Phase-locked loop controller using AT89S51 microcontroller

1. Circuit Principle

The following figure is the schematic diagram of the controller circuit using the AT89S51 single-chip microcomputer. Four 0.5-inch red LED digital tubes are used to display the transmission frequency of BH1415F, and a 4×4 matrix keyboard is used to adjust and preset the transmission frequency.

Crystal oscillator JT1, capacitors C3 and C4 form the clock circuit of the microcontroller; R1 and C2 form the reset circuit of the microcontroller; R5~R16, VT1~VT4, and four LED common anode digital tubes form a dynamic display circuit for displaying the operating frequency of the transmitter: buttons KO~K15 form a 4x4 keyboard for adjusting the transmission frequency and presetting the transmission frequency. The entire circuit is very simple and easy to install and debug.

⑤ The socket J1 is the connection socket between the controller and the BH1415F transmitter board. On the one hand, it obtains 5V power from the BH1415F transmitter board to power the microcontroller, and on the other hand, it sends the control data of the microcontroller to the BH1415F. IC2, R3, and R4 are reserved memory circuits that can be used to upgrade this phase-locked loop controller. LED1 and R2 are used as "stereo/mono" indicators and are not used in this production.

LED digital tubes can be of other colors. But common anode digital tubes must be used. IC1AT89S51 should not be directly soldered on the circuit board. A 40-pin IC socket should be soldered on the circuit board first, so that the software can be modified in the future to increase the functions of the controller.

The whole circuit is relatively simple. As long as the components are selected correctly, installed correctly, and soldered reliably, it can be successfully produced without any debugging.

2. Control Software

In order to facilitate the production of the CNC phase-locked loop transmitter introduced in this article by the majority of electronic production enthusiasts and FM enthusiasts, the author has compiled the assembly source program, and obtained the HEX file and BIN file. Readers can use the programmer to write it into the AT89S51 microcontroller chip. Then insert the chip into the 40-pin socket, and then connect the controller circuit board and the BHl415F transmitter board through the socket J1. After careful inspection, you can power on the machine for testing.

3. Usage

The 16 buttons on the panel are used to set the operating frequency of the transmitter. The four buttons +100, +10, +1, and +0.1 on the top row, together with the red digital tube display, are used to adjust the hundreds, tens, units, and decimal places of the transmission frequency. The second, third, and fourth rows of buttons, a total of 11 buttons, are used to set preset frequencies. These 11 buttons can be used to quickly switch the transmission frequency. The last button S/M on the fourth row is used to adjust the stereo/mono mode. The software provided in this article only uses some of the buttons on the panel.