Fig. 1 - 2.5KM FM transmitter, using transistor 2N3866 with PCB

Ultimate Guide: Building a Powerful 2.5KM FM Transmitter with 2N3866 Transistor and PCB

This is a simple FM transmitter, with great range, being able to reach more than 2.5 km of distance, using a suitable antenna, powered by a power supply or a 12Vdc battery.

The circuit has a frequency range that can be tuned between 88 and 108 MHz, and is quite stable, and can be used for small audio transmission links, or as community radio, and with great audio quality.

The Transmitter

The FM - Frequency Modulated transmitter circuit is a wireless device that operates in a high frequency range.

Circuit Operation

The circuit uses two RF transistors; Q1 2N2218 used as RF oscillator, and transistor Q2 2N3866, used for power stage.

The decouple electrolytic capacitor C1, receives the audio signal, who comes from a signal source, which can be a soundboard, a USB audio card, a musical instrument, or any other signal source.

This modulated signal is sent to the base of transistor Q1, it works as an oscillator circuit, the trimmer VC1 in parallel with the coil L1, adjusts the circuit operating frequency.

Transistor Q2 works as the power stage of the transmitter, it amplifies the RF signal generated by Q1, and sends it to the output, composed by the antenna.

Trimmers VC2 and VC3 connected to the antenna, adjust the impedance of the antenna coupled to the output, which we must adjust for better impedance matching, and to obtain the best signal at the output.

Applications!

• Audio transmitter
• Audio link for instruments
• Wireless microphones
• Spy Microphone
• Homemade FM radio
  

Schematic diagram

The schematic diagram of the 2.5 km FM Transmitter is in Figure 2 below. As we can see, it is a very simple circuit, however, it is not recommended for those who have no experience with electronic circuit assembly. 

It is recommended to mount this circuit in a metal box, if you do not have a metal box, glue aluminum foil on the walls of the box to shield the entire circuit from external interference.

Fig. 2 - Schematic 2.5KM FM transmitter, using transistor 2N3866

Circuit Adjustments 

Components List

• Semiconductors
• Q1 .............  2N2218 or 2N2219 NPN transistor
• Q2 .............. 2N3866 or 2N4427 NPN Transistor 
  
  
• Resistors
• R1, R2 ....... 10KΩ 1/4W Resistor (brown, black, orange, gold)
• R3 .............  47Ω 1/4W Resistor (yellow, violet, black, gold)
• PT1 ........... 10KΩ Potentiometer 
  
  
• Capacitors
• C1 .............  2.2uF /16V Electrolytic Capacitor
• C2, C3 ....... 1nF Ceramic/Polyester Capacitor
• C4, C5 ....... 8.2pF Ceramic Capacitor
• VC1, 2, 3 ... 0 ~ 47pF Trimmers
  
  
• Coils
• L1 ............... 4 Turns, 7mm diameter Inductor
• L2 ............... 3 Turns, 7mm diameter Inductor
• L3 ............... 5 Turns, 7mm diameter Inductor 
• L4 ............... RFC -  10uH Inductor *See Text
  
  
• Miscellaneous
• P1, P2 .... Screw Terminal Type 5mm 2-Pin Connector
• Other ........................... PCB, Wires, Speaker, etc.
  
  

PCB - Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass. 

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 3 - PCB - 2.5KM FM transmitter, using transistor 2N3866

Files to download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

I hope you enjoyed it!!!

If you have any questions, suggestions or corrections, please leave them in the comments, and we will answer them soon.

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My Best Regards!

Fig. 1 - 14V 4 Channel 200W MOSFET Quad Bridge Power Amplifier using TDA7850 with PCB

Unleash Power and Sound with a 14V 4-Channel 200W MOSFET Quad Bridge Amplifier using TDA7850 and PCB

This is a 14V 4 Channel 200W MOSFET Quad Bridge Power Amplifier, it uses an TDA7850 Integrated Circuits, in Quad Bridge Mode to drive four power speakers.

The circuit provides a total output power of 200W, and this with good sound quality, powered from a unipolar 14V power supply.

The Amplifier responds very well to all audible frequency ranges, and has a minimalist, compact design, which makes this amplifier a good choice for an unprecedented range of application. 

IC Description

The TDA7850 is a breakthrough MOSFET technology Class AB audio power amplifier in Flexiwatt 25 package designed for high power car radio. 

