Week 4 (24th of February 2017)

Transmission circuit design changes

The fourth project week required more research to be performed to find a new transmission circuit design. After the fourth group meeting, several different designs were discussed, although it was agreed that one particular design appeared more effective than most. The group decided the best course of action was to include a 555 timer to produce the required oscillation, while also using a BJT and MOSFET as a voltage amplifier (and a high-speed switch). The newly chosen circuit design can be observed in figure 5a. 

Figure 5: Circuit diagram for new transmission circuit design

The timer produced an oscillation as required, while the frequency was calculated using the formula.

Copper wire coil design change

It was also discovered that the method used to produce the copper wire coils was not effective, meaning that a new design had to be considered instead. This newly chosen design can be observed in figure 6.

Figure 6: Newly chosen copper wire coil design

The inductive loops and number of turns were calculated using a new formula.

Turns ratio was 1:1 for both coils, so that N_T = N_R

The new circuit was simulated step by step, starting from the transmitter circuit. The simulation produce the expected values when calculated from the aforementioned formula to get the required output frequency from timer. The Inductors from the previous design were removed and replaced with a short circuit before adding the coils.

The receiver circuit was also put together on PSPICE, while a linear transformer (with a 1:1 turns ratio) was added. 

Calculate the     for the MOSFET :

Design inductance loop:

The simulation was successful and provided the required outputs. The schematic diagram can be observed in figure 7, while the results of the testing stages can be observed in figures 8, 9 and 10.

Figure 7: Design simulation using PSPICE

Figure 8: INPUT Voltage and OUTPUT Voltage

Figure 9: INPUT voltage, OUTPUT voltage from 555 Timer and the Final OUTPUT Voltage

Figure 10: INPUT voltage for TX-coil and OUTPUT voltage through RX-coil

The circuit was then transferred to an SK10 board to test the input/output voltage and current. This testing can be observed in figure 11.The results of the test were as expected. The circuit was working effectively and was therefore able to transfer electricity from the transmitter to the receiver. 

A demonstration of this can be observed in the video.

Figure 11: Testing the circuit

Receiver circuit design changes

The only changes that occurred in the receiver circuit were changed to the values of the components within (C3 & C4 were changed to 2.2nF & 10μF).

Figure 12: circuit diagram for Receiver circuit