USB Ozone Generator With Timer

This is a mini ozone generator which uses 5V USB its current consumption is around 100-110mA. Usage of ozone is freshing or cleaning air by oxidizing the pollutants (bacterias, mold, viruses) in the air. Especially in winter this device can be useful when proper ventilation of rooms is hard (due to heating issues).

Mini high voltage transformer

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2 small signal transistor (2N2222,BC547, 2N3904 or similar I've used 2SC1815)

3.3kΩ resistor (2 pieces)

470Ω resistor (2 pieces)

220kΩ resistor (1 piece)

10kΩ resistor (1 piece)

10nF ceramic capacitor (1 piece)

Push button (1 piece)

100uF 16V electrolytic capacitor (1 piece)

3300uF 16V electrolytic capacitor

47nF X2 capacitor

50-150uH inductor

Indicator LED (3 or 5mm)

NE555 (1 piece)

This is a classic royer oscillator which drives a mini high voltage transformer (primary of the transformer is removed rewound 7+7 turn for primary, 5 turn in feedback winding)

Principal of operation

When you power up the circuit one of the transistor will open then it connects voltage one half of the primary which induces voltage at the secondary and also at the auxilary (feedback) which keeps the other transistor off when current is reached its maximum the voltages starts to the and first transistor closes and second transistor opens repeats same cycle in reverse direction since there is capactior in paralel with the primary coil induced voltages are sinusoidal its frequency can be determined by altering the LC tank circuit. Inductor in series with the center limits current (high inductances leads lower current values)

Here is article about royer oscillator

https://en.wikipedia.org/wiki/Royer_oscillator

NE555 works in mono stable mode when you press the it activates the bd139 transistor and oscillator section starts to work. While oscillator is running 3300uF capacitor is slowly charging via 220kΩ resistor once it reaches certain threshold value NE555 closes its output and oscillator stops. The working time of the oscillator can be calulated using this formula 1.1 X R X C = t(s) when you put r = 220kΩ, c =3300uF t comes as 798 seconds which about 13 minutes

Output of the transformer connected to a metal disc and a needle, adjust the distance between needle and disc until you see purple glow (corona discharge) in the tip of the needle after that you can the smell ozone which indicates circuit is working.

Due to low power and limited time of operation I've used small signal transistors but you can use medium power transistor like BD139, but using the 2SC1815's doesnt produce too much heat and they didn't overheat.

Here is waveform in the scope's screen (voltage reading is wrong because the measurement is taken by putting scope probe near the circuit) Output is nearly sine wave. The reason it is not a pure sine wave is that the secondary loaded with the corona discharge at the secondary at no load circuit will produce pure sine wave

This circuit produces high voltage touching parts at the secondary side can lead electric shock and burns.

Ozone is a quite irritative gas inhaling too much can lead irritation in respiratory system.

Article about ozone

https://en.wikipedia.org/wiki/Ozone

Video about ozone in home use by Big Clive

https://www.youtube.com/watch?v=1ymcJ9qKC7I&t=88s

Do not plug this circuit to a computer or sensitive USB power source. If insulation breaks high voltage at the output can reach to input and could destroy appliance.

I suggest to use this circuit only with powerbanks.

Everything you do on your own risk and responsibility.