Probe indicator without batteries

The simplest work related to electricity is difficult to perform without measuring tools. It is not necessary to measure the electrical circuit parameters with a tester, in many cases it is more convenient to do with a universal probe that infects the presence of these parameters by means of light signals. This is quite enough for convenient and safe operation of electrical circuits. The circuit of the indicator probe in question does not contain any power elements. Instead of the energy commonly used in battery probes, the energy of a charged capacitor is used here. Functionality. The probe allows you to monitor the presence of AC and DC voltage from 24 to 220 V, to carry out the test of an electrical circuit with a resistance of up to 60 kOhm and detecting polarity in DC circuits. When connecting the XP1 and XP2 probes to a DC power source in accordance with the input polarity, the green LED HL1,indicating not only the presence of a constant voltage in the monitored circuit, but also the presence of a plus at the point of contact of the probe XP1. Reversing the polarity of the probes on the opposite causes the red LED HL2 to light up, which, besides the presence of voltage, indicates contact with the probe HP2 . When AC voltage is monitored, both LEDs light up simultaneously. The continuity of the circuit during a dial tone is indicated by the red HL2 LED lighting up. This information can be obtained with just two LEDs built into this simple probe indicator.
 indicator probe circuit
The design of the probe. Radio components.To implement the device, you need to purchase or find the following parts in your inventory: Resistors R1-220 kΩ and R2-20 kΩ, power 2W, R3-6.8 kΩ; LEDs HL1 - AL 307G, HL2 - AL 307B; Diodes KD2 - VD5 - KD103 (possible replacement of KD 102); Zener diode VD1 - KS222ZH (possible replacement of KS220Zh, KS522A); Capacitor C1 - К50-6 1000х25. Enclosure.The choice of the case should be given special attention - its configuration and dimensions depend on the convenience of working with the probe. Consider two options for buildings.In the first version, a relay cover is used, in the second, the case of an unknown gadget.
 probe case
In cases, holes are made for the output of the wire with the XP2 probe, LEDs are installed, (only for first version) and the XP1 probes are attached. The board.The size of the case determines the geometry of the board. The installation can be mounted, but it is not difficult to do on the PCB. All radio components (except for the LEDs in the first version) are mounted on the board, which is mounted inside the case.
 indicator board
board bottom view

After installing the board into the case and soldering the conductors to the XP1 and XP2 probes, the probes are ready for operation. The device does not need to be adjusted. The charging time of the probe capacitor with a voltage of 220-24 V is 3-25 seconds. The discharge time of the capacitor during a short circuit probe probes at least 2 minutes.
 probe indicator

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