Pi is monitored, when this is set high the corresponding FAN is turned on (P1/P2 = FAN1 and P3/P4/P5 = FAN2) as required to cool the Pi.

You can use any software on the Raspberry Pi nodes (Raspbian/Ubuntu/etc.). To control the nodes you will need to install the clusterctrl software. Currently, this needs to be manually installed - see the FAQ entry for manual installation steps.

To enable the fans to be turned on/off automatically when a Raspberry Pi requires cooling add the following to /boot/config.txt on each Raspberry Pi (in the example below it will turn the FAN on at 75C and off at 65C).

dtoverlay=gpio-fan,gpiopin=18,temp=75000

Connecting the ClusterCTRL Controller (via the Micro USB connector) you can use our "clusterctrl" tool which allows you to.

• Control power for each Raspberry Pi individually.
• Ganged FAN On/Off (when "off" the individual fans are still controlled via GPIO as above).
• Measures both the voltage supplied to the Raspberry Pi and the 12-24V input voltage.
• Configure power-on state (each individual Pi can be set on/off by default).
• A single Controller Pi can control many ClusterCTRL devices (Stack/Triple/Single/etc).

8086 recommend using two 70mm fans for cooling, one for the ClusterCTRL Stack Controller+P1+P2 (FAN1) and the other for P3/P4/P5 (FAN2). However, users may wish to utilise different fan options.

What comes with the ClusterCTRL Stack

• ClusterCTRL Stack Backplane
• ClusterCTRL Stack Controller
• 4x M2.5 12 mm F-F spacer
• 24x M2.5 25 mm M-F spacer
• 8x M2.5 6 mm screws

Note: Raspberry Pi boards and heatsinks not included.

What do I need to use the ClusterCTRL Stack?

• 12-24 Volt Power Supply with 5.5 mm 2.1/2.5mm barrel jack (60 Watt recommended minimum)
• 5x Raspberry Pi (Pi2/3/3+/4)
• 2x 5V fans and heatsinks (optional)
• Controller Pi (can be one of the stack) (optional)
• USB Cable to connect to controller (optional)
• Gigabit Ethernet Switch (optional)

When choosing a power supply for the Stack searching for laptop/monitor power supplies with an output of 12/19 Volts and more than 60 Watts of power should help (ensuring they're 5.5mm jack with 2.1/2.5mm pin).

Due to the backplane being a fixed size you can only add an additional board under the last Pi.

Cases

• STL files for a 3D printed case are available on Pinshape