When carrying out electrical work is often necessary to identify the phase wire network. Without phase indicator to make it fail.
The simple indicator consists of series-connected neon lamp and current limiting resistor of a few hundred shortfall. Free the output of the lamp is connected to a touch contact. Holding your finger over the contact free output resistor check the related circuits. If the probe is connected to the phase conductors, through the elements of the probe and the human body is a small the current is high enough so that the lamp is lit.
Unfortunately, the glow of light so weak that it is virtually invisible when bright lighting conditions.
Phase indicator, which would be convenient to use in a good light, can be performed on the liquid crystal display (LCD), which is widely used in electronic clocks. Since the LCD is capable of working with small voltage and current, they easily replace the probe of a neon lamp. Faulty electronic clock is always there, so finding the LCD will not be big labor. Fit the LCD of any size and miniature of watches, and big - from a table and wall. Of course, the latest version of the indicator would be cumbersome.
Diagram of a simple indicator on the LCD is shown in Fig. 1. It contains series-connected current limiting resistor R1 and the LCD HG1. When the touch pad and connecting the X1 probe to the phase conductors on the LCD appears arbitrary readings. Small-size LCD should be protected from over-voltage Zener diode VD1.
For indicator suitable electronic watch with a working LCD and failed electronics. The LCD is usually placed in a plastic compartment hours and connect with electronic part via the contact strip of conductive rubber. In this embodiment, it is convenient to use the plastic case by removing faulty an electronic unit and used to connect to the LCD traces going of conductive rubber to the chip.
Conclusions the LCD is better to use, is determined experimentally to have worked all or at least some of the segments. This can be done using the methodology described in the compilation of readers ' suggestions "about checking the LCD" in "Radio", 1998, No. 10, pp. 76.
It is permissible to use the watch. In this case, the resistor R1 is placed in the probe and connect it to the indicator insulated wire. Touch contact strengthen your watch, if it is plastic. If the metal casing, he will perform the role of a contact.
The indicator can be collected in any other suitable plastic housing - from used pen, from under mint pills "Tick-tock", from the casing of the tooth brushes, etc External contact will serve as a segment of foil or wire, laid along the body. For the LCD in case it is necessary to saw through the respective window sizes. One example of such design is shown in Fig. 2.
In order to use the indicator was comfortable in both bright sunlight and in the dark, you will need to add a neon lamp (Fig. 3), incorporating it in series with the LCD. However, for placement of parts will have to find a more roomy case.
In both indicators, the limiting resistors - MLT or nominal S power not less than 0.5 watts. The two-anode Zener diode is permissible to replace the two included counter-consistently low-power Zener voltage stabilization of 3.3 and 6.8 V. Neon lamp in the second device - TN-0,2, TN-0,5, TN-0,95, MN-6.
In conclusion, it should be noted that the light from the LCD is able to work in networks with a much smaller voltage than the indicator with neon lamp.
Author: I. Nechaev, Kursk