8-MOSFETS Solid State Stackable Card for Raspberry Pi

The 8-MOSFETS card is a stackable expansion card for the Raspberry Pi. It has four high current channels which can drive 8A/24V loads and four high voltage channels which can drive loads of 2A/240V.

Stackable to 8 layers, the card can provide up to 64 solid-state outputs to each Raspberry Pi!

Pluggable connectors make the 8-MOSFETS card easy to use when multiple cards are stacked up. Status LEDs show when MOSFETs are on or off.

For any technical questions about this product please email support@sequentmicrosystems.com

Features

• Eight MOSFETs with Status LEDs
• Pluggable Connectors 26-16 AWG wires
• Four High Current Loads, 8A/24VDC
• Four High Voltage Loads, 2A/240VDC
• RS485 Port
• Reset pushbutton
• All mounting hardware included: stand-offs, screws and nuts
• Software self-test
• Command Line
• Python Drivers
• Node Red Nodes

Compatability

The card is compatible with all Raspberry Pi versions from Zero to 4. All stacked cards share the I2C bus using only two of the Raspberry Pi’s GPIO pins to manage all eight cards. This feature leaves the remaining 24 GPIOs available for the user.

Power Requirements

The 8-MOSFETS card needs 5V to operate and can be powered from Raspberry Pi or from it's own pluggable connector. The card draws about 10mA. If power is applied to the card, no other power supply is needed for the Raspberry Pi.

Stacking Multiple Cards

Up to eight 8-MOSFETS cards can be stacked on your Raspberry Pi.

Each card is identified by jumpers you install to indicate the level in the stack. Cards can be installed in any order. The three-position jumper on the upper right corner of the card selects the stack level.

For your convenience, two jumpers are provided with each card.

Reverse Power Supply Protection

The board is protected to accidental reverse power supply with a 5.8A, 39 mOhm MOSFET which breaks the ground line if reverse power is applied.

Reset Pushbutton

Shutting down the Raspberry Pi by turning off the power can result in SD Card failure. To prevent this, a shutdown command needs to be used before power cut-off. But this requires a monitor, keyboard and mouse connected to the Pi.

A momentary 'on' push button installed at the edge of the board provides a convenient way to shut down the Raspberry Pi. The button is routed to pin 37 (GPIO 26). You need to write a script that monitors this pin, and if pressed for more than the desired time, issues the shut-down command.

Accessories

DIN-Rail Mounting

The 8-MOSFETS card can be installed parallel on a DIN-Rail using the DIN-Rail Kit Type 1, or perpendicular using the DIN-Rail Kit Type 2.

Smart Fan (coming soon)

The Smart Fan provides a stackable cooling solution for Raspberry Pi. Its onboard processor powers the fan just enough to maintain the preset temperature of the Pi.

If the 8-MOSFETS card is used to drive multiple high current loads, a secondary Smart Fan can be installed on top of the card to provide adequate cooling.

Package Contents

• 1. 8-MOSFETS Card
• Mounting hardware
• Four M2.5x18mm male-female brass standoffs
• Four M2.5x5mm brass screws
• Four M2.5 brass nuts
• Two stack level jumpers
• Eight 3-pin male connector plugs for MOSFETs and two 2-pin connector plugs for RS485 and power.

Card Layout

Electrical Specifications

• Power supply: Pluggable connector
• Power consumption: 10mA
• Onboard resettable fuse: 3A
• MOSFETS 1-4: 125V, 7.5 mOhm
• MOSFETS 5-8: 250V, 280 mOhm
• Connector ratings: 250V/8A
• MOSFETS gate voltage: 12V

Mechanical Specifications

Resources

• Open Source Hardware Schematic
• 3D Printing Enclosure
• Command Line (GitHub)
  
• Python (GitHub)
• Node Red (GitHub)

Software

Software Interfaces

You can write your own application using the Command Line or Python Libraries provided. No programming is required if you use the Node-Red nodes provided. You can drag-and-drop the functional blocks to design your application. Examples are provided at GitHub.

Self Test

The 8-MOSFETS card can be tested before installation by running a simple command from the command line. The card will cycle each MOSFET on and off at 0.5 seconds interval. The lighting of the LEDs will assure that all MOSFETS are functioning. Optional loads on each channel can extend the user's confidence in the hardware.

Quick Start

Plug your 8-MOSFETS card on top of your Raspberry Pi and power up the system using only one 5V/3A power supply.

Enable I2C communication on Raspberry Pi using raspi-config.

Install the 8-MOSFETS software from github.com:

git clone https://github.com/SequentMicrosystems/8mosind-rpi.git
cd /home/pi/8mosind-rpi
/8mosind-rpi$ sudo make install
/8mosind-rpi$ 8mosind -h

The program will respond with a list of available commands.

Connect your load between pin 2 of any of the load connectors and the positive side of your external power supply. Connect the negative side of your external power supply to pin 1 of the output connectors. Turn on and off the load using the corresponding command.