Thursday, April 30, 2015

Week 5 (In Lab) - Wiring Relay

Today, we had another very insightful lab. The team first visited the electrical materials department for advice and supplies concerning the setup of the relay structure. After getting some information from the department on current, circuits, breadboards, and the relay itself, the team split up to focus on certain tasks, which are described below.
  • Davina continued to familiarize herself with the software to be used for the control application. She was able to create a sketch for the Arduino that would blink an LED endlessly at intervals defined by a serial command, and also allowed a termination command to come through the serial port.
  • Michelle altered the pump to secure any leakage by re-glueing and taping down the open area. The hot glue from last week's modification had begun to peel away because it doesn't bind well to plastic, so the addition of tape is a hopefully permanent solution. 
  • Le and Parmpuneet got started on the relay while consulting both Dr. Boettcher and the electrical materials department, understanding the importance of precision when working with AC power. After some time, the final relay was designed, as can be seen in Figure 1.
    • With the plug cut off the pump, the power cable's "hot" and "neutral" wires were separated and stripped. Using alligator cables, the hot of the power cable will be attached to the normally open pin on the relay - this will be wrapped in electrical tape to prevent shorts, as will all further steps. 
    • Meanwhile, the hot and neutral wires of the severed plug will also be split and stripped. The hot of this section will be attached to the "com" pin of the relay using alligator clips. 
    • The two neutrals will be twisted together. 
    • The +5V of the Arduino will attach to the coil opposite the normally open pin, an the ground will connect to the coil opposite the normally closed pin. 

Figure 1. A diagram of the entire relay structure, including the pump on the top right, part of the power cable on the bottom right, the relay in the center, and the power-supplying plug on the bottom left.

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