Hi folks,
I wanted to share some experiences and thoughts about some Zigbee tests I've done recently.
I purchased from a vendor a 2.4 GHz Zigbee kit, and programmed 2 boards in order to do following ping test:
- The first one is the PAN coordinator. 2. The second one is a simple device that joins the PAN coordinator. 3. After joining the coordinator, the device sends a 64 byte message to it. 4. If the coordinator receives the message, it reverses it and sends it back to the device. 5. If the device receives the reversed message it increments a counter, blinks a led for 1 second, and proceeds with the next ping. 6. The test ends after 300 ping sessions (300 seconds).
The 2 boards were programmed to transmit at the maximum RF power, and the pcb antennas were the typical F-shape.
Test A (location: house with 3 floors)
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- I placed the coordinator at the ground floor.
- I started to walk, at the ground floor with the device in my hands.
- I noticed that if between the two boards there were more than 3 walls, the led stopped to blink.
- Then I went out and started to walk in the garden, and noticed that every once in a while the led stopped to blink.
Test B (location: house with 3 floors)
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- I placed the coordinator at the ground floor.
- I went to the second floor and started to walk with the device in my hands.
- I noticed that if I was in the vertical axis of the coordinator, the led blinked, but if I moved into a different room, the led stopped.
Test C (location: house with 3 floors)
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- I placed the coordinator at the ground floor
- I went to the third floor and started to walk with the device in my hands.
- The led did not blink at all.
Test D (location: 100 square meters house with 1 floors)
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- I placed the coordinator in the kitchen.
- I placed the device on the bed of my room.
- The distance between the 2 boards was 6 meters, and there were 3 walls between.
- I noticed that the led blinked regularly.
- I than placed the device in the closet of my room, and noticed that the led stopped to blink.
- I then moved around and noticed that the blink would blink.
These tests make me not very happy. I expected for the 2 boards to cover a longer distance, and I'm gonna repeat these tests with a different antenna, in the next few days.
I heard that the 868 and 915 MHz Zigbee modules cover longer distance but they transmit over a single channel and the RF signal is not spread spectrum modulated.
Comments are welcome.
Enrico