PIC Microcontroller

Quick view of serial LCD interface for PIC

If you are developing applications for the PIC mcu, and miss debugging tools, or don't have enough I/O pins for a parallel LCD interface in your design, this serial interface can help printing debug messages and/or reduce the pin count. This version uses a Hitachi HD44780 compatible LCD module in 4-bit mode...

Greenhouse irrigation controller ( PIC16F84 )

Greenhouse irrigation controller ( PIC16F84 )

This is a simple one-valve irrigation controller made for our greenhouse. The code contains a software real-time clock (RTC) and a multiplexed 8-digit LED display and keyboard you can use in other projects. The operating software is simple, it contains a real-time clock and a day counter. The valve is turned on in regular intervals in the same time. Day setting specifies the number of days between the activations, time setting specifies the time of the day when to start. Duration is the time after which the valve will be turned off. MODE button cycles through clock, start time and duration settings. the interval and starting time set will be stored in the DATA EEPROM. Scheduling can be totally turned OFF by the ENABLE button. Irrigation can be manually turned ON/OFF any time by the START/STOP buttons ..

Serial IR transmitter using PIC16F628

Serial IR transmitter using PIC16F628

This is a programmable infrared (remote control) transmitter, which can be controlled from a PC serial port. It is capable of sending many remote control formats, including the Philips RC-5 standard. The controller will accept commands on the serial port. Settings are: 19200 bps, 8 bits, no parity, 1 stopbit, no flow control (XON/XOFF or RTS/CTS). Commands consist of hex coded bytes and must be written on the port as ASCII characters separated by space, terminated by ENTER (ASCII char 0d). You can use a terminal emulator program to test out the circuit (for example minicom on linux, NC terminal on DOS, or hyperterminal on windows), but the settings usually won't work at first, so it is recommended that you write a small program to set the parameters and send commands by pressing keys on the keyboard...

Light timer switch with PIC12F629

Light timer switch with PIC12F629

This is a lamp timer capable of operating two separate relay switches. Outputs can be in three (or restricted to two) states: OFF, delayed ON and constant ON. Delayed ON mode is indicated by the LEDs. The source code is easily customizable for your needs: set your desired delay time or disable constant ON state. press the button once to turn on the lamp for a pre-defined delay. while ON, press the button again to turn the lamp constant ON (turn off delay timer). press the button again to turn the lamp OFF. alternative operation, if you disable the constant ON mode: press the button once to turn on the lamp for a pre-defined delay. while ON, press the button again to turn the lamp OFF...

Digital LCD thermometer ( PIC16F871 )

Digital LCD thermometer ( PIC16F871 )

The circuit drives the LCD pins with 50% square waves. Each segment on this LCD is connected to the COM backplane and a separate pin. When a pin is driven in phase with the COM pin, the corresponding LCD segment gets zero voltage, and is off. When a pin is driven in reverse of the COM pin, the corresponding segment gets an alternating voltage, and lights up. The interrupt routine is called periodically to invert all pins of the LCD to generate the 50% square wave. The pin states are stored in the RAM labeled segments_buffer, 5 bytes long. The interrupt also reads the temperature sensor for the actual values. The main program gets the temperature value from tc77_ioread, and calculates the temperature in celsius. All digits of this decimal value are then converted into the values of the 7 segment of the LCD digits. This mapping table is located at the label segtable. For example, the digit 0 turn on the following digits: F, E, D, C, B, A because it sets bits as "00111111"...

USB digital I/O using PIC18F14

USB digital I/O using PIC18F14

The device is powered by the USB bus. The ports RB4-7, RC0-7 can be set on a bit-by-bit basis to input or output direction. All LEDs on the schematic are optional, and are only shown for testing the device. You can find the USB connector pinouts at http://pinouts.ws/usb-pinout.html. I have an SMD version PCB for the circuit, which will be published here. If you don't want to make your own PCB, you can buy an MCP2200 breakout board. The MCP2200 is a PIC18F14K50 mcu pre-programmed with firmware from Microchip...

Combination lock using PIC16F84

Combination lock using PIC16F84

This is my electronic combination lock to use with an outdoor gate. The functionality is implemented in software. It turns on a relay (usually to open a door) for a few seconds if someone enters the valid code. Alternatively, it works as an ON/OFF switch, which toggles the relay each time the code is entered. This relay can operate a power-to-open type electric strike with a shorting contact or a power-to-hold type electromagnetic lock with a breaking contact (we need the relay because these locks usually work with AC, not DC). The code can be changed any time after entering the current code. Current consumption of the circuit is low, because the PIC sleeps most of the time, and wakes up only for processing key presses. If you don't have a crystal, you can use the RC oscillator of the PIC16F84 as well, just check the PIC datasheets for details on oscillator configurations. The 16F628 already contains an internal RC oscillator, so no crystal is needed...

Digital Encoder with PIC16F57

Digital Encoder with PIC16F57

This encoder can transmit the state of up to 16 TTL digital inputs using an RF or infrared transmitter. When enabled, the included modulator automatically generates the 38kHz IR carrier. Containing a PIC microcontroller, the circuit is very flexible. You can decide which transmitter inputs will trigger a transmission. You can control the receiver outputs to be latched or momentary with the LATCH input. The Manchester-coded transmitter output is well suited for the cheapest ASK radio modules or for infrared control. Address decoding is not yet supported. If you have trouble with programming PIC microcontrollers, you can consider builing other circuits based on Holtek HT-12D, HT-12E and Motorola MC145026, MC145027, MC145028 encoders/decoders...

