Basics of Resistors. Design Note 5


For a Beginner, identification of Resistors is a big problem. So byhearting the Colour code is essential. But some tricks are available to identify the resistors easily. A Resistor is a passive component inevitable in circuits to reduce the voltage and current in a particular section of circuit. Resistor is non polarized with two leads for connections.
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How to make TSOP 1738 Circuits . Design Note 4


TSOP 1738 is the Infrared receiver Module widely used in remote control applications including TV. It is a versatile sensor that receives the coded Infrared pulses from the transmitter and directs the functions of the device. TSOP 1738 sensor is designed to receive IR rays pulsating in the 38 KHz and hence the number 1738. It has a circutry inside a black coloured filter case . The black coloured filter case prevents the effect of sunlight and other lights on the Photodiode present inside. There is a PIN Photodide inside the module which is the receiver of the Infrared rays from the transmitter. In addition to the Photodiode, there are signal amplifier, AGC ( Automatic Gain Control), output driver etc inside the module.
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Understanding IC 555. Design note 3

We all used IC 555 in many applications. Why it is called as 555 Timer? There are three 5K resistors inside the IC that makes it as versatile IC for Timer applications. IC555 was introduced in 1971by the Signetics corporation as SE555 / NE555 and was called as IC555“IC Time Machine”. Later its CMOS version IC 7555 and Dual Timer IC 556 were introduced.
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How to use MOSFET. Design note 2

MOSFET is Metal Oxide Semi conductor Field Effect Transistor, a very efficient type of switching transistor used in power devices like Inverters, UPS, Power amplifier etc. Its high current capability and fast switching makes it as an ideal choice for these applications. MOSFET is a four terminal device. The terminals are Drain, Source, Gate and the Substrate or Body terminal. The Drain and Source terminals are connected to the heavily doped regions. The Gate terminal is connected top on the oxide layer while the Substrate terminal is connected to the intrinsic semi conductor.
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SCR and its Applications.Design Note 1


Silicon Controlled Rectifier (SCR) is a kind of semi conductor device used in switching applications. When a positive voltage is applied to its gate, SCR conducts and latches. It remains conductive even if its gate current is removed. The latched SCR can be switched off by removing its Anode current.
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Amplifier for Mobile Phone


You can use this simple Amplifier to hear Music from Mobile Phone or MP3 player. It gives very clear sound through two 8 ohm speakers. It uses two identical circuits for Stereo operation. IC LM386 is the low power Amplifier IC ideal for battery operation. The output from Mobile phone is Pre amplified so that it can be provided to the input of the Amplifier using a Stereo jack. The filter circuit comprising resistors and capacitors at the front end filters the audio entering into the amplifier to give clear sound.

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Mobile Bug- Page updated


This is one of my most attracted circuit published in Electronics For You years back. But still it is in limelight .More than 200 students selected the circuit as their engineering project. It detects an active mobile phone even in the silent mode and beeps. It’s range is 2 meters radius. It is ideal to monitor Mobile phone restricted areas like Examination hall and Confidential rooms. It detects, Incoming and Outgoing calls, SMS, MMS, Video capturing, Photo capturing etc. I have slightly modified the circuit to increase its range. Check this updated page to get full details including the project report and video of the circuit.