Monthly Archives: March 2019

App note: Miniature, precision negative reference requires no precision resistors

via Dangerous Prototypes

an_maxim_AN824

App note from Maxim Integrated creating voltage negative reference from charge-pump inverter plus positive voltage reference combo. Link here (PDF)

This application note discusses how to build a negative voltage reference without using external resistors or a negative supply by simply combining a simple charge-pump inverter and a positive output voltage reference.

App note: Simple test method for estimating the stability of linear regulators

via Dangerous Prototypes

an_rohm_linear_reg_stability_test

Tips from ROHM Semiconductor to estimate the stability of linear regulator using simple step response method. Link here (PDF)

Low drop-out (LDO) regulators developed back in the age when large-capacitance multi-layer ceramic capacitors (hereinafter, MLCCs) were uncommon cause a phase delay, leading to oscillation when connected to a low-ESR capacitor like an MLCC. Often, MLCCs are used to save board space and prolong the lives of electronic components. A resistor placed in series in the circuit increases apparent ESR and establishes a phase lead that enable the use of an MLCC as an output capacitor. Phase margin measurement is practical on an LDO having variable output voltage, since its feedback loop is outwardly exposed. However, on a fixed output voltage LDO, the phase margin cannot be measured because of its closed loop circuit.

App note: Understanding the safety certification of digital isolators

via Dangerous Prototypes

Understanding the safety certification of digital isolators

This application note summarizes the international safety standards and certifications that apply to digital isolators. Link here

Digital isolators provide signal isolation and the level shifting required for the correct operation of many circuits. Equally important, they insulate the user from electric shock. With basic human safety considerations so pertinent here, these isolators must undergo extensive testing and certification to ensure user safety. This article briefly summarizes the international safety standards and certifications that apply to digital isolators. An example exercise using the MAX1493x family shows how an IC designer must use a data sheet and the standard’s specification tables to determine which digital isolator will be optimal for an application.

Op amp on the Moon: Reverse-engineering a hybrid op amp module

via Dangerous Prototypes

bg001-w200

Ken Shirriff has written an article on reverse engineering a hybrid op amp module:

I recently obtained a mysterious electronic component in a metal can, flatter and slightly larger than a typical integrated circuit.1 After opening it up and reverse engineering the circuit, I determined that this was an op amp built for NASA in the 1960s using hybrid technology. It turns out that the development of this component ties connected several important people in the history of semiconductors, and one of these op amps is on the Moon.

See the full post on his blog.

Gorgeous Nixie clock features three types of tubes

via Arduino Blog

Nixie tubes require electricity in the range of 180VDC, making them challenging to work with. Maker Christine Thompson, however, decided to take Nixie art to a new level, creating a clock with three different types of tubes! 

This clock, or perhaps more accurately “info display,” shows the time and date with six IN-18 tubes mounted on the top. In the front, six IN-12A and two IN-15A tubes are also available to show time, date, pressure, temperature, and humidity.

A pair of Arduino Mega boards are used to control this retro-inspired contraption, along with an array of wiring, perf board, and other components, stuffed inside a very nice wooden enclosure. 

This is my first Nixie styled clock I have constructed. The clock actually consists of two clocks, the first being a 6 x IN-18 tube clock which is mounted on the clock’s top and displays both time and date. The second clock, this time based on 6 x IN-12A and 2 x IN-15A nixie tubes displays at the front of the clock and can display, time, date, pressure (with units and trend), temperature (both Centigrade and Fahrenheit) and, humidity (with units and trend). The time and date are separated with two single neon lamp-based separators, while only one of these lamps is displayed, to represent a decimal point, when the pressure, humidity or temperature is displayed. Both these clocks use “Direct/Static Drive” to power the displays and are based on two Arduino Mega 2560 boards. The fourteen tubes are driven by 12V to 170V DC to DC boost power supplies and 14 x K155 IC chips. The clock also powers two sets of Neon Lamps which switch off while the clock goes through its cathode cleaning cycle which happens at 19, 39 and 55 minutes past each hour. This cathode cleaning cycle consists of all six tubes displaying the digits 0 through 9 in sequence 6 times.

In addition the clock will sound a chime at 15, 30, 45 and 60 minutes. At the 60 minute chime the hour chime is also sounded. The chimes are standard MP3 files using a simple MP3 player controlled by the Arduino mega. In order to save on tube life all tubes are switched off automatically when the light level in the room dims to a predefined level, this is achieved using a LRD resistor located at the back of the clock. To help dissipate any heat build up both Arduino Mega ICs have copper heat fins attached and a 5V fan draws air out of the clock, cool air entering through a hole in the bottom plate.

The user can adjust the time, date, chimes, and chimes volume using one of two 16×2 LCD displays, located at the back of the clock. The BME280 temperature, humidity, and pressure sensor is mounted on the back of the clock so as to not be affected by the clock’s internal temperature.

A demo is seen in the video below, while more info and Arduino code can be found in the project’s write-up.

A brilliant clock made out of 128 LED-lit ping pong balls

via Arduino Blog

Ping pong balls have long been known as excellent LED diffusers, but few have taken this technique as far as Thomas Jensma. His colorful clock features 128 LEDs, arranged in an alternating pattern, and housed in a stretched-out hexagonal wood frame. 

For control, the device uses an Arduino Nano, along with a RTC module for accurate timekeeping. Demos of the clock can be seen below, cycling through numbers and testing out the FastLED library.

Code for the build is available in Jensma’s write-up. This also includes tips on using table tennis balls as diffusers, as well as how to create an orderly array out of these spheres—useful in a wide range of projects.