The example below is only one way how to set up the Relay Module.
In this examples we have connected a Raspberry Pi 4 to the BEVRLink Manager HAT V2 with BEVRLink 8 Channel Relay V1 12V. With this relay module board you need the BEVRLink Power Supply 12V 2A.
Optional for a safe setup we recommend to use case for both the manager and relay boards: BEVRLink Cases
Install Raspberry Pi OS
1.
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2.
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3. This example uses Raspberry Pi OS Lite
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4. Choose Storage
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5. Set hostname, enable ssh (and WiFi credential if needed)
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6. Press Save
7. Press Write
8.
ssh pi@bevrlink.local
replace “pi” with the user you wrote in the settings earlier, “bevrlink” with the hostname you wrote earlier.
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Enable i2c
9.
sudo raspi-config
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10. Select 3 Interface Options and then I5 I2C. A prompt will appear asking Would you like the ARM I2C interface to be enabled?, select Yes, press Enter, Press enter to OK and navigate down to <Finish> press Enter and reboot.
11.
sudo reboot
Install i2c and Python libraries
12.
sudo apt update
sudo apt install python3-smbus python3-dev i2c-tools
13. test if it works
sudo i2cdetect -y 1
14. Example with chip 9554A used in 4 ch relay
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nano relay.py
Each relay is a bit in the sent byte, so 0x55 converted to binary number 01010101 turns on relay 1,3,5 and 7
Add a jumper to position 1 on the expander to increase the address to 0x21
Remove or add lines contaning the i2c address for each relay board removed or added
from smbus import SMBus # Import the i2c library
import time # Import time library to use sleep
i2cbus = SMBus(1) # Create the i2c bus object
i2caddress_Relay_1 = 0x20 # Address of relay card 1
i2caddress_Relay_2 = 0x21 # Address of relay expansion card
# Registers
INREG = 0x09 # Input read register
OUTREG = 0x0A # Output write register
IOCONF = 0x00 # Configure IO as Input or Output register
# Config all pins as outputs
i2cbus.write_byte_data(i2caddress_Relay_1, IOCONF, 0x00)
i2cbus.write_byte_data(i2caddress_Relay_2, IOCONF, 0x00)
while (True): # Loop
# Turn on half the relays
i2cbus.write_byte_data(i2caddress_Relay_1, OUTREG, 0x55)
i2cbus.write_byte_data(i2caddress_Relay_2, OUTREG, 0x55)
time.sleep(1) # Wait 1 second
# Turn on the other half
i2cbus.write_byte_data(i2caddress_Relay_1, OUTREG, 0xAA)
i2cbus.write_byte_data(i2caddress_Relay_2, OUTREG, 0xAA)
time.sleep(1) # Wait 1 second
python relay.py
15. CTRL+C to stop script