AN7223 LM7001 PLL FM Stereo Tuner, JQ8400 USB MP3, Bluetooth Audio Player - 16F690

Audio Player

This is my new project, 3 in 1 audio player that design for my amplifier. It built in FM radio, USB player and Bluetooth module. Also include a simple mixer with op-amp.

Bottom PCB

Top PCB

Side View

For tuner section I used AN7223 and TA7343 and for PLL here I used LM7001 low cost IC. JQ8400 used for USB function and it controlled by a PIC16F690 microcontroller. U can use any Bluetooth audio module for this. I used MH-M18 Bluetooth module for this.

JQ8400 Module

Bluetooth Module

Please read my previous post for detailed information about PLL FM tuner and jq8400. I wrote a small sample program for control this unit and u can modify it according to your need. Don’t use relay. Just connect I2C directly to R37 & R39.

Control Circuit

Usage of usb command

// --------- commands ----------------- Write_Df(0x06,0,0); // mp3 next Write_Df(0x05,0,0); // mp3 prev Write_Df(0x02,0,0); // mp3 play Write_Df(0x03,0,0); // mp3 pause Write_Df(0x04,0,0); // mp3 stop Write_Df(0x21,0,0); // mp3 random Write_Df(0xA3,0,5); // mp3 ff 5s Write_Df(0xA2,0,5); // mp3 fr 5s write_Df(0x87,Cur_Tr>>8,Cur_Tr); // mp3 track play (max 9999)

Mikro c source code for Control circuit, source code for PLL FM, Hex file for jq8400 controller and PCB file and circuit are in download section. Hope you like it.

PLL FM Code

Controller Code

JQ8400 Controller HEX

PCB And Sch File

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7 Band Real Time Audio Spectrum Analyzer Circuit - 16F819 BA3834S

16F819 Audio Spectrum Analyzer

This is the new version of my previous spectrum analyzer. Used PIC16F819 microcontroller and BA3834 Band-pass filter for spectrum analyzer. It has two versions, BA3834S and BA3834F. Here i used BA3834S. BA3834 are 7-band, band-pass filter ICs that use microprocessor time division to produce serial output for spectrum analyzer displays. To minimize the number of attached components required and enable compact and reliable designs, all of the capacitors for the filters are on the chip. So we can build spectrum analyzer easily

Analizer circuit

This circuit included 11 modes (9 patterns, off and random) and it shows which pattern currently running at start-up (S1, S2, etc.). In off mode it shows S0 on display and S+ for random mode. The pattern mode saved to Eeprom to run at next power up. In random mode it changes its pattern in every 3.5 minutes.
PCB, Circuit, and hex available in below

Schematic, PCB and Hex

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Uart Controlled DF Player Mikroc Code - 16F628A

  The DFPlayer Mini MP3 Player is a small and low cost MP3 module with an simplified output directly to the speaker. The module can be used as a stand alone module with attached battery, speaker and push buttons or used in combination with a PIC, Arduino or any other with RX/TX capabilities. For this project, I would control the MP3 Player module with a microcontroller and RS232.

DF Player

  The DF Player module has all the features which a MP3 player should have. Including advance equalizers, looping and shuffling functions. But here I will show you how to build a simple player with Play/Pause, Next/Preview and vol Up/Down functions. Later you can add more features.

DF Player Pin

Specifications:

• Supported sampling rates (kHz): 8/11.025/12/16/22.05/24/32/44.1/48
• 24 -bit DAC output, support for dynamic range 90dB , SNR support 85dB
• Fully supports FAT16 , FAT32 file system, maximum support 32G of the TF card, support 32G of U disk, 64M bytes NORFLASH
• A variety of control modes, I/O control mode, serial mode, AD button control mode
• Audio data sorted by folder, supports up to 100 folders, every folder can hold up to 255 songs
• 30 level adjustable volume
• 6 -level EQ adjustable

Stand-alone Circuit

Circuit:

DF Palyer Circuit

In this circuit I used PIC16F628A and its configure to run using its internal oscillator. For sending commands to the PIC i used uart terminal that built in with Mikroc and u need a TTL converter module fo that. Rx pin of df player connected to the PIC's Tx and Rx pin of PIC connected to the TTL converter's Tx.
Rx pin of TTL converter connected to the df player's Tx (optional)

Uart TTL Module

USB TTL Module

Connect circuit as above and plug usb or TF card.Then open uart terminal and enter commands as below..
r - Play, s - Pause, n - Next, p - Previous, u - Vol+, d - Vol-.

