The Joule Thief circuit is a simple, self-oscillating voltage booster that allows low-voltage sources, like a nearly depleted 1.5V battery, to power devices requiring higher voltages. It uses a single transistor, a resistor, and a toroidal transformer with a feedback winding. When the circuit is energized, the transistor initially conducts, allowing current to flow through the primary winding of the transformer. This builds a magnetic field. As the current increases, the voltage across the resistor also increases, eventually turning the transistor off. The collapsing magnetic field in the transformer induces a voltage in the secondary winding, which, combined with the remaining battery voltage, creates a high voltage pulse suitable for driving an LED or other small load. The feedback winding further reinforces this process, ensuring oscillation and efficient energy extraction from the battery.
Researchers at the National University of Singapore have developed a new battery-free technology that can power devices using ambient radio frequency (RF) signals like Wi-Fi and cellular transmissions. This system utilizes a compact antenna and an innovative matching network to efficiently harvest RF energy and convert it to usable direct current power, capable of powering small electronics and sensors. This breakthrough has the potential to eliminate the need for batteries in various Internet of Things (IoT) devices, promoting sustainability and reducing electronic waste.
Hacker News commenters discuss the potential and limitations of the battery-free technology. Some express skepticism about the practicality of powering larger devices, highlighting the low power output and the dependence on strong ambient RF signals. Others are more optimistic, suggesting niche applications like sensors and IoT devices, especially in environments with consistent RF sources. The discussion also touches on the security implications of devices relying on potentially manipulable RF signals, as well as the possibility of interference with existing radio communication. Several users question the novelty of the technology, pointing to existing energy harvesting techniques. Finally, some commenters raise concerns about the accuracy and hype often surrounding university press releases on scientific breakthroughs.
The "Thermoelectric Solar Panel" project explores generating electricity from sunlight using a combination of solar thermal collection and thermoelectric generators (TEGs). A Fresnel lens concentrates sunlight onto a copper pipe painted black to maximize heat absorption. This heat is transferred to the hot side of TEGs, while the cold side is cooled by a heatsink and fan. The goal is to leverage the temperature difference across the TEGs to produce usable electricity, offering a potential alternative or complement to traditional photovoltaic solar panels. The initial prototype demonstrates the concept's viability, though efficiency and scalability remain key challenges for practical application.
Hacker News users discussed the practicality and efficiency of the thermoelectric solar panel described in the linked article. Several commenters pointed out the inherent low efficiency of thermoelectric generators, making them unsuitable for large-scale power generation compared to photovoltaic panels. Some suggested niche applications where the combined heat and electricity generation might be advantageous, such as powering remote sensors or in hybrid systems. The durability and lifespan of the proposed setup, especially concerning the vacuum chamber and selective coating, were also questioned. One commenter mentioned a similar project they had worked on, highlighting the challenges in achieving meaningful energy output. Overall, the consensus seemed to be that while conceptually interesting, the thermoelectric approach faces significant hurdles in becoming a viable alternative to existing solar technologies.
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https://news.ycombinator.com/item?id=43235671
Hacker News users discuss the Joule Thief circuit's simplicity and cleverness, highlighting its ability to extract power from nearly depleted batteries. Some debate the origin of the name, suggesting it's not about stealing energy but efficiently using what's available. Several commenters note the circuit's educational value for understanding inductors, transformers, and oscillators. Practical applications are also mentioned, including using Joule Thieves to power LEDs and as voltage boosters. There's a cautionary note about potential hazards like high-voltage spikes and flickering LEDs, depending on the implementation. Finally, some commenters offer variations on the circuit, such as using MOSFETs instead of bipolar transistors, and discuss its limitations with different battery chemistries.
The Hacker News post titled "Understand the Joule Thief Circuit" linking to an Electronics Stack Exchange question about the same topic has several comments discussing various aspects of the circuit and its functionality.
Several commenters focus on correcting or clarifying details about the Joule Thief's operation. One commenter points out that the circuit doesn't actually "steal" joules but rather makes use of energy otherwise wasted in a nearly depleted battery. They emphasize that the voltage is boosted, not the current, allowing the LED to operate at a higher voltage than the battery can directly provide. Another commenter builds upon this by explaining how the circuit functions as a self-oscillating boost converter, using the transformer's feedback to regulate the switching.
Another thread of discussion revolves around the efficiency and practicality of Joule Thief circuits. One commenter questions the circuit's actual efficiency, suggesting that the rapid switching might lead to significant losses in the components. Another commenter responds, agreeing about potential inefficiencies, but acknowledges that the simplicity of the design makes it useful for extracting the last bit of energy from a battery in low-power applications. This commenter further suggests a potential improvement using a CMOS 555 timer for potentially higher efficiency.
A few comments delve into more technical aspects of the circuit. One explains how the circuit exploits the transformer's behavior during the "flyback" period, where the collapsing magnetic field induces a higher voltage. Another discusses the role of the feedback winding in controlling the transistor's switching, clarifying why it is wound in the opposite direction to the primary winding.
Other comments offer practical advice, such as selecting appropriate components, like the transistor and the ferrite core for the transformer. One comment specifically cautions against using higher voltages, emphasizing the circuit's design for single-cell batteries, and highlighting safety concerns.
Finally, some comments discuss alternative circuits and applications. One user mentions using a similar circuit to power a white LED from a single AA battery and discusses component selection based on desired brightness.
Overall, the comments provide a wide range of perspectives, from basic explanations of the circuit's function to deeper discussions about its efficiency and limitations, as well as practical tips and alternative approaches.