Raj of Embedded Lab has a series of chipKIT tutorials. This 5th project will show you how to build a digital stopwatch on seven segment LED display with the chipKIT Uno32:
In this project, we will use the chipKIT Uno32 board to build a digital stopwatch capable of timing minutes, seconds, and 1/10th of seconds, and with a basic start and stop control feature. A MAX7219-driven 8-digit seven segment LED display is used to display the time elapsed. The Reset switch on the Uno32 board will be used to reset the current time back to 0 when the stopwatch is stopped.
chipKIT Project 5: Digital stopwatch on seven segment LED display - [Link]
What is a Stepper Motor? All About Stepper Motors @ The Adafruit Learning System.
Stepper motors are DC motors that move in discrete steps. They have multiple coils that are organized in groups called “phases”. By energizing each phase in sequence, the motor will rotate, one step at a time.
With a computer controlled stepping you can achieve very precise positioning and/or speed control. For this reason, stepper motors are the motor of choice for many precision motion control applications.
Stepper motors come in many different sizes and styles and electrical characteristics. This guide details what you need to know to pick the right motor for the job.
What is a Stepper Motor? All About Stepper Motors - [Link]
Instructables user Slomi posted this useful project on how to build a wireless indoor and outdoor thermometer using an Arduino! Via Embedded Lab.
This Arduino-based wireless thermometer uses two Arduino boards to measure indoor and outdoor temperatures. The outdoor Arduino board sends out the outdoor temperature measured by DS18B20 sensor to the indoor Arduino board using inexpensive 433MHz RF transmitter and receiver modules. The indoor Arduino board then displays the indoor and outdoor temperatures on a character LCD display.
Indoor/outdoor wireless thermometer using Arduino - [Link]
Phys.org has the story on the latest in photovoltaics.
Northwestern University researchers are the first to develop a new solar cell with good efficiency that uses tin instead of lead perovskite as the harvester of light. The low-cost, environmentally friendly solar cell can be made easily using “bench” chemistry—no fancy equipment or hazardous materials.
“This is a breakthrough in taking the lead out of a very promising type of solar cell, called a perovskite,” said Mercouri G. Kanatzidis, an inorganic chemist with expertise in dealing with tin. “Tin is a very viable material, and we have shown the material does work as an efficient solar cell.”
Kanatzidis, who led the research, is the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences.
The new solar cell uses a structure called a perovskite but with tin instead of lead as the light-absorbing material. Lead perovskite has achieved 15 percent efficiency, and tin perovskite should be able to match—and possibly surpass—that. Perovskite solar cells are being touted as the “next big thing in photovoltaics” and have reenergized the field.
Kanatzidis developed, synthesized and analyzed the material. He then turned to Northwestern collaborator and nanoscientist Robert P. H. Chang to help him engineer a solar cell that worked well.
“Our tin-based perovskite layer acts as an efficient sunlight absorber that is sandwiched between two electric charge transport layers for conducting electricity to the outside world,” said Chang, a professor of materials science and engineering at the McCormick School of Engineering and Applied Science.
Environmentally friendly solar cell pushes forward the ‘next big thing in photovoltanics - [Link]
by Roy McCammon:
The traditional three op-amp differential amplifier’s signal to noise ratio can be improved by 6dB by adding a resistor and slightly changing the connections. There is a trade-off though: The traditional topology has a high input impedance, whereas the low-noise version has a lower input impedance.
Differential amp has 6dB lower noise, twice the bandwidth - [Link]
Nich Fugalfrom @ Makeatronics is working on a BLDC motor controller.
Icall it a smart BLDC commutator. In a nutshell it’s a dedicated atmega328 that monitors the hall effect sensors on a brushless DC motor and takes care of the commutating and driver circuitry.
It’s smart because it has the ability to extract and keep track of motor position while monitoring the hall sensors. There’s also an option to plug in a quadrature encoder for higher resolution. The position can be sampled via a sample and hold input and communicated to a host controller via SPI.
I designed it to be an easy to use black box for interfacing with BLDC motors. All the host controller has to do is feed it direction (high/low) and PWM and the rest is done for you.
BLDC motor control using Atmega328 - [Link]
Design your PCB involving QFN or DQFN packages with this App note from Microchip.
Successful implementation of QFN and DQFN packages requires special consideration for printed circuit board (PCB) layout and solderpaste stencil production. This application note describes the important items to consider.
QFN packages are physically robust, thermally efficient, and occupy much less PCB space than equivalent QFP packages. They generally have superior lead inductance characteristics. They also present some particular design constraints. QFN packages generally have a row (QFN) or two (DQFN) of perimeter pads (“pads”) around a larger central pad (“flag” or “Epad”) encapsulated in a plastic body. These packages are surface-mounted to the target system PCB by a solder reflow process.
App note: PCB Design Guidelines for QFN and DQFN Packages - [Link]
The LTC®3114-1 is a versatile, wide operating voltage range synchronous monolithic buck-boost DC/DC converter with programmable average output current. The LTC3114-1’s proprietary buck-boost PWM control circuitry delivers low noise operation across the entire operating voltage range. Current mode control ensures exceptional line and load transient responses.
LTC3114-1 – 40V, 1A Synchronous Buck-Boost DC/DC Converter with Programmable Output Current - [Link]
The LTC2338 fully differential 1Msps SAR ADC family offers a wide ±10.24V true bipolar input range for high voltage industrial applications. The proprietary internal reference buffer maintains less than 1LSB error during sudden bursts of conversions, enabling true one-shot operation after lengthy idle periods. The internal reference can be overdriven to interface to a range of signal levels that swing above and below ground. The LTC2338 family eliminates complicated circuitry required to interface true bipolar signals to ADCs, and provides a compact solution for easy interfacing to 1.8V to 5V serial logic. The LTC2328 offers similar performance with a pseudo-differential input.
LTC2338-18 – 18-Bit, 1Msps, ±10.24V True Bipolar, Fully Differential Input ADC with 100dB SNR - [Link]
This device is a receiver circuit for a Digital Remote Thermometer. The thermometer operates by converting the sensor’s output voltage, which is calibrated and proportional to the measured temperature, to output cycles. The output cycles are transmitted in the supply cables and the receiver section counts the cycles from the transmitter; the calibrated counting are then displayed in the 7-segment LED displays.
The receiver circuit uses the 4093 Quad two input Schmitt NAND Gate IC as one of the logic components. Another component used is the 74HCT4520 dual 4-bit synchronous binary counter which is a high-speed Si-gate CMOS device. It has a dual 4-bit internally synchronous binary counters with an active high clock input and an active low clock input and buffered outputs. In this circuit, only two output levels from each of the binary counters, are utilized and the rest are connected to ground. The 74HCT4520 is coupled to the 74HCT4017 5‑stage Johnson decade counter for synchronized clocking. The MC14553B 3-digit BCD counter is also used in this circuit. The MC14553B consists of three negative edge triggered BCD Counters that are cascaded synchronously. In this circuit, the MC14553B controls the most significant (leftmost) value of the thermometer display. Lastly, the HEF4511B BCD to 7-segment BCD decoder is coupled to the MC14553BCP 7-segment displays. The HEF4511B decoder controls each of the displays to indicate the calibrated temperature.
The circuit is ideal for room temperature measurement. It displays the temperature in centigrade within the range of 00.0 to 99.9 degrees centigrade. Adjustments in the circuit are necessary to change the temperature ranges that can be accommodated by the circuit. Read the rest of this entry »