Df palyer connection

Circuit in dot board

Code:

This code was written by using mikroC PRO for PIC v6.

/**************************************************************************

DF Player
Copyright (C) 2019 Scorpionz

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.

>> Email: scorpionzblog@gmail.com
>> Blog : scopionz.blogspot.com

***************************************************************************/

char df_rd[10], dump, j, u_data;

void Write_Df_Data(char cmd, char data_H, char data_L) //------- df data ----
{
  char m = 0;
  char df_wr[] = {0x7E,0xFF,0x06,0,0,0,0,0xEF};
       df_wr[3]= cmd;
       df_wr[5]= data_H;
       df_wr[6]= data_L;

   Delay_ms(100);
   for (m=0; m<8; m++) UART1_Write(df_wr[m]);
   Delay_ms(300);
}


void interrupt() {   //-------- interrupt --------------------------------------

 if (PIR1.RCIF) {    //------- Usart interrupt ----------
      PIE1.RCIE = 0;
      u_data = UART1_Read();

    if(u_data==0x7E)  {    // check first byte 0x7E
      for (j=1; j<10; j++) { // read next 9 bytes 0xFF, 0x06, 0x03, 0x00, 0x00, 0x01, 0xFE, 0xF7, 0xEF
No:
        if(UART1_Data_Ready()) {    // Check, is data Ready..?
           df_rd[j] = UART1_Read();
           }
          else goto No;
        }
       
        delay_ms(50);
        if(UART1_Data_Ready()) dump = UART1_Read(); //remove duplicate data
      
        if(df_rd[9]==0xEF) { //check last byte 0xEF
         delay_ms(100);
         if(df_rd[3]==0x3C) Write_Df_Data(0x01,0,0); //play next song
         for (j=0; j<10; j++) df_rd[j]=0;            //clear read buffer
        }
      }
     
     else { //------ keyboard commands -------------
            if(u_data=='n') Write_Df_Data(0x01,0,0); //next
            if(u_data=='p') Write_Df_Data(0x02,0,0); //prev
            if(u_data=='u') Write_Df_Data(0x04,0,0); //vol+
            if(u_data=='d') Write_Df_Data(0x05,0,0); //vol-
            if(u_data=='r') Write_Df_Data(0x0D,0,0); //resume
            if(u_data=='s') Write_Df_Data(0x0E,0,0); //stop
           }
    PIE1.RCIE =1;
    PIR1.RCIF =0;
  }
}


void main()
{
 PCON.OSCF = 1;   //4MHz Internal OSC
 CMCON  |= 0x07;  //Disable Comparators

 INTCON.GIE=1;
 INTCON.PEIE=1;
 PIE1.RCIE=1;

 TRISA = 0x00;
 TRISB = 0xFE;  //Tx Rx
 PORTA = 0;
 PORTB = 0;

 Delay_Ms(3000);   // Df initialization 1.5 ~ 3Sec
 UART1_Init(9600);
}

Datasheet
DF Player Files

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DS3231 RTC Clock mikro C Demo Code - 16F648A

LCD Clock

Introduction:

The DS323x is a low-cost, extremely accurate I²C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input, and maintains accurate timekeeping when main power to the device is interrupted. The integration of the crystal resonator enhances the long-term accuracy of the device as well as reduces the piece-part count in a manufacturing line. The DS323x is available in commercial and industrial temperature ranges, and is offered in a 16-pin, 300-mil SO package.

DS3231 Block Diagram

The RTC maintains seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with an active-low AM/PM indicator. Two programmable time-of-day alarms and a programmable square-wave output are provided. Address and data are transferred serially through an I²C bidirectional bus.

