Project for control of hydrogen filling station.
Initially control of 3 stage gas booster compression system (to 700 bar) via touch screen GUI using Python + Tk
Control(via pneumatic 24v relays x 5 expandable to 8)of: hydrogen input valve Air to each booster High pressure H2 vent (NO) (for emergencies)
Monitoring of H2 pressures (4-20 mA x 4, expandable to 8) input output interstage (x2)
Monitoring of Temperatures (themocouples i2c interface x 4, expandable to 8) input output interstage (x2)
Monitoring of car IR data via RS485 serial link
For future use: i2c 4- 20 mA ~24v transmitter - for control of proportional H2 valve 2 x SPDT relays. Additional temperature sensors DS18B20
Hardware:
RPi 4 in Argon case with 250 Gb SSHD OS bullseye version ID 11 Python 3.9.2 I2C on pins GPIO2 /SDA1 and GPIO3 /SDL1
For current loops: DFROBOT Gravity: Analog Current to Voltage Converter + 8 channel, 12c, Pi ADC 17 bit,(2 x 4 channel MCP3424 A/D 12c address 0x68, 0x69) (Channel 8 for hydrogen alarm)
For temperature: Adafruit MCP9600 thermocouple breakout 12c (Address 0x67 - 0x60)
Additional Temperature measurement with DS18B20 sensors on GPIO 22
For 24v pneumatic relay control: Jee Labs Output plug - i2c, 8 channel, uses MCP23008 + darlington array ULN2803 (i2c Address 0x26 / 0x27)
For current loop transmitter: DFROBOT Gravity: I2C 4-20mA DAC Modul, uses chip GP8302 (i2c Address: 0x58)
For 5v relays: R1 GPIO 17 R2 GPIO 27
For RS485 (Ir serial from car): RS485 to ttl board MAX 3485 (NB 5v to 3.3 - need voltage divider) RPi Tx GPIO 14, Rx GPIO 15