Relay Card allows you to control the circuit of high voltage with a low voltage, say 5V from the Carduino. The relay on the Relay Card is normally-opened. You can connect any high voltage appliance through the 2-pin terminal block connector on the front of the board. The maximum voltage ratings for the high voltage appliances are 3A@250V AC and 3A@30V DC. When you apply a 5V signal to the Relay Card, the relay gets close, and the connected device will turn ON.
Caution: Don't touch the Relay Card while connected to the mains electricity or high voltage DC.
- Operating voltage: 5V
- Maximum switching voltage: 250V AC/30V DC
- Maximum switching current: 3A
- Relay life: 100,000 Cycle
The default I2C address is printed on the back side of the card which is 0x41. However, you can change it to a different address with the card firmware (Read our wiki for how to change the default I2C address of a card.).
The edge connector (gold fingers) has total of 30 contacts (each side has 15 contacts).
On the front side of the Relay Card, a white arrow is printed near the edge connector indicates the pin #1. You can find some pin numbers printed on the edge connector itself (1, 15, and 29). You can count the pin numbers starting with 1 and count by twos from right to left would be 1, 3, 7, 9, 11, 15, 17, 19, 21, 23, 27, and 29. Notice that all the counts are odd numbers.
On the back side of the Relay Card, you also can find some pin numbers printed on the edge connector itself (2, 16, and 30). You can count the pin numbers starting with 2 and count by twos from left to right would be 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 and 30. Notice that all the counts are even numbers.
Among the 30 pins, following pins can be used for I2C communication.
- SDA: Digital I/O, I2C bus serial bidirectional data line (Front: pin #5, #25 / Back: pin #6, #26)
- SCL: Digital Input, I2C bus serial clock input (Front: pin #7, #23 / Back: pin #8, #24)
Also, following pins connect with the common power bus of the board.
- VCC: Power supply (Front: pin #1, #29 / Back: pin #2, #30)
- GND: To be connected to the system ground (Front: pin #3, #27 / Back: pin #4, #28)
How to Use¶
The Relay Card can be plugged into an edge connector slot of one of the following Longan boards.
- Game board
- Car board
- Sensor board
- Extension board
- PI Hap
When you plug, the white arrow head printed on the card should be pointing toward the white arrow head printed near the edge connector slot of the board. Once plugged, it can communicate with the Carduino through the I2C bus line of the board. It will also connect to the common power bus of the board.