Most RTCs use an external 32kHz timing crystal that is used to keep time with low current draw. And that’s all well and good, but those crystals have slight drift, particularly when the temperature changes (the temperature changes the oscillation frequency very very very slightly but it does add up!) This RTC is in a beefy package because the crystal is inside the chip! And right next to the integrated crystal is a temperature sensor. That sensor compensates for the frequency changes by adding or removing clock ticks so that the timekeeping stays on schedule.

DS3231 module

This is the finest RTC you can get, and now it in a compact, breadboard-friendly breakout. With a coin cell plugged into the back, you can get years of precision timekeeping, even when main power is lost. Great for data-logging and clocks, or anything where you need to really know the time.

The Circuit:

The circuit is very simple. It used PIC16F648A Pic micro, 16x2 LCD and DS3231 RTC module. The PIC used it's internal oscillator and run at 4MHz. Proteus and Hex file can download from the bottom of the page.

DS323x RTC Clock Circuit

MikroC PRO Source Code:

/**************************************************************************

DS323x RTC Clock Demo
Copyright (C) 2017 Scorpionz

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.

>> Email: scorpionzblog@gmail.com
>> Blog : scopionz.blogspot.com

***************************************************************************/


// Software I2C connections
sbit Soft_I2C_Scl at RB2_bit;
sbit Soft_I2C_Sda at RB1_bit;
sbit Soft_I2C_Scl_Direction at TRISB2_bit;
sbit Soft_I2C_Sda_Direction at TRISB1_bit;
// End Software I2C connections

// LCD module connections
sbit LCD_RS at RB0_bit;
sbit LCD_EN at RB3_bit;
sbit LCD_D4 at RB4_bit;
sbit LCD_D5 at RB5_bit;
sbit LCD_D6 at RB6_bit;
sbit LCD_D7 at RB7_bit;

sbit LCD_RS_Direction at TRISB0_bit;
sbit LCD_EN_Direction at TRISB3_bit;
sbit LCD_D4_Direction at TRISB4_bit;
sbit LCD_D5_Direction at TRISB5_bit;
sbit LCD_D6_Direction at TRISB6_bit;
sbit LCD_D7_Direction at TRISB7_bit;
// End LCD module connections

char seconds, minutes, hours, day, date, month, year, tem_l, tem_h; // Global variables

//--------------------- Reads time and date information from RTC (DS3231)
void Read_Time()
{
Soft_I2C_Start(); // Issue start signal
Soft_I2C_Write(0xD0); // Address DS3231, see DS3231 datasheet
Soft_I2C_Write(0); // Start from address 0
Soft_I2C_Start(); // Issue repeated start signal
Soft_I2C_Write(0xD1); // Address DS3231 for reading R/W=1

seconds = Bcd2Dec(Soft_I2C_Read(1)); // Read seconds byte
minutes = Bcd2Dec(Soft_I2C_Read(1)); // Read minutes byte
hours = Bcd2Dec(Soft_I2C_Read(1)); // Read hours byte
day = Bcd2Dec(Soft_I2C_Read(1)); // Read day byte
date = Bcd2Dec(Soft_I2C_Read(1)); // Read date byte
month = Bcd2Dec(Soft_I2C_Read(1)); // Read month byte
year = Bcd2Dec(Soft_I2C_Read(1)); // Read year byte

Bcd2Dec(Soft_I2C_Read(1)); // Alarm
Bcd2Dec(Soft_I2C_Read(1));
Bcd2Dec(Soft_I2C_Read(1));
Bcd2Dec(Soft_I2C_Read(1));
Bcd2Dec(Soft_I2C_Read(1));
Bcd2Dec(Soft_I2C_Read(1));
Bcd2Dec(Soft_I2C_Read(1));

Bcd2Dec(Soft_I2C_Read(1)); // Data
Bcd2Dec(Soft_I2C_Read(1));

