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Relay Expansion

In this demo we will show how to use the EXP-RELAY for turning on and off a led.

You need:

Connect the ZM1-DB to the EXP-RELAY via te ZBus and connect the wires as in the picture:

Wiring and selectors of EXP-RELAY

For controlling the LED with the relay, it is necessary to interrupt the circuit using the common (COM1) and normally open (NO1) contacts:

  • connect a wire (blue) from the NO1 contact of the relay to GND pin of the ZBus
  • connect a wire (white) from contact COM1 of the relay to the cathode of the LED
  • connect a wire (red) from the anode of the LED to the 3.3V contact of the ZBus

In VSCode, create a new project and paste the following code into

from bsp import board
from expansions import relay

# Initialize board
# Pass te rotative switch selector position
# address = 0x11
relay_sw_sel = (1,)
# Add the EXP-RELAY to the board
# All pin of the EXP-RELAY will be initialized correctly
exp = board.next_expansion(relay, relay_sw_sel)

REL1 = exp.OUT1

# Use gpio api to turn the led on and off
while True:
    print("Toggling relay 1")
    # Switch relay state
    if exp.is_relay_on(REL1):
    # Sleep 3 seconds

The code above configures the EXP-RELAY by attaching a new expansion to the board passing the correct selectors. It then starts a loop that every 3 seconds toggle the relay from NO1 to NC1.

The expected output is:

Toggling relay 1
Toggling relay 1
Toggling relay 1