Photo. This is the test circuit -the basic driver is only two transistors, two resistors, the circuit was evaluated using a white LED, but when it was time to button it up and archive it, I replaced the expensive white LED with a cheap green one. Othere LED Driver Circuits on this site: White LED …
Series Connected Voltage Boost Circuit for a Battery Operated LED Lantern Using Atmega Read More »
Overview Where I live most of the time, the AC power drops out upon occasion. This used to leave me groping around in the dark for a flashlight. I could have bought a battery-backed up “emergency light” for about US$35, but being basically metal boxes with floodlights attached, they would make my living room look …
White LED Battery Powered Power Failure Light Using Atmega Read More »
Based on the Atmel ATtiny12L-4PI microcontroller -A real Time Clock/Calendar for less than US$1.50 in moderate quantity. This is the timekeeping test circuit. It includes a one-transistor circuit to switch in the 5V power supply when present and drop back to the 3v battery the rest of the time. That loop of blue wire-wrapping wire …
Introduction: My project is a self-powered solar data logger. Put out in the sunlight, it will measure the light level and log this to memory to be later downloaded to a computer. The system is powered by a small solar panel and battery. Summary: The solar logger I built uses a photodiode to measure the …
Overview Batwatch is a simple monitor for a solar panel battery charger, using an Atmel ATtiny13V. It periodically measures the charge current and battery voltage, and shows them by blinking two LEDs. I built this circuit into the plug of a VW solar charger panel that is used to prevent a discharge of the battery …
An application note from Microchip: Interfacing a 4×4 Matrix keypad with an 8-Bit GPIO expander This application note discusses interfacing a 4×4 matrix keypad with MCP23X08 8-Bit GPIO Expander. This application note references the MCP23X08/17 GPIO Expander Keypad/LCD Demo Board (GPIODM-KPLCD). GPIO Expanders provide easy I/O expansion using standard serial interfaces such as I2C and SPI. …
Interfacing a 4×4 Matrix keypad with an 8-Bit GPIO expander Read More »
Seven segment LED displays and discussed about a time-division multiplexing technique that reduces the number of required microcontroller I/O pins to drive multiple seven segment LED displays. Today we will move a step further and discuss about a serial interface (SPI) for driving 8 seven segment LED displays. The technique uses MAXIM’s MAX7219 LED driver …
Netduino and MAX721 interfacing for driving seven segment LED displays Read More »
