DIY USB power bank from laptop battery


DIY USB power bank made from an old laptop battery @ DoItYourselfGadgets:

A situation many can relate to: an empty smartphone battery and no outlet around! That’s exactly why I recycled an old laptop battery into an USB power bank.
This article will show you the basic powerbank circuit consisting of Lithium cell charging circuit, boost converter and toggle switch as well as my improved version with self activating boost converter and LED status indicator and homemade housing.

DIY USB power bank from laptop battery – [Link]

Reverse Engineering a Simple Four Function Calculator: die decap


Electronupdate did a teardown and analysis of a cheap four function calculator:

It’s such an amazingly old looking die.
Even with 400x magnification it would not be too hard to reverse engineer back to a schematic! This must be a very old design indeed. When one thinks of high-tech it’s always the new-new thing… however some designs can be very old indeed and still be in production.

Reverse Engineering a Simple Four Function Calculator: die decap – [Link]

Whoa Board: Dream With Touch Sensing EL Wire, Panels, Paint


The Whoa Board makes things glow. It also makes glow-y things sense touch. It’s an open prototyping platform for wearable electronics!

Turn any EL (Electro-Luminescient) material into a touch sensor with no additional hardware. It’s an open prototyping platform for wearable electronics! Open source and Arduino IDE compatible.

Whoa Board: Dream With Touch Sensing EL Wire, Panels, Paint – [Link]

ElbSupply – Linear Bench Power Supply With Constant Current and Voltage Modes

A lot of power supply designs are here and there on the Internet, but not all of them have constant current and voltage modes. You can read the following Q&A in electronics.stackexchange to learn what constant current and voltage modes mean.

Elia over built a linear bench power supply with the following features:

  • Output voltage range: 0 – 15V.
  • Output current range: 0 – 3A.
  • Constant voltage with current limiting and constant current modes.
  • LCD interface.


ElbSupply Inside


LT3083 the adjustable 3A low dropout regulator from Linear technology is used to provide the output voltage.
To reduce the power dissipation in the linear regulator, supply voltage is not connected directly with the adjustable LDO regulator input. Elia added a stage to reduce the input voltage of LT3083 to (Vout+2) using a buck converter. This Buck converter, TI TPS54331, is configured to follow the output voltage of the adjustable regulator plus 2 volts as an output voltage of the buck converter.

ATmega8 MCU is used to drive the 16*2 LCD, read values from the rotary switch STEC12E08, read user buttons and to produce the reference PWM signals for voltage and current.

These PWM signals are converted to analog value, the way used to convert the PWM signal to an analog value proportional with PWM is by using “resistor, a capacitor and an opamp”.
LM334, an adjustable current source, used in the output voltage of LT3083. Elia said in a log, it is needed for stable operation, the LT3083 needs a minimum load current of 1mA.

Design Files and Source Code


ElbSupply is an Open-source hardware project. You can download the source files from the GitHub repository.

PCB and schematic are designed using KiCAD and source code was written in C with state machine code methodology.
[Project Page]

DIY USB to TTL Converter


ams31 @ show us how to build a DIY USB to TTL Converter using CH340G IC.

Lots of USB to TTL modules are available in the market based on various chips like PL2303, FT232, CP2102 and CH340g. I have decided to use CH340g IC. Low costing clones of Arduino UNO & Arduino Nano also uses CH340g IC. And this IC is now easily available in India. Reasons for not using other converter IC’s.

DIY USB to TTL Converter – [Link]

25V, 600 mA buck-boost DC/DC with 1.6 µA Iq


LTC3130 and LTC3130-1 are synchronous current mode buck-boost converters that deliver up to 600 mA of continuous output current from a wide variety of input sources, including single- or multiple-cell batteries as well as solar panels and supercapacitors. By Graham Prophet @

Their 2.4V to 25V input voltage range and 1V to 25V output range (LTC3130 is adjustable) provide a regulated output with inputs above, below or equal to the output. User selectable Burst Mode operation lowers quiescent current to 1.6 µA (1.2 µA at no load) improving light load efficiency and extending battery run time. The proprietary buck-boost topology incorporated in the LTC3130/-1 provides low noise, jitter-free switching through all operating modes, for RF and precision analogue applications that are sensitive to power supply noise.

