Free Circuit Diagram

To know someone is lying  or not we can use lie detector. This is a simple lie detector that can be made in minutes. It works to detect the someone who telling lie but it is not as sophisticated as the ones the professionals use. Here is the schematic diagram of this circuit: [...]

This is a circuit of Temperature-Compensated Capacitive Proximity Detector. it will lights the LED when a person approaches the antenna plate. Here is the circuit : The 4-inch-square antenna plate and a 33pF capacitor (C1) in parallel with 15pF (6 inches of coaxial cable at 30pF per foot)  are used to form delay [...]

Silicon pezoresitive-bridge pressure transducer (SPPT) is very popular in medical, industrial, environmental, and automotive pressure sensor application. The general architecture of SPPT uses a thin micromachined silicon diaphragm incorporates a implanted piezoresitive Wheatson-bridge strain-gauge. The transducer design allows only a small diaphragm deflection sin it has limited elasticity, and this produces only a very [...]

If you have a digital voltmeter, or any voltmeter with millivolt resolution and high input impedance, then you can use this temperature-to-voltage adapter circuit to measure room temperature. Here is the circuit’s schematic diagram: Note that the voltage output of this circuit is floating, not referenced to ground. You have to [...]

The temperature of a quartz crystal for oscillator should to be kept constant to operate at very stable frequency. This oven temperature controller is suitable for such purpose.  Here is the schematic diagram of the temperature control circuit: Although this circuit is small and simple, the design use a PWM output to preserve [...]

In some temperature-sensing applications there are some problems caused by the placement of sensors on location where the potential is very different from that of the data-acquisition-system common. So the operating temperature sensor must be isolated from its data-acquisition system galvanically.  And the power’s source for the sensor was isolated. This circuit is designed to [...]