This AVR-based Frequency Meter is capable of measuring frequencies from 1Hz to 10MHz with 1 Hz resolution. The hardware of this project consists of seven 7-segment displays, AVR ATtiny2313 uController, and a few transistors and resistors. The AVR counts input pulses for a precise 1 second interval (generated using the built-in Timer) and displays the result on the multiplexed seven segment LED displays.
AVR frequency meter
Jesus Echavarria tipped us off about his latest project of controlling multiple HD44780 LCD displays through an I2C interface. He used Microchip’s MCP23017 I/O port expanders and successfully drove eight LCDs with only two microcontroller pins.
Connecting multiple LCDs on an I2C bus
The MCP23017 device provides 16-bit, general purpose parallel I/O expansion for I2C bus. Upto 8 such devices can be connected on to the same I2C bus by varying their slave addresses through the hardware address pins. In his project, Jesus used eight MCP23017 devices (one for each LCD) to control eight LCDs over an I2C bus.
TrH Meter is a DIY digital room thermometer plus hygrometer that displays temperature and relative humidity on 4 large (1 inch) seven segment LED displays which adjust their brightness level according to the surrounding illumination. It consists of a closed loop system that continuously assesses ambient light condition using an inexpensive light-dependent resistor (LDR) and uses that information to adjust the brightness of the display. An inexpensive DHT11 sensor is used to measure temperature and relative humidity. You can buy a complete TrH Meter kit with a preprogrammed PIC microcontroller for $26.00.
Displaying temperature in degree F
Temperature display in degree C
Humidity is displayed in percentage (P)
SPI7SEGDISP8.56 is a MAX7219 based serial seven segment LED display module that allows you to add 8 digits of seven segment LED displays to your project using only 3 I/O pins, and provides full control of all the digit segments including decimal points. The LED display size is 0.56″ and all 8 digits are arranged into two rows of four. SPI7SEGDISP8.56 display kit is now also available with blue LED color. You can buy one for $13.50 on Tindie.
SPI7SEGDISP8.56-1R module in blue color
SPI7SEgDISP8.56-1R Buying links:
SPI7SEGDISP8.56 buying link – Red color
SPI7SEGDISP8.56 buying link – Yellow color
SPI7SEGDISP8.56 buying link – Green color
SPI7SEGDISP8.56 buying link – Blue color
More mini breakout boards for 18-pin PIC16F series microcontrollers are now available as DIY kits on Tindie.
Mini PIC breakout board
You can buy this as a DIY kit for $8.50 on Tindie.