Nuts and Volts - April 2014

sphere or toroid to avoid sharp edges. Most all Tesla coils demonstrate beautiful electrical arcs or coronas that are discharged from the toroid by using some kind of breakout point. The size of the toroid you construct will make a difference in how the electricity is discharged. If you use a smaller toroid, electricity will be discharged more rapidly, but the arcs will not be as long. If you use a larger toroid, electricity will be discharged less rapidly, but the arcs will be much longer.

The next most popular demonstration would be the wireless lighting of gas filled tubes such as flourescent or even neon. I have purposely kept the power low on this design for safety, but you should be able to see one to three inch coronas from the toroid if you attach a breakout point. With as little as 12V input to the primary, a five foot CFL glows very brightly, drawing as little as only 100 mA. At 30 volts, the coronas are very pronounced and make a hissing sound, and just begin to influence nearby electronics. There is little risk of an electric shock but there may be a risk of RF burns from nearby metals. The material is not heating but is actually arcing to the skin at high frequencies.

Software

The code driving the coil is the small Basic program in Figure 13.

Voltage Check

1) The first voltage point indicated as TP1 on the schematic should be approximately 38V DC. If no voltage is present, check that there is 120V AC on the primary side of the transformer. If the 120V AC is present, check for continuity to the AC terminals of the bridge rectifier marked ~. There should be an AC voltage of approximately 24V AC. If this voltage is present, check for continuity to the electrolytic C2. If the capacitor is connected correctly, the rectifier may be defective.

2) The second voltage point labeled TP2 should measure about 3.7V DC that powers the 08M2. If no voltage is present, check the orientation of the zener diode Z1. If the diode is installed correctly, check that resistor R3 is connected to the +V DC potential on TP1.

Conclusion

Even though the design has been intentionally engineered to be safe, there is always the potential for electric shock. If you are unsure about working with any portion of the circuit, please seek help with the design from a more experienced person. I hope this project will spark your interest. NV

setfreq m32 ‘remark setfrequency 32 Mhz b2 = 3 : b4 = 8 ‘remark set intial values for b2 and b4 ( 2 Mhz, 50% duty) symbol FRQ = b2: symbol DUTY = b4 ‘remark symbolize variables FRQ and DUTY Do while b0<255 ‘remark loop until voltage on pickup coil is maximum readadc c. 4,b0 ‘remark read the voltage on pickup coil Gosub TESLA ‘remark jump to PWMOUT routine Loop TESLA: DUTY = DUTY + 1 ‘remark increment DUTY cycle FRQ = FRQ + 1 ‘remark increment FREQUENCY PauseUs 1200 PWMout 2, FRQ, DUTY ‘remark frequency generated on pin C. 2 PauseUs 1200 If b0>150 then TESLA ‘remark If voltage on pickup-coil is MAX, repeat loop return ; FIGURE 13.