Drone The Quadcopter


Sameer Gupta tipped us with his latest project, a DIY Quadcopter:

“Drone The Quadcopter” is an featured UAV. I design my project with F450 arm in X-mode design. The full operation takes place via a Flysky FSCT6 remote control unit which gives a better operating range of 800 Meter to 1.2KM.

Drone The Quadcopter – [Link]

Everything You Need To Know About Bluetooth beacons in A White Paper

Image courtesy of Google

Bluetooth 4.0 introduced the Bluetooth low energy (BLE), which is a version of Bluetooth protocol designed for devices with power constraints like battery powered sensors. Bluetooth low energy beacons are BLE (Bluetooth Low Energy) enabled devices, they repeatedly broadcast radio signals to nearby smartphones, containing a small amount of data.
Mobile apps can listen to the signals being broadcast and trigger an action after analyzing beacon’s information.

Beacons are used for proximity-aware applications like positioning and navigation indoors like anti-lost tracking tags, another application is for location based advertisements.

There is no official Bluetooth Special Interest Group (SIG) beacon standard, so beacons have pseudo-standards. For example, iBeacon standard is used by Apple and Eddystone is used for Google.

Apple iBeacon Advertising Packet
Apple iBeacon Advertising Packet

As you can see in the above image, there is one byte (power) value indicating the iBeacon’s calibrated output power in dBm measured at a distance of 1 meter.
So Beacons can be used to calculate the proximity distance between the beacon and the receiver of beacon’s information. This calculation relies on a comparison of a Received Signal Strength Indicator (RSSI) to a beacon’s transmit (Tx) power to approximate the distance to the beacon.
The calculated distance can’t be very accurate, since RF signals fade unpredictably according to real-world environmental factors like walls. Future versions of BLE will solve this by using Angle-of-Arrival (AoA) and Angle-of-Departure (AoD) which allow a multi-antenna Bluetooth device to accurately determine the spatial location of another Bluetooth device.

Beacons typically use non-connectable advertising, providing all of useful information in the advertising packet itself. So the radio can be shut off immediately after advertising hence this will save power.

A white paper from Silicon Labs covers a lot of informations about Beacons. The paper examines beacon applications, provides a short description of how BLE work, contains further description of iBeacon and Eddystone standards and highlights SoC solutions for BLE from Silicon Labs such as BLE112 and BLE113 which can have fully standalone applications through a simple scripting language called BGScript developed by Silicon Labs.

BGScript iBeacon example code for the BGM111 Bluetooth low energy module
BGScript iBeacon example code for the BGM111 Bluetooth low energy module


Developing Beacons with Bluetooth Low Energy (BLE) Technology

Beacons: Everything you need to know

Reading “Getting Started with Bluetooth Low Energy by Kevin Townsend, Carles Cufí, Akiba, and Robert Davidson (O’Reilly)” is advisable for anyone like to know more about who BLE works which is a corner stone to understand how beacons work.

How to compare your circuit requirements to active-filter approximations


By Bonnie C. Baker (WEBENCH® Senior Applications Engineer):

Numerous filter approximations, such as Butterworth, Bessel, and Chebyshev, are available in popular filter software applications; however, it can be time consuming to select the right option for your system. So how do you focus in on what type of filter you need in your circuit? This article defines the differences between Bessel, Butterworth, Chebyshev, Linear Phase, and traditional Gaussian low-pass filters. A typical Butterworth low-pass filter is shown in Figure 1.

How to compare your circuit requirements to active-filter approximations – [Link]

RFM69 WIFI Gateway


The RFM69GW is a RFM69 to MQTT gateway that uses the ubiquitous ESP8266 chip. There are two or three similar projects that I’m aware of but I’ve put together some hardware and firmware features that make it different. by Xose Pérez:

  • I’m using Felix Rusu’s RFM69_ATC library so it supports Monteino nodes with Auto Transmission Control feature enabled for an adaptative transmission power: longer battery life & less radio pollution
  • RFM69CW footprint, compatible with RFM12B and hence with old Monteinos or even with JeeNodes (untested)
  • Web configurable map between node messages and MQTT topics.
  • EEPROM persistent configuration using the awesome Embedis library by PatternAgents

RFM69 WIFI Gateway – [Link]