Bcd2Dec(Soft_I2C_Read(1));

tem_h = Bcd2Dec(Soft_I2C_Read(1)); // Temp
tem_l = Bcd2Dec(Soft_I2C_Read(0));

Soft_I2C_Stop(); // Issue stop signal
}

void write_data(char address, char w_data)
{
Soft_I2C_Start(); // issue I2C start signal
Soft_I2C_Write(0xD0); // send byte via I2C (device address + W)
Soft_I2C_Write(address); // send byte (address of DS3231 location)
Soft_I2C_Write(w_data); // send data (data to be written)
Soft_I2C_Stop(); // issue I2C stop signal
delay_ms(50);
}

//-------------------- Output values to LCD
void Display_Time()
{
Lcd_Chr(2, 7, (hours / 10) + 48);
Lcd_Chr(2, 8, (hours % 10) + 48);
Lcd_Chr(2,10, (minutes / 10) + 48);
Lcd_Chr(2,11, (minutes % 10) + 48);
Lcd_Chr(2,13, (seconds / 10) + 48);
Lcd_Chr(2,14, (seconds % 10) + 48);

Lcd_Chr(2,16, (day % 10) + 48); // day
}

void Display_Date()
{
Lcd_Out(1,1,"Date: "); // Prepare and output static text on LCD
Lcd_Chr(1,9,'-');
Lcd_Chr(1,12,'-');
Lcd_Out(1,13,"20"); // start from year 2000

Lcd_Chr(1, 7, (date / 10) + 48);
Lcd_Chr(1, 8, (date % 10) + 48);
Lcd_Chr(1,10, (month / 10) + 48);
Lcd_Chr(1,11, (month % 10) + 48);
Lcd_Chr(1,15, (year / 10) + 48);
Lcd_Chr(1,16, (year % 10) + 48);
}
void Display_Temp()
{
Lcd_Out(1, 1,"Temp: +");
Lcd_Out(1,13,"ßC ");
Lcd_Chr(1,10,'.');

tem_l=tem_l*25;

Lcd_Chr(1, 8, ((tem_h & 127) / 10) + 48);
Lcd_Chr(1, 9, ((tem_h & 127) % 10) + 48);
Lcd_Chr(1, 11, (tem_l / 10) + 48);
Lcd_Chr(1, 12, (tem_l % 10) + 48);

if(tem_h & 128) Lcd_Chr(1, 7, '-');
}

//------------------ Performs project
void Init_Main()
{
PCON.OSCF = 1; //4MHz
CMCON |= 0x07; // Disable Comparators CMCON |= 7;
OPTION_REG = 0;

Soft_I2C_Init(); // Initialize Soft I2C communication
Lcd_Init(); // Initialize LCD
Lcd_Cmd(_LCD_CLEAR); // Clear LCD display
Lcd_Cmd(_LCD_CURSOR_OFF); // Turn cursor off

Lcd_Out(1,3,".:Scorpionz:.");
Delay_ms(500);
Lcd_Out(2,1,"Ds3231 RTC Clock");
Delay_ms(1500);
Lcd_Cmd(_LCD_CLEAR);
Lcd_Out(2,1,"Time: ");
Lcd_Chr(2,9,':');
Lcd_Chr(2,12,':');

write_data(14,0x40); //SQWE output at 1 Hz
}

//----------------- Main procedure
void main() {
Delay_ms(500);

Init_Main(); // Perform initialization

while (1) { // Endless loop
Read_Time(); // Read time from RTC(DS3231)
Display_Time(); // Prepare and display on LCD
Display_Date(); Delay_ms(450);
Display_Temp();
Delay_ms(450);
}
}

DS323x RTC Clock Demo Code

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Multi Stage Simple Programmable Timer Circuit - 16F628A

Electronic delay timers are devices which are able to count and produce different time delay intervals as per the external settings. The elapsing of the set time is mostly indicated through an audible alarm to alert the user. Timers play an important role in our everyday life, whether it’s your cell phone, wall clock, TV/DVD sets, computers they are present everywhere.

