DC or AC Voltage Indicator

Detects 1.8 to 230 Volts DC or AC, Minimum parts counting This circuit is not a novelty, but it proved so useful, simple and cheap that it is worth building. When the positive (Red) probe is connected to a DC positive voltage and the Black probe to the negative, the Red LED will illuminate. Reversing […]

Fluid Level Detector using LM1830N

The IC is ideal for detecting the presence, absence or level of water or other conducting liquids. A detector determines the presence or absence of fluid by comparing the resistance of the fluid with the IC’s internal reference resistance. An AC signal is used to prevent plating of the probe. When the probe resistance increases […]

Transistor quality checker with buzzer

You checked the transistor by measuring the resistance between the different pins. Sometimes it has problems, such as when measuring the resistance between the various legs correctly. But it does not work in the real circuit. Because while there is no measurement bias junction between CE. therefore, the detection transistor good or bad for sure. […]

Mobile Bug Detector

his handy, pocket-size mobile transmission detector can sense the presence of an activated mobile phone from a distance of one-and-a-half metres. So it can be used to prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorised video transmission. […]

Simple RF Detector For 2M

This simple circuit helps you sniff out RF radiation leaking from your transmitter, improper joints, a broken cable or equipment with poor RF shielding. The tester is designed for the 2-m amateur radio band (144-146 MHz in Europe). The instrument has a 4-step LED readout and an audible alarm for high radiation voltages. The RF […]

High Quality FM BUG

This project requires a high degree of soldering. It uses surface-mount resistors, capacitors transistors and diodes. It can only be assembled on the PC board supplied in the kit as the Latching Circuit is already soldered to the board and the project will not work with substitute components. The Infinity Bug connects across the phone […]

Over Voltage Protection

Safety devices like fuses provide protection against excess current, but do nothing for transients and short duration spikes of high voltahe on the power supply lines.This circuit uses the “crowbar” method and provides fast protection against transient voltage spikes, transients that could cause damage to sensitive components. The thyristor will trigger in a few microseconds. […]

Voltage Cut Off Circuit Using Time Delay

This is a design for protection voltage. This circuit is called as high and low voltage cut off. The circuit is using time delay for cut off the voltage. This is a low cost and reliable circuit for protecting such equipments from damages. This is the figure of the circuit. Whenever the power line is […]

Fuse with status indicator

Here is the circuit diagram of a fuse that has an automatic status indicator. This circuit can be added to circuit that operates from 12V DC. As long as the fuse is intact, the LED D3 will glow continuously and when the fuse blows off the LED will start and continue blinking. The first part […]