“Cigarette Pack”- 14MHz SSB QRP Micro-Transceiver

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Peter Rachow (DK7IH) built a 14MHz SSB QRP Micro-transceiver into a cigarette packet size case:

This article describes the “Cigarette Pack” SSB QRP transceiver” for 14MHz that I first had mentioned some months before. Recently, when taking it from the shelf, the transceiver dropped to the floor and was severely damaged. This lead to serious defects in the front panel area, the main frame, the cabinet and so on. The interior parts were, luckily, not affected by the crash. So, I had to revise the whole radio, make a new front panel and cabinet, ply the frame straightly (as far as possible) and so on. This is the full description of the rig now to complete the files here. The good news: The radio is fine again and fully operational!  And the even better news: I still have not started smoking!

See the full post on Amateur Radio Engineering Projects blog.

App note: Core independent voltage window signal detection using a single comparator

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Presenting the usage of Core independent paripheral of PICs in this app note from Microchip. Link here (PDF)

It is possible to find out whether a measured signal is below or above a certain value/reference using a single comparator. But, what if the desired interval is between two values, the undervoltage and overvoltage protection?

The most convenient and fastest solution is to use two comparators and two references. The results are analyzed to decide which of the three intervals houses the measured signal. Using an Analog-to-Digital Converter (ADC) and core post-processing will yield the same result, but the process is slower and dependent on core availability.

App note: Power supply rejection ratio of low dropout voltage regulators

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Here’s an app note about PSRR of LDO from Microchip. Link here (PDF)

The Power Supply Rejection Ratio is the ability of a device, such as a Low Dropout Voltage regulator, to reject the various perturbations that can be found in its input supply rail by providing a greatly attenuated signal at the output. Generally, the main source of the perturbation will be the output ripple of the DC/DC converters that typically power LDOs.

High PSRR LDOs are recommended for powering line ripple sensitive devices such as: RF applications, ADCs/DACs, FPGAs, MPUs, and audio applications.

One important clarification must be made: PSRR is NOT the same with output noise. PSRR is a measure of rejection. It shows what the part will output based on the given input.

A development board for an STM32G081 MCU

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Andy Brown designed and built an STM32G081 development board:

I’ve been an avid user of ST’s F0 series ever since it was launched. The 48MHz Cortex M0 is almost always the perfect MCU for every project that I tend to build and it’s so easy to program and debug that, for me, it’s the default answer to ‘which MCU should I use for this project?’ So when I noticed that ST had launched a ‘G0’ range I just had to have a closer look.

See the detailed writeup and download the Gerber files on Andy’s Workshop.

Check out the video after the break. Continue reading “A development board for an STM32G081 MCU”

Build an ESP8266 web server – Code and schematics (NodeMCU)

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A detailed instructions of how to build an ESP8266 Web Server using NodeMCU firmware:

This tutorial is a step-by-step guide that shows how to build a standalone ESP8266 Web Server that controls two outputs (two LEDs). This ESP8266 NodeMCU Web Server is mobile responsive and it can be accessed with any device with a browser in your local network.

Via Random Nerd Tutorials.

Check out the video after the break. Continue reading “Build an ESP8266 web server – Code and schematics (NodeMCU)”

Simple DataFlash board

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David Johnson writes:

This is a small board that plugs into one of the headers on an Arduino Uno or other board to provide 4Mbytes of non-volatile storage
It works with either 5V or 3.3V boards, and is based on the low-cost 4Mbyte Winbond W25Q32FVSIG DataFlash chip. It is ideal for applications such as data logging, playing audio samples, and storing text.
I also describe a simple DataFlash library to interface to the board.

More details on Technoblogy.

App note: Comparison of LED circuits

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Another application note from OSRAM on different LED circuit design failure mode. Link here (PDF)

In recent years, Light Emitting Diodes (LEDs) have become a viable alternative to conventional light sources. The overriding advantages long life, high efficiency, small size and short reaction time have lead to the displacement, in ever increasing numbers, of incandescent bulbs. One of the markets where this change has become most evident is Automotive, where LEDs are used now not only for backlighting dashboards and switches, but also for exterior illumination in Center High Mounted Stop Lights (CHMSL), Rear Combination Lamps (RCL), turn signals and puddle lighting.

Despite the long life and low failure rates of LEDs, cars can be found, on occasion, with failed LEDs in their CHMSL. Most often this is due to a flawed circuit design wherein the LEDs were allowed to be overdriven. It is with that supposition in mind that this application note is written: to identify, characterize and comment on LED behavior and failure modes in serial and matrix circuits.

