Discussion
Considerations / Assumptions
Some considerations made to the design of the Power Line Appliance Controller are as follows:
- Needed to choose a frequency for the signal, which must be larger that than the 60Hz which the frequency of the power line is. It should not be a multiple of 60Hz either. We will preferably use 1 KHz.
- Needed to detect the signal of the right frequency and amplitude because we don't want a power surge voltage spike to be wrongly interpreted as a signal.
- Need control circuitry to flip the state of the appliance (the flip-flop and relays)
- Needed to wait a while before another signal is sent (this is to prevent toggling the appliance on and off many times on receiving one signal pulse)
- Once the appliance has been toggled after receiving a signal pulse, we will send out a handshake signal onto the power line.
- It is assumed that we can place a relay on the power wire going to the appliance and that we control the appliance by only controlling the power going to it.
- Even though an extended parallel port is being used, no signal is being sent back to the computer i.e. any acknowledgements.
Constraints
From our original designs discussed in our proposal, there were many changes which came about due to problems encountered during our troubleshooting and testing phase of our the project.
The report is based on our final circuits being used. Due to time constraints, some of the circuitry mentioned e.g. handshaking, were not actually in our working design. It was not necessary for these additional circuitries, at the point in time of testing. These were needed to make the design perfect.
Some things from the final report may differ from the proposal, this is due to the fact that many things had to change when troubleshooting and if the team was allowed to build their original circuit we would not have been in this situation.
Cost
The overall cost of our design, Power Line Appliance Controller, not including manpower is approximately $720.00.
Team
It was a wonderful experience for all team members even though we had some tension because some member didn't start his task on time. However we got it through and were able to complete our project successfully.
