Week 6 - Transmission of wireless signals

For Week 6, our final activity before work really gets underway on our project, we are transmitting signals. Sounds fun huh? It is fun! We got to play around with some Wireless Sensor Network (WSN).

What is WSN?

WSN are spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location.

We used 2 Xbee units, which are being connected to 2 separate computers to send the signals.

Figure 1: Xbee units

Figure 2: Connecting Xbee to Arduino

Task 1: Establishing a connection

We are required to set up a connection. In order to do this, there must be a receiver and an transmitter. The Xbee that has the USB port can be connected directly to the computer port. This setup will be the transmitter. The other Xbee that has no port will be connected to and Arduino. The Arduino is being connected to a second computer. This setup will be the receiver.

Figure 3: Connection of Xbee with Arduino

A code will be uploaded into the Arduino in order for the Xbee unit to receive and process the signal. After uploading the code, we have to set up the destination address. This is to ensure that we send the signal to the right receiver.

After setting up the destination address, our transmitter sends out a signal and it is being picked up by the receiver.

Task 2: Ring or get ring

The next task is to allow another group to ring our team's buzzer. For this task, we are working with team 7, where they are the transmitter and we are the receiver.

We will first have to connect the buzzer to the Arduino and set up a code.

Figure 2: Connection of buzzer

After that, we set up the destination address with group 7. From there, they send a signal to us to ring our buzzer.

Task 3: Connecting Week 1 pH sensor to lecturer's connection

The last activity is to establish a connection with our lecturer and send the data we collected from our pH sensor to her. So, this is how it works:

1) We set up the code and the destination address
2) We use our pH sensor to measure the pH of a unknown liquid.
3) The data is detected by the Arduino
4) Xbee unit send this data to our lecturer
5) Data is displayed on lecturer's computer screen


Here are some photos of us in action:

Figure 4

Figure 5

Figure 6

Figure 7

As most of the action for the activities involve only programming and connecting small electronics, we are mostly seated while doing the activities. Not much walking and usage of big machinery this week. Stay tune for the following weeks if you want to see us in action with the big machinery.

Some of the problem we faced while carrying out the activities include:

• Program error
• Wrong destination address being set up with group 7
• Arduino and Xbee software being unable to detect the components, even when connected to the computer

Should such situation arise again, we have the following measures to solve the problems:

Program error - Solve by troubleshooting and debugging errors in the code used. In some cases, the Arduino had been configured incorrectly, and in some other cases, the code provided by the lecturer had a non-obvious bug.

Wrong destination address - To solve this problem, one way is effective communication with others. This will allow each other to understand the problem and work together to solve it. In the case of the activities, we set up the wrong destination address with group 7. We communicated with them and through this interaction, we realised we set up the wrong address. We managed to correct the address and sound the buzzer.

Computer unable to detect Xbee or Arduino - This issue was quite unpredictable. To solve this, we may need more than 1 computer installed with the Xbee or Arduino software. If it cannot be detected, we will use the next computer. We usually face this problem when using Keith's or Joel's laptop. Only Lucas's or Pei Yong's laptop can detect the components. 

Reflection

From this activity, we can see that the Xbee unit is simple to use and it is quite effective in data transmission. However, as we plan to use a wire for data transmission for our robot project, so this is not as relevant to us as it is to other groups.

Underwater signals have to be strong enough to pass through the water. Unfortunately for us, the Xbee wireless data transmission system is not strong enough to do so.. A cable will be able to transmit the signal directly to the robot, which is more effective and efficient. 

Stay tuned to this blog for updates on our robot.



Lucas

Keith