Introduction to the design process of the multi-purpose electroscope pen
Design a multi-purpose electric pen, whose appearance is the same as that of ordinary electric measuring pens. It can not only judge whether electrical appliances are charged, but also distinguish the polarity and quality of diodes and triodes, judge whether capacitors are good or bad, measure whether the circuit is on or off, and whether the measuring equipment is Leakage, sensing electricity, etc.
1. Production materials
1. Three npn low-power triodes, two button batteries, one 100Ω resistor, one light-emitting diode, and one ordinary test pen.
2. Tools, electric soldering iron, tweezers, diagonal pliers, multimeter.
2. Production method
1. Identify components
(1) The triode (Figure 2) has 3 pins, which are emitter (e), base (b) and collector (c). There are two types of triode: npn type and npn type. They have similar functions but the current in the opposite direction.
(2) The light-emitting diode (Figure 3) has only 2 pins, which are positive and negative. Generally, the longer one is the positive pole and the other is the negative pole. It cannot be reversed in the circuit.
2. Shorten the leads of all components, scrape off the oxide layer, and weld them as tightly as possible according to Figure 4.
3. Put the welded circuit into the electric pen, pay attention to make the A terminal of the resistor contact with the metal part of the front end of the electric pen, and the positive pole of the button battery pack should be connected with the metal screw at the tail of the electric pen through a spring.
3. Learning to use
1. Electricity measurement by induction method
Hold the electric pen and touch the outer skin of the mains line (not the metal part of the wire) with the front end. If the LED is on, it means that the contact is the phase wire (live wire), otherwise it is the neutral wire (ground wire). If several wires are not bright after testing, it means there is no electricity.
2. Identify diodes and triodes.
Touch one pole of the diode with one hand, and touch the other pole of the diode with the other hand. If the light-emitting diode is on, it means that the tip of the pen is touching the negative pole; if it is not lit, the tip of the pen is touching the positive pole. Then reverse the two pins and try again. If the two measurements are not bright, it means that the diode is broken. The method of measuring the triode is similar to this, it can be regarded as two diodes connected together.
3. Measure the continuity of the line and whether there is leakage
On the premise that the line is not connected to the power supply, touch one end of the line with an electric pen with one hand, and pinch the other end of the line with the other hand. The light-emitting diode lights up to indicate that it is connected, otherwise it is not connected. The line is connected to the mains, hold the electric pen, touch the electrical shell, and the light-emitting diode lights up to indicate leakage.
