current shunt in our circuit is that heat would change the resistance so the measurements wouldn’t be as accurate with the rise of the current since the resistance would be a different value and this wouldn’t serve project’s main goal is to measure power with accuracy. This accuracy may not be achieved if Eddy Current Sensor was our choice current measuring component neither. In our power measuring strip design, out of many components more or less all of them will have magnetic fields since they are all electrical instruments. These components would interrupt the precision of the Eddy Current Sensor. On the other hand; Hall Effect Current sensor looks way more superior in measuring the circuit task because of its advantages such as: High speed and repeatability highly linearity, a very long life and isolation from another high voltage in the same system, so it wouldn’t be affected by the other components just like Eddy Current sensor would. Current transformers were a no go as well since they are really good for higher voltage measurements but their sizes are usually larger than the our design would allow and they wouldn’t be as beneficial as neither magneto resistive field sensor nor hall effect current sensor. The superiority of two sensors above compared to current transformer would be summarized as: for Hall effect current sensor; logic capability, highly linearity, non mechanical structure, resistance against heat, perfect to measure high currents for safety concerns, are insensitive to dust, vibration, humidity, cold and hot and well sealed structure. On the other hand for magneto resistive field sensor advantages over current transformer would be: good accuracy and high sensitivity, durability, fast response rate, decent size, can be used in harsh conditions and reasonable price. The two alternatives left, Magneto Resistive Field Sensor and Hall Effect current sensor were both good choices for our power measuring circuit design but our choice was towards Hall Effect Current Sensor. Besides the advantages they would bring to our power measuring circuit design reviewed in the above paragraph we had to go into detail to compare the two in order to make the best decision for our design. When two compared, we sow that Magneto resistive sensor had limited linear range, temperature drift and was sensitive to interfering magnetic fields from other components. Under these circumstances, our choice of going with Hall Effect current sensor was justified. Below in figure 44 is HONEYWELL S&C CSLA2CD; our choice of Hall Effect Current Sensor as a part of the Power Measuring Circuit Blog Diagram: Figure 44: Power measuring circuit block diagram
4.1.3 Wireless Case Name: Case three – Wireless Unit tested: CC2500 Transceiver Assumptions: The MSP430 MCU is able to read and output power consumption information to the transceiver from a given outlet. Test Data: Hard coded data from software and power measurements given by the MSP430. Steps to be executed: Hard code data into the EZ430-RF2500 wireless Development Tool Using this code send a data packet to a different transceiver Read data from the transceiver and compare it to the original packet Autonomously send measured data from one power strip to another. Each power strip contains one microcontroller and one transceiver. Test low power consumption using wireless information. When a sleep mode signal is received the MSP430 should enter sleep mode. If a turn-on signal is received the MSP430 should send a second packet of information. The MSP430 should send a packet of information every 5 seconds. Repeat steps 1 through 4 indoors with a line of sight range from 10ft to 100ft. Again test for this range between 2 to 3 rooms on the same floor and then between rooms from adjacent floors. Expected Result: The transceiver should be able to send and receive accurate packet information between rooms. Summary: The wireless modules will need to be checked first for functionality and then for range and reliability. Communication between two to three rooms at 50 feet is necessary. If adequate range is not met then considering different antenna options can increase the range. Each unit should be able to consistently receive and transfer data bytes. Once all power strips are functional then the design will be tested to find the limitations in range of the design. The open air tests will be used to determine to maximum range of our design. By adding walls in between the wireless communication we can see how much of an effect different materials have on the range of the system. Case Name: Case four – LCD Unit tested: QSscreen Controller Assumptions: MSP430 is functional and can correctly send and receive data to other microcontrollers.