4-20mA TRANSMITTER ARDUINO

The board integrates an ATMega328P processor, RS-485 communications and three 4-20mA output channels. Each channel is independent with its own electrical ground.
The board must be powered at 12V.
It is compatible with the Arduino development environment, giving access to the processor pins through screw terminal holes.

ATMEGA328P:

The high-performance ATMEGA328P Microchip picoPower® 8-bit AVR® RISC-based microcontroller combines 32 KB ISP Flash memory with read-while-write capabilities, 1024B EEPROM, 2 KB SRAM, 23 general purpose I/O lines, 32 general purpose working registers, three flexible timer/counters with compare modes, internal and external interrupts, serial programmable USART, a byte-oriented Two-Wire serial interface, SPI serial port, a 6-channel 10-bit A/D converter (8-channels in TQFP and QFN/MLF packages), programmable watchdog timer with internal oscillator, and five software selectable power saving modes. The device operates between 1.8-5.5 volts.
By executing powerful instructions in a single clock cycle, the device achieves throughputs approaching one MIPS per MHz, balancing power consumption and processing speed.

Features

• High performance, low power AVR® 8-bit microcontroller
• Advanced RISC architecture
  • 131 powerful instructions – most single clock cycle execution
  • 32 x 8 general purpose working registers
  • Fully static operation
  • Up to 16MIPS throughput at 16MHz
  • On-chip 2-cycle multiplier
• High endurance non-volatile memory segments
  • 32K bytes of in-system self-programmable flash program memory
  • 1Kbytes EEPROM
  • 2Kbytes internal SRAM
  • Write/erase cycles: 10,000 flash/100,000 EEPROM
  • Optional boot code section with independent lock bits
    • In-system programming by on-chip boot program
    • True read-while-write operation
  • Programming lock for software security
• Peripheral features
  • Two 8-bit Timer/Counters with separate prescaler and compare mode
  • One 16-bit Timer/Counter with separate prescaler, compare mode, and capture mode
  • Real time counter with separate oscillator
  • Six PWM channels
  • 8-channel 10-bit ADC in TQFP and QFN/MLF package
    • Temperature measurement
  • Programmable serial USART
  • Master/slave SPI serial interface
  • Byte-oriented 2-wire serial interface (Phillips I2C compatible)
  • Programmable watchdog timer with separate on-chip oscillator
  • On-chip analog comparator
  • Interrupt and wake-up on pin change
• Special microcontroller features
  • Power-on reset and programmable brown-out detection
  • Internal calibrated oscillator
  • External and internal interrupt sources
  • Six sleep modes: Idle, ADC noise reduction, power-save, power-down, standby, and extended standby
• I/O and packages
  • 23 programmable I/O lines
  • 32-lead TQFP, and 32-pad QFN/MLF
• Operating voltage:
  • 2.7V to 5.5V for ATmega328P
• Temperature range:
  • Automotive temperature range: –40°C to +125°C
• Speed grade:
  • 0 to 8MHz at 2.7 to 5.5V (automotive temperature range: –40°C to +125°C)
  • 0 to 16MHz at 4.5 to 5.5V (automotive temperature range: –40°C to +125°C)
• Low power consumption
  • Active mode: 1.5mA at 3V – 4MHz
  • Power-down mode: 1µA at 3V

4-20mA XTR115:

The XTR115 is precision current output converters designed to transmit analog 4-to-20mA signals over an industry standard current loop. They provide accurate current scaling and output current
limit functions.
The on-chip voltage regulator (5V) can be used to power external circuitry. A precision on-chip VREF (2.5V for XTR115) can be used for offsetting or to excite transducers. A current return pin (IRET) senses any current used in external circuitry to assure an accurate control of the output current.
The XTR115 is a fundamental building block of smart sensors using 4-to-20mA current transmission.
The XTR115 is specified for operation over the extended industrial temperature range, –40°C to +85°C.

Features

• LOW QUIESCENT CURRENT: 200µA
• 5V REGULATOR FOR EXTERNAL CIRCUITS
• VREF FOR SENSOR EXCITATION: XTR115: 2.5V
• LOW SPAN ERROR: 0.05%
• LOW NONLINEARITY ERROR: 0.003%
• WIDE LOOP SUPPLY RANGE: 7.5V to 36V
• SO-8 PACKAGE

RS-485 SN75HVD08:

The SN75HVD08 combines a 3-state differential line driver and differential line receiver designed for balanced data transmission and interoperation with ANSI TIA/EIA-485-A and ISO-8482E standard-compliant devices.
The wide supply voltage range and low quiescent current requirements allow the SN75HVD08s to operate from a 5-V power bus in the cable with as much as a 2-V line voltage drop. Busing power in the cable can alleviate the need for isolated power to be generated at each connection of a ground-isolated bus.
The driver differential outputs and receiver differential inputs connect internally to form a differential input/output (I/O) bus port that is designed to offer minimum loading to the bus whenever the driver is disabled or not powered. The drivers and receivers have active-high and active-low enables respectively, which can be externally connected together to function as a direction control.

Features

• Operates With a 3-V to 5.5-V Supply
• Consumes Less Than 90-mW Quiescent Power
• Open-Circuit, Short-Circuit, and Idle-Bus Failsafe Receiver
• 1/8th Unit-Load (up to 256 nodes on the bus)
• Bus-Pin ESD Protection Exceeds 16-kV HBM
• Driver Output Voltage Slew-Rate Limited for Optimum Signal Quality at 10 Mbps
• Electrically Compatible With ANSI TIA/EIA-485 Standard