### basis of DC MOTOR

today I am going to discuss on the basic structure and the principle of DC motor,
what is a motor - actually motor is a electrical device that converts electricity into mechanical power,
A DC motor runs only on DC current, if we put a DC motor to AC power supply it starts to vibrate with the frequency of the supply.
basic parts of a DC motor - it has mainly a stator coil, a rotor coil wounded on the motor shaft, and the frame of the motor called yoke,
in household purpose this type of motor is not used, but in large industrial purpose it is till used,  you may see a little model of DC motor in toys (made in China). one interesting thing about this small motor is that you can listen music using this motor as a speaker,  you don't believe it?  just put the wires to the CD DVD OR AMPLIFIER,  and listen the music with a special bass tune  ,
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let's discuss on "how it works "
we all aware about the electromagnetic induction, (if a wire is wounded on a magnetic core,when the current passes through the wire, it behaves like a permanent magnet,).  in a DC motor there is a stator winding inside the yoke,  in some special cases a permanent magnet is placed instead of stator windings. a DC power supply is applied on the stator winding that makes it a magnet, and also a power supply is given to the rotor that makes it a magnet,  as we all know that the same pole of two magnet deflects each other,  as the polarity of the stator is static constant, for keeping the balance the rotor moves slightly ,  as the power supply is given to the rotor by a brush contact do the deflection action happens continually and the rotor rotates  ,

### কীভাবে নিজের হাতে বানাবেন এফ এম ট্রান্সমিটার। আসুন সবকিছু বুঝে করি।

কেমন আছেন সবাই? অনেক দিন পর আবার পোস্ট করছি।

রেডিও ট্রান্সমিটার নিয়ে অনেক পোস্ট হয়েছে। সবগুলোইখুব ভালো ছিল। কিন্তু কমেন্টগুলো পড়ে মনে হচ্ছিল পাঠকেরা আর একটু গভীরে জানতে চায়।কয়েক টা বিসেশ ইনফরমেশনের অভাবে তারা সেশ অবধি সফল হতে পারে না। আমিও কিছুদিন আগে এদের দলেই ছিলাম। যাই হোক, কথা না বাড়িয়ে শুরু করি। এফ এম কথার পুরো মানে হল ফ্রিকুয়েন্সি মডিউলেশন। সোজা কথায় একটা ফ্রিকুয়েন্সি কে আর একটা ফ্রিকুয়েন্সির প্যাকেটের ভিতর পুরে সাপ্লাই দেওয়া। এই ফ্রিকুয়েন্সির রেঞ্জ টা পড়ে ভেরী হাই ফ্রিকুয়েন্সী রেঞ্জে(VHF). ৮৮ থেকে ১০৮ মেগা সাইকেলস প্রতি সেকেন্ড।

পুরো সারকিট টা কে কয়েক টা ভাগে ভাগ করে নিলে বুঝতে সুবিধা হবে। ১।অসিলেটর পারট- এই পারট তা মূলত ক্যারিয়ার ফ্রিকুয়েন্সী তইরি করে। একটা ক্যাপাসিটর আর একটা ইন্ডাক্টার এর প্যারালাল কানেকশন এই কাজ টা করে থাকে। এটাই ট্রান্সমিটারের সবচেয়ে সেন্সিটিভ অংশ। এবার অসিলেটর এর ফ্রিকুয়েন্সী কত হবে সেটা বের করতে হবে নিচের সূত্র দিয়ে f = 1 / 2 x √LC = Hz   Where f is the frequency in hertz, x is the coil length, C is the capacitance of trimmer in Farads, and L is the inductan…

### Make Three phase full wave rectifier circuit.

We know that three phase power supply is a very efficient way to supply power. Most of the industrial purpose three phase power is supplied. But sometimes industry need a high power DC supply to drive some special device like trolley buses, cranes etc. So, we need to rectify the three phase AC power supply to DC. There are mainly two methods of three phase full wave rectification 1. Three phase full wave uncontrolled bridge rectifier and 2. Full wave control rectifier. Three phase full wave uncontrolled bridge-

The uncontrolled version of three phase full wave bridge rectifier can be constructer by connecting by connecting six diodes in bridge configuration across the three phase AC power supply. Look the picture carefully Six diodes rectifies the three phase power supply then a large capacitor is used at the bridge output terminals across the load in order to minimize the ripple contents in the wave across the load. This in turn results in a constant output voltage which is pulsating DC i…

### Basics of stepper motor

Basics of stepper motor
A stepper motor is a widely used device that converts electrical pulses to equivalent mechanical movement with high accuracy.
A stepper motor is widely used in disk drivers ,dot matrix printers , robotics and many other automatic applications.
Construction-
Stepper motor has a permanent magnet rotor that is also called shaft. The most common stepper motor has four stator winding and they are paired with a center-tapped common.
These types of motors are generally called “four phase stepper motor”.  Centre tap needs to change the direction of current flow in each two coils when a winding is grounded. This change in direction in current in stator coil changes the polarity of electromagnetic stator. It helps to control the direction of movement of shaft.

A conventional motor runs freely, but in stepper motor the shaft moves in a fixed repeatable increment which allows one to move it to a precise position. This repeatable fixed movement is possible by using …