The fully complementary P-Channel / N-Channel output structure allows a rail to rail output voltage swing which, combined with high output current and minimized saturation losses sets new power references in the car-radio field, with unparalleled distortion performances. The TDA7850 integrates a DC offset detector.

You might also be interested in:

• 24W Stereo Hi-Fi Audio Amplifier using TDA2616 + PCB
• 68W Hi-Fi Audio Power Amplifier using LM3886T IC + PCB
• 4 x 50W High Power Amplifier, 14.4V - IC TDA7563A + PCB
• 320W Power Audio Amplifier, Powered with 14.4V - 2Ω with IC TDA7560 + PCB
• 100W RMS Audio Amplifier IC TDA7294 + PCB
• 200W RMS Stereo Power Amplifier with IC STK4231II + PCB
  

IC Features

The Schematic Circuit

In Figure 2 below, we have available the schematic diagram of the 14V 4 Channel 200W MOSFET power amplifier circuit, this circuit is quite simple to assemble.

As we can see there are very few external components, making the circuit very simple to assemble, even for a technician or hobbyist with little experience in electronics can assemble it without much difficulty. 

Fig. 2 - Diagram 14V 4 Channel 200W MOSFET Quad Bridge Power Amplifier using TDA7850

It is important to remember to be careful when assembling the circuit, as simple as the circuit is. We must be careful not to invert any components, such as capacitors, or invert the input voltage of the circuit, because the integrated circuit or other components can be damaged easily.

Components List

• Semiconductors
• U1 ............ TDA7850 Integrated Circuit 
  
  
• Resistors
• R1 ............ 47KΩ Resistor (yellow, violet, orange, gold)
• R2, R3 ..... 10K resistor (brown, black, orange, gold)
  
  
• Capacitors
• C1 to C4 ... 220nF Ceramic/Polyester Capacitor
• C5, C6 ...... 1μF Ceramic/Polyester Capacitor
• C7 ............. 470nF Ceramic/Polyester Capacitor
• C8 ............. 47μF / 25V Electrolytic Capacitor
• C9 ............. 2.200μF / 25V Electrolytic Capacitor
• C10 ........... 100nF Ceramic/Polyester Capacitor
  
  
• Miscellaneous
• P1 to P9 .... Screw Terminal Type 5mm 2-Pin Connector
• Other ........ PCB, Wires, Speaker, etc.
  

Power Supply

This amplifier is powered by unipolar source, with direct current, the maximum current required by the circuit is approximately 15 Amperes.

And you can connect it directly to a car battery, or a motorcycle battery, or a no-break battery, or a bench power supply... 

The power will be according to the power supply, and as already shown in the IC features above, to have 4 outputs of 50W we have to supply the circuit with 14.4V. 

Printed Circuit Board

In Figure 3, we provide the PCB - Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass. 

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 3 - PCB 14V 4 Channel 200W MOSFET Quad Bridge Power Amplifier using TDA7850

Files to Download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

I hope you enjoyed it!!!

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

Subscribe to our blog!!! Click here - elcircuits.com!!!

My Best Regards!!!

Fig. 1 - 140W Class AB Amplifier using MJL4281A and MJL4302A transistors with PCB

You might also be interested in:

The Power Transistors

The MJL4281A and MJL4302A transistors are power transistors designed for high power audio, they have a collector-emitter sustaining voltage of 350 V.

It's high gain – 80 to 240, with the hFE = 50 (min) 8A collector current, and a low harmonic distortion, which makes a transistor excellent for high power operation and audio quality.

The Circuit

This circuit has a moderate complexity, it is not recommended for those who have no experience in electronics and in the assembly of amplifier circuits.

You should have minimum knowledge in an intermediate to advanced level to assemble this type of power amplifier.

The schematic diagram of the complete circuit, shown in Figure 2 below, is a very robust amplifier, with great sound quality and very stable, responding very well at all audible frequencies, with little attenuation in the 20Hz to 20Khz hearing frequency range.

Fig. 2 - Schematic Diagram 140W Class AB Amplifier using MJL4281A and MJL4302A transistors

Power supply

The power supply is symmetrical, with a voltage of +45V | 0V | -45V, and direct current, with at least 6 Amps of current. For continuous use, we recommend 4A, especially if used in a subwoofer.

In Figure 3 below, we have a suggestion for a power supply that we use in our projects. In this article, besides having the schematic diagram with the Printed Circuit Board, you will understand how to easily calculate your own Power Supply, with the desired voltage.

