Here is an app note from Mitsubishi Electric Research Laboratories describing how to implement short-range low-bandwidth bidirectional communication using common LEDs. It’s called LEDComm and requires only two pins of a microcontroller and a current limiting resistor to function. It works by making use of the fact that LEDs, once reverse biased, are also pretty […]
Category Archives: app notes
App note: video playback and streaming using the PIC MCU
This application note describes four methods of playing a video file using a PIC microcontroller (MCU) and hardware solutions available from Microchip. Methods discussed include video playback on PIC32 using upscaling by interpolation, streaming raw video from a micro-SD card using the SSD1926 LCD graphics controller on the Multimedia Expansion Board (MEB), streaming uncompressed AVI […]
App note: Software real time clock and calendar.
Here is an app note from Microchip that provides information on how to implement a real time clock and calendar on the PIC16f18xx series of microcontrollers. It uses an external 32.768KHz crystal that drives the Timer1 resource of the uC. The neat thing about a 32.768Khz clock source is that it can be divided by […]
App Note: Low-Cost Electric Range Control Using a Triac
While this app note is intended to replace mechanical thermostats, we’re not really interested in that part of it. What does interest us is how to build a controller that interfaces with loads on the mains power line. The neat thing about this design is that it is powered from mains, using a capacitor, zener […]
App note: GPIO Expander Provides Charge Pump for Blue LEDs
Adding blue LEDs to a interface panel looks cool. The down side is that some blue LEDs require more than 3.5V to work, which can be a hassle if your design works on 3.3V. This app note from Maxim explains how to implement a charge pump on their I2C GPIO expander ICs using the built […]
App note: AVR Butterfly
AVR butterfly is a cheap LCD development platform for the ATmega169 microcontroller. This board features: LCD-on-Glass display with 120 segments. 4 direction joystick with a push-button. Piezo element as a speaker. 32KHz crystal for real time clock projects. 4Mbit DataFlash memory. RS-232 level converter. NTC thermistor as a temperature sensor. Light dependent resistor as a […]
App note: nRF24L01+ 2.4GHz wireless transceiver
The nRF24L01+ ICs are 2.4GHz transceivers that only need a few external parts. They’re controlled by a simple SPI protocol, and two extra pins. The IRQ pin signals when data is available and can be used to wake a microconroller with an interrupt. The CE pin is an input activates/deactivates the transceiver. 126 channels are […]
App note: Tire pressure monitoring system
The rfPIC12F675F is a microcontroller with a built in UHF transmitter operating at frequencies between 380Mhz and 450Mhz. It’s basically a PIC12F675 microcontroller strapped onto a UHF transmitter, even the top 8 pins of the rfPIC12F package are pin comparable with the 8pin PIC12F device. This reference design outlines a wireless tire pressure monitoring system […]
App Note: Non-isolated 360mA buck DC/DC converter
This buck converter design uses the LinkSwitch-TN IC to output DC directly from rectified mains outlet. It converts mains high voltage to smaller DC voltages suitable for electronics devices, and has the ability to output up to 360mA of current. It’s based on the standard buck topology, except that the IC tolerates and works at […]
App note: RC Model Aircraft Motor Control
Modern RC model aircraft designs incorporate some hefty standards regarding motor speed control: The motor should not be started until the speed is at its lowest setting Motors with gearboxes should have acceleration limits If the control signal is lost the motor should shut off Motor shut off in case of low battery, to save […]
App note: 1000VA Digital pure sine UPS
Here’s a reference design from Microchip for a 1000VA pure sine uninterpretable uninterruptible power supply. UPS usually use 3 circuits to function. A charger for battery, a inverter to convert DC battery power to mains AC, and a controller that switches from mains to battery when the power is interrupted. This design utilizes a single […]
App note: Battery/charger load switch approximates ideal diode
Portable devices require a circuit that switches the power supply between battery and charger. This is usually done by using a diode on the battery line – when the charger is plugged in, the diode is reversely polarized and disconnects the battery from the rest of the circuit. This method however has drawbacks, namely power […]
App note: Acoustic thermometry
Orcinus tiped us about this interesting app note on acoustic thermometry from Linear Technology: People usually measure temperature in order to correct the distance determined using ultrasonic transducers. Acoustic thermometry takes the opposite approach – the distance is fixed and the time it takes for an acoustic pulse to make a round trip is used […]
App note: Inductive and capacitive Li-ion cell balancing methods.
No two lithium ion battery cells can ever be the same. There are variations in state of charge, capacity, impedance, and temperature characteristics. These slight differences lead to cells being disproportionately charged or discharged when they are connected in series. This shortens battery life, and even total breakdown of cells is possible. To solve these […]
App note: Digital HID Ballast Reference Design
High intensity discharge ballasts, used in cars today, require a large set of analog controllers to ignite an HID bulb and reach steady-state operation. This reference design from Microchip describes how to make an HID ballast using a dsPIC and a few discrete components. The reference design uses 9-16VDC and outputs 35W of steady state […]
App note: Lithium Ion/Polymer portable power supply
Portable devices need an uninterrupted power supply both when the circuit runs on a battery, and when it is connected to a charger. This app note shows how to design a portable power supply outputting 5volts and 3.3volts. The MAX1811 battery management IC handles the charging of a lithium ion/polymer battery. A DC/DC boost circuit […]
App note: CPLD special function pins
Here is some basic information about special CPLD pin functions you might need when getting started with Xilinx or any other CPLD: Global Clock (GCK) pins Many high-speed digital logic designs need a clock signal that reaches all components simultaneously. While any CPLD pin can input a clock signal and distribute it to the design, […]
App note: Choosing and using bypass capacitors
Bypass capacitors ensure a device has a stable and clean power supply. In most cases capacitors are chosen out of habit, such as the typical 0.1uF ceramic capacitor we use. This app note describes how calculate, model, and use different types of bypass capacitors. Included is a table with all the relevant information on different […]
App note: Layout and physical design guidelines for capacitive sensing
We think DIY capacitive touch sensing buttons, and sliders are cool. Designing and shaping your capacitive panels can be a pain. Here is an app note by Microchip that covers all the basics required to get your capacitive touch sensing project started. This app note starts with which pad shape and size is best suited […]
App note: Charlieplexing, using 9 pins to drive 8 digit 8-segment display
Back in 1995 Charlie discovered a way to drive large led matrices using a small number of pins. His technique makes use of the fact that many microcontrollers have tri-state outputs, and the fact that diodes pass current in only one direction. This app note by Maxim describes how to implement charlieplexing to drive 8 […]