TENSION INDICATOR
You may call this bio medical equipment as a lie detector also. This device measures the change in the skin resistance. The skin resistance changes with the changes in the emotional state. When the tension increase in the skin resistance falls, when the tension the decreases there is increase in the skin resistance. Tension affects sweat glands and with the changes in the sweat gland there is change in the membrane permeability of the skin and this change in the permeability is the major cause of the change in electrical parameters. This particular phenomenon is used here to indicate the tension. Two test probes or steel rods or plates can be used to detect the body resistance. you can hold these probes in your both hands. BC 547 NPN transistor is used as a buffer and amplifier. Preset P1 can adjust the base drive. IC1 LM3914 is a dot/bar display driver used in dot mode. The collector of transistor T1 is connected to the input of the IC1 pin 5. The resistor R2 controls LED current. Preset P2 is used to calibrate the scale. The reference voltage of the IC is in between pin 7 and pin 8. LM3914 drives the arrays of ten LEDs which lights up in ten equal steps of the selected full scale voltage. Give 9VDC supply to the unit. Hold both the probes in your both hands in normal mental condition. Adjust preset P1 so that LED1 will just light up. As the tension increases the natural tendency of the human being is to hold the probe firmly. Also in addition to that sweating will decrease the resistance in between the probes. The arrays of the LEDs will start proceeding. Try to adjust it at LED10 at maximum tension level with the help of preset P2. Now the unit is ready for the actual operation.
Component List
LM3914 dot/bar display driver (IC1) Qty 1
BC547 NPN transistor (T1) Qty 1
3mm LED (color as require) (LED1-10) Qty 10
1K 1/4W CFR resistor (R1, R2, R3) Qty 3
1M preset (P1, P2) Qty 2
For layout leave your email id below.
For layout leave your email id below.
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