Simple applications of neon glow lamps


Posted on Feb 5, 2014

To obtain such a monitor it`s enough to connect a resistor in series with the bulb and connect at a main outlet. The resistance of that resistor may vary on the type of bulb and the main voltage but it`s not critical: about 150K © for 220. 230Vac and about 39K © for 110. 120Vac. It`s very important to choose a resistor that can support the desired v


Simple applications of neon glow lamps
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oltage or connect two or more usual resistors in series. The power of that resistor is quite low and a 0. 25W is usually enough. To light a neon glow lamp a relatively high voltage is necessary (about 70V) and this make the realization of a telephone ring monitor quite easy: the voltage of the telephone line is usually less than 50V and it`s not enough to start the lamp. When the phone rings an AC voltage of about 150Vac is present on the line and the bulb will glow. The low current consumption of glow lamps is very useful in this case since it doesn`t overload the phone line. In certain countries the connection to a telephone line of non certified devices (such as this one) is not allowed. This application is only presented for didactic proposes. If the lamp keeps glowing after the ringer, the maintaining voltage of the lamp is too low (lower than the telephone idle voltage). To solve this problem just connect two Zener diodes of about 20 to 30V in series back to back in series with the lamp. In facts the neutral wire and the earth wire are usually connected together in the transformer and this connection short circuits the lamp that cannot glow. If the earth wire is not connected or if the live and neutral wires are inverted the full voltage would be present on the terminals of the lamp that would glow indicating the presence of a problem. This circuit is very simple and cannot detect every false connection; for example...




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