Vishay’s application note on zener diode voltage stability. Link here (PDF)
The Zener voltage (VZ) of a Zener or avalanche diode depends on the diode’s junction temperature. Any current running through the p/n junction barrier generates the electrical power of: P = IZ * VZ. This electrical power is equivalent to the thermal power applied to this junction. Depending on the duration and the intensity of the current, the applied thermal energy increases and heats the junction.
App note from Vishay about tight tolerances that sense resistor requires for accurate and efficient Li-ion battery chargers. Link here (PDF)
Intelligent Li-ion rechargeable batteries utilize current sensing resistors with ultra low ohm, low TCR, tight tolerance, high withstanding surge current and low thermal EMF.
App note from Vishay on selecting grid resistors base on their application as resistors vary over continuous duty. Link here (PDF)
Nearly all resistor materials change resistance as temperature increases. Depending on the material, this change can range from a few percent to 50 % and higher at 100 % duty on the resistor (100 % duty raises the resistor temperature to ~ 375 °C over ambient).
John Boxall from Tronixstuff has written an article on using Blynk with Arduino:
There are many ways of remotely-controlling your Arduino or compatible hardware over the Internet. Some are more complex than others, which can be a good thing or a bad thing depending on your level of expertise. Lately we’ve become more interested in this topic and have come across Blynk, which appeared to be a simple solution – and thus the topic of our review.
What is Blynk?
From their website: “Blynk is a Platform with iOS and Android apps to control Arduino, Raspberry Pi and the likes over the Internet. It’s a digital dashboard where you can build a graphic interface for your project by simply dragging and dropping widgets.
More info at Tronixstuff site.
Check out the video after the break. Continue reading “Control your Arduino over the Internet using Blynk”
KF5OBS writes, “In this video I’m showing how to generate a PWM signal that’s behaving proportionally to analog control signal.”
Details at KF5OBS’ blog.
Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:
Continue reading “Free PCB coupon via Facebook to 2 random commenters”
Ashish Derhgawen’s article on rediscovering the magic of wireless communication:
In this article, I will tell you the story behind one of the most important technological inventions of modern times – wireless communication. I will also describe some of my own experiments with high voltage spark transmitters and coherers! But before I talk about those, a little background is necessary to appreciate how they work. We’ll have to step into the shoes of the early pioneers in the field of electricity and see the world in a completely different way!
More info at Ashish’s blog.
Check out the video after the break.
Continue reading “Rediscovering the magic of wireless communication”
Merry Christmas and Happy Holidays to all. May you find many PCBs and other electronics wizardry under your tree or pole.
Remember, support is available on Christmas. Just give us a shout in the forum.
Alex Weber has posted a new project on building a DIY Paint Machine, he writes:
Here is my latest creature, the Paint Machine. It’s a machine the prints simple bitmaps with spray chalk on the street or sidewalk. For a large-scale project like a home exterior painting Edmonton, it is advised that you hire a professional painting contractor.
Some of the key features:
*dimension: width: 220cm, length: 38cm, height: 24cm, weight: 12kg
*printing speed: ca. 0.036 km/h
*resolution (4:3): 61px * 46px, print: 225cm * 170cm
*swappable print head
*remote controlled with smartphone app
Project info at Tinkerlog site.
Check out the video after the break.
Continue reading “Paint Machine, a printer that prints small bitmaps on the street”
Tutorial on the theory, design and characterization of a CMOS transimpedance amplifier from The Signal Path:
In this episode, Shahriar and Shayan discuss the design and characterization of a deceptively simple CMOS inverter-based transimpedance amplifier. The the large and small signal behavior of the CMOS inverter is discussed and measured using the Keithley 2450 and 2460 source meters. The transient response is also measured using a Keysight MSO-S series oscilloscope.
The small signal gain of the circuit is calculated from small signal parameters which are extracted directly by measuring the devices I/V characteristics. The NMOS/PMOS devices used are from an ADL1105 quad-discrete transistor IC. Through the use of a shunt-shunt feedback, the CMOS amplifiers is converted to a transimpedance amplifier which is capable of amplifying the current from a photo-detector diode by a gain of 30kV/A. The feedback theory is used to calculate the gain of the amplifier.
Sjaak designed and built a C64 RAM/ROM cartridge, which has a 6264 SRAM chip and an Atmel 644. He did program an Atmega with a Bus Pirate:
Today came in the Atmega644P’s in TQFP package I scored on eBay. Today I’m focusing on the SD2IEC part of the RAM cartridge. I was a bit scary to order them there as ebay is wellknown for knockoffs, nonworking or rebadged stuff. Even the big players will sometimes fall into this trap. However it seems to be working (avrdude is capable of reading the ID and seem to program them correctly) Is it my lucky day?!
When designing this board, which I do usually at night after work, I tend to make little sloppy mistakes (I will write a post about that) and things turn out not as easy after receiving the PCB’s. Notice there aren’t any pins or testpads for an ICSP connection? Because there aren’t any :) I desoldered the Atmega and put it onto an old protoboard I designed ages ago and go my trusty old Bus Pirate out. Programming took ages (a whopping 2097 seconds to write and 2087 seconds to verify) for just a 10k Hex file (I choose to upload only a bootloader), but seems to be programming the chip ok. Next I also programmed the fuses. and prepared a microsd card with the SD2IEC firmware on it and stick it into the memory card holder.
