Resistor R2 in the transistor base is necessary should the pads be accidentally touched together. It will be seen that with the pads fitted to the fingers, the tone level will be dependent on the setting of VR1 and skin resistance. The base of TR1 is connected between one electrode pad and the voltage divider formed by potentiometer VR1 and resistor R1. Whereas the trigger input of IC1 is normally connected to the positive rail via a resistor in a conventional 555 oscillator, here it is connected via resistor R4 to the emitter of transistor TR1. The latter allows users to set a desired level and avoid it becoming a distraction. Circuit Details In the circuit diagram of Fig.1, IC1 is configured as an astable multivibrator to drive an 8-ohm miniature speaker LS1 via capacitor C3, resistor R6 and volume control potentiometer VR2. During use, a sudden moment of stress, even a deep sigh, will increase the pitch and cause a shift of the meter needle. The monitor is quite sensitive to fluctuations. A visual indicator in the form of a panel meter also aids the user in monitoring tension levels. A decrease in pitch therefore signifies a decrease in tension, and vice-versa. These signal fluctuations are amplified and fed to an oscillator to produce an audible tone.

DC Input Voltage (pin 12 to pin 7): Vmax + 5

LM723 works with 9.5V input voltage to 40 V DC and the LM723 can generate its own current of 150mA when the output voltage is not more than 6-7V under input voltage. So the current through R3 can not exceed 0.65 / R3 although output short-circuit in his.Ĭ3 and C4 are ceramic capacitors, as much as possible directly soldered to the PCB, this is because the LM723 is prone to oscillation that is not cool. The maximum current is determined by R3, over-current protection circuit inside the LM723 to detect the voltage on R3, if it reaches 0.65 V, the voltage output will be off her.

Skema power ampli 170watt