Usually an ordinary electronic timer is able to produce single-shot delay intervals and setting up its initializing point becomes inaccessible. The present simple programmable timer circuit design eliminates this drawback.

Simple Programmable Timer Circuit

This is a one of the simple circuit of programmable timer circuit. The time range of this timer is 1 second to 255 hours. The delay time can be change by dip switches. The whole circuit of programmable timer is build using cheap PIC16F628A microcontroller and few passive components.

Circuit Operation

After power applied, the START led will turn on and you need to configure the delay time, timer mode and repeat mode. The delay time of this circuit can change by using dip switches. Those dip switches are represent 8-bit binary number and that number use to set delay time. When the delay time over, RLY ON led will turn on.

Eg:
If you need to set delay time to 150 then, dip switch configuration is 10010110 (RB0-RB7).
1 = Off and 0 = On

When you pressed the START button, START led will begin to blink and you can observe timer status by that.

Time Mode

This circuit can operate in 3 different time modes (Seconds, Minutes and Hours). Those modes can select from MODE buttons.

1. If both PORTA.F6 and PORTA.F7 are low or high, then circuit is running in seconds’ mode (0 – 255 seconds)
2. If PORTA.F6 high and PORTA.F7 low, then the circuit is running in minutes’ mode (0 – 255 minutes)
3. If PORTA.F6 low and PORTA.F7 high, then the circuit is running in hours’ mode (0 – 255 hour)

Repeat Mode

If PORTA.F1 is low then repeat mode will turn on. The circuit running continuously and RLY ON led will turn on and off repeatedly.

To control heavy load, remove RLY ON led and connect 5v relay through NPN transistor. Then connect you device across the relay. Supply voltage for this circuit is 5v and use voltage regulator ic such as LM7805, if you use voltage above that.

Simple Programmable Timer
MikroC Code

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Simple and Accurate LC Meter Circuit - 16F690

Digital LC Meter

A LCR meter [Inductance (L), Capacitance (C), and Resistance (R)] is a piece of electronic test equipment used to measure the inductance, capacitance and, resistance of a component. Inductance is the property of an electrical circuit causing voltage to be generated proportional to the rate of change in current in a circuit. In Electronics, capacitance is the ability of a body to hold an electrical charge. Capacitance is also a measure of the amount of electrical energy stored (or separated) for a given electric potential. The electrical resistance of an electrical element measures its opposition to the passage of an electric current. The meter reads L, C and R directly with no human calculation required.

Recently I found this LC meter project on internet and I was looking for that kind of project. Therefore, I build. Amazing it is work! Also the accuracy of this LC meter is great and it is very easy to build. So that, I post it here, because I think it is useful to you. You can visit original post from using this link: LMC3

The data below were determined based on theoretical calculations, the scale and the display automatically change.

	Min	Max	Resolution	Accuracy
Non Polar Condenser	1pF	1nF	0.1pF	1%
	1nF	100nF	1pF	1%
	100nF	1uF	1nF	2.5%
Electrolytic Capacitor	100nF	100,000uF	1nF	5%
Inductor	10nH	20H	10nH	5%
Resistance	1mΩ	0.5Ω	1mΩ	5%
Inductance	0.5Ω	30Ω	10mΩ	10%

Specifications of the LC Meter

LC Meter Diagram

LC Switch:
The purpose of this is, switch between inductance and capacitance mode. When you turn on the LC meter, you should set it to C mode.

Calibration Switch:
You can calibrate LC meter by pressing this. See Calibration for more details.

LC Meter Calibration

You have 3 modes to calibrate. When the process is completed, calibrated values are saving to the microcontroller’s internal EEPROM, so of course they are available after the re-start.

