Sergei Bezrukov writes:
In this project we send and receive digital data by using a 433MHz transmitter and receiver modules TXM-433 and RXM-433 manufactured by LINX. We also use LINX helical whip-style antennas. The following images show the first part of the project – assembling the modules on a PCB and establishing RF connection between them.
Transmitting digital data over RF with LINX modules - [Link]
Here’s an app note about a circuit for detecting and locating radio frequency transmitters. The circuit is based around the MAX2015 RF detector which outputs a voltage proportional to the strength of a received RF signal in the 100 MHz to 3 GHz range – [via]
This design idea showcases a circuit that detects RF “bugs,” such as hidden wireless cameras, eavesdropping microphones, and other spying devices that emit RF frequencies in the 100MHz to 3000MHz range. A modification to this circuit not only detects RF bugs, but also locates their hidden positions.
App note: Detecting and locating RF bugs - [Link]
One of the first companies to focus on Wi-Fi was the AsyncLabs, who proposed a famous WiFi shield, including the appropriate libraries. What we propose is a new solution for Wi-Fi: this is a shield that the hardware was inspired by that of AsyncLabs, but in addition, we have provided a slot for microSD memory.
The basic component of the shield that we have made is a Wi-Fi module MRF24WB0MA manufactured by Microchip. The device is a Wi-Fi IEEE 802.11 RF transceiver, with a data rate between 1 and 2 Mbps, and with an internal antenna.
The WiFi shield supports both types of wireless networks infrastructure (BSS) and ad-hoc (IBSS) and is also allowed to connect to secure networks (cryptographers and are supported 64 and 128-bit WEP, WPA/WPA2 and TKIP, AES and PSK).
The library is constantly evolving, so we have provided a space where they will be published on http://code.google.com/p/wifi-shield-oe/ various versions available. http://www.open-electronics.org/arduino-wifi-shield/
Arduino WiFi Shield - [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]
Pittsford, NY, USA: Saelig Company, Inc. has introduced WiPry-Combo – the worldʼs first dynamic power meter and spectrum analyzer accessory for the iPad, iPod Touch, and iPhone – offering a modern touch interface not available on PC-based instruments. WiPry-Combo turns an iOS device into an ultraportable spectrum analyzer and dynamic power meter. WiPry-Combo brings RF power measurements to a graphical interface to show RF waveforms like an oscilloscope – instead of showing voltage, RF amplitude is displayed on an iOS portable device. Actual power output can be triggered, captured, and recorded for protocol verification or for troubleshooting wireless devices. Data is collected at up to 12 MSa/s, allowing analysis and verification of the smallest protocol level on/off times. WiPry-Combo offers data logging in csv format, while screenshot results can be instantly emailed via the iOS host phone.
In its Spectrum Analyzer mode, WiPry-Combo offers a practical solution for identifying interference or open channels in the 2.4GHz ISM band, or for identifying unauthorized WiFi access points. Operating in the frequency range: 2.400 to 2.495 GHz, it measures signals from -40dBm to +20dBm with an amplitude resolution of 2.0dBm and a bandwidth resolution of 1MHz. The band sweep time is 200ms. Read the rest of this entry »
NXP Semiconductors has launched the CLRC663, the first member of a new generation of high-performance proximity contactless reader ICs. It combines robust multi-protocol support with the highest RF output power and patented low-power card detection technology. The CLRC663 is targeted at a wide variety of use scenarios, including banking, e-government, transport and mobile payment.
Supporting all 13.56-MHz contactless standards, NXP’s new reader IC is compatible with all established smart card, smart tag and smart label technologies, including NFC Forum tag types and Mifare products. It ensures best-in-class interoperability with smart cards, electronic documents and NFC-enabled phones based on NXP technology. [via]
Contactless card reader IC handles multiple protocols - [Link]
I’ve finally gotten around to assembling a breakout board for the Skyworks SKY65116 UHF amplifier. It’s really amazing how the state of the art in RF ICs has advanced. They can still be on the expensive side ($6 at digikey), but still relatively cheap when you consider the cost of all the support parts that it takes to build an amplifier from a RF transistor. This particular amplifier has a 50 ohm input and output, and 35dB of gain. It works from 390Mhz to 500Mhz, which means its perfect for the 70cm ham band. The breakout board is stupid simple, copied directly from the evaluation board schematic in the datasheet, but I’ll include schematic and design files anyway.
SKY65116 Amplifier - [Link]
PCB layout is tough. Laying out a PCB isn’t in itself too hard once you learn how the tools work, but high-speed (10MHz+) introduces a virtual mine field of potential issues that you may not be aware of until it’s too late. While experience is the best teacher, Analog Devices has a great application note explaining some of the key pitfalls to avoid when dealing with high speed designs (which is basically anything today): A Practical Guide to High-Speed Printed-Circuit-Board Layout. Some of it is a bit heady, but not more than it needs to be, and it really does lay out a lot of key information that you may not have been aware of. Want to improve your PCB design skills? Print this out, and keep reading through it until it starts to make sense. There’s years of bench time worth of information in there.
EEBookshelf: High Speed PCB Layout - [Link]
RF networking is getting huge these days. With new RF nodes being developed on what seems like a monthly schedule. This means new and established companies are getting in the game. I’m pretty sure that everybody knows of Digi international (manufacturers of Xbee RF nodes) and regard them to be the current King of RF networking, BUT with ninja-like progress companies like Synapse Wireless have snuck up on them and started offering superior products. Syanpse nodes have the ability to wirelessly program Arduino UNOs at distances of >250ft without hardware mods or painful configuration processes. The nodes are both a network module and user-programmable microcontroller in one and on top of that they have to ability to do self-healing mesh networking. Their specs seem to outdo xbees on many levels, which begs the question, Synapse Wireless where have you been all my life???
There’s a New SheRifF in Town and Their Name is Synapse Wireless - [Link]
A lot of times we need to keep track of data from a device or a sensor located in a remote location from the point where it is processed. In other situations we desire wireless solutions for ease. Using long cables, infrared (IR) or other means are often tedious and not loss-less. Imagine collecting pH level data from a chemically lethal or toxic treatment plant where human presence is highly health hazardous. Running long cables from the pH sensor to the control or monitor station will surely introduce noisy signals and signal-to-noise ratio will thus drastically decrease. The result is erroneous data acquisition and thereby false decisions may be generated. If infrared signals or other optical means including lasers are used, they will need good obstacle-free line of sight or expensive and delicate optical fibers. Thus the solution stays in the radio frequency (RF) domain. This article talks about interfacing low cost RF modules (KST-TX01 and KST-RX806) for transmitting data between two remotely located PIC microcontrollers.
Wireless data transmission between two microcontrollers using KST-TX01 and KST-RX806 rf modules - [Link]