IR 8 channels PIC remote control

IR 8 channels PIC remote control

Control up to 8 devices by this easy constructable remote control. It can work as a radio or infrared remote control, depending on the components. Each device output can be configured to be momentary (turned on while you press the button) or latched. Latched outputs can be toggled on/off by one button per channel, or turned on and off by two buttons per channel. Containing a PIC microcontroller, the circuit is very flexible. You can decide which receiver outputs are latched and which are momentary. The Manchester-coded transmitter output is well suited for the cheapest ASK radio modules or for infrared control. The units are configurable to a unique address, which must match to control the devices...

PIC Light Chaser with PIC16C84

PIC Light Chaser with PIC16C84

The circuit this month is a simple 8 light chaser built around a PIC. This will demonstrate how easy it is to program a PIC and to utilize it in a circuit. The circuit works as follows. When power is supplied to the circuit the PIC resets and starts to process instructions that are programmed into it. The program will turn on each LED in sequence with a small delay between each one. It will continue to do this until power is removed. The nice feature with this circuit is that you can program it to perform many complex lighting sequences. Normally you would have to rebuild a hardware based circuit to change the light sequence. With a PIC all you need to do is reprogram it and plug it back into the circuit. I am assuming that you will be using an IC socket. The circuit is show below and then I will discuss the program that is programmed into the PIC...

Aircraft band / AM Receiver with PIC16F84

Aircraft band / AM Receiver with PIC16F84

Aircraft communication is still AM modulated and the frequency is about 110-125 MHz. What differ this construction from my two previous is that I have implemented many blocks into one circuit and therefore I will have superior performance with less components. The receiver is working with a Frequency Synthesizer which gives a very stable reception and it is easy to change frequency as well. The RF signal is first amplified before it enters mixer 1. To mixer1 is also a VCO (Voltage Controlled Oscillator). The tuning voltage to the oscillator is controlled by the PLL synthesizer. There is also a feedback from the output of the VCO to the PLL synthesizer. The synthesizer will control the VCO-voltage until the frequency is locked to the desired frequency you have programmed into the PIC circuit. The product of the mixer 1 is filtered into a standard 10.7MHz ceramic filter and then enter mixer 2. At mixer 2 the RF will be mixed with a constant frequency from a crystal (10.245MHz). The product will enter a new ceramic filter and finally into a AM demodulator which brings out the audio. ..

DTMF FM PLL Receiver

DTMF FM PLL Receiver

This project is a PLL synthesized FM radio which can decode DTMF. The receiving frequency can be set by the PLL circuit from 80-140MHz. The receiver is VERY stable, high sensitivity and easy to build and tune. The FM receiver can decode DTFM signals from a transmitter and present the DTMF data on three LED display. The complete background about this project can be found at my "Wife replace" project. This part is a FM receiver based on a PLL synthesizer UMA1015. The frequency of the PLL synthesizer is programmed by a PIC processor which also control the DTMF circuit and the LED to display information. The Audio output from the FM receiver is connected to a DTMF circuit which is specialised to identify and decode DTMF signals. If there is a valid DTMF tone the PIC will read the data and present it on the LED display. Since I have 3 LED I can display 000 to 999 on the display. ..

FM PLL transmitter 88-108MHz with PIC16F870

FM PLL transmitter 88-108MHz with PIC16F870

This transmitter is PLL controlled and the frequency is very stable and can be programmed digitally. The transmitter will work from 88 to 108 MHz and the output power is up to 500mW. With minor changes the frequency can be set from 50 to 150 MHz. The main oscillator is based around the transistor T1. This oscillator is called Colpitts oscillator and it is voltage controlled to achieve FM (frequency modulation) and PLL control. T1 should be a HF transistor to work well, but in this case I have used a cheap and common BC817 transistor. The oscillator needs a LC tank to oscillate properly. In this case the LC tank consist of L1 with C1, C2, C3, and the varicap BB139. The coil is parallel with C1 and C2 which are in serial . The same with the varicap and C3. You can think that L is parallel with [ (C1//C2) + (Varicap//C3)] ..

2.5 GHz Frequency meter with 2x16 LCD display

2.5 GHz Frequency meter with 2x16 LCD display

This project explain a very powerful frequency counter which has many useful software functions. The software can add or subtract 3 different IF frequencies (±455 kHz ,±10.7 MHz and ±21.4 MHz). You have also two level of resolutions, 1kHz and 100Hz. The main oscillator can be on-board 13MHz or external 10 MHz. The counter data can easy be transmitted to computer with RS232 cable. The counter is based around a LCD display with 2 lines and 16 chars. I have used a HD44780 based display which is very common. A PIC16F870 circuit controls all counting and display functions. A prescaler is added to make it possible to measure up to 2.5GHz with high sensitivity. The Display Module Size (W x H x T): 80mm X 36mm. The controller PCB has the same size. This makes the unit very small and slim...

50MHz Transmitter alarmer with PIC16F84

50MHz Transmitter alarmer with PIC16F84

This project is about an IR-detector (Infra Red) combined with a 100mW 50MHz transmitter. The detector is sensitive to changes in IR-spectrum and is commonly used in burglar alarms. When the detector sens a person/animal/ghost/angry clown, it will transmitt a warning signal to a portable receiver and you will get a pre-warning. This project is aimed for typical 007-persons who doesn't want to be surprised by other. Maybe you have been in some situation where you wanted to know if there was any person comming or leaving. I will not ask you why! Maybe you sleep on the second floor and you want to have a pre-warning if any one should be at first floor or if you are out camping and you don't want any "blairwitch" to sneak up on you! This project is very useful in many situation, I just want you to use this in good purpose. The total project consist of a 50MHz portable transmitter with an IR-detector sensitive for motion, and a 50MHz portable receiver. In this page I will explain the transmitter part...