C Calibration

1. Switch on
2. Switch L/C switch to C position
3. Leave the test probes freely. Do not even touch it
4. Press and hold the CALIB button until the message Switch to meas. Then release the button
5. Wait for the appearance of 0.00 pF

L Calibration

1. Switch on
2. Switch to the L position
3. Connect L/C probe and GND probe together
4. Press and hold the CALIB button until the message Switch to meas. Then release the button
5. Wait for the appearance of 0.00 uH

ESR Calibration

1. Switch on
2. Switch to the C position
3. Connect LE probe and GND probe together
4. Press and hold the CALIB button until the message Switch to meas. Then release the button
5. Note the value shown on the screen

Calibration Values

• F0 = 499.9k
• Fcal = 355.9k

• Re = 180Ω

• Uesr0 = 58.3mV
• Fesr = 83.6k
• Rx = 0mΩ [-5mΩ to 5mΩ]

Critical Components

All the below resistors are 1%.
(In my circuit, I used normal resistors and those are measured using digital multimeter)

• 47Ω - R11
• 47kΩ - R8
• 100kΩ - R3-R5

• 1nF - C8, C11 (Polypropylene or Polyester)
• 33nF - C10 (Polypropylene 275V AC)
• 10uF - C7, C9 (Tantalum)

• 100uH - L1 (Low-loss DC resistance of 0.3-0.4Ω)

Testing

check 22pF ceramic capacitor

check 100uF electrolytic capacitor

check 100uH inductor

I was unable to find a reed relay, so I put 5v ordinary relay temporarily. In addition, my PCB designed for the TL2285 switches. But, I bought TL2230 by mistake :)

If the back-light brightness is low, you can increase back-light brightness by decreasing the value of the resistor R2 to 470Ω - 1k. You can change display contrast by adjusting 10k preset.
For PCB, Schematic and hex file, click download button.

You need to discharge capacitors properly before measuring.

LC Meter

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Programmable Digital Seven Segment Timer Circuit - 16F628

Seven Segment Timer

A timer is a specialized type of clock for measuring time intervals. By function, timers can be categorized to two main types. Those are Counts upwards and counts downward.

Timers originally designed to fulfill a need in industry for a means of keeping time on certain devices. Originally, these timers were mechanical devices and used clockwork mechanisms as a means of keeping a regular time. The invention of two electromechanical timer designs allowed for more precise time measurement. The first uses the principle of heat expansion to increase the temperature of a metal finger made of two different metals with differing rates of thermal expansion. As electric current flows through the metal, it begins to heat and one side expands more quickly than the other does, which in turn, moves the electrical contact away from an electrical switch contact. The second uses a small AC motor, which turns at a predetermined rate due to the application of an alternating current.

Finally, digital timers invented. Digital logic circuits are now so cheap that it has become a better investment to buy a digital timer than a mechanical or electromechanical timer. Individual timers implemented with single chip circuits.

This is a very simple adjustable digital timer circuit based on the PIC16F628A microcontroller and it can be programmed to schedule the on and off operation of an electrical appliance. This timer consists of three parts: power supply, control circuit and display. Working voltage of the circuit is 5v - 12v. It depends on the relay voltage. If you use 5v relay then you can omitted the LM7805 regulator IC and apply 5v directly. Otherwise, you have to use regulator IC and apply suitable voltage according to the relay voltage. The schematic is very simple and accurate of the circuit is very good. PIC use its internal oscillator.

Programmable Digital Timer Schematic

There are two versions of hex file are available. Those are "4dg_tmr_min.hex" and "4dg_tmr_hr.hex". The first file for the minute timer. It display minutes and seconds. Adjustable time is 1 second to 60 minutes. Other hex file for hourly timer and its adjustable time is 1 minute to 24 hours. This will display hours and minutes on the seven segments.

Configuration

If the time runs too fast or too slow, you can able to adjust the speed by changing the value of Eeprom address 0. Default value is 44 (0x2c). Typical value is 59 (0x3B). Maximum is 255 (0xFF). In repeat mode delay time before restart the timer, determine by value of Eeprom address 3. Default value is 10 (0x0A). Maximum is 255 (0xFF). See below picture for more details.

Eeprom Configuration

Operation of the timer

This circuit uses 5 push buttons to control the their functions.

