29-01-2013, 11:44 AM
Griposcope of ckt
[attachment=48699]
INTRODUCTION
The modern electronics makes it possible to know your muscle power using this simple circuit named as 'GRIPOSCOPE'. It can also be used as a lie detector and moisture level monitoring or simply for conjuring tricks.Two probes are left to calibrate you. Hold them tight. As you increase your grips on these wires, the LED dot jumps into lower order. The stronger the grip, the lower the position of the dot. If you can not keep a steady hand, the LED dot oscillates up and down.
Operation
The circuit is designed using linear voltage display IC3914 (IC1). It consists of 11 comparators and associated network in a single chip packed.The resistance of the body RB, applied to the input pin 5 of IC1 changes according to the grip of the leads. The proportional voltage is applied to the inverting input of each 11 comparators, which compares this voltage with non inverting voltage set by battery, pot VR1 and chain of 1K resistors internally designed. Depending on the output of comparators, corresponding LED will flash. The position of glowing LED changes with the change in resistance across points X and Y. As the position of glowing LED increases, strength decreases. Glowing of Green LED D1 indicates minimum strength.
Callibration
Preset VR1, VR2 and resistor R1 can set the sensitivity and the range of deviation. In the absence of body resistance RB, VR1 is adjusted so that LED D10 glows.
Note on probe wires
Two highly insulated wires such as multimeter probes, can act as a sensor. The area of contact between the probes and skin plays an important role in varying the resistance between them.
Power supply
A mains derived power supply is not used for the circuit. Operational voltage is derived from two 1.5V batteries. The operation of the device becomes critical if the supply voltage falls below 2.25V approximately.Resistor R2 sets the current to around 1mA through the LED. The power set by the device is well below 40mW in all the positions.
[attachment=48699]
INTRODUCTION
The modern electronics makes it possible to know your muscle power using this simple circuit named as 'GRIPOSCOPE'. It can also be used as a lie detector and moisture level monitoring or simply for conjuring tricks.Two probes are left to calibrate you. Hold them tight. As you increase your grips on these wires, the LED dot jumps into lower order. The stronger the grip, the lower the position of the dot. If you can not keep a steady hand, the LED dot oscillates up and down.
Operation
The circuit is designed using linear voltage display IC3914 (IC1). It consists of 11 comparators and associated network in a single chip packed.The resistance of the body RB, applied to the input pin 5 of IC1 changes according to the grip of the leads. The proportional voltage is applied to the inverting input of each 11 comparators, which compares this voltage with non inverting voltage set by battery, pot VR1 and chain of 1K resistors internally designed. Depending on the output of comparators, corresponding LED will flash. The position of glowing LED changes with the change in resistance across points X and Y. As the position of glowing LED increases, strength decreases. Glowing of Green LED D1 indicates minimum strength.
Callibration
Preset VR1, VR2 and resistor R1 can set the sensitivity and the range of deviation. In the absence of body resistance RB, VR1 is adjusted so that LED D10 glows.
Note on probe wires
Two highly insulated wires such as multimeter probes, can act as a sensor. The area of contact between the probes and skin plays an important role in varying the resistance between them.
Power supply
A mains derived power supply is not used for the circuit. Operational voltage is derived from two 1.5V batteries. The operation of the device becomes critical if the supply voltage falls below 2.25V approximately.Resistor R2 sets the current to around 1mA through the LED. The power set by the device is well below 40mW in all the positions.