Build your own HF balun

Miguel, EA4EOZ, posted this great DIY tutorial on building your own balun:

A balun is a MUST for dipoles or similar antennas when they are feed with coaxial cables. Many hams connect the center conductor of the coaxial cable to one side of the dipole, and the shield to the other. Wrong!
From the RF point of view, the shield can be modeled as two conductors, the internal shield (the real shield, this is, ground) and the external shield, who is really far to be ground. In this way, your dipole has 3 arms, the two from the dipole and the coaxial cable shield (external face).

See the full post on EA4EOZ blog.

App note: Charging capacitive loads with eFuse

App note from ON Semiconductors on how eFuse manage to cope up with large capacitive loads. Link here (PDF)

The eFuse protection devices are used for limiting the system load current in the events of overload or short circuit. Many applications employ On Semiconductor eFuses at the power input stage of the system between the main power input connector and DC−DC converters or power regulators. The systems utilizing eFuse protection devices at the power input stage may represent inductive, resistive, capacitive or mixed types of loads.
One of the common load characteristics for various systems is large capacitive load, typically starting from 1mF all the way to few hundred milli Farads. The challenge presented by such load to an overcurrent protection system is large inrush current due to the excessive capacitance which will cause the device to shut down during startup.

App note: Tuning linear redrivers

App note from ON Semiconductors about linear redrivers setting. Linear redrivers are used in systems in order to improve high speed signal integrity in systems transmitting digital data. Link here (PDF)

Linear redrivers are used in many applications that transmit data at high speeds. They can be found on computer motherboards, gaming consoles, graphics cards, cables, and any other environment that transmits digital data. More specific examples of common applications using linear redrivers include USB, DisplayPort, HDMI, PCIe, and SATA ports.

App note: Tutorial selecting the optimum voltage reference

App note from Maxim Integrated guiding you when selecting voltage references. Link here

What could be more basic than a voltage reference – a simple, constant reference voltage? As with all design topics, there are tradeoffs. This article discusses the different types of voltage references, their key specifications, and the design tradeoffs, including accuracy, temperature-independence, current drive capability, power dissipation, stability, noise, and cost.

App note: Voltage Reference Application and Design Note

App note from Renesas on the basics of voltage reference. Link here (PDF)

Conceptually, a voltage reference is a very simple device with only one purpose in its life. Quite simply, the purpose of a voltage reference is to generate an exact output voltage no matter what happens with respect to its operating voltage, load current, temperature changes or the passage of time.

DIY OpenDPS power supply

Evan’s DIY OpenDPS power supply:

Years ago I heard about the OpenDPS project to give open source firmware to cheap and available chinese power supplies. These aren’t strictly whole power supplies, they are configurable CC and CV buck converters. That means that it needs a stable DC source to back it to be used as a bench power supply. Perhaps you may not want to do this if you intend to use the DPS as a battery charger run from a solar supply or something, but most people I see want to use them for bench supplies so that requires an existing DC supply. Today I finally finished mine.

App note: How to monitor state-of-charge in small batteries with tiny, ultra-low-power comparators

App note from Maxim Integrated about low current and voltage battery monitors. Link here

Many of today’s portable consumer electronic devices are powered by small button or coin-cell batteries. Users, of course, expect long battery life and reliable charge-level information. However, it can be quite challenging to efficiently monitor the health and state-of-charge (SOC) of these batteries without significantly affecting said SOC. In this application note, learn how simple, low-power monitoring circuits for small batteries can address this challenge.

App note: Effects of different resistor tolerances in a differential ADC for THD performance

App note from Maxim Integrated demonstrating the effects of different resistor tolerances on the analog front end of ADC’s performance. Link here

This application note explains how the different tolerances of the same value resistors at the inputs can alter the THD performance of the fully differential ADC. The cost of resistors changes significantly with each lower increment in tolerance

(Not a) triple tube geiger counter

Doz’ triple tube geiger counter project, that is available on GitHub:

So, two little switching power supplies, one for the DOB-50 and CTC-5 as they have similar operating voltages, and one higher voltage one for the DOB-80, a simple op-amp comparator to output the pulses to an Arduino to process and display the results.
The power supplies are controlled using two MC3406AD’s, driving an IRF840. I’ll just refer to the component numbers on the top supply, the bottom one is almost identical. The back EMF from the inductor L2 is rectified by a UF4007. There’s a feed back loop, R14,15 & 16 and the pot is used to adjust the HT..

More details on Doz’ blog.

