The latest version of the 8-MOSFET card (V5.0), now in stock, has several major improvements:
- On board processor permits proportional load control using PWM at 1kHz
- RS485 port connected to the local processor permits operation as MODBUS RTU slave, replacing the Raspberry Pi with any PLC
- Heavy duty, 5mm pluggable connectors can control loads up to 12A
- High current channels are galvanically separated from the High Voltage channels
- TVS diode protection on high current outputs, diode protection on high voltage
- All jumpers replaced with DIP Switches
- Software compatible with previous version
- Eight MOSFETS 8-Layer Stackable HAT for Raspberry Pi
- Status LEDs on each output
- Pluggable Connectors 24-12 AWG wires
- Four High Current Loads, 12A/24VDC
- Four High Voltage Loads, 2A/240VDC
- RS485 with TVS protection and MODBUS protocol
- Reverse polarity power supply protection
- General purpose pushbutton
- All mounting hardware included: brass stand-offs, screws and nuts
- Software self-test
- Uses only I2C port (address 0x20..0x27 or 0x38..0x3f ), all GPIO pins available
- Command Line
- Python Drivers
- Node Red Nodes
- OpenPLC module
The 8-MOSFETS card is a stackable expansion card for Raspberry Pi. It has four high current channels which can drive 12A/24V loads and four high voltage channels which can drive loads of 4A/240V. Stackable to 8 layers, the card can provide up to 64 solid state outputs to each Raspberry Pi.
The card is compatible with all Raspberry Pi versions from Zero to 5. 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.
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 50mA. If power is applied to the card, no other power supply is needed for the Raspberry Pi.
DIP SWITCH CONFIGURATION
A six position DIP switch is used to select the source of the RS485 port and the position of the card in the stack, if multiple cards are used.
The card has an RS485 port which can be driven from the Raspberry Pi, or from the local processor. Leave the TX and RX switches in the OFF position to connect the port to the local processor. Set both to ON to connect to USART1 of the Raspberry Pi.
When DIP Switches are ON, Raspberry Pi can communicate with any device with an RS485 interface. In this configuration the card is a passive bridge which implements only the hardware levels required by the RS485 protocol. To use this configuration, you need to tell the local processor to release control of the RS485 bus:
~$ 8mosind  rs485wr 0 0 0 0 0
When DIP Switches are OFF, the card operates as MODBUS slave and implements the MODBUS RTU protocol. Any MODBUS master can access all the card's inputs, and set all the outputs using standard MODBUS commands. A detailed list of commands implemented and parameters addresses can be found on GitHub:
In both configurations the local processor needs to be programmed to release (jumpers installed) or control (jumpers removed) the RS485 signals. See the command line online help for further information.
The last position on the DIP switch is the RS485 line terminator. Set it to ON if the card is last on the RS485 chain.
- Power supply: Pluggable connector
- Power consumption: 10mA
- On board resettable fuse: 3A
- MOSFETS 1-4: 125V, 7.5 mOhm
- MOSFETS 5-8: 250V, 280 mOhm
- Connector ratings: 250V/8A
- MOSFETS gate voltage: 12V
- Four M2.5x18mm male-female brass standoffs
- Four M2.5x5mm brass screws
- Four M2.5 brass nuts
- 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
This board is fantastic, great for controlling a wide range of loads, trivially easy to interface with, comes with everything you need, scalable and flexible.
It's faster, they pretty much rectified all of the previous shortcomings of the past models, most notably the absolutely crippling front side bus bottleneck (making older versions very... Impractical to say the most). Interface throughput rates make sense now, resources are up, and critical features have been added.