Dimitar Kolev writes:
I test both, just with one LED for now (like 15mA) – they was working quite OK for distances up to 1-2cm, just some paper and thin air between TX and RX coils. With appropriate ferite it seems distance and coupling can be even better.
Just to fire further my interest, chip labels on board were erased, but fortunately I found a good picture where most of the labels were visible. Unfortunately no results after some googling, but finally I think I found the manufacturer of chips and some other wireless power/charging modules – it should be Elecoteq Electronics Website is only in Chinese, so I read what I can via Google translate. I found no datasheets, but for one there was some basic description
Wireless power and charging test and some reverse engineering - [Link]
Bill Schweber writes:
The power-management IC (PMIC) supports and manages the transducer and energy-collection channel, the energy-storage element (battery, conventional capacitor or supercapacitor), and the processor/wireless link. This critical block of any energy-harvesting design implements several major functions: Captures and extracts the random, miniscule energy from the source transducer, Transforms that extracted power into energy for the storage element, usually via a DC/DC converter, Manages the outflow of power from the storage element, while ensuring that power is not drawn when the stored energy is below a threshold value and would be wasted, Perhaps most challenging, it has to manage its own start-up sequence in the transition from when there is insufficient available stored energy for the PMIC itself.
Choosing a Power Management IC for Energy-Harvesting Applications - [Link]
by Publitek European Editors:
In today’s wireless, connected world, ambient Radio Frequency (RF) energy is everywhere. Technically, this free-flowing energy can be captured, converted and stored for use in other applications. In fact, it is already in use in a number of ultra-low-power, battery-free applications, such as RFID tags, contactless smart cards, and wireless sensor networks. As a result of technological advances, harvested RF energy is just beginning to realize its wider potential, including charging batteries in smartphones and other portable devices. These enabling technologies include RF transceivers, power conversion circuits, and ultra-low-power microcontrollers, all of which are becoming ever more efficient.
Tune In, Charge Up: RF Energy Harvesting Shows its Potential - [Link]
JN Lygouras, University of Thrace writes:
The control circuit in Figure 1a allows you to manually adjust the power delivered to a load. By changing the setting of potentiometer R3, you change the phase angle at which the thyristor (Q3) fires (Figure 1b), thereby altering the load current’s duty cycle. The adjustment range is about 0 to 180°. Q3’s off time is linear with R3, but of course the resulting load power is not linear with R3.
555 timer triggers phase-control circuit - [Link]
Battery-Charging Controllers for Energy Harvesters by Jon Gabay:
Whether your energy harvesting application uses large solar panels with high voltages and currents or, more often the case, must make do with minute amounts of power derived from various other ambient energy sources, one thing is almost certain: some type of energy storage is on board, whether in the form of a small rechargeable lithium ion battery, a supercapacitor, or solid-state energy storage technology. For the engineer this means that not only do we need to design circuits to harvest and convert ambient energy, but we also have to include an energy-harvesting interface (and protection circuitry) as well as a charge controller. This article looks at single chip energy harvesting devices that also provide some form of charge control. It discusses the different conditions under which energy can be extracted as well as what to expect when trying to squeeze power out of the ambient environment. Finally, the article will present some typical integrated solutions for small-sized low-power energy-harvesting designs.
Battery-Charging Controllers for Energy Harvesters - [Link]
Publitek European Editors writes:
Many security and motion detector systems rely on small, semi-autonomous nodes that are easy and simple to install. This implies the use of a battery-based power source and low-power operation in order to minimize the number of battery changes during the lifetime of the product.
Over its lifetime, the output voltage of a battery falls, with the biggest decline when the charge is nearing full depletion. A converter type that can accommodate this change in voltage but can still provide relatively high voltages for sensors and RF transmitters is the buck-boost converter – it operates the buck part of the circuit when the battery is fresh, moving to boost operation when the voltage falls below the threshold of the electronic circuitry it powers. A number of vendors have developed integrated buck-boost converters optimized for battery systems
Buck-Boost Converters Help Extend Battery Life for Motion Detection - [Link]
TI’s latest Power Management devices, design tools and support resources in the new 2013 Power Management Guide
TI’s Power Management Guide 2013 edition - [Link]
This DC-DC Converter start-up from as low as 330mV input! Marian Stofka writes:
The bq25504 from Texas Instruments is a good candidate to become a milestone on the road to micro-power management and energy harvesting. A prominent feature of this IC is its ability to start up at a supply voltage as low as 330 mV typically, and 450 mV guaranteed. With an SMD inductor and a few capacitors and resistors, it forms a dc-dc converter with a high power efficiency that is unprecedented, especially in the ultralow-power region.
DC-DC converter starts up and operates from a single photocell - [Link]
mic @ wemakethings.net writes:
For a long time I wanted to enter the 21st century by stopping using NiCad or NiMH batteries and upgrading to Lithium accumulators as they provide more power per volume and are cool in general. Constant flow of obsolete cell phones provides a nice source of reasonably high-performance batteries for free – I felt compelled to tap into this resource for my battery operated projects.
Open source Lithium battery charger modules - [Link]
Kennith needed a 1A constant current lead-acid battery charger for his HAM radios so he writes:
Since the SLAs are relatively small, and I only need them charged between radio outings, I opted to build a 1A constant current charger, based on the 555 Battery Charger which won first place in the 555 Design Contest Utility category. Using a 555 is a rather clever way to get two comparators and a Set-Reset latch in a single 8DIP package, which is needed for the high and low trip points. The major difference between my design and Mike’s is that instead of using a relay like him, I use an LM317 as a constant current source to limit my batteries charge rate.
555 based constant current lead-acid battery charger - [Link]