You can in the link below:

• Symmetrical Power Supply for Power Amplifiers using Calculation + PCB

Fig. 3 - Symmetrical Power Supply for Power Amplifiers

Components List

Printed Circuit Board - Download

We are offering the PCB – Printed Circuit Board, in GERBER, PDF and PNG files, for you who want to do the most optimized assembly, either at home.

If you prefer in a company that develops the board, you can is downloading and make the files in the Download option below.

Fig. 3 - PCB - 140W Class AB Amplifier using MJL4281A and MJL4302A transistors

Files to Download, Direct Link:

Fig. 1 110/220VAC 4 Step Control Touch Dimmer Switch Lamp Circuit with PCB

Enhance Your Lighting: Build a 110/220VAC 4-Step Touch Dimmer Switch Circuit for Lamps with PCB Control

This type of circuit is widely used in lampshades that are sold in residential lighting stores, it activates an incandescent bulb through the touch on the device's casing.

It works as a dimmer with 4 pre-set levels, activated by touching a part of the sensor with your finger, which can be a metallic point, or a metallic housing, etc. The entire 4-level brightness control circuit is based on the LS7237 IC.

LS7237 IC Description

LS7237 is a 8-Pin monolithic, MOS integrated circuit designed to control the brightness of an incandescent lamp, as show in Figure 2 above. The output of the LS7237 triggers a Triac connected in series with a lamp. 

Fig. 2 - Pinout LS7237

The lamp brightness is determined by controlling the output conduction angle (Triac triggering angle) in relation to the AC line frequency.

CAUTION!!!

This circuit works directly connected to the 110/220V electrical network, and has a high power load, any carelessness, or wrong connections, error in the project, or any other occasion, can lead to irreversible damage. 

We are not responsible for any type of event. If you do not have enough experience to assemble this circuit, do not do it, and if you do, when testing, be sure to have the proper protections and be accompanied by someone else.

How the Circuit Work

The circuit works as follows: when a touch is made to the board, it causes the brightness of the lamp to change in specified steps as follows:

• LEVEL - - - BRIGHTNESS(% Rated Wattage)
• Off .................... 0
• Night Light ....... 9
• Mood Light ...... 29
• Medium ............ 66
• Maximum ......... 99
  

After AC power-up, the output comes up in the OFF state. Following that, every time the Touch Plate is touched, the output steps to the next level of brightness. The next step following the maximum brightness is the OFF state, initiating a new sequence.

Features

• PLL synchronization allows use as a Wall Switch
• Provides brightness control of an incandescent lamp with a touch plate or mechanical switch
• Can control speed of shaded pole and universal AC motors
• Controls the "duty cycle" from 23% to 88% (conduction angles for AC half-cycles between 45˚ and 158˚, respectively)
• Operates at 50Hz/60Hz line frequency
• Extension input for remote activation
• +12V to +18V DC Power Supply (VSS - VDD)
• 8-Pin Plastic DIP , 8-Pin SOIC
  

The Schematic Circuit

The 110/220VAC 4 Step Control Touch Dimmer Switch Lamp Circuit diagram is shown in Figure 3 below.  

Is a moderately simple circuit to assemble, with few external components, however one must have at least basic to advanced experience to assemble this circuit, if you are not experienced enough, ask someone more experienced to help you.

Fig. 3 - 110/220VAC 4 Step Control Touch Dimmer Switch Lamp Circuit

110Vac or 220Vac

This circuit was designed to work with 220Vac voltage, for use in 110Vac power network, the following components must be replaced in the component list.

• R1, R2 .... 2.7MΩ 1/4W (red, violet, red, gold) 
• R6 ........... 270Ω 1W (red, violet, brown, gold)
• C5 ........... 330nF / 400V polyester Capacitor 
• L1 .......... 60µH (RFI Filter)
  

Components List

• Semiconductors
• U1 ............ LS7237 Integrated Circuit
• Q1 ............ BT136 Triac Transistor
• D1 ............ 1N4007 Diode
• DZ1 ......... 1N4744 15V/1W Zenner Diode 
• 
  
• Resistor
• R1, R2 .... 4.7MΩ 1/4W (yellow, violet, green, gold) 
• R3 ........... 1.8MΩ 1/4W (brown, gray, green, gold)
• R4 ........... 1.5MΩ 1/4W (brown, yellow, green, gold)
• R5 ........... 100Ω 1/4W (brown, black, brown, gold)
• R6 ........... 1KΩ 2W (brown, black, red, gold)

• Capacitor
• C1 ........... 680pF / 400V Polyester Capacitor
• C2 ............47nF / 400V Polyester Capacitor
• C3 ........... 470pF/ 400V Ceramic Capacitor
• C4 ........... 47µF / 25V Electrolytic Capacitor 
• C5 ........... 220nF / 400V Polyester Capacitor
• C6 ........... 150nF /400V polyester Capacitor
  
  
• Miscellaneous 
• L1 .......... 120µH (RFI Filter)
• P1, P2 .... 2-pin PCB soldering terminal blocks
• F1 .......... 3A/250V Soldering fuse
• Others .... PCB, heat sink, power supply, wires, etc.
  

