by dkroeske @ github.com:
A cheap 555 timer chip acting as Schmitt trigger combined with a phototransistor or LDR is taped to the ‘flashing light’ or ‘pulsing magnet’ on the electricity meter. The output of the 555 timer chip is connected to one of the GPIO pins on the Raspberry Pi. A Python script (executing in the background) recording 555 events is calculating actual energy usage [e.g. Watt] every time the 555 is signaling and stores epochs in an SQLite3 database. From this, another Python script (executed from e.g. cron) generates all kinds of energy usage information (e.g. kWh or kWday or whatever). Using Node.js (running on the same Pi) all data is ‘RESTified’ enabling spreading out to the W3. To maintain privacy JSON web tokens are required every time the service is queried. Oh, and there is also a Pimatic plugin available (here)
Emon-server – 555 Timer as power usage sensor – [Link]
AC Voltage and current continually alternate, as the name suggests, if we draw a picture of the voltage and current waveform over time, it will look something like the image below (depending on what’s using power – the current waveform – blue in the diagram below – is what you get if you look at a typical laptop power supply. There’s an incandescent light bulb in there as well).
The image was made by sampling the mains voltage and current at high frequency, which is exactly what we do on the emontx or Arduino. We make between 50 and a 100 measurements every 20 milliseconds. (100 if sampling only current, and 50, if sampling voltage and current – we’re limited by the Arduino analog read command and calculation speed).
AC Power Theory – Arduino maths – [Link]
by R. Colin Johnson @ eetimes.com:
PORTLAND, Ore.– Researchers sponsored by the Semiconductor Research Corp. (SRC, Research Triangle Park, N.C.) claim they have extended Moore’s Law by finding a way to cut serial link power by as much as 80 percent. The innovation at the University of Illinois (Urbana) is a new on/off transceiver to be used on chips, between chips, between boards and between servers at data centers.
The team estimates the technique can reduce power up to whopping 44 times for communications, extending Moore’s Law by increasing computational capacity without increasing power. “While this technique isn’t designed to push processors to go faster, it does, in the context of a datacenter, allow for power saved in the link budget to be used elsewhere,” David Yeh, SRC director of Integrated Circuits and Systems Sciences told EETimes.
Researchers Claim 44x Power Cuts – [Link]
Determine the power absorbed by the VCVS in the figure. Solution: The VCVS consists of an open circuit and a controlled-voltage source. There is no current in the open circuit, so no power is absorbed by the open circuit. The voltage vc across the open circuit is the controlling signal of the VCVS. The voltage Vc (across 2 ohm resisitor) measures vc to be vc = 2V. The voltage of the controlled voltage source is vd = 2 vc = 4V. The current in the controlled voltage source is 6V/4 ohm= 1.5A. The element current id and voltage vd adhere to the passive convention. Therefore, p = id*vd = (1.5)(4) = 6W is the power absorbed by the VCVS.
Power and Dependent Sources – [Link]
Spacewrench over at Dorkbotpdx published a new build, a Power Playground project:
It’s a PMOS/NMOS H-Bridge with FETs that can handle 3 amps or so, plus a SPI current sensor, some switches & a rotary encoder (not stuffed yet), and a 7-segment display, all controlled by a Teensy-3.1 running FreeRTOS.
I made this because I’m always running into battery, power, inductor and transformer issues I don’t have any experience with. The idea is to use the H-bridge configuration and current sensors to experiment with moderate-current PWM, motor control, power-line synchronization, battery charging and discharging, etc.
Power playground project – [Link]
In a world with a growing population and ever-expanding need for energy, achieving more efficient electrical power conversion is crucial, but presents a number of challenges. GaN technology offers a solution, delivering a number of advantages to ensure availability of reliable electric power.
TI’s latest whitepaper explores the role of GaN in the power supply chain. Read up on its advantages over silicon for power supply switching, and technology advancements required to create complete system-level solutions for GaN-based designs.
Delivering efficient, reliable power through GaN – [Link]
Have you ever been curious about the power consumption of an appliance? For example did you wonder how much it will cost you to leave your television in standby mode whole night? Or did you want to learn how much change your refrigerator settings will make on your electric bill? If your answer is yes, you can use a wattmeter to measure the power consumption of a device. In this project we are building one.
This is an AC Watt Meter which can measure the real power consumption of a device connected to the 230Vrms/50Hz mains line. The PIC microcontroller collects the voltage and the current information with the help of ADCs and then calculates the RMS voltage of the mains line, RMS current drawn by the device and the resulting average power consumption. All these information is then displayed on the dot matrix LCD.
DIY Digital AC Watt Meter – [Link]
kraftwerk opens up a whole new dimension in freedom and independence when it comes to supplying your mobile electronic devices with energy. Why? Because kraftwerk enables you to generate your own energy using a small, handy device – in such large amounts that you can run your iPhone, tablet, or even your GoPro camera for weeks!
The Kraftwerk Fuel Cell – [Link]
by Nurgak @ github.com:
To measure my electricity usage I decided to build a small system that would count LED blinks on my power meter which indicate the used Wh. It was pretty straight forward system requiring an Internet connected microcontroller to log the data and some sort of sensor that would detect LED blinks on the power meter which is not my property and thus not accessible or modifiable.
The main reason to do this project is to get a better overview of the electricity usage as the house is heated by a heat pump so basically everything works on electricity or other free (thermal solar collector) and renewable sources (stove).
I had a CC3200 development kit laying around, it’s featuring a chip with Wi-Fi and an ARM Cortex-M4 processor running at 80MHz, it was more than enough to fill all the needs of this project.
Electricity usage monitor – [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]