Category Archives: Sensor



LEDs Temperature Indicator

A well-known IC LM35 is chosen to be the temperature sensor in this circuit. Output voltage of LM35 will increase by 10mV per degree rise in temperature. Output of LM35 is joined to the non inverting input of the operational amplifier (op-amp) of CA3130. The inverting input of the same op-amp could be provided using the required reference voltage using variable resistor R2.

Tone Detector / Sound Activated Switch

The following circuit diagrams are tone detector circuit diagrams which also known as sound activated switch circuit. Actually, these circuits  use microntroller for switching because the circuits were designed for robot start up activation. But you can build switching module using relay. You may make a trial to use this circuit for other applications such… Read More »

Color Detector

This is the color detector / sensor circuit diagram. This circuit will sense eight colors that are: green, red and blue (as primary colours); magenta, cyan and yellow (as secondary colours); and black and white. It’s will be very useful for robotics project. The circuit is based on the fundamentals of optics and digital electronics.… Read More »

Touch Switch

Turn on and turn off your electrical devices using touch switch, so you can “play” your electronic devices more fun.. 🙂 . Touch switch don’t need mechanical part, so they will not worn out due to mechanical contact. Touch switches can be used in places where regular switches would not last, such as wet or… Read More »

Simple Fire Alarm with Thermistor and NE555

The following circuit is a simple fire alarm circuit based NE555 timer and use thermistor as a temperature detector. This sensor will activate the transistor when the temperature is in high value. The thermistor will have a low resistance at high temperature, while at low temperature, the transistor resistance is high. This characteristic of thermitor… Read More »

Ultrasonic Sensor Switch

Here is the circuit diagram of ultrasonic sensor switch. There are many methods of wireless switching such as by using infrared, AM/FM signal, bluetooth, etc. This is an alternate wireless switching by using ultrasonic sensor. The distance of switching range should be more than 10 meters. This circuit produces and transmits ultrasonic sound of frequency… Read More »





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