By Stephen Evanczuk
For circuits relying on lithium-ion cells, determining the amount of charge remaining in a cell requires specialized techniques that can complicate the design of energy-harvesting applications. Engineers can implement these techniques with MCUs and ADCs normally used in these applications, but at the cost of increased complexity. Instead, engineers can easily add this functionality to existing designs using dedicated “fuel-gauge” ICs available from manufacturers including Linear Technology, Maxim Integrated, STMicroelectronics, and Texas Instruments.
Determining the state of charge (SOC) in lithium-ion batteries is essential yet challenging due to the great variability in capacity not only across different cells, but also in the same cell. As a Li-ion cell ages, it loses its ability to store charge. Consequently, even if fully charged, an older cell would deliver usable voltage for a shorter period of time than a newer cell. With any Li-ion cell, SOC varies greatly depending on the temperature and discharge rate, resulting in a unique family of curves for any particular cell (Figure 1).
Fuel-Gauge ICs Simplify Li-Ion Cell Charge Monitoring - [Link]
bogdan @ electrobob.com wanted to know how much heat a heatsink can dissipate so he build a simple setup using a temperature sesnsor and a mcu. He writes:
It’s quite a common problem when building electronics that some components need cooling which is usually done through some sort of heatsink and optional fans. Choosing the right cooling solution can be a difficult task because the real life behavior of the system is hard to predict or model. In my case I have faced the simple question quite a few times: how much heat can a cooling system dissipate? The thermal resistance of a particular heatsink may vary quite a lot depending on the surroundings or it can simply be unknown to start with. The aluminum side wall of an enclosure made me build this thing.
This is why I have made this little device: a thermometer, a transistor and a microcontroller with a simple command line interface. I could have answered my questions in quite a lot of simpler ways, but since I made a simple thermometer not much else is needed to control the transistor when a DAC is available in the microcontroller.
Heatsink Tester - [Link]
It consists of a power supply, the basic components for running the microcontroller (i.e. crystal, reset pin, …) and ICSP connector for In-Circuit programming. All pins are available on a header strip, so it is ideal for rapid prototyping.
PIC16F/18F Experiment Board - [Link]
Raj @ embedded-lab.com build a mini LED Christmas tree for his son. He writes:
My two and a half year old son loves toys with flashing lights. For this Christmas I thought of making a mini LED Christmas tree for him. This project uses 22 multi-color LEDs which are driven by a PIC12F683 microcontroller using the Charlieplexing technique. The details of the build procedure is described in the following sections.
Making a mini LED Christmas tree - [Link]
Embedded Lab’s new development board for PIC12F series microcontrollers:
The 12F series of PIC microcontrollers are handy little 8-pin devices designed for small embedded applications that do not require too many I/O resources, and where small size is advantageous. These applications include a wide range of everyday products such as hair dryers, electric toothbrushes, rice cookers, vacuum cleaners, coffee makers, and blenders. Despite their small size, the PIC12F series microcontrollers offer many advanced features including wide operating voltage, internal programmable oscillator, 4 channels of 10-bit ADC, on-board EEPROM memory, on-chip voltage reference, multiple communication peripherals (UART, SPI, and I2C), PWM, and more. Today we are introducing a new development board (rapidPIC-08 V1.0) for easy and rapid prototyping of standalone applications using PIC12F microcontrollers.
Rapid development board for PIC12F series microcontrollers - [Link]
Jie Qi from the MIT Media Lab and Bunnie from Studio Kosagi are hoping to crowdfund their idea for a new method of circuit building called Circuit Stickers.
A crossover between high tech and arts and craft, Circuit Stickers are not a serious prototyping tool but aim to find new uses for easily configurable electronics circuits so that they can be incorporated into other media such as books (basic science or fiction) or even wearable electronics.
Interconnect and power tracks made from sticky copper tape (or other conducting material) are laid out on any non conducting surface such as paper, material or flexible fabric. The individual components come ready-mounted and connect to the copper tracks via pads with sticky anisotropic (Z) tape. These can be peeled off later for reuse. There are two kits available containing a sketchbook to take you through the basics, colored LEDs, sound, light and trigger sensors and a tiny microcontroller with an ISP programming connector. That old Tee shirt looking a bit tired? Spruce it up with a running light display. [via]
Circuit Stickers: Cut and Paste Circuitry - [Link]
By Jim Harrison:
The human-machine interface, once simply known as an “operator panel” or “terminal”, is changing rapidly, due to the graphical, visual way operators now interact with an industrial machine or process. At one time, designers of these systems could get by with a three-line segmented LCD display. Today, LCD interfaces are quickly replacing traditional LED and segment LCD displays as designers take advantage of the aesthetic, flexibility, and cost benefits they provide.
MCUs with High-Resolution Graphics Control - [Link]
This project is an Automatic School bell system. Such a system triggers a bell (or operates any other load) at predifined time. In this version some advanced features are introduced. I used PIC18f4520 microcontroller as the brain of the system. RTC1307 IC is used to maintain the clock,date and day with a 3V backup voltage battery. Bell timings are stored in the internal EEPROM of mcu.
Automatic School Bell - [Link]
Stephen Evanczuk writes:
We all might have fond (or maybe not so fond) memories of the first MCU we used, but where does that device and the many others that you may have also used and read about. So we asked MCU manufacturers to tell us which of their MCU lines has been the most popular ever and list their selections in this slideshow.
But are these the MCUs you’d choose as the most popular? Take a look at each participating MCU manufacturer’s top MCU – and then tell us which you’d call the most-popular. Or if another MCU not listed here deserves to be called the most popular, tell us!
The most-popular MCUs ever - [Link]