Author: jiajunma

This week I assisted with final topload testing, where we tried three additional sizes to find the best match for the secondary coil’s resonant frequency. The 1.5-inch diameter sphere ended up being optimal, though it still wasn’t enough on its own — adding a small spike to the top of the topload is what finally produced successful free-air arcing. I also helped with recalculating and installing the revised primary coil to match the updated resonant frequency. The system now arcs freely, though it produces stronger arcs when a conductive surface is nearby, and can produce basic tonal outputs. Audio modulation still needs improvement for clear musical reproduction. Next week I plan to help with the cooling system improvement targeting the MOSFET, and contribute to getting fuller audio modulation working ahead of the final demo.

This week I participated in full system testing in the lab where we successfully generated small arcs to a conducting metal surface, confirming that the system can transfer enough energy through the coils to ionize air. During testing, we identified a major issue — the secondary coil’s self-capacitance was too low, pushing its resonant frequency to approximately 3.54MHz, nearly double the design target of ~1.834MHz. This mismatch meant the primary and secondary could not efficiently couple energy. The fix was installing a much larger topload on the secondary to add capacitance, which brought the resonant frequency down to approximately 1.48MHz. The primary coil was also adjusted from 6.9 to 7.75 turns to increase its inductance and lower its resonant frequency to better match the secondary’s new value. I assisted with diagnosing and evaluating these changes throughout the week. The coil assembly is now mounted on the housing lid and Caleb is printing the final enclosure piece. The team is meeting Sunday for final testing ahead of the Wednesday interim demo, where the goal is to achieve stable free-air arcs with audio modulation.

This week I integrated the interrupter circuit with the newly repaired gate driver and ran initial audio modulation tests. The LCR meter finally arrived, allowing me to verify the primary coil inductance and tune the interrupter frequency to match the resonant circuit. I tested the audio input with simple waveforms (sine, square) and confirmed the plasma arc responds to the modulation, though the audio quality needs improvement – higher frequencies (>10kHz) modulate better than bass frequencies. I also adjusted the duty cycle potentiometer range for finer control. Next week I’ll optimize the audio input circuit with better filtering and work on improving low-frequency response for clearer musical reproduction.

This week progress was limited due to waiting on component delivery – the LCR meter needed for precise tuning and testing hasn’t arrived yet due to repeated Amazon delivery failures. I used the time to refine the interrupter circuit design and verify my previous duty cycle fix is still holding stable across the full frequency range. I also assisted Caleb with diagnosing the gate driver failure and confirmed the interrupter output wasn’t the cause – the issue was no output load causing power to dissipate in the chip. Next week once the LCR meter arrives, I’ll work with the team to tune the primary-secondary coil coupling and verify the complete audio modulation chain functions properly.

This week I completed assembly and initial testing of the 555 timer interrupter circuit with audio modulation capability. I soldered all components including the duty cycle potentiometer, timing capacitors, and the 3.5mm audio jack with DC blocking capacitor. During unit testing with the oscilloscope at TechSpark and the 220 lab, we discovered the interrupter frequency range stays on target in the expected 20kHz+ range, however the duty cycle is running too high with the minimum duty cycle at 40%. This needs to be corrected for proper audio modulation. Next week I’ll debug the interrupter circuit to adjust the duty cycle range down to the designed specifications, then work with the team to complete full system integration testing.

This week I finished assembling and testing the 555 timer interrupter circuit with audio modulation. The circuit functions properly when tested standalone – duty cycle modulates from 35Hz to 35kHz and the 3.5mm audio jack accepts input signals correctly. However, I’m encountering integration issues when combining it with the oscillator and gate driver circuits, likely due to grounding or timing problems. Next week I’ll systematically debug these interfaces with the oscilloscope and coordinate with Caleb on proper grounding between circuit boards.

This week I ordered the components for the secondary coil, mainly consisting of the PVC pipe body, the winding wire, and the topload. My progress as of now is on schedule, and next week I hope to be able to begin assembling the secondary coil.

This week I designed the interrupter for the Musi-Coil, primarily focusing on component selection and circuit layout. After significant research, I decided that the best option was to modify a standard 555-timer based interrupter design, where the control voltage to the timer takes input from a 3.5mm audio jack with a series capacitor in order to offset bias voltage. I also was sure to add a capacitor between the 3.5mm audio jack’s output and ground to protect whatever device is being used as an audio input. I am still working out what the driving circuitry for this 555-timer will be, but the current plan is to have the 555-timer act as an amplitude modulator, where its output is a carrier signal for the musical audio. Next week will be spent primarily designing that circuitry.