Electronic cave detector 2

The electronic acupoint detector introduced in this example measures the impedance of each acupuncture point on the human ear to determine the lesions in various parts of the human body. When a disease occurs somewhere in the human body, the excitement of the nerve endings at the corresponding auricle sensitive points increases, the electrical conductivity increases, and the impedance of the acupuncture points decreases, causing the frequency of the buzzer to sound higher.
Circuit Working Principle
The electronic acupoint detector circuit is composed of acupoint detection circuit, oscillator, sound and light indication circuit and power supply circuit. As shown in Figure 9-39.

The acupoint detection circuit consists of electrodes a, b, resistors R2, R3, capacitor Cl and potentiometer RPl.
The oscillator circuit consists of transistors V1, V2, potentiometer RP2, capacitors C2-C4, diode VD and windings Wl and W2 of the oscillation transformer T.
The sound and light indication circuit is composed of oscillation transformer T, resistor R4, light-emitting diode VL2 and buzzer HA.
The power circuit is composed of battery GB, power switch S, current limiting resistor Rl and power indicator light-emitting diode VLl.
When in use, turn on the power switch S, hold one electrode in the hand of the subject, and use the other electrode to detect the auricle acupoints. The 9V DC voltage of GB is added to the base of V2 through S, R2, acupoint resistance, RPl and R3. pole, causing the oscillator circuit to oscillate and make the HA buzz. The smaller the resistance of the acupoint, the higher the oscillation frequency of the oscillator, the higher the flicker frequency and luminance of VL2, and the higher the tone of HA; conversely, if the resistance of the acupoint is large, the oscillation frequency of the oscillator is also low. HA
also has a lower pitched voice.
By adjusting the resistance of RPl, the reference value of each acupuncture point can be set when a person is healthy.
Adjusting the resistance of RP2 can change the flashing frequency and luminance of V.
Component selection
Rl-R9 uses 1/4W metal film resistors or carbon film resistors.
Both RP1 and RP2 use small synthetic carbon film potentiometers.
C1 uses an aluminum electrolytic capacitor with a withstand voltage of 16V; C2-C4 uses monolithic capacitors or polyester capacitors.
VD uses 1N4007 silicon rectifier diode.
Both VLl and VL2 use φ3mm high-brightness light-emitting diodes.
Vl selects S9015 or 3DG9015 silicon PNP transistor; V2 selects S9011 or 3DG9O11 silicon NPN transistor.
T uses the input transformer of a small semiconductor radio.
HA uses a piezoelectric buzzer with a sound-assisted cavity.
S uses a small single-pole toggle switch.
GB uses 9V laminated batteries.
The electrodes can be replaced by the probes of a multimeter.