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.

4zerobox, industrial module by italian startup with ESP32 heart

With great pleasure, I want to introduce you today the project of an Italian startup4zerobox.

4zerobox is a module, DIN-rail mountable (9 modules), designed to complement or replace a classic PLC in industrial automation applications. As the name suggests, the features of 4zerobox can help companies interested in implementing Industry 4.0 solutions.

4zerobox-001

4zerobox is a project by the italian startup TOI (Things On Internet), born within the University of Pisa. Currently a Kickstarter campaign is active to found the production.

The “heart” of 4zerobox – and that’s the reason why I’m writing about it in this blog – is the esp32 chip. Thanks to the partnership with Zerinth (I’ll blog about it more widely in a future article) you can program the module using the Python language and leverage already available high-level libraries for the different I/O and communication interfaces.

In details, 4zerobox offers:

  • wifi, ethernet, BLE, serial (RS-232 e RS-485) and CAN connectivity
  • 4 analog input channels configurable as 4-20mA (single-ended o differential) or 0-10V
  • 4 analog channels for RTD or contact/proximity sensors
  • 2 opto-isolated digital inputs
  • sink digital output
  • 3 non-invasive current sensor channels
  • 2 NO/NC relays
  • a MicroSD slot
  • the possibility to connect and manage a LiPo battery
  • 2 mikroBUS sockets

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Very interesting is the possibility to connect, using the MikroBUS bus, several external devices. MikroBUS is indeed a standard interface (defined by MikroElektronica) and soon adopted by many manufacturers: there are already more than 300 different boards that offer the MikroBUS interface and can therefore directly connected to 4zerobox.

In conclusion 4zerobox can allow companies to respond easily to integration, IoT, cloud… requirements that are relevant to the Industry 4.0 trend.

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.

ESP32, the new Wemos Lolin32 LITE

On my blog I’ve already posted about the development board Wemos designed for the esp32 chip and that, on many webstores, you can find boards that “copy” the Lolin32 name but are instead clones of other opensource projects.

Few weeks ago Wemos published on its official site and make available on its store on Aliexpress a new revision of the board, now named Lolin32 LITE. Thanks to my friend Mauro Alfieri I was able to test a copy:

lolin-lite-001 lolin-lite-002

The main features of the board are the same as the old one:

  • esp32 chip
  • PH-2 (2mm) connector for a LiPo 1S battery
  • charging circuit via USB (max 500mA)

At a visual comparison it is immediately noticeable that the LITE is slightly smaller than the previous, being 5mm long compared to the 5.8mm of the Lolin32:

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The smaller length forced Wemos to reduce the number of available pins (19 instead of 26) and to abandon the use of the ESP-WROOM-32 module soldering the esp32 chip and flash memory directly onto the PCB, which also accomodates the antenna.

Speaking of components, for the LITE version Wemos decided to change the chip used to perform the USB-serial conversion and adopted the CH340G IC (which I also used in this project). Finally, the card in my possession uses the latest revision of the esp32 chip (labeled 302017):

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esp32, chip revisions

In the same way that software programs have bugs, even hardware chips may have problems due to errors in their design. Producers resolve these errors by producing a new chip revision and keeping updated a document with the known bugs for the different revisions and the possible workarounds.

Espressif manufactured two different revisions of the esp32 chip to date:

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If you want to know the revision of a chip, you can use the espefuse.py utility included in the esptool package:

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specify the serial port (-p) your board is connected to and the summary command.

Observing the values of CHIP_VERSION and CHIP_PACKAGE you can determine the revision of the chip, for example my Lolin32 board has a chip with revision 0:

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while the new Lolin32 LITE a chip with revision 1:

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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.