Printed Circuit Board - Download

We are offering the PCB - Printed Circuit Board, in GERBER, PDF and PNG files, for you who want to do the most optimized assembly, either at home.

If you prefer in a company that develops the board, you can is downloading and make the files in the Download option below.

Fig. 4 - PCB 110/220VAC 4 Step Control Touch Dimmer Switch Lamp Circuit

Files to download, Direct Link:

Click Here to Download the Files

I hope you enjoyed it!!!

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

Subscribe to our blog!!! Click here - elcircuits.com!!!

My Best Regards!!!

Fig. 1 - How to Wire LEDs in 110V or 220 Volts - 6 Different Circuits! Formulas & Calculations!

Illuminating Insights: Wiring LEDs for 110V or 220V - Explore 6 Distinct Circuits with Formulas and Calculations!

Today we will show you 6 different ways to wire 3mm or 5mm LEDs, which are low voltage DC components, into a 110V or 220V AC voltage grid!

We can use LEDs in several ways connected to 110V or 220V power grid, knowing that some types of connections bring advantages over others, and that each type has its characteristics that best fit each specification. 

We will use some basic formulas to calculate the components in our circuit, for this we will use the capacitive reactance formula, and the Ohms Law formula.

So let's start by showing the basic formulas that we will use with the models we made in this post. 
We'll apply the basic formulas as needed, so we'll start first by determining the supply voltage. 

CAUTION! 

The working voltage

In our country the working voltage is 110VAC, if your electrical network is 220VAC, just substitute the working voltage of your region in the formula.

It is necessary to know that our grid voltage has peak voltages, as showing in Figure 2 below, and for our safety we will use the peak to peak voltage (VPP) in our calculations.

Fig. 2 - Peak to Peak 110Vac Calculation - VPP

The calculation is determined by the mathematical equation:

• VP = VAC * √(2)

As our power grid is 110VAC:

• VP = 110 *1.414
• VP = 155.54VAC

If you use the 220VAC power grid:

• VP = 220V * 1.414
• VP = 311,08VAC
  
  

The LED

Determine the resistor resistance:

Determine the Resistor's Power:

• P = R * I²

Determine Capacitive Reactance:

This model is the simplest we have, and it is very often used in cheap electrical extensions of those Chinese products, and also as a Pilot lamp in equipment,... 

The circuit presented has only one resistor R1, which limits the current that passes through the LED, and is connected in series with the LED, as we can see in Figure 3 below.

Fig. 3 - Wire LED in 110v or 220V Circuit 1 - ELC

2° Circuit:

This model is still quite simple, it is a circuit widely used also in cheaper electrical extensions of those Chinese products... 

The circuit presented has a resistor R1, which limits the current that passes through the LED, and a Diode, which polarizes the AC voltage coming from the power grid, which is connected in series with the LED, as we can see in Circuit 2.1 in Figure 4 below. .

We also have Circuit 2.2, which is the same circuit, but we have added a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit. 

Fig. 4 - Wire LED in 110v or 220V Circuit 2 - ELC

Designing the Circuit

Just like the previous circuit, the calculations are the same, we already calculated the resistance, after all the process, it was 12K with 5W of power.

Project Finished - Circuit 2

Here we finish the development of our circuit 2, the calculated values are

• LED1 ....... Light Emitting Diode 3.2V / 20mA
• D1 ............ 1N4007 Diode
• C1 ............ 2.2uF / 25V Electrolytic Capacitor (Optional)
• R1 ............ 12K / 5W resistor for 110V. (27K at 220V).

Advantages:

• It is a simple and easy circuit to assemble
• Only 3 or 4 components
• Safer circuit for LED lifetime

Disadvantages:

• Voltage dissipation will be on the resistor (Joule effect)
• Consumption higher than necessary
• Circuit operating in half wave, LED half off
• Low Efficiency
  

3° Circuit

This model, different from the previous one, adopts a rectifier bridge, this implies that the energy that comes to the LED, is no longer a half wave, but a full wave, which gives more brightness to the LED.

