Odd application of neon glow lamps

Posted on Feb 5, 2014

Neon glow lamps can also be used only for their U/I characteristic and not for producing light. These lamps are electrically very close to diacs: no current can flow through them since the voltage is lower than a trigger value (about 70V for neon glow lamps and about 40V for diacs). If the voltage is high enough to trigger the device a current can flow through it and the voltage drop

Odd application of neon glow lamps
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is a little lower than the trigger voltage (about 50V for neon glow lamps and about 30V for diacs). In this circuit of a dimmer the diac is replaced with a neon glow lamp, but it works exactly in the same way than a classic one: an RC network delays the trigger pulses on the gate of the triac. The glow lamp rises the trigger voltage from about 40V to about 70V. Some adjustments to R and C values may be required to match specific glow lamps and triacs. A stroboscope is another application that requires a diac (or a neon glow lamp) for triggering the xenon tube: this circuit uses a neon glow lamp but it works in the same way as a classic diac one. The main voltage is rectified by a diode and charges two electrolytic high voltage capacitors (in parallel) that are used as an energy tank for the xenon lamp. A current also flows though a resistor and slowly charges a trigger capacitor: when the voltages reaches the trigger value of the glow lamp the SCR discharges this capacitor through a trigger transformer into the xenon lamp that flashes. Once the energy in the tank is over this cycle repeats; the frequency is adjusted by varying the resistance that charges the trigger capacitor. The energy in the electrolytic capacitors can be lethal even when the circuit is switched off. Always discharge these capacitors before touching the circuit. This is the oddest application of a neon glow lamp, that is used as a electromagnetic field...

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