PLL Synthesized FM Receiver Circuit with LCD - 16F88 LM7001

FM Tuner

This is high quality stereo digital PLL synthesized FM radio receiver circuit that can scan with 76 MHz and 108 MHz seamlessly between 100 kHz step, although the sensitivity is high.

Main components of this receiver are a PIC16F88 micro-controller, 16x2 LCD, LM7001 PLL Frequency Synthesizer, AN7223 IF Amp, TA7343 MPX and a FM Tuner. This system is design to work with 12V DC power supply and the LM7805 and 7808 regulators used to manage power requirements to the above-mentioned components.

User interface of this system consist with 6 push buttons and a 16×2 character LCD module. All the functions of this receiver can control by this buttons and necessary information displayed on the LCD.

Specifications of this receiver

• High sensitivity
• Standby mode
• Preset memory stations up to 250 (default 20)
• 3-user selectable frequency ranges (default 87.5-108)

Schematic of PLL and Power circuit

Schematic of micro-controller and user interrface

LM7001

The LM7001 is a PLL frequency synthesizer LSIs for tuners, making it possible to make up high performance AM/FM tuners easily. These LSIs are software compatible with the LM7000, but do not include an IF calculation circuit. The FM VCO circuit includes a high-speed programmable divider that can divide directly seven reference frequencies. Serial input circuit for data input (using the CE, CL, and DATA pins)

Tuner 

Anticipating the objection that these tuners do not find, I assure you that if you do not be lazy and go through the repair shops where repair radio. In addition, you can get this tuner from old audio system and car set. There are 3 types.

Types of tuner

1. FM Front End only (you need to build IF Amp, MPX circuit)
2. FM Front End with IF (you need to build MPX)
3. FM Front End IF and MPX

IF Amp and MPX

For IF amp I used AN7223 because it need few external parts and it has high sensitivity and stability. If you cannot find FM quad coil then you can use 2pin 10.7MHZ ceramic resonator for that (see datasheet for more details). However, it is possible to use another IC for this as AN7220, TA7640 and KA2297 etc.

For MPX decoder here I used TA7343. This IC decode mono signal to stereo. This is an optional part. If you wish to work with mono, then omit this part and connect amplifier input with ‘AF’.

IF and MPX circuit

Complete circuit

Operation

Numbers of memory locations are determine by the value of Eeprom 1 (default value 0x14) and frequency range is determine by the value of Eeprom 2 (default value 0x00).

• If value is 1 then range is 76-108MHz
• If value is 2 then range is 76-90MHz
• Else, range is 87.5-108 MHz

Selecting the station:
When we are in the power on mode, on the screen we can see "Frq:106.5 Ch:15" - tuned frequency of the station and then the number of the cell where the recorded frequency of the station. Pressing ‘CH_UP’ and ‘CH_DN’ we can move the recorded stations. Pressing ‘FR_UP’ and ‘FR_DN’ we can change the frequency. ‘STORE’ stored the current frequency to the current station and ‘PWR’ used to toggle standby mode and power on mode

Micro-controller runs using its internal oscillator. RA6 pin can directly connect with background light of LCD display. As well as it is also can used for the controlling another device like mute pin of power amp. For VCC (tuning voltage) you can use up-to 12v.

Firmware of this system was written by using MikroC for PIC and schematic, hex and Proteus files are available for download.

PLL Tuner

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DS1302 Real Time LCD Clock Circuit - 16F88

Clock Schematic

This clock use DS1302 as timekeeping chip and this was my first time I used this IC for my project. It used three wires for communication. It communicates with a microprocessor via a simple serial interface. Three wires are required to communicate with the clock/RAM: CE, I/O (data line), and SCLK (serial clock). The real-time clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The DS1302 will run with a voltage from 2.0V to 5.5V.

Here I used PIC16F88 micro-controller and 16x2 LCD. No switches were added to edit time and date. To add switches you have to modify the code and it is not difficult. The DS1302 uses an external 32.768kHz crystal. The oscillator circuit does not require any external resistors or capacitors to operate. The accuracy of the clock is dependent upon the accuracy of the crystal and the accuracy of the match between the capacitive load of the oscillator circuit and the capacitive load for which the crystal was trimmed. Please refer datasheet for more information.

DS1302 Features

• Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year with Leap-Year Compensation Valid Up to 2100
• 31 x 8 Battery-Backed General-Purpose RAM
• Serial I/O for Minimum Pin Count
• 2.0V to 5.5V Full Operation
• Uses Less than 300nA at 2.0V
• Single-Byte or Multiple-Byte (Burst Mode) Data Transfer for Read or Write of Clock or RAM Data
• Simple 3-Wire Interface
• DS1202 Compatible

MikroC used as programming language but you can easily convert it to MikroC Pro. Micro-controller is running by its internal clock at 8MHz.The project files can be download from below with Source files, Proteus and Hex file.

DS1302 Real Time Clock

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