# 555 Touch Switch Circuit

Schematic Diagrams      Comments Off on 555 Touch Switch Circuit

This circuit uses a 555 timer as the bases of the touch switch. You can learn more about 555 timers in the Learning section on my site. When the plate is touched the 555 timer is triggered and the output on pin 3 goes high turning on the LED and… Read more »

# 555 Timer Circuit With Variable On/Off Times

Schematic Diagrams      Comments Off on 555 Timer Circuit With Variable On/Off Times

This circuit enables the on/off times of a 555 timer to be independently varied over a wide range. This is not possible with a conventional 555 circuit with the RC network being charged from the positive supply rail and discharged via pin 7. Instead, the capacitor at pins 2 &… Read more »

# Simple Darkness Activated Alarm

Schematic Diagrams      Comments Off on Simple Darkness Activated Alarm

Most darkness activated alarms employ opamps and some logic ICs. Here, a less expensive approach is shown based on the eternal 555, this time in monostable multivibrator mode. Components R2 and C1 represent a one-second network. When the LDR (light dependent resistor) is in the dark, its resistance is high,… Read more »

# Overheat Detector Alarm/Switch

Schematic Diagrams      Comments Off on Overheat Detector Alarm/Switch

At the heart of this circuit is a precision integrated temperature sensor type LM35 (IC1), which provides an accurately linear and directly proportional output in mV, over the zero to +155 degrees C temperature range. The LM35 develops an output voltage of 10 mV/K change in measured temperature. Designed to… Read more »

# Panic Alarm

Schematic Diagrams      Comments Off on Panic Alarm

Imagine the Panic situation in the Midnight when an intruder tries to break into the house. This Alarm will help you with its loud Police siren to abort the attempt of intrusion. With a single clap, the circuit generates the alarm for three minutes and then goes off. This is… Read more »

# Wire Tracer (Transmitter)

Schematic Diagrams      Comments Off on Wire Tracer (Transmitter)

The circuit depicted here forms one half of a device that will prove extremely handy when tracing the path of electrical wiring in a building or to locate a break in a wire. The system is based on similar equipment that is used by technicians in telephone exchanges. The operation… Read more »

# SDR Soundcard Tester

Schematic Diagrams      Comments Off on SDR Soundcard Tester

The key to using a soundcard successfully in digital signal processing or digital radio applications lies principally in the characteristics of the soundcard itself. This applies in particular to SDR (software deﬁ ned radio) programs that turn your PC into a top-class AM/SSB/CW receiver, assuming your soundcard cooperates. If you… Read more »

# Remote-Controlled Fan Regulator

Schematic Diagrams      Comments Off on Remote-Controlled Fan Regulator

Using this circuit, you can change the speed of the fan from your couch or bed. Infrared receiver module TSOP1738 is used to receive the infrared signal transmitted by remote control. The circuit is powered by regulated 9V. The AC mains is stepped down by transformer X1 to deliver a… Read more »

# Battery Charger Regulator

Schematic Diagrams      Comments Off on Battery Charger Regulator

Most off-the-shelf car battery chargers cannot not be left connected to the battery for long periods of time as over-charging and consequent battery damage will occur. This add-on circuit is placed in series with the battery being charged and is powered by the battery itself. In effect, the circuit uses… Read more »

# PWM Modulator

Schematic Diagrams      Comments Off on PWM Modulator

If you ever thought of experimenting with pulse-width modulation, this circuit should get you started nicely. We’ve kept simplicity in mind and used a dual 555 timer, making the circuit a piece of cake. We have even designed a small PCB for this, so building it shouldn’t be a problem… Read more »