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| Transmitter circuit |
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| Receiver circuit |
After do all the researches for the circuits and components, the circuit for transmitter and receiver was designed. We can see that the LC tuned circuit use 8 of capacitor wired in parallel. Capacitor connected in series will will the total of capacitance. The LC tank circuit is the part where heavy current circulates, and is required to be sturdy. The copper pipe used as conductor heats up significantly under ~20A it's passing continuously. To handle the current while keeping losses tolerable, capacitor consists of 8 paralleled 6.8nF 630V FKP capacitors. It's important that capacitors are polypropylene dielectric and foil or foil+film based - other types will heat up and melt in this application.
On the receiver side only a single capacitor and a loop of 1.25mm solid copper wire was used. The total capacitance at the transmitter must be approximate with the capacitance at the receiver. The easier way to get the same resonance frequency is by using the same loop and capacitor. We noticed that the total capacitance at the transmitter is 54.4 nF. But I was used 47 nF capacitor at the receiver because the receiver loop that I use is thinner than at the transmitter.
There is had one problem - if the supply voltage rose too slowly, such as while DC filter capacitance is charging, it tended to fail to oscillate and just keep shorting the power supply with one mosfet ON. In the final design this was solved with a relay, which acts as undervoltage lockout of sorts, applying power rapidly after supply voltage rose high enough.The relay that was choosen is SRC-12VDC-SH.
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| SRC-12VDC-SH relay |
CIRCUIT DESIGN WITH THE LOOP
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| Receiver loop design |
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| Transmitter loop design |
Both of the loop that are used is a single loop. At the transmitter, the size of the copper tube is 6mm diameter. Then, the size of the loop is 15cm diameter. The loop at the receiver that I used is solid copper wire 1.25mm diameter and the loop is about 11cm.
In week 5, I have carried out the experiment to measure the output of the circuit. There is some picture of the expeiment....
The input that was used...
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| Voltage ~~ 12VDC Current ~~ 1 amp |
For the oscillator circuit and receiver circuit, I was used just breadboard before proceed to etching. For the bank capacitor and transmitter loop, I was compiled that with the PCB board to avoid the breadboard become heating.
Then, I separate the receiver circuit and transmitter circuit with some distances to get the result using from the oscilloscope.
Distance = 1 inch
The output>>>
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| The output voltage ~~ 12V peak ac Resonant frequency ~~ 1.25 MHz |
Distance = 2 inches
The output>>>
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| The output voltage ~~ 8V peak ac
Resonant frequency ~~ 1.25 MHz |
Distance = 3 inches
The output>>>
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| The output voltage ~~ 5V peak ac
Resonant frequency ~~ 1.25 MHz |
Distance = 4 inches
The output>>>
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| The output voltage ~~ 2.5V peak ac
Resonant frequency ~~ 1.25 MHz |
Distance = 5 inches
The output>>>
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| The output voltage ~~ 1.5V peak ac
Resonant frequency ~~ 1.25 MHz |
Distance = 6 inches
The output>>>
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| The output voltage ~~ 1V peak ac
Resonant frequency ~~ 1.25 MHz |
Apart from the experiment, we can see that the output of the receiver is enough to supply some application of the dc load. This can be considered as successful and the objective of the project was achieved. Refer to the title of the project, I need to supply the mobile application such as mobile phone. So, the output of the receiver need to transferred in DC voltage first. So, the AC-DC converter is needed after receiver circuit. After this, I will construct the AC-DC converter circuit and compile the receiver circuit with the load.
And then, I want to construct the power supply myself to supply the transmitter circuit. The parameter of the power supply is 12V DC with 1amp output.
