Switch Mode Power Supply (SMPS) Topologies (part I)


Microchip’s application note describes the basics of different SMPS topologies:

The industry drive toward smaller, lighter and more efficient electronics has led to the development of the Switch Mode Power Supply (SMPS). There are several topologies commonly used to implement SMPS. This application note, which is the first of a two-part series, explains the basics of different SMPS topologies. Applications of different topologies and their pros and cons are also discussed in detail. This application note will guide the user to select an appropriate topology for a given application, while providing useful information regarding selection of electrical and electronic components for a given SMPS design.

Switch Mode Power Supply (SMPS) Topologies (part I) – [Link]

Replacement LED driver for AN6877


Dilshan Jayakody has designed a board to replace AN6877 base LED drivers using discreet transistors. He writes:

AN6877 is linear AF level meter IC produced by Panasonic and it is commonly found on many audio equipment. This chip is no longer manufactured by Panasonic and finding replacement chip for AN6877 is also quiet difficult.
The circuit described in this article is design to replace AN6877 base LED drivers and it is based on commonly available components. This replacement LED driver is design using 10, MMBT3904/2N3904 transistors and it can easily modify to get necessary number of outputs.

Replacement LED driver for AN6877 – [Link]


Raspberry Pi Tutorial: Create your own GUI with TkInter and Python

educ8s.tv shows us how to build a graphical user interface on Raspberry Pi using TkInter and Python.

Having a Graphical User Interface (GUI) on a touch screen makes controlling your Raspberry Pi so much easier. With Python and TkInter one can develop his own GUI very easily. In this video we are going to see how to achieve that.

The project we are building today is very simple but very useful. As you can see I am using an application that I have developed to turn on or off the LED simply by touching an on screen button. In this video we are going to see how to develop an application like this, and as you are going to find out, it is extremely easy!
The hardware setup of today’s project is this. I am using a Raspberry Pi A+ but you can use any Raspberry Pi you want that has 40 GPIO pins. I am also using a 5 Inch touch display from Waveshare. I have prepared a detailed tutorial on that display few weeks ago, you can check it out. If you don’t have a touch display, the Graphical User Interface we are developing will work fine with a mouse as well.

Raspberry Pi Tutorial: Create your own GUI with TkInter and Python – [Link]

Tutorial on the Theory, Design and Characterization of a CMOS Transimpedance Amplifier

In this episode, Shahriar and Shayan discuss the design and characterization of a deceptively simple CMOS inverter-based transimpedance amplifier. The the large and small signal behavior of the CMOS inverter is discussed and measured using the Keithley 2450 and 2460 source meters. The transient response is also measured using a Keysight MSO-S series oscilloscope.

The small signal gain of the circuit is calculated from small signal parameters which are extracted directly by measuring the devices I/V characteristics. The NMOS/PMOS devices used are from an ADL1105 quad-discrete transistor IC. Through the use of a shunt-shunt feedback, the CMOS amplifiers is converted to a transimpedance amplifier which is capable of amplifying the current from a photo-detector diode by a gain of 30kV/A. The feedback theory is used to calculate the gain of the amplifier. The slides for this tutorial can be downloaded from The Signal Path website.

Tutorial on the Theory, Design and Characterization of a CMOS Transimpedance Amplifier – [Link]

LT3091 – –36V, 1.5A Negative Linear Regulator with Programmable Current Limit


Linear Technology Corporation announces the LT3091, the latest addition to our LDO+ family, a 1.5 A low dropout negative linear regulator featuring low noise, rail-to-rail operation, precision programmable current limit and a bidirectional output current monitor. The device is cable-drop compensation capable, easily paralleled for higher current or circuit board heat spreading, and configurable as a 3-terminal floating regulator. The LT3091’s input voltage range is –1.5 V to –36 V. A single resistor programs the adjustable rail-to-rail output voltage from 0 V to –32 V and dropout voltage is only 300 mV (typical at full load).

LT3091 – –36V, 1.5A Negative Linear Regulator with Programmable Current Limit – [Link]

Dual Motor L298 H-Bridge Motor Control


Dual Motor L298 H-Bridge Control project can control two DC motors connected to it. The circuit has been designed around popular dual H-Bridge L298 from ST. This circuit has current sense resistors for both H-bridges to provide voltage which enables this board to use in stepper motor applications.


  • Motor supply : 7 to 46 VDC
  • Control Logic Supply : Standard TTL logic level
  • Output DC drive to motor : up to 2 A each
  • Current Sense Output available
  • Enable and direction control pins available
  • External diode bridge for protection
  • Heat-sink for IC
  • Power-On LED indicator
  • Screw terminal connector for easy input supply (PWR) / output (Motor) connection
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 61 mm x 63 mm

Dual Motor L298 H-Bridge Motor Control – [Link]

Arduino MKR1000 – 32-bit board with WiFi


The MKR1000 development board from Arduino provides a simple way to add wireless connectivity to IoT battery-powered projects.

Arduino MKR1000 is based on the Atmel ATSAMW25 SoC (System on Chip), that is part of the SmartConnect family of Atmel Wireless devices, specifically designed for IoT projects and devices.

The ATSAMW25 is composed of three main blocks:
• SAMD21 Cortex-M0+ 32bit low power ARM MCU
• WINC1500 low power 2.4GHz IEEE® 802.11 b/g/n Wi-Fi
• ECC508 CryptoAuthentication
The ATSAMW25 includes also a single 1×1 stream PCB Antenna.

Arduino MKR1000 – 32-bit board with WiFi – [Link]

ATiny does 170×240 VGA with 8 Colors


AtomicZombie @ avrfreaks.net used an ATtiny85 ATMEL microcontroller to produce a 170×240 VGA signal and also send audio along with video.

The original plan was to just bit bang some mono VGA and do up a Pong or Tetris game, but things went MUCH MUCH further than I ever thought possible, so over the next few weeks I will detail this fun project here. I call it The QUARK-85 VGA DEMO System.

So what can one do with an ATTINY-85 and no other external components, an 8 pin package that leaves ONLY 4 IO lines after you feed it a clock??

How about 4 color rock solid VGA with stereo sound!!!

ATiny does 170×240 VGA with 8 Colors – [Link]


Raspberry Pi Zero Information Display


Frederick @ frederickvandenbosch.be has build an Internet connected OLED display using Raspberry Pi Zero module.

After last week’s Pi Zero mod, I thought I’d try a slightly more useful project. Using an Adafruit OLED display, two push buttons, a wifi dongle and a Pi Zero, I made an internet connected information display. The information could be anything: time and date, weather, social media status, etc … The two push buttons are used to cycle through the data and trigger certain actions.

Raspberry Pi Zero Information Display – [Link]

DIY I2C LCD Display


sspence @ instructables.com shows how to interface a character LCD using I2C and only two IO pins.

The typical parallel LCD used with an Arduino (16×2 or 20×4) has 16 pins. Only 6 I/O pins are required on the Arduino, but what if you could get that down to two I/O pins, and still have those pins available for other devices?

The I2C interface is on pins A4 and A5 of the Arduino. These are addressable, and are therefore shareable with other I2C devices that have different addresses.

DIY I2C LCD Display – [Link]