Power category

ESPurna-H, A Compact Open Source Hardware Wireless Power Wall Switch

Controlling your AC loads using wireless power switch is not a new concept. Several commercial products from several vendors can be found on the market such as Xiaomi’s Mi Smart Socket Plug, SAMSUNG’s SmartThings Power Outlet and Sonoff Pow WiFi Switch from ITEAD.

Using ESP8266 makes the building of a customized WiFi power switch more affordable especially if you start with Sonoff Pow WiFi Switch design and you use a special Arduino C firmware called ESPurna developed by Xose (tinkerman) which is an open source firmware for ESP8266 based wireless switches such as Sonoff POW and many others.

After Xose has built the software ــ ESPurna, he decided to build his own smart switch board to meet his special needs. ESPurna-H electronic design is very similar to Sonoff POW’s one; it uses ESP12 module as a controller and as WiFi transceiver.


AC power monitoring is done using HLW8012 IC which is also present in Sonoff POW. This IC monitors both voltage and current of the AC power, and output RMS voltage, current and active power encoded as a 50% duty cycle square wave where the frequency is proportional to the magnitude. I should mention that ESPurna supports interfacing with HLW8012. In addition AC load is enabled/disabled by using a 10A relay.

ESPurna-H uses HLK-PM01 AC-DC step-down power supply module. The 100-240 VAC input range so the board can be used anywhere in the world and the good performance made Xeos select this module.

HLK-PM01 Inside (Image Source ــ lygte-info.dk )
HLK-PM01 Inside (Image Source ــ lygte-info.dk )
HLK-PM01 Inside (Image Source ــ lygte-info.dk )
HLK-PM01 Inside (Image Source ــ lygte-info.dk )

ESPurna-H has another option to enable/disable the relay using a capacitive touch switch using TTP223 module.

Xose designed the board with Eagle CAD and released the schematics, PCB layout and other hardware design files on Github.

Source: cnx-software

Body Heat Provides Wearables With Eternal Power

The first watch to make use of the body’s natural heat to uphold battery charge in wearables is now even being crowdfunded on Indiegogo. Who else but researchers from Texas A&M University (a hot place) came up with the solution.

In today’s wearables battery life is a bottleneck, as increasing amounts of technology gets packed into lightweight designs comfortable enough for everyday wear. That’s why Texas A&M professor Choongho Yu and his PhD student, Suk Lae Kim, designed a thermally-chargeable solid-state supercapacitor.

Despite having no apparent links with the researchers, a smartwatch which uses the same thermoelectric concept has arrived on Indiegogo seeking crowdfunding. The MATRIX PowerWatch claims to be the world’s first smartwatch that you never have to charge.

Thermoelectric technology converting heat to electric power is based on the Seebeck effect discovered in 1821. In the absence of an applied voltage gradient, an electric current can still be generated if there is a temperature gradient. A thermoelectric material must have a low thermal conductivity and high electrical conductivity to function efficiently.

PowerWatch runs off your body heat and when you take it off, your data is stored in memory and it goes to sleep. When you put it back on, the watch resumes where you left it. It’s got a power meter that tells you how much electricity your body heat is producing.

The standard Indiegogo pricing is $139, the crowdfunding page is here. On January 14, 2017 the product  was 937% funded.

Source: Elektor

Flow battery can run for 10 years with zero maintenance

by Jan Buiting @ elektormagazine.com:

Harvard University researchers have developed a low-cost flow battery that stores energy in organic molecules dissolved in neutral pH water. In their report (see below) they claim that the new battery can run for a decade or more without maintenance.

Flow battery can run for 10 years with zero maintenance – [Link]

Increasing Battery Life With UB20M Voltage Detector

Engineers at the University of Bristol have developed a three terminal pico-power chip that can cut standby drain in sensor nodes – even compared with today’s low-power microcontrollers.

It does this by replacing the low duty-cycle sleep-wake-sleep pattern used on MCU-based sensor monitors, with ‘off’. A voltage detector powered by the sensor – there is no other power source –  starts the processor when the sensor produces a voltage.

At 5pA (20°C 1V), power draw from the sensor through the input/supply pin is so low that the chip can directly interface with high-impedance sensors such as antennas, piezo-electric accelerometers, or photodiodes. With so little current required, the chip does not collapse the sensor voltage.

