OddMix.com - Technology Note - TN1003 - Karl Nagy
|Warning! - Higher voltages are dangerous! - Never use both hands at the same time while working on high voltage circuits! - Disconnect power from a circuit when work on it! Think carefully when around high voltages!|
|Figure 1. Schematic of High Voltage Neon Lamp Multivibrator Circuit|
This unusual, simple multi-vibrator has only five components and uses neither vacuum tubes nor semiconductors but two miniature NE2 type neon lamps. This circuit interfaces best with vacuum tube or FET type high-impedance circuits. Almost any type of neon bulbs would work fine in this circuit not just the NE2 type but they have to be in their own separate glass envelope. The high voltage to operate this circuit may be supplied by batteries or it may be less expensive and more convenient to use a high voltage DC to DC converter.
|Figure 2. NE2 Neon Lamps|
This oscillator has a fix frequency that is determined by the two resistors R1 and R2, capacitor C1 and the ionization voltages of the types of neon lamps. If the two resistors are identical than the output waveform would be nearly squarewave - a wave with a near 50% duty cycle, otherwise the duty cycle will more or less than 50%.
With a bit of experimentation the required frequency could be easily set up as required. When a low frequency is selected the lights blink on and off alternating and the circuit provides a blinking light. The output drive available from this oscillator is rather limited. The available output signal can best be utilized driving a separate amplifier stage; otherwise the frequency would be affected. A single vacuum tube or solid state amplifier is the best for isolating the oscillator frequency from unwanted outside caused feedback changes.
Parts and materials:
B1 - Battery, 80 Volt
C1 - Capacitor 0.1 uF, 50V, Disc
C2 - Capacitor 0.01 uF, 150V, Disc or Film
NE1, NE2 - Neon Lamp, Type NE2 or similar
R1, R2 - Resistor 1K, 5%, 1/4W, CC