Check out the video after the break.

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App note: LV5980MC step-down switching regulator

Single chip high efficiency step-down converter, app note from ON Semiconductors. Link here (PDF)

The LV5980MC is a fixed 370 kHz, high−output−current, Non−synchronous PWM converter that integrates a low−resistance, high−side MOSFET and a Customer Chosen, External Diode for the rectification. The LV5980MC utilizes externally compensated current mode control to provide good transient response, ease of implementation, and excellent loop stability. It regulates input voltages from 4.5 V to 23 V down to an output voltage as low as 1.235 V and is able to supply up to 3.0 A of load current. The LV5980MC includes Power Save Feature to enhance efficiency during Light Load. In low consumption mode, the device show operating current of 63 A from VIN by shutting down unnecessary circuits.

App note: Designing a PSR Quasi-Resonant adaptor driven by the NCP1362

ON Semiconductor’s app note featuring 12V 12W adaptor design using NCP1362 primary side regulation controller with valley lockout that hold its switching frequency at light loads. Link here (PDF)

Quasi−square wave resonant converters also known as Quasi−Resonant (QR) converters are widely used in the adaptor market. They help designing flyback Switched−Mode Power Supply (SMPS) with a reduced Electro−Magnetic Interference (EMI) signature and improved efficiency.

A new, fully modular CNC controller

bdring’s new universal CNC controller for Grbl_ESP32 , that is available on Github:

The blog post details a new CNC controller I designed. I have probably designed 40-50 different controllers over the years, but this one has me really excited. My past controllers were generally application specific. My recent controllers have all been for the Grbl_ESP32 firmware. The I/O on the ESP32 is very flexible, but somewhat limited in pin count. There have always been enough pins to control the machine, but not enough to make a general purpose CNC controller that can target any machine.

Project details at buildlog.net.

Check out the video after the break.

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The Hayes Chronograph, a remake for 2020

smbakeryt built his own Hayes Chronograph:

I’ve always wanted a Hayes Chronograph, but have never been able to acquire one, so I finally broke down and just made my own. The Hayes Chronograph was a compliment to Hayes line of smart modems, and implemented a real time clock for computers that didn’t have a built-in clock. They were popular in the early 1980s, and became less popular as computers began to either come with clocks built in, or add-on boards with clocks became popular. My “remake” keeps the theme of having a Vacuum Fluorescent Display (VFD), but switches to a GPS as a source of time synchronization. A raspberry pi is used as control — this thing could be used as an NTP server!. My design retains the DB25 for communication with the host computer, and attempts to replicate the original Hayes protocol.

See the full post at smbaker.com.

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μSim: PICmicro instruction simulator

Dilshan has published a new build:

μSim is a lightweight PIC™ CPU and ALU simulator. This simulator supports the PICmicro mid-range instruction set and designed to work on both PC and Arduino platforms.
Compare with most of the other emulators, μSim does not provide all MCU features and peripherals. This simulator design as a minimalistic system, and based on the requirements, it can extend with additional peripherals and features.

See the full post on Dilshan blog.

App note: FT90X ethernet LED control

App note from FTDI/Bridgetek demonstrating LED control over Ethernet. Link here (PDF)

In an increasingly connected world, more and more devices are going online. To enable online connectivity typically requires an MCU with Ethernet or Wi-Fi capabilities. To demonstrate the principle, this Application Note describes an implementation of a web server which allows for control of 2 WS2812 serial addressable LEDs. A web server is implemented on an FT90X device which when connected to a Local Area Network (LAN) allows a web browser to control the LEDs on an MM900EVxA board from a graphical web page.

100 MHz third overtone crystal oscillator

100 MHz third overtone crystal oscillator @ DIYfan:

Couple of years ago I purchased from a local store 100 MHz crystal resonator and tried several times to make a working schematic on breadboard using standard circuits I found on the internet. It never worked good enough, usually oscillating at 33.3 MHz instead of 100 MHz. Finally, I found that the crystal is third overtone type.

Chaac weather station

An update on Chaac weather station project we covered previously:

With this latest redesign, I made a few more changes. First of all, I decided I would no longer be afraid of LoRa and put in a LoRa radio module. This will, with the right firmware, allow for standalone operation using LoRaWAN and The Things Network. It will also allow for much longer range, with its lower 900MHz frequency, with some slightly higher power consumption. I can continue using it with my Raspberry Pi point-to-point setup as well.

More details at alvarop.com. Project files are available on GitHub.

Check out the video after the break.

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