Free electronic circuit design and schematic diagram
This is a simple circuit of beeper using 555 timer. This circuit can be employed to energize lights, horn, or other signaling device at any desired interval when the mercury switch is triggered. Since the current handling capability of mercury switch is not so high, an SCR is used to handle current drawn by the 555 timer circuit. Chose the […]
Read more
Using this continuity tester circuit, a failure of PCB tracks be examined without looking directly at the tracks routing, which is can be very frustrating. The indication of this circuit is done by an audible alarm (a buzzer). This circuit can be used to indicate continuity below any resistance value up to 35 ohms by adjusting the circuit. To make […]
Read more
This is a transceiver saver circuit that protect a transceiver device (applicable to other device as well) from overvoltage of the power supply. This circuit is used to protect the device by regulating the power supply, avoiding damaging the device if overvoltage occurs. If the transceiver transmits current of above 2A, a heatsink should be used for the transistor. The […]
Read more
This circuit can provide 5,000 VDC from 26 VDC. This circuit has ripple of under 0.01% due to Voltage-doubling capacitors. As sinusoidal oscillator, a 2N217 transistor is used. The diode and the capacitors at the output stage should be of high voltage type. Here is the schematic diagram of the circuit:
Read more
This is a SCR timer circuit. Here, SCR is used to drive the final actuator, the buzzer. The time constanst of this circuit is determined by R1 and C1. The buzzer will sound when C1 charges up to a desired level, it will cause the Q1 to conduct and triggers SCR1. The use of FET for Q1 make the RC […]
Read more
This is a schematic diagram of auto fuse monitor circuit. This circuit is very useful for automobile application, checking a live fuse without wasting any electrical power if the fuse is working fine. This circuit can check the fuse without removing the fuse from the working circuit. When the fuse is being tested, this fuse tester is connected across it. […]
Read more
This is a 4-range AC millivolt meter circuit. This circuit is used to measure a AC voltage in millivolt range. This circuit has frequency response of a few Hz to about 50 kHz. The non-linearity of the rectifier circuit is eliminated by placing the rectifier inside the op amp feedback path. This circuit read the input signal’s full-wave rectified average. […]
Read more