Wednesday, April 27, 2022

2.5KM FM transmitter, using transistor 2N3866 with PCB

Circuits to Assemble , Electronic Circuits
2.5KM FM transmitter, using transistor 2N3866 with PCB
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.

It can transmit audio signals to the atmosphere through electromagnetic waves, and can be received by an FM receiver circuit tuned to the same frequency as the transmitter, to reproduce signals from; songs, voice, musical instruments, etc. on the FM receiver.

⚠️ Caution!⚠️

For each Country, Region, State... There are Laws on broadcasting, telecommunications, audio and video transmission, etc.

Do not use telecommunications equipment without authorization from the entities responsible for transmitting Radio Frequencies.

Electronic Circuits teaches electronics applied to various segments, with the aim of improving knowledge, we do not support or take responsibility for any type of illegal operation.

For any operation with RF, we recommend looking for the competent regulatory agencies, seeking certification and/or legalization.

🛠️ Characteristics!

  • High sensitivity of audio pickup
  • 12V to 16Vdc supply voltage
  • Simple circuit to assemble
  • Great range, about 2.5km
  • Easy assembly

🧮 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 

The transmitter frequency adjustment, is regulated through the CV1 trimmer, and the CV2 and CV3 trimmers, to regulate the antenna impedance matching, must be done with patience for a better use.

The coil L1, L2 and L3 must be made with enameled wire 22 AWG of 1 cm in diameter with air core, the number of turns is described in the component list.

L4 is a 10uH RF shock, and you could be building your own RF shock by winding 15 vols of thin enamel wire around a 1MΩ resistor, soldering to both ends of the copper wire, at each end of the resistor.

The antenna can be a length of rigid wire between 20 and 50 cm for short ranges, or use a 1/2 wave dipole antenna for long ranges.

⚡ The Power Supply

The power source can be from 12Vdc to 16Vdc, if a power supply is used, well filtered sources must be used, due to the sensitivity of the circuit.

Don't use large wires, always use short wires, and shield the transmitter circuit source. The current consumed by the circuit is around 120mA when powered by 12V, and 400mA when powered by 16V.

🧮 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.

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

My Best Regards!!!

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Wednesday, April 6, 2022

14V 4 Channel 200W MOSFET Quad Bridge Power Amplifier using TDA7850 with PCB

Amplifier , Circuits to Assemble
14V 4 Channel 200W MOSFET Quad Bridge Power Amplifier using TDA7850 with PCB
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:

🧮 IC Features

  • High output power capability:
    • 4 x 50W / 4Ω max.
    • 4 x 30W / 4Ω @ 14.4 V, 1 kHz, 10 %
    • 4 x 80W / 2Ω max.
    • 4 x 55W / 2Ω @ 14.4V, 1 kHz, 10 %
  • MOSFET output power stage
  • Excellent 2Ω driving capability
  • Hi-Fi class distortion
  • Low output noise
  • ST-BY function
  • Mute function
  • Auto mute at min. supply voltage detection
  • Low external component count:
    • Internally fixed gain (26 dB)
    • No external compensation
    • No bootstrap capacitors
  • On board 0.35 A high side driver

🔌 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!!!

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    Friday, April 1, 2022

    140W Class AB Amplifier using MJL4281A and MJL4302A transistors with PCB

    Amplifier , Circuits to Assemble
    140W Class AB Amplifier using MJL4281A and MJL4302A transistors with PCB

    140W Class AB Amplifier using MJL4281A and MJL4302A transistors with PCB

    Discover High-Fidelity Sound: Build a 140W Class AB Amplifier with MJL4281A and MJL4302A Transistors along with PCB

    This is a simple 140W Class AB amplifier using MJL4281A and MJL4302A transistors, which stands out for its simplicity, quality, and is a moderate amplifier to build.

    You can be making two of these boards, to be able to work with two outputs, in stereo, and make an amplifier with total power of 280W RMS.

    This amplifier works with a simple power supply, that is, a unipolar, non-symmetric power supply.
     
    This amplifier circuit can be used in almost any type of application that requires a simple amplifier, with great performance, low noise and low distortion, and good sound quality.

    It uses 2 output power transistors, NPN transistor MJL4281, and PNP transistor MJL4302, forming a pair of complementary transistors.

    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:

    Fig. 3 - Symmetrical Power Supply for Power Amplifiers

    🧮 Components List

    • Semiconductor
      • Q1, Q2, Q3 .... 2N5551 NPN Transistor
      • Q4, Q6 ........... BD139 NPN Transistor
      • Q5, Q7 ........... BD140 PNP Transistor
      • Q8 .................. MJL4302A NPN Transistor
      • Q9 .................. MJL4281A NPN Transistor
      • LED1 ............. Light Emitter Diode (general use) 

    • Resistor
      • R1, R3 ........... 2K2Ω resistor (red, red, red, gold) 
      • R2, R4, R8 ..... 22KΩ resistor (red, red, orange, gold)
      • R5, R6 ........... 560Ω resistor (green, blue, brown, gold)
      • R7 .................. 1K2Ω resistor (brown, red, red, gold)
      • R9 .................. 1KΩ resistor (brown, black, red, gold)
      • R10, R11 ....... 3K3Ω resistor (orange, orange, red, gold)
      • R12, R13 ....... 220Ω resistor (red, red, brown, gold)
      • R14, R15 ....... 0.22Ω / 5W resistor (red, red, silver, gold)
      • R16 ................ 10Ω / 1W resistor (brown, black, black, gold) 
      • RP1 ................ 2K Potentiometer
    • Capacitor
      • C1 .................. 2.2uF / 25V electrolytic capacitor 
      • C2 .................. 330pF ceramic, polyester capacitor
      • C3, C5 ........... 100uF / 65V electrolytic capacitor 
      • C4, C6, C7 .... 100nF ceramic, polyester capacitor

    • Miscellaneous 
      • P1, P2 ............ Screw Terminal Type 5mm 2-Pin Connector
      • P3 .................. Screw Terminal Type 5mm 3-Pin Connector
      • Others ............ PCB, tin, wires, heat sink, soldering Iron, 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. 3 - PCB - 140W Class AB Amplifier using MJL4281A and MJL4302A transistors

    📥 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!!!

    Read more »
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