A relaxation oscillator with neon lamp is the basis of this circuit that can be used as a bench instrument. Powered from the 110V or 220V power grid it has extremely low power consumption. With it we can generate audio signals for various equipment tests. The signal is small in amplitude and can be used with transistorized equipment. The circuit generates signals in the range of 500 to 10,000 Hz.
The circuit is shown in figure 1, serving both 110V and 220V mains.
Caution: This circuit is not isolated from the power grid except its output (after the transformer)
Material list
D1-1N4004 (110V) or 1N4007 (220V) - Silicon Diode
NE-1 - Common Neon Bulb - NE-2H or equivalent
P1 - 1 M ohm - Potentiometer
T1 - Transformer with 110 V primary and 5 to 12 V secondary with 50 to 250 mA
C1-8 uF x 300 V - Electrolytic Capacitor
C2 - 47 nF - Polyester or Ceramic Capacitor
C3 - 10 nF - Polyester or Ceramic Capacitor
R1 - 47k ohm x 1 W- resistor - yellow, violet, orange
R2 - 47k ohm x 1/8 W - resistor - yellow, violet, orange
R3 - 47k at 100k x 1/8 - resistor
PP1 - Probe
G1 - Alligator clip
Miscellaneous: power cable, terminal strip, mounting box, wires, soldering, etc.
