Just type and press 'enter' Search for: A photo relay or light activated relay is a circuit which opens and closes the relay contacts according to the light.
FM Transmitters Powerful microtransmitter that can cover 3km range. In our case the output power is about mW depending on the input power of 10mW and 9V battery power supply.
The transistor Q1 must be mounted with a heatsink, the heatsink must have small dimensions cylindrical in order not to increase the parasitic capacitance.
The trimmer R2 serves to adjust the bias of the transistor, start with the trimmer fully open and close by measuring the current absorbed by the 9V, in my case you get mW at the output with a current of 50mA not increase this value as you only increase the absorption by heating the transistor without increasing output power, because the input power is too low.
Clearly the 9V battery will be able to provide 50mA only for a few hours, if necessary have greater autonomy should be used a larger battery, but it is no longer a bug but simply an FM transmitter.
FM Transmitters This tiny Mhz FM transmitter bug measures just 10mm x 17mm in size and as you can see in the photos the biggest components are just the microphone and the battery. You can use a small microphone from an older cell phones, they are small in size and have an excellent sensitivity.
For an effective power supply the 9V battery Duracell is excellent and allows several hours of battery life, but if you want to have a smaller size it is better to use 2 or 3 lithium cells like the used in PCs. The circuit works well from 3 to 12V, the maximum range is obtained with 12V and a piece of cm cable as an antenna.
It started with a self-build kit from the Danish manufacturer Jostykit that allowed everyone to build a small FM transmitter for a few Euros. Such transmitters generally consist of a single transistor oscillator with a simple resonance circuit, sometimes with an extra transistor that is used as audio pre-amplifier.
The image shows a few examples that were available in European electronics shops in the mid s. The transmitter shown here was built in the mids and measures just 1 x 2 cm. When properly built, it may have a range of several kilometers. You may use it to run your own private neighborhood radio, just replacing the microphone capsule with a male audio jack connected to your pc or MP3 player.
You may also use this as a spy transmitter, but be reasonable in that case. It's rated for 1 Watt, so you can listen to it even from a few kilometers, with a good antenna and not too much obstacles in the way.
The circuit is based on LM positive and LM negative voltage regulators. LM series of adjustable 3 terminal regulator is capable of supplying in excess of 1. But the frustrating part is most transmitters refuses to work at all, and secondly the internet is full of crappy transmitter circuits.
Designing a stable FM transmitter circuit is rather a difficult job, many calculations are involved their.
There are also some construction error and component value tolerance. Here you can find a reasonably stable and well tested transmitter that actually works.
You don't have to understand the precise working of the transmitter to build it. But some basic information won't harm.
A transmitter alone is, as you probably know, is not enough to start your radio station. In the simplest form you need 4 things.
First an input device such as an amplifier you also use with your home stereo. You need a regulated power supply. In this case a Volts 2.Resistor Color Code and Types of Resistors Introduction to Resistors: A resistor is an electric element that limits the flow of the electric current into an electric circuit.
This new version of the CCK adds capacitors, inductors and AC voltage sources to your toolbox!
Now you can graph the current and voltage as a function of time. The resistance of the resistor and its tolerance are marked on the resistor with color code bands that denotes the resistance value.
There are 3 types of color codes: 4 . Experiment with an electronics kit! Build circuits with batteries, resistors, light bulbs, and switches.
Determine if everyday objects are conductors or insulators, and take measurements with an ammeter and voltmeter. View the circuit as a schematic diagram, or switch to a lifelike view. An electronic color code is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others.
A separate code, the pair color code, is used to identify wires in some telecommunications cables. Sep 16, · Most are printed with either a color code or an alphanumeric code to indicate their ohmic value and tolerance -- how much their resistance may vary. Learning the codes, along with using a helpful mnemonic device, will allow you to identify resistors easily%(32).