“It will work from five infra-red diodes in series, powered from a TV remote control 5m away, or an un-powered accelerometer”, Bristol engineer Bernard Stark told Electronics Weekly.

Called UB20M, the only power it draws from the system is 100pA(max) leakage through its open drain output transistor. Input threshold is set at 0.6V.

Once the sensor presents greater than 0.6V to the input, the output FET turns on (RDSon~800Ω), and its low resistance can either be used to turn on a p-FET to power up a microcontroller, or can wake a microcontroller from sleep.

In an extreme application example, said the University, an earthquake detector could be held in sleep for years, until a tremor caused the chip to wake its host.

Despite its impedance and sensitivity, the device can withstand 20V on its input/supply pin, and it has ESD protection. Maximum output pin parameters are 5.5V 7mA. Output turn-on time is 0.25μs, while turn-off depends on load resistance and capacitance – typically 8μs with a 5MΩ load and 180μs with 100MΩ.

Because patents are pending, exactly how the chip works is not being disclosed. It has around 40 transistors, and is made on a 180nm CMOS process, is all Stark could say.

Samples are available – through a multi-project wafer deal with Europractice and IMEC, fabricated at AMS in Austria, and the University has created an evaluation board. Due to Europractice and IMEC going the extra mile, said Stark, samples are in SOT323-5 rather than clunky research packages.

The team cautions that anyone trying the chip will need to understand high-impedance circuits, as otherwise stray mains fields, for example, will trigger it continuously and the output transistor will remain on. Lengthy sensor connections should be avoided.

In general, the sensor has to be connected to the input/supply pin with enough parallel resistance to leak away stray charge and ensure the UB20M turns off.

“We are now working on ways of bringing other power drains such as data-capture, computation, and transmission, to within the nW-power budget of a sensor, completely eliminating batteries from sensor nodes,” said the University. “An example of this (right) is where power management with a few tens of nW quiescent is actively matching its input impedance to an 80MΩ energy harvester with 10 ms intermittent output pulses.”

UB20M data sheet and eval board details can be reached from this introductory web page, and there is an introductory video.

Source: Electronics Weekly

Open source 12V powerbank

A custom 12V powerbank for Cube i7 Stylus from Muxtronics:

Why would anyone even try to build a power bank – i.e. an external battery for charging mobile devices – these days? These things are commodity, it’s impossible to compete. Right? Well, that is until you find out that the type of power bank for your application, namely charging a higher-end tablet with 12V input, does not exist cheaply. Looking around for 12V power banks yields a lot of li-ion car jumpstarters (*) and very few actual power banks. Those that exist are pretty expensive and often don’t even perform that well.

Open source 12V powerbank – [Link]

Ultra thin supercapacitor for peak power assist

Peggy Lee @ newelectronics.co.uk discuss about MURATA’s ultra thin supercapacitor.

The DMH series from Murata is said to be the lowest profile supercapacitor. The product is designed for peak power assist duties in wearable applications and various other devices.

Measuring 20 x 20mm, the 0.4mm thick DMHA14R5V353M4ATA0 supercapacitor is claimed to be suitable for use in the thinnest devices. A 4.5V rated voltage, 35mF capacity and low ESR of 300mΩ enable peak power assist in tens of milliseconds, with lithium-ion batteries.

Ultra thin supercapacitor for peak power assist [Link]


In order to synthesize chlorates and perchlorates in the home lab it is always good to have a way to regulate the current flowing through the electrolyte. Because the load is purely resistive the simplest solution is a small PWM (Pulse Width Modulation) regulator. So I decided to make my own.

PWM Power Regulator – [Link]

TP4056 3V3 Load Share Upgrade

A lot of project are battery powered and some of them need dual battery links. Robert on hackaday.io had shared his new project that shed light on this issue. He built an load sharing addon board with the ability to charge the battery while the project is operating.

Many Chinese charger boards are out there based on TP4056, but these boards don’t have the load sharing or voltage regulator features.

