Eight Thermocouples Data Acquisition HAT for Raspberry Pi
Compatible with all Raspberry Pi versions from Zero to 4, the Eight Thermocouples card offers a compact and inexpensive solution for reading and storing data from up to 64 thermocouple temperature sensors. Using 24 bit delta-sigma A/D converters with four channels each, the card achieves better than 0.1% accuracy. Field calibration with a precision 100Ω resistor can lead to 0.01% precision.
COMPATIBILITY
The Eight Thermocouples card is compatible with all Raspberry Pi versions from Zero to 5. It shares 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 Eight Thermocouples DAQ Card needs 5V to operate and can be powered from Raspberry Pi or from it's own pluggable connector. The cards needs 50mA to operate.
LED INDICATORS
The Eight Thermocouples DAQ board has eight LEDs that can be activated when the input reaches a preset threshold. The threshold can be set in software for each input.
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.
STACKING MULTIPLE CARDS
Up to eight cards can be stacked on your Raspberry Pi. Three positions of the configuration DIP Switch labeled ID0, ID1, ID2 are used to select the stack level. Cards can be stacked in any order.
RS485/MODBUS PORT
The Card has an RS485 port which can be driven from the Raspberry Pi. Set both to ON to connect the RS485 port 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.
When DIP Switches are OFF, the Raspberry Pi GPIO pins can be used for other functions. If multiple cards are stacked, only one card can have the DIP Switches ON.
RS485 TERMINATOR
The first position on the DIP switch is the RS485 line terminator. Set it to ON if the card is last on the RS485 chain.
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 which monitors this pin, and if pressed for more than a desired time, issues the shut-down command.
CARD LAYOUT
MECHANICAL SPECIFICATIONS
