If you design circuits powered by CR2032 batteries here’s an article located by Joe Desbonnet which you should consider: [via]
This is an interesting article on how the performance of a cell/battery under pulsed loads can vary dramatically depending on period, peak current, duty cycle and other factors. The article discusses the performance of a CR2032 button cell driving low power wireless protocols such as ANT+ and Bluetooth v4.0.
The impact of high pulse drain on CR2032 coin-cell battery capacity - [Link]
Imec and Holst Centre announce that they have made a micromachined harvester for vibration energy with a record output power of 489 µW. Measurements and simulation show that the harvester is also suited for shock-induced energy harvesting in car tires, where it could power built-in sensors. In a tire, at 45 mph, the new device can deliver a constant 42 µW, which is enough to power a simple wireless sensor node. These results, obtained within the research centre’s program for Micropower Generation and Storage, are presented at the 2011 IEEE International Electron Devices Meeting (IEDM) in Washington (December 7-9).
Imec’s innovative harvester consists of a cantilever with a piezoelectric layer sandwiched between metallic electrodes, forming a capacitor. At the tip of the cantilever a mass is attached, which translates the macroscopic vibration into a vertical movement – putting strain on the piezoelectric layer and generating a voltage across the capacitor. As piezoelectric material, AlN (aluminum nitride) was chosen. The harvesters are packaged with a 6-inch wafer scale vacuum packaging process. The micromachining production process is compatible with low-cost mass-production fabrication. [via]
Car tires harvest energy - [Link]
Micropelt has launched compact thermogenerator package (TGP) devices that makes thermal energy harvesting ready for mass production. The devices enable automatic assembly of autonomous DC power supplies for ultra low power wireless sensors and actuators. Battery maintenance, a stumbling block in the deployment of wireless sensor networks, can be eliminated by TGP autonomous DC power modules whenever a temperature difference of 5 °C or more is available.
Output power ranges from 100 microwatts to over 10 milliwatts, sufficient to replace most batteries. Micropelt’s standardised TGP package comes in two interchangeable versions: TGP-651 and TGP-751. This allows output power and cost to be matched to target applications and markets without any changes to the PCB design. [via]
Surface-mount thermogenerators supplant batteries - [Link]
Stephen Evanczuk writes:
Micro-harvesting, or energy scavenging, relies on extracting power from minute but pervasive sources of ambient energy such as light, heat, RF, or vibration. With piezoelectric devices, energy from vibration can supply low-power applications, such as wireless sensors that are difficult to reach and maintain, for equipment or structural monitoring. By following a few key design considerations, engineers can build applications powered by piezoelectric transducers from Parallax, Measurement Specialties/Schaevitz, and Mide Technology and power management devices from Linear Technology.
Compared to other micro-harvesting energy sources, vibration and motion are relatively robust sources of ambient power (Figure 1). Placed on motors, for example, vibration-powered sensors can harvest power precisely when it is needed during motor operation. In a practical application, the piezoelectric transducer would likely be used to charge a high efficiency storage device rather than provide power directly to application circuits.
Energy Scavenging with Piezoelectric Transducers - [Link]
Since I’m planning to build two bench power supplies, I needed to build a current load to test them. So, I’m going to show you my version of the dummy load. Please note that this project was built ONLY using existing parts in my personal stock. I had to be silly to put this project on a wood box, but it was the only box I found around. I don’t recommend you to do it, instead use plastic or metal cases. I wanted to build something simple but with a minimum protection circuit. Thus I added a control circuit to limit the maximum dissipation power to protect the main transistor.
The main specifications are as follows:
- Current regulation: 0 to 10A
- Maximum input voltage: 40V
- Maximum dissipation power: 100W (limiting circuit with warning LED)
- Analog control: 10 turn potentiometer
- Analog display: 10A ammeter
- External power: 12V/0.3A
- Enable/disable switch
- Fuse protected: 15A
Constant Current Dummy Load - [Link]
Sweet n’ Salty Capacitor by Emily Daniels – [via]
I started this experiment attempting to create a low voltage non-toxic battery that would be easy to make and carry around. I may yet do this but for now I’ve created acapacitor, which is a electrical component used to store energy in an electric field. I chose to make the housing or shell out of hard candy because sugar heated to high temperatures takes on some of the properties of glass and is an easy insulator to create cheaply.
Sweet n’ Salty Capacitor - [Link]
If you’ve ever wondered how decoupling and bypass capacitors work, or why you should use them on every digital circuit, you need to check out Bertho’s excellent tutorial on the subject. He writes:
While enjoying the 7400 contest, it occurred to me that many of the submitted logic designs lacked some of the most elementary safeties to ensure a working result. One of the most disregarded aspects of the designs was the lack of bypass capacitors. Then, with an article about Murphy’s law linking a Maxim application note, it was decided to write a bit about decoupling and bypass capacitors.
As a person, who can be considered “old” in this line of work, I have experienced the problems of missing decoupling first hand. My first high-speed build was in the mid-eighties as an apprentice at a large electronics firm. The design I was building, a digital frequency measurement, used 74Fxx logic at a speed of 11MHz (which was very fast for the time). It was wire-wrapped on a double euro-card size board and used about 40 logic chips. When the time came to turn it on, I noticed that it didn’t work as expected and all kinds of stuff happened all over the place. After checking the build several times I talked to my supervisor about the problem and he just looked at it and said: “There are no bypass capacitors; mount them on all chips over the power supply and we’ll talk then.”. Completely bewildered I did what he said and, as a miracle, everything just worked. Why would seemingly inert capacitance on the power supply make things work?
My supervisor then told me all about switch/surge currents and inductance of the wiring and went on to tell the tale of decoupling. I admit that it took several years before I really understood what he was talking about, but the lesson was learned: always put capacitors on the power supply of logic chips.
Decoupling Capacitors Explained - [Link]
A simple charge controller suitable for wind or solar applications. Uses a TL-084 Op Amp, automotive spotlight relay and a handful of other components. The same circuit could also be used as a low voltage cut off to disconnect your battery before its fully discharged. Suitable for 12 and 24v operation.
The controller uses two trimpots to set a low and high switching voltage. When the applied voltage ( battery ) exceeds the high voltage setting, a relay is turned on. The relay will remain on until the applied voltage drops below the low voltage setting.
Wind or Solar Charge Controller - [Link]
BYU-student-built electric car sets land speed record at Salt Flats – [via]
An electric car designed and built by BYU engineering students set a world land speed record for its weight class, averaging 155.8 mph over its two required qualifying runs, one of which was clocked at 175 mph.
The milestone marks the end of a seven-year quest of more than 130 students, led by Perry Carter, who just retired as an associate professor.
“This is a wonderful closure to 31 years of teaching at BYU and many projects,” Carter said after the record was certified. “But this is the one that takes the cake. I’m done.”
BYU-student-built electric car sets land speed record at Salt Flats - [Link]
For the last year I’ve been working on a prototype for a Solar Inverter that can be Grid Intertied. A solar inverter takes the 12V DC (or other voltages) from the solar panels and converts it to 120V AC which is the power that most of your household appliances use. A Grid-Intertied inverter allows you to feed that power back into power grid (your house power) to help power your household appliances.
My goal was to design a small inverter, about 100W, that could be used with one solar panel and could be grid intertied. My second prototype (pictured above) has achieved these design goals. So on these web pages I’m going to document the design of the hardware and the software of my solar inverter. I’m releasing these designs to public without restrictions. All I ask is that if you use any of my design that you credit me and add a link back to this website. I hope these designs will help further the work of other people in this area.
Solar Grid-Intertie Inverter - [Link]