Project info at smdprutser.nl.
Get an assembled Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.
Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:
Some stuff:
We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.
Jelmer Tiete designed and built a development board for the TI CC2538, that is available at GitHub:
It’s a nice little system-on-chip with an ARM Cortex M3, 2.4 GHz 802.15.4 radio and it runs at 32 MHz. Perfect for all your favorite Internet Of Things (IOT) shenanigans. Contiki supports this chip pretty well, which means easy 6LoWPAN, RPL and CoAP support.
Project info at Jelmer’s blog.
Dilshan Jayakody writes:
74181 is 4-bit arithmetic and logic unit introduced by Texas Instruments in March 1970 and it is known for being the first ALU in single package. This chip is no longer in manufacturing but still it is quite popular in CA (computer architecture) courses in many colleges.
To test the behavior of this 4-bit ALU we decided to construct it on Altera MAX II CPLD. For this project we choose EPM240T100C5 CPLD and logic design is implement using Altera Quartus II. For logic design we refer Fairchild Semiconductor’s DM74LS181 datasheet. This setup is tested on basic EPM240 series development board with some mechanical switches and couple of LEDs.
Project info at Jayakody’s blog and elect.wikispaces.com.
Quinn Dunki created an Apple II ROM tool project and posted a great write-up on digging into the ROM of her Apple IIc Plus:
You may recall way back when I started my Apple II ROM Tool project, that I had intended to fix some bugs. That was the whole point of this adventure. It took a bit longer than I expected to get here, but we can finally put our kilohertz where our mouth is and fix some brokeass code. But wait, you might be asking, what bugs are in the Apple II ROM? It’s code that shipped in millions of machines, and had hundreds of thousands of pieces of software built around it. What bugs could there be? Well, sometimes a bug is in the ear of the beholder.
Check out the video after the break. Continue reading “Apple II ROM Dumper”
Silicon Labs’ app note featuring low power boost for microcontrollers. Link here (PDF)
Boosting the output voltage of common alkaline button-cells to at least 1.8 V needed by microcontrollers provides an “always on” standby power source sufficient for low-power oscillator interrupt/sleep state operation. Two ultralow power op amps are used in a charge pump configuration to double an input voltage, creating an output voltage of approximately 2x the input voltage. Output currents up to 100 µA are available at 90% efficiency; even load currents as low as 10 µA achieve 80% efficiency, beating commercially available charge pump ICs and inductorbased boost regulators.
We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:
An app note from Alpha and Omega Semiconductor on using their AOZ1016 buck regulator to generate negative voltage. Link here (PDF)
The negative voltage source is widely used in various applications such as computing systems, LCD panels, audio amplifiers, etc. Using the additional secondary winding of a transformer is the widely used approach to generate the negative voltage source for computing systems, but it requires isolation transformer which may not be possible in other applications, and regulation is also bad. The LCD panels usually employs the charge pump to generate the negative voltage due to low cost, but the drawback is obvious: power delivery is limited and regulation is very bad and changes with input voltage since charge pump can only generate the integral times input voltage. In some high-end audio amplifier applications, the text-book method – buck boost – is applied. The lack of dedicated commercial buck-boost controllers, and the essential control difficulty of buck-boost (right plate zero) prevent the method from being widely used. And thus, designing a high qualify negative voltage source is always the challenge in system applications.
This article illustrates how to use buck converter to generate negative voltage source. The basic operation theory is introduced, and one practical example is presented.
An app note (PDF!) from Texas Instruments on importance of latency in factory automation:
Latency is a critical parameter in Ethernet networks developed for Factory Automation applications. Latency is not a defined value for Ethernet as specified by the IEEE 802.3 standard. Nor is Ethernet inherently synchronous or repeatable. This disconnect between the inherent characteristics of Ethernet and the needs of Factory Automation applications must be bridged though careful architecture of Ethernet Physical Layer devices like the DP83867.
The latency through the Ethernet Physical Layer is a key limiting factor of control cycle time in these applications. The capability of the DP83867 to operate with less than 400ns latency in 1000Base-T operation can improve the cycle time. This low level of latency is also comparable to levels seen in 100Base-TX operation, thereby simplifying the process of upgrading a 100Base-TX network to 1000BaseT and increasing the network bandwidth.
Here is an app note (PDF!) from Microchip describing the basics of different SMPS
topologies:
The industry drive toward smaller, lighter and more efficient electronics has led to the development of the Switch Mode Power Supply (SMPS). There are several topologies commonly used to implement SMPS.
This application note, which is the first of a two-part series, explains the basics of different SMPS topologies. Applications of different topologies and their pros and cons are also discussed in detail. This application note will guide the user to select an appropriate topology for a given application, while providing useful information regarding selection of electrical and electronic components for a given SMPS design.