App note: Dimming LEDs with respect to grouping current

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App note from OSRAM describing the behaviour of LEDs in respect to brightness by varying the current and to suggest solutions for avoiding negative influence for the application. Link here (PDF)

In the design of a driving circuit for LEDs, the dimming behaviour is an important topic to fulfill the end customer requirements. The behaviour of the LEDs in respect to brightness is investigated by varying the current and solutions for avoiding negative influence for the application are suggested.

Building a bluetooth DAC with Raspberry Pi Zero W

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Sami Pietikainen has written an article detailing the build of his Bluetooth DAC using Raspberry Pi Zero W:

My car comes with a built-in Bluetooth hands-free but unfortunately it does not support audio streaming. Luckily there is an AUX input available which uses a regular 3,5 mm jack. Perfect opportunity for a DIY project. I built the Bluetooth DAC using Raspberry Pi Zero W and a DAC hat. This post depicts the details of this project.

See the full post on Page Fault Blog.

A DIY SMD pick and place tool for electronics assembly

Here’s a DIY vacuum pick-up tool for SMD components:

This video describes a DIY Vacuum Pick-up tool for picking and placing parts from an SMD component tape. The basic design for this tool involves using a vacuum pump and a solenoid to control the vacuum to a handpiece under control of a foot pedal.

Via SDG Electronics.

Looking inside a 1970s PROM chip that stores data in microscopic fuses

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Ken Shirriff did teardown of a 1970s PROM chip:

The MMI 5300 was a memory chip from the early 1970s, storing 1024 bits in tiny fuses.1 Unlike regular RAM chips, this was a PROM (Programmable Read-Only Memory); you programmed it once by blowing fuses and then it held that data permanently.

See the full post on his blog.

#FreePCB via Twitter to 2 random RTs

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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:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter 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.

Programmable seven segment LED tester

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A Seven segment LED tester project from Arduino Enigma:

Here is the finished Seven Segment Tester. All of the available Arduino Nano pins, except for analog input pins A6,A7 and Serial Port pins D0 and D1 are connected. This leaves us with 18 pins to bring to the 3M Zero Insertion Force (ZIF) socket. Any display up to 9 pin DIP can be tested.
Here are some pictures of the device testing a 16 segment display, a 7 segment display and a 3 digit 7 segment display. The common cathode and common anode versions are programmed as test patterns.
Once the Arduino is programmed, the device can work standalone using a 9v battery.

More details on Arduino Enigma Machine Simulator blog.

Check out the video after the break. Continue reading “Programmable seven segment LED tester”

63 dB step attenuator

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DuWayne published a new build:

While I was working on the power meter function for the latest version of the SNA, I used several fixed attenuators for checking linearity and calibration. It would be a lot easier if I had a variable step attenuator. I have several digital controlled attenuator modules that I bought one eBay a while ago, and I guess it is time to use some of them. There are several models available. The ones I plan on using are the simplest with only 6 control pins for a total attenuation of 31.5 dB in .5 dB steps. I am going to connect two in series with the control lines paralleled for a total of 63 dB in 1 dB steps.

See the full post on his blog.

App note: Passive entry door system with proximity sensor

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A full implementation of a keyless entry from Microchip. Link here (PDF)

The door access systems have evolved from simple physical keys to more sophisticated keyless entry systems. Now, we have a system that automatically unlocks the door when user carrying an access key approaches the door handle. As it does not require any user action this system is referred to as Passive Entry

App note: Low Power POE Flyback Converter

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App note from Microchip about their MIC2145 boost switching regulator to do POE Flayback conversion. Link here (PDF)

The MIC2145 skip mode controller is used to implement a flyback converter that is intended for use in nonisolated, low power, POE applications. The circuit has a nominal 48V input and supports the POE voltage range of 36V to 57V. The output voltage is 2.5V at 350mA.

Open source hardware ESP32-ADF

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Here’s an open source hardware development board for Espressif audio development framework, the ESP32-ADF, from Olimex:

With ESP32-WROOM-B module with 8MB RAM and 4MB of Flash, two microphones, two 3W speakers, codec, amplifier, Lipo charger, USB with programming, Audio 3.5mm jack, ESP32-ADF board offers everything you need to start playing with Espressif Audio Development Framework.

Check out the video after the break. Continue reading “Open source hardware ESP32-ADF”

DC40 receiver

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Michael LeBlanc has a nice write-up on building a direct conversion radio receiver:

In the late winter of 2018-19, I decided to build a receiver that would provide a performance improvement to the regen I built a couple of years ago. I wanted the radio to receive AM and SSB signals between 160m and 20m (1.8-14.5 MHz).

Via Intellectual Curiosity.

Check out the video after the break. Continue reading “DC40 receiver”