Load sharing means that you can power your circuit in two ways, from battery and from Vcc if a charger is connected. Once the charger is connected the battery will start charging and the load will be powered directly from Vcc. Robert added this feature to a recent design and also he added voltage regulation by using MCP1252.

The Components needed to build this project:

  • 1x  MCP1252-33X50/MS Power: Management IC / Switching Regulators
  • 1x  FDN304P: Discrete Semiconductors / Diode-Transistor Modules
  • 1x  SGL1-40-DIO: Schottky diode
  • 2x  100k 1206 resistor
  • 3x  10uF 1206 capacitor X7R
  • 1x  2.2uF 0805 capacitor X7R
  • 1x  ON/OFF switch (optional)
  • 2x  2 pin pcb connector
  • 1x  PCB from OSHpark

This schematic was inspired by multiple designs and modified by Robert.

“The advantage of MCP1252 is automatic buck/boost feature, it will maintain the regulated output voltage whether the input voltage is above or below the output voltage (2.1 to 5.0 V input range) so it is ideal for the lithium battery voltage. If you read the datasheet for the MCP1252-33X50I/MS there is clearly specified what type of MLCC capacitor should be used.”

The maximum output current of this board is 120mA and the output voltage is 3.3 V. It may sound not that suitable for your projects if you want to power an ESP8266, but still you can build your own board with different components to achieve the outputs you need. For example, by using MCP1253, which is identical to MCP1252, you will get  higher switching frequency (1MHz). Robert’s plan is to use this board with CO2 sensor (about 30 mA) and other low power sensors, some MCU and LCD, which can be powered using 120 mA.

Some measurements will be done to test the functionality of this board. To keep updated with the news of this project, you can follow the project on hackaday.io. You can also check other projects by Robert here.

The Next-Generation Semiconductor for Power Electronics

Researchers have demonstrated the high-performance potential of an experimental transistor made of a semiconductor called beta gallium oxide, which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft.

The semiconductor is promising for next-generation “power electronics,” or devices needed to control the flow of electrical energy in circuits. Such a technology could help to reduce global energy use and greenhouse gas emissions by replacing less efficient and bulky power electronics switches now in use.

The schematic at left shows the design for an experimental transistor made of a semiconductor called beta gallium oxide, which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft. At right is an atomic force microscope image of the semiconductor. (Purdue University image/Peide Ye)


The schematic at left shows the design for an experimental transistor made of a semiconductor called beta gallium oxide, which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft. At right is an atomic force microscope image of the semiconductor. (Purdue University image/Peide Ye)The transistor, called a gallium oxide on insulator field effect transistor, or GOOI, is especially promising because it possesses an “ultra-wide bandgap,” a trait needed for switches in high-voltage applications.

Compared to other semiconductors thought to be promising for the transistors, devices made from beta gallium oxide have a higher “breakdown voltage,” or the voltage at which the device fails, said Peide Ye, Purdue University’s Richard J. and Mary Jo Schwartz Professor of Electrical and Computer Engineering.

Findings are detailed in a research paper published this month in IEEE Electron Device Letters. Graduate student Hong Zhou performed much of the research.

The team also developed a new low-cost method using adhesive tape to peel off layers of the semiconductor from a single crystal, representing a far less expensive alternative to a laboratory technique called epitaxy. The market price for a 1-centimeter-by-1.5-centimeter piece of beta gallium oxide produced using epitaxy is about $6,000. In comparison, the “Scotch-tape” approach costs pennies and it can be used to cut films of the beta gallium oxide material into belts or “nano-membranes,” which can then be transferred to a conventional silicon disc and manufactured into devices, Ye said.

The technique was found to yield extremely smooth films, having a surface roughness of 0.3 nano-meters, which is another factor that bodes well for its use in electronic devices, said Ye, who is affiliated with the NEPTUNE Center for Power and Energy Research, funded by the U.S. Office of Naval Research and based at Purdue’s Discovery Park. Related research was supported by the center.

The Purdue team achieved electrical currents 10 to 100 times greater than other research groups working with the semiconductor, Ye said.

One drawback to the material is that it possesses poor thermal properties. To help solve the problem, future research may include work to attach the material to a substrate of diamond or aluminum nitride.

The research was based at Discovery Park’s Birck Nanotechnology Center.
Source: Purdue University