• START/PAUSE: When the timer is on, the device is in pause condition even the switch was in closed position. Pressing this button, you can switch between the start and pause timer.
• FOR/BACKWARD: This allows you to select counter mode. Either upwards or count down.
• REPEAT: When the timer reaches 00:00, it starts again from previous value you set.
• LEFT/RIGHT: This allows you to change values on display. The selected digit is incremented by pressing those buttons and values on the display are stored to the Eeprom.

Now connect device you want to operate, through the relay. Set the desired time using left and right buttons and press start. When the timer reaches 00:00, relay will activate.

Programmable Digital Timer

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Digital LCD Speedometer and Odometer Circuit - 16F628

Speedometer

In my previous post, I explained how to build a simple speedometer circuit using a micro-controller and seven segments. Read it from here. This is a further development of that circuit. This circuit indicates both speed and distance.

A speedometer or a speed meter is an instrument that measures and displays the instantaneous speed of a vehicle. An odometer or odograph is an instrument that indicates distance traveled by a vehicle.

Speedometer + Odometer Circuit

For this circuit I used PIC16F628A micro-controller and 16x2 LCD. You can able to see speed in first line and distance in second line on the LCD. Distance will update every 100 meters and speed updates every one second. Value of distance writes to Eeprom in every 1 km. I also added a button to this circuit. The purpose is, reset the distance to zero.

Same as the Speedometer Circuit, micro-controller count the signals received to RA4 pin and then calculate speed and distance, then display information on LCD. 8 MHz resonator is use to generate clock signals. However, you can always use crystal for it and make sure to add 22pf ceramic capacitors if you use crystal oscillator.

Measure the radius of the wheel and enter it to Eeprom address 0x00. Default value for radius is 30cm (0x1E). I used two magnets to operate reed switch. Please refer my previous post for more details and circuit connection.

Maximum speed is 999 kmh
Maximum distance is 9999 km
Supply voltage is 5v

Speedo + Odometer

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Digital Seven Segment Speedometer Circuit - 16F628

Speedometer

How Electronic Speedometers Work

In Electronic speedometer, small magnets attached to the vehicle's rotating drive shaft sweep past tiny magnetic sensors (either reed switches or Hall-effect sensors) positioned nearby. Each time the magnets pass the sensors, they generate a brief pulse of electric current. An electronic circuit counts how quickly the pulses arrive and converts this into a speed, displayed electronically on the display. Since the circuit is measuring the number of wheel rotations, it can also keep a count of how far you have traveled, doubling-up as an odometer (distance-measuring meter). Electronic speedometers can also display speeds with analog pointers and dials, just like traditional eddy-current speedos: in that case, the electronic circuit drives a highly controllable electric motor (called a stepper motor) that rotates the pointer through an appropriate angle. Electronic speedometers are more reliable and compact than mechanical ones and the motion sensors can be any distance from the display that shows you your speed, making them suitable for any kind of vehicle!

1. A magnet connected to one of the wheels rotates at high speed.

2. Every time it makes one complete revolution, it passes a magnetic sensor and the field from the magnet triggers the sensor.

3. A circuit translates them into your instantaneous speed and distance traveled.

4. A digital display displaying the speed and distance.


Here I will show you how to build simple yet accurate digital speedometer circuit using just a single IC, seven segments and a few external passive components. The design can be used for all vehicles for indicating their speeds.

Speedometer Circuit

The main component of this circuit is PIC16F628A. It count signals receive to RA4, then calculate speed and display it on seven segment. A Reed switch used to sense the speed. If the brightness of seven segments is too much, add 220 – 330 Ohms resistors between PORTB and the display. There are two version of hex files are available. In v1 micro-controller use its internal oscillator and v2 used external 4MHz oscillator.

Measure the radius of the wheel and enter it to Eeprom address 0x00. Default value for radius is 30cm (0x1E). You can change update interval by changing the value of Eeprom address 0x01. Default value is 20 (0x14). To increase the sensitivity in this circuit I used two magnets.

Eeprom Settings

Maximum Speed is 999 Kmh
Maximum Radius is 255 cm
Supply voltage is 5v

Circuit Connection

SSD Speedometer

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