Post-break Update

Here are a few updates on the work completed over break.

Most importantly, the 3D-printed coil has been completed. The final dimensions are 11 cm diameter and 2 cm height. The winding also took a good amount of work to complete and resulted in some very sore hands. The completed coil can be seen in Figure 1. It consists of around 100 turns on the outside and twice that on the inside for increased signal sensitivity.

Figure 1: Completed Coil

The design for the amplitude detection circuit is also complete. It consists of a half-wave rectifier (just a diode) fed into a two-stage integrator to give different DC voltages for varying input amplitudes. The amplitude detection circuit can be seen in Figure 2.



Figure 2: Amplitude Detection Schematic

To verify the design, I performed a simulation with a 5 kHz sinusoidal signal with various amplitudes. Figure 3 shows the output waveform for input signals with amplitudes up to 5 Volts, stepped by 1 volt. 
Figure 3: Amplitude Detection Waveforms

The difference in output for every variation in input may be a bit small for what we are working with. If this appears to be the case in development, we will have to amplify the signal with a simple non-inverting op-amp circuit.



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