The circuit presented has a resistor R1, current limiter, and a bridge of diodes, which polarize the AC voltage that comes from the grid, and feeds the LED, as we can see in Circuit 2.1 in Figure 5 below.

We also have Circuit 2.2, which is the same circuit, but we add a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit. 

Fig. 5 - Wire LED in 110v or 220V Circuit 3 - ELC

Designing the Circuit

Just like the previous circuit, the calculations are the same, we already calculated the resistance, after all the process, it was 12K with 5W of power.

Project Finished - Circuit 3

Here we finish the development of our circuit 2, the calculated values are

• LED1 ....... Light Emitting Diode 3.2V / 20mA
• D1 ............ 4 x 1N4007 Diode, or a diode bridge any model
• C1 ............ 2.2uF / 25V Electrolytic Capacitor (Optional)
• R1 ............ 12K / 5W resistor for 110V. (27K at 220V).

Advantages:

• It is a simple circuit to assemble
• Only 3 or 4 components
• Full wave, which gives more brightness to the LED.
• Safer circuit for LED lifetime

Disadvantages:

• Voltage dissipation will be on the resistor (Joule effect)
• Consumption higher than necessary
• Low Efficiency

4° Circuit:

This circuit is widely used in Mosquito Bats, rechargeable flashlights, i.e. cheaper Chinese products. 

In this circuit we replaced the current limiting resistor with a capacitor. When a capacitor is connected to an AC source, it allows current to flow in a circuit.

With the process of successive charge and discharge of a capacitor, it gives rise to a resistance, in the passage of current in the circuit, and this resistance is called capacitive reactance. With these properties, we can use the capacitor in our circuit as a resistor.

In the case of the capacitor, all of this energy is used, because the capacitor needs to charge and discharge, it "holds" the energy and therefore does not consume it, making the circuit much more efficient. 

We also have Circuit 4.2, which is the same circuit, but we have added a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit. The complete circuits are in Figure 6 below.

Fig. 6 - Wire LED in 110v or 220V Circuit 4 - ELC

5° Circuit:

This model is a more complete and improved circuit, because it brings with it a diode bridge, improving efficiency even more, since the LED will no longer work for half a wave period, but for a full wave period.

This circuit is widely used in small luminaires, even in LED lamps, rechargeable flashlights, or in commercial products. 

This circuit is the junction of circuits 3 and 4, thus forming an efficient circuit, with good LED brightness, with full wave, it is almost the perfect circuit. 

The circuit presented has a diode bridge, which polarizes the AC voltage coming from the mains, which is connected in series with the LED, as we can see in Circuit 5.1 in Figure 7 below.

We also have Circuit 5.2, which is the same circuit, but we add a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit.

Fig. 7 - Wire LED in 110v or 220V Circuit 5 - ELC

Designing the Circuit

First you need to determine the capacitive reactance, which was already done in the previous circuit, the capacitance is 5.340Ω or 5.3K.

Project Finished - Circuit 5

We finish here the development of our circuit 5, the calculated values we will have:

• LED1 ....... Light Emitting Diode 3.2V / 20mA
• D1 ........... 4 x 1N4007 Diode, or a diode bridge, any model
• C1 ........... 560nF / 250V Polyester Capacitor
• C2 ........... 2.2uF / 25V Electrolytic Capacitor (Optional)

Advantages:

• It is a simple circuit to assemble
• Only 3 or 4 components
• Safer circuit for LED lifetime
• No consumption of excess heat energy (Joule effect)
• High Efficiency
• Circuit operating in full wave, LED always on

Disadvantages:

• High current in the initial steady state of the capacitor, causing those "pops" and sparks in the socket.
  

6° Circuit:

This model is more complete and, like the previous circuit, is more efficient. This circuit is widely used in small light fixtures, some LED lamps, rechargeable flashlights, and in some commercial products. 

The circuit presented is identical to circuit 5, with the only difference that we put a resistor R1, that serve to limit the capacitor inrush current. A diode bridge, which polarizes the AC voltage coming from the mains, which is connected in series with the LED, as we can see in Circuit 6.1 in Figure 8 below.

We also have Circuit 6.2, which is the same circuit, but we have added a 2.2uF capacitor that serves to minimize the ripple voltage in the circuit.

Fig. 8 - Wire LED in 110v or 220V Circuit 6 - ELC