by Einar Abell @ edn.com:
This Design Idea gives two versions of an indicator light that changes from green to red as a battery discharges. There are many circuits that do this sort of thing, but all the ones I have seen are too complex and costly for my taste. This DI shows a method that uses an absolute minimum of low cost parts: a dual-color LED and four other parts.
Voltage indicator transitions between colours - [Link]
by Ilija Uzelac @ edn.com:
This Design Idea presents a simple, proven, reliable, and robust method for charging large capacitor banks, using a series connection of power MOSFETs to raise the breakdown voltage over that of an individual MOSFET.
When a power supply drives a large capacitive load, inrush current, if not limited, can reach tens or hundreds of amps for a high voltage power supply. In general, maximal ratings of a power supply could be transiently exceeded by many times, but this is generally acceptable when the transient lasts a few AC-line cycles. This is typical for load capacitances up to a couple of hundred microfarads, but for load capacitances in thousands of microfarads, an inrush current limiter is a must.
Series-connected MOSFETs increase voltage & power handling - [Link]
The LTC2645 is a family of quad 12-, 10-, and 8-bit PWM-to-voltage output DACs with an integrated high accuracy, low drift, 10ppm/°C reference in a 16-lead MSOP package. It has rail-to-rail output buffers and is guaranteed monotonic. The LTC2645 measures the period and pulse width of the PWM input signals and updates the voltage output DACs after each corresponding PWM input rising edge. The DAC outputs update and settle to 12-bit accuracy within 8μs typically and are capable of sourcing and sinking up to 5mA (3V) or 10mA (5V), eliminating voltage ripple and replacing slow analog filters and buffer amplifiers.
LTC2645 – Quad 12-/10-/8-Bit PWM to VOUT DACs - [Link]
by Steven Keeping @ digikey.com
Switching DC-to-DC voltage converters (“regulators”) comprise two elements: A controller and a power stage. The power stage incorporates the switching elements and converts the input voltage to the desired output. The controller supervises the switching operation to regulate the output voltage. The two are linked by a feedback loop that compares the actual output voltage with the desired output to derive the error voltage.
The controller is key to the stability and precision of the power supply, and virtually every design uses a pulse-width modulation (PWM) technique for regulation. There are two main methods of generating the PWM signal: Voltage-mode control and current-mode control. Voltage-mode control came first, but its disadvantages––such as slow response to load variations and loop gain that varied with input voltage––encouraged engineers to develop the alternative current-based method.
Today, engineers can select from a wide range of power modules using either control technique. These products incorporate technology to overcome the major deficiencies of the previous generation.
This article describes voltage- and current-mode control technique for PWM-signal generation in switching-voltage regulators and explains where each application is best suited.
Voltage- and Current-Mode Control for PWM Signal Generation in DC-to-DC Switching Regulators - [Link]
Get to know the Shunt and Series selection guide parameters to choose the right Vref for your application.
Voltage Reference Overview - [Link]
By Dean Segovis @ makezine.com:
A transistor is an electrical component that functions, most basically, as a switch — in principle not so different from a light switch. Instead of a physical movement, however, a transistor is controlled by a flow of electricity. And unlike your basic light switch, a transistor can be on, off, or somewhere in between.
Non-Contact Voltage Detector - [Link]
If you are doing any electrical work, one of these Non Contact Voltage Test Pens can be quite handy. Just touch the wire that you want to make sure isn’t live and check that the tester doesn’t beep and start flashing. This test pen is on all the time monitoring for AC between 90V and 1000 V. I would have preferred the device to have an on/off switch which would allow the battery to last even longer but I guess they figured that the 1.5 year life that they rate this for when in standby was good enough. This impressive life is because they got the current draw down to under 10 micro amps! Even when operating it only draws a handful of milli amps.
Non Contact Voltage Test Pen Teardown - [Link]
Mooshimeter: The Wireless Graphing Multimeter with Data Logging and Multichannel Simultaneous Sampling
The Mooshimeter makes multi-channel measurements possible in situations that are too fast, too slow, too sensitive, or too dangerous to use a traditional multimeter. And by harnessing your smartphone’s hardware, it does so at an insanely low price.
The Mooshimeter was born out of our frustrations as electrical engineers at the limitations of the “standard” digital multimeter.
Almost every digital multimeter will only let you use one mode at a time, meaning that to watch relationships in an active system you need to use multiple meters. Most have a front panel dominated by a numeric LCD display and a gigantic mode selection knob. And having the display mounted on the measurement hardware makes it very difficult to measure moving or enclosed systems, because the user must have clear line of sight to the meter to be able to read it.
Mooshimeter – Measure 600V and 10A with 24 bit precision through 50 meters - [Link]
SUF shared his voltage reference project in the forum:
To achieve the things above I designed a small battery good indicator circuit with a zener an opamp two LEDs and a few resistors. If you switch it on and the battery fall below 8V the red LED will lit instead of the green. I wanted to have a SOB style case. I designed a new one with a trick on it. I used a third acrylic plate what has a hole inside. The hole can accommodate the battery and the battery clip. This setup keeps the battery in place.
Voltage reference project - [Link]
A team of Columbia Engineering researchers, led by Mechanical Engineering Professor James Hone and Electrical Engineering Professor Kenneth Shepard, exploring the properties of graphene have demonstrated a new electro-mechanical resonant component.
The resonator’s structure consists of a 2-4 micrometer long strip of graphene suspended over a metal gate electrode. The strip of graphene has a natural resonance governed by its physical dimension and is used in the demonstration as the frequency determining element in an RF feedback oscillator circuit. Applying a voltage to the gate electrode stresses and deflects the graphene strip changing its resonant frequency. The team applied baseband audio and tones to the gate electrode to produce a 100 MHz FM signal.[via]
Tiny FM Transmitter uses Voltage Controlled Graphene Resonator - [Link]