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MC2831A assembled FM wireless transmitter
MC2831A FM transmitter
Time :2010-11-15 22:46:45 Source: Internet Author: Unknown Editor: 【Close】
FM wireless transmitter MC2831A assembly, MC2831A FM transmitter
Keywords: MC2831A FM wireless transmitter assembly
The assembly with MC2831A FM wireless transmitter
Author: Wang Zemin
Recommended to readers a production by the U.S. company Motorola chip FM transmitter the integrated circuit MC2831A assembled wireless transmitter. It has a good sound quality, small distortion, no run frequency phenomenon, stable RF transmission.
The input terminal of the emitter can be inserted into the electromagnetic microphone for mutual contact in the fleet travels. You can also play audio sources such as MP3, CD music program.
TV sound can also be forwarded to the headset with FM radio reception at night to avoid disturbing others sleep. Available in the use of the car 12V car cigarette lighter power supply, AC-DC power supply can be used at home.
MC2831A emission ASIC has a low voltage power supply, low power consumption. DIP-16 DIP package. Its main technical parameters are as follows:
The assembly with MC2831A FM wireless transmitter
1. Operating frequency: 14MHz ~ 60MHz; 2. Operating voltage: 3V ~ 8V; 3. Operating Current: 4mA (VCC = 4V when); 4. Microphone amplifier: IC 5 feet, lost man-1mV, f = 1.0kHz, the closed-loop gain of 30dB. Its internal block diagram is shown right.
The assembly with MC2831A FM wireless transmitter
In order to make the circuit is simple, there is no audio pager MC2831A internal voltage detector.
The working principle of the circuit shown in the figure below.
The assembly with MC2831A FM wireless transmitter
Microphone BM or audio signal amplified by the IC internal operational amplifier from 5 feet entered the modulated high-frequency signal output to 3 feet by 6 feet, the inductor 11 and the crystal BC series in the internal circuit to oscillate between 1 foot and 16 feet 11 also has the role of expanding the frequency offset. 14-pin output by audio modulated carrier frequency signal VT1 enlarged. VT1 collector on the 1C form 4-fold the resonant and further expand the frequency offset. The output signal is coupled by C10 to VT2 then amplified antenna out C13.
Circuit R9, C14, C11, C2, and C3, and VD1 played buck regulator, the filtering effect. To make MC2831A voltage stability in 6V.
Components Selection: VD1 select 5V ~ 6V regulator. Quartz crystal 22M ~ 26.9M crystal, crystal determine the emission frequency, the swap crystal dodge the frequency of the radio station, the machine is 25M crystal. VT1 9018, β 70 to 100 as well. The VT2 optional 3DA18, 3DG12B domestic power tubes, β is greater than 50 can. 11 is a color code inductance 5μH ~ 10μH can. 12,13 0.8mm enameled wire in φ6mm drill tightly wound turns bodiless.
The assembly with MC2831A FM wireless transmitter
The antenna pedestal can be used a walkie-talkie with the Q9 outlet, so that connection to the car antenna.
Printed circuit board diagram see right, it is recommended that the integrated circuit with 16-pin IC socket, can avoid the welding craft in damage to the integrated circuit, but also conducive to the maintenance!
Check, after the power is turned on, the pin voltage is measured with a multimeter MC2831A to and Schedule values similar. Adjustment of R6, R8 VT1 collector current is 15mA, VT2 collector current of 40mA.
The plug electromagnetic microphone connected to a a 75cm long period copper wire for the antenna, open the FM radio frequency modulation at 100MHz, hands shot microphone radio speakers should send a "popping" sound. Can also be made of a simple field strength meter. Carefully adjust the field strength maximum.
The required press forwards MP3 diagram making a connection cable.
At close range, the antenna can be used a computer terminal 50Ω dummy load instead. If the car can be accessed VU segment car antenna, car radio can be satisfied within 400m receiver!
The assembly with MC2831A FM wireless transmitter
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