In the searchers for hidden wiring as sensors are mainly used various inductive elements (relay coil with lots of turns on a steel or ferrite core coils high resistance phones type TONE-1. TONE-2 and similar, dynamic microphones MD. MD. the magnetic head from tape recorders, etc.). The best result I managed to get by using old universal head reel to reel tape recorder "Yauza". Well proved to be "non-traditional" element as a throat microphone from tank helmet (Fig.1).
The output of the throat microphone has three pins: housing (screen) and two contact -"+"and"-". The sensor is connected to the amplifier with the correct polarity (Fig.2).
Chart orientation of the resulting device - wide that can be used when you search for hidden wiring in smaller networks of utilities in apartments, private homes). In production areas where electric cables "entangled" all the walls, the device will be ineffective. But where there is single electric wiring, but it is deeply hidden in the concrete or is under a thick layer of wood walls, the device detects it at a distance of 80 see
As a sound projector used phone calculi dam-4M, providing sufficient sound volume. The power source of the device is stable, 5-volt. Current consumption at maximum gain is 10... 12 mA. On the elements R4, VD1, C3, C4 assembled a voltage regulator. The Capacitor C4 filters out low frequency interference on nutrition, C3 - interference by high frequency. Resistor R4 provides an operating mode of the Zener diode VD1. The device can be powered from two elements A316. Then R4, VD1, C3, C4 are not needed. The voltage DA1 may be in the range from 1.4 to 5 V, but the voltage over 3.5 V the amplifier is prone to delays, and the noise level increases.
Local acoustic effect due to the proximity of VM and HA1, which appears when the supply voltage increases to 5 V, you can remove the adjustment resistance R9. however, this decreases and total gain. The amplification of the input signal is adjusted by the variable resistor R5. At frequencies of 1000...5000 Hz gain DA1 is about 100.
All fixed resistors except R4, - WFC-0.25 (R4 - MLT-0,5). Oxide capacitors - C50-6, others-km-6. Instead of a throat microphone as a sensor VM you can apply any dynamic capsule resistance 180...250 Ohm. for example, DAMS-1A. The pickup 1 can be replaced by the TM-4. VP-1. The device can be placed in any suitable housing. For example, I used plastic the body from the torch (Fig.3).
The location of the transaction is determined by the maximum volume in your phone. Naturally, sought wires should proceed alternating current. More than the current the from a greater distance and with greater accuracy detected posting.
Literature
Author: A. Kashkarov, St. Petersburg