Free PCB coupon via Facebook to 2 random commenters

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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:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • We’ll contact you via Facebook with a coupon code for the PCB drawer.
  • Limit one PCB per address per month, please.
  • Like everything else on this site, PCBs are offered without warranty.

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.

A full review of EasyEDA: A circuit EDA online tool

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Yahya Tawil wrote in to share his review of a web based EDA tool, the EasyEDA. He explains the general structure of this tool and some of its cool features:

EDA cloud tools which are related to electronics are emerging exponentially in almost all aspects (i.e. simulation, PCB design, footprint creation, gerber files viewing and 3D PCB viewing). Even well-known desktop programs like EAGLE CAD and Altium are trying to compete in this field by making their own services or by acquiring others.
Web-based EDA tool suites like EasyEDA and Upverter are getting rapidly famous. These online tools offer some outstanding solutions for collaboration and providing some viable features for teams with financial limits like multi-layer PCB designing, while it costs a lot to buy a licence for other EDA tool with a multi-layer feature, for example.

More details at allaboutcircuits.com.

Reverse engineering of BK Precision 1696 switching power supply’s LCD protocol

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Kerry Wong writes:

As mentioned in my previous post, besides the broken LCD there was also an issue with the power supply portion of the unit and the output voltage was clamped at around 10 to 11V. The digital circuitry portion however seemed to be intact. Unfortunately since an identical LCD is virtually unobtanium, I thought I’d reverse engineer the LCD protocol so once the power supply is fixed I can fix the display by hooking up a different LCD.

See the full post on his blog.

Check out the video after the break.

App note: Characteristics and applications of fast recovery epitaxial diodes (FRED)

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All about ultrafast diodes app note from IXYS. Link here (PDF)

During the last 10 years, power supply topology has undergone a basic change. Power supplies of all kinds are now constructed so that heavy and bulky 50/60 Hz mains transformers are no longer necessary. These transformers represented the major part of volume and weight of a traditional power supply. Today they have been replaced with smaller and lighter transfomers, whose core materials now consist of sintered ferrites instead of iron laminations and which can operate up to 250 kHz. For the same power rating, high frequency operation significantly reduces the weight and volume of the transformer. This development has been significantly influenced by new, fast switching power transistors, such as MOSFETS or IGBTs, working at high blocking voltages (VCES > 600 V).

Apart from the characteristics of the transitor switches, the on-state and dynamic characteristics of the free wheeling diodes have a significant impact on the power loss, the efficiency and the degree of safety in operation of the whole equipment. They also play a decisive role when it comes to increasing the efficiency of a SMPS and to reduce the losses of an inverter, which clearly mandates that ultrafast diodes be used. The ultrafast diodes described here embrace all characteristics of modern epitaxial diodes, such as soft recovery, low reverse recovery current IRM with short reverse recovery times.

App note: Optimized diodes for switching applications

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An app note from IXYS about choosing the right diode for efficiency and cost. Link here (PDF)

Great efforts have been made to improve power switches – MOSFETs and IGBTs – to decrease forward voltage drop and as well as to decrease turn-off energy. In switching inductive loads, the turn-on losses depend strongly of the behavior of the companion free-wheeling diode and now form the major part of over-all power losses. New developments like series connected diodes in a single package can greatly improve a given design. This paper shows how to choose the optimum diode using the specific example of a PFC circuit.

Overdrive guitar effects pedal

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Eddie over at Bantam Tools shared detailed instructions of how to build this DIY overdrive effects pedal:

This project shows you how to make your very own effects stompbox! We’ll go through the steps of downloading the .brd file, loading the file into our software, milling the board on the Bantam Tools Desktop PCB Milling Machine, and soldering the components. This is a great tutorial for those new to milling printed circuit boards (PCBs) or for those who want practice soldering components to the board as a part of a larger assembly.

More info at Bantam Tools project page.

Arduino controlled Dual Mono AK4490 DAC (part 1)

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This article is the first of a series detailing the design and build process of an Arduino controlled Dual Mono AK4490 DAC by DimDim:

The design goal was to do a dual mono design so as to maximize SNR and channel separation. A 4-layer PCB design was chosen so as to have a very solid, low impedance ground plane as well as proper power and signal planes. The I2S, audio signals and power after the local LDO regulators are routed on the top layer, the 2 middle layers are ground and power planes, and the bottom layer serves to route I2C signals and some power lines.

See the full post here, Dimdim’s blog.