Small FM Receiver Circuit

This is the most simple fm radio receiver with good performances that works great even if the sensitivity is not too high. The working principle of this fm receiver may seem a little unusual. It is made of an oscillator (T2 and T3) that is synchronized with the received frequency of T1. This transistor works as a broadband preamplifier in VHF range. The oscillator is adjusted between 87 … 108 MHz with C5. Because of the synchronization, the oscillator output will have the same frequency deviation as the received signal from the fm antenna. This deviations are caused by the broadcasted audio informations. The frequency modulated signal show up on P1 + R5. Low pass filter R6/C6 extracts the audio signal and then is amplifier by T4 … T6 and transmitted...

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Long Range FM Transmitter Circuit Diagram

The power output of most of these circuits are very low because no power amplifier stages were incorporated. The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres. The circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2...

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How do motion sensing lights and burglar alarms work?

T­here are many different ways to create a motion sensor. For example: It is common for stores to have a beam of light crossing the room near the door, and a photosensor on the other side of the ­room. When a customer breaks the beam, the photosensor detects the change in the amount of light and rings a bell. Many grocery stores have automatic door openers that use a very simple form of radar to detect when someone passes near the door. The box above the door sends out a burst of microwave radio energy and waits for the reflected energy to bounce back. When a person moves into the field of microwave energy, it changes the amount of reflected energy or the time it takes for the reflection to arrive, and the box opens the door. Since these...

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How Batteries Work

Imagine a world where everything that used electricity had to be plugged in. Flashlights, hearing aids, cell phones and other portable devices would be tethered to electrical outlets, rendering them awkward and cumbersome. Cars couldn't be started with the simple turn of a key; a strenuous cranking would be required to get the pistons moving. Wires would be strung everywhere, creating a safety hazard and an unsightly mess. Thankfully, batteries provide us with a mobile source of power that makes many modern conveniences possible. While there are many different types of batteries, the basic concept by which they function remains the same. When a device is connected to a battery, a reaction occurs that produces electrical energy. This is known...

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How Capacitors Work

In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons on the other terminal. A capacitor is much simpler than a battery, as it can't produce new electrons -- it only stores them. In this article, we'll learn exactly what a capacitor is, what it does and how it's used in electronics. We'll also look at the history of the capacitor and how several people helped shape its progress. Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting...

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How to Make a Line Following Robot

Project Summary The motors I used for this robot are 2 servomotors modified for speed. You can also use other motors if it's good enough. I didn't have any so I modded 2 servomotors. Project Description  Figure 1  microcontroller-schematic How to Mod the Servomotors (look at the pictures) Remove the four screws from the servo and take it all apart. Remove the electronics keeping only the wires from the motor (I kept the other 3 wires from the potentiometer but you don’t have to). Try to fit the gears except for one. I glued the big gear to the one beneath it so to be high enough to “get out” of the case. It isn’t exactly a rule for how to do this. Various servos will have various gears so you will need to try until you...

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How Circuit Breakers Work

The circuit breaker is an absolutely essential device in the modern world, and one of the most important safety mechanisms in your home. Whenever electrical wiring in a building has too much current flowing through it, these simple machines cut the power until somebody can fix the problem. Without circuit breakers (or the alternative, fuses), household electricity would be impractical because of the potential for fires and other mayhem resulting from simple wiring problems and equipment failures. In this article, we'll find out how circuit breakers and fuses monitor electrical current and how they cut off the power when current levels get too high. As we'll see, the circuit breaker is an incredibly simple solution to a potentially deadly...

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On 2014 Smart Electric Scooter

Last month, the German automaker Smart, revealed that their all-new electric scooter would be released in 2014. Despite making the release date public, Smart chose not to clue consumers in on any additional details. That is until now. The company, primarily known for manufacturing microcars, has just specified several characteristics of its upcoming escooter, including its price, range, battery type, construction and tech capabilities. The 2014 Smart Electric Scooter Smart’s electric scooter will feature a 48-volt lithium-ion battery pack, which supplies power to a 4-kW electric motor. The scooter’s motor is a wheel-hub unit, located at the rear wheel. As for performance, Smart’s scooter will turn out approximately 5.4-horsepower. Smart...

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Using Analog Circuit to Manage Power in Low-Power Solar Systems

From large panels to harvested microwatts from a few photodiodes, solar power is increasingly prevalent in autonomously powered systems. With the worldwide evolution toward lower power operation using more “green” energy sources, emphasis on deploying solar power in a greater variety of environments has been on the rise. In low-power solar systems, it is critical to assess whether there is sufficient sunlight at a given time to power the system. In some cases, this involves determining whether there is sufficient power to enable the microcontroller. In many ultra-low-power systems, the simple act of waking the microcontroller to make a voltage measurement might collapse the solar source or waste precious power from a reservoir capacitor. One...

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Mesh/Current Analysis

The technique of nodal analysis described in the preceding topic is completely general and can always be applied to any electrical network. This is not the only method for which a similar claim can be made, however. In general, we shall meet a generalized nodal analysis method and a technique known as loop analysis. Let us first consider a method known as mesh analysis. Mesh Method is perhaps the most popular technique used by engineers to solve complex circuit problems.Even though this technique is not applicable to every network, it is probably used more often than it should be and it can be applied to most of the networks to be analyzed. Mesh analysis is applicable only to those networks which are planar, a term we hasten to define. The...

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Some Useful Techniques of Circuit Analysis

Describing voltage and current relationships in electric circuits are often precisely analogous with the resultant equations when dealing with mathematical behavior of fluid-flow and heat-flow systems, the dynamic response of aircraft control surfaces and other non-electrical phenomena. Rather than building a prototype of the actual physical system, it is much easier and cheaper to construct the analogous electric circuit. As various elements are changed, the electric circuit may then be used to predict the performance of the other system. One of the primary goals of this tutorial is to learn the methods of simplifying the analysis of more complicated circuits. Among these methods include nodal analysis, mesh, loop and superposition. In order...

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IR Introduces Family of Rugged, Reliable Automotive-Qualified Power MOSFETs Housed in TO-220 Fullpak Package

International Rectifier introduced a family of automotive-qualified power MOSFETs housed in a rugged TO-220 fullpak package for automotive applications including BLDC motors, pumps and cooling systems. The new 55V planar devices are available as standard and logic level gate drive MOSFETs in N and P channel configuration, and offer a maximum on-state resistance (RDS(ON)) as low as 8mOhm. The TO-220 fullpak package eliminates the need for additional insulating hardware to simplify design and improve overall system reliability. IR’s automotive MOSFETs are subject to dynamic and static part average testing combined with 100 percent automated wafer level visual inspection as part of IR’s automotive quality initiative targeting zero defects....

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