Sonicare toothbrush teardown: microcontroller, H bridge, and inductive charging


Ken Shirriff did a teardown of a Sonicare electric toothbrush:

The photos below show the top and bottom of the toothbrush internals. I expected to find a simple, low-cost mechanism, so I was surprised at how much complexity there was inside. The vibration mechanism (right) is built from multiple metal and plastic parts screwed together, requiring more expensive assembly than I expected. The circuit board is literally gold-plated and has a lot of components, even if it doesn’t quite reach Apple’s level of complexity. Overall, the toothbrush’s internal design is high quality (except, of course, for the fact that it quit working, as did an earlier one).

Sonicare toothbrush teardown: microcontroller, H bridge, and inductive charging – [Link]

LT3086 – 40V, 2.1A Low Dropout Adjustable Linear Regulator with Monitoring and Cable Drop Compensation


Graham Prophet  @ discuss about LT3086 LDO.

The 40V, 2.1A low dropout linear regulator (LDO) includes current monitoring with externally settable current limit and temperature monitoring with external control of thermal limit temperature. The device includes a programmable power-good status flag, cable drop compensation and easy paralleling. The current reference in the LT308x LDO family provides regulation, independent of output voltage.

The new 800V CoolMOS MOSFET from Infineon


Thomas Scherer @ shares the news about a CoolMOS Mosfet from Infineon.

The latest 800V CoolMOS P7 800V MOSFET from Infineon is based on their superjunction technology. The device is available in twelve classes of RDS(on) beginning with  0.28 Ω and in six package options. It is particularly suited to high voltage switching applications, flyback applications including adapter and charger, LED lighting, audio SMPS, AUX and industrial power.

The new 800V CoolMOS MOSFET from Infineon – [Link]

230V AC dimmer, mains isolated, using PIC12F629


This is a very simple mains isolated dimmer with a triac output (phase control). It uses timer0 to do the timing.

There is no user interface, the value of the triac ignition delay after a zero crossing is defined by setting the reload value of timer0 (Tmr0) in the software directly. This value can e.g. be derived from a user interface or sensor or some algorithm. In the example it is stepped trough a number of values sequentially.

230V AC dimmer, mains isolated, using PIC12F629 – [Link]

Short circuit tracer uses low power


shares his design idea on

This Design Idea presents a low power short circuit finder that capitalizes on the ear’s sensitivity to changes in frequency. The heart of the circuit is a voltage-to-frequency converter (based on Linear Tech’s AN45, Figure 13, by Jim Williams), which converts millivolt-level DC voltages to a wide range audio frequency output.

Short circuit tracer uses low power – [Link]

L293D Motor Direction Controller


baelza.bubba @ show us how to build a DC motor direction controller using L293D.

I designed this DC Motor Direction Controller so that I could give direction control to DC motors that I am building into mini tools (drill, lathe, table saw, solder smoke extractor, etc.). While, I don’t need direction control for all of the tools that I’m building, it IS necessary for some. Plus, who doesn’t want to spin their DC motor backwards?

L293D Motor Direction Controller – [Link]

Convert $2 LED Lamp to $50 Smart Lamp


taifur @ show us how to convert a simple LED lamp to a smart one that can be controlled using a smartphone.

A smart bulb is an internet or Bluetooth-capable LED light bulb that allows lighting to be customized, scheduled and controlled remotely. Smart bulbs are among the most immediately successful offerings in the growing category of home automation and Internet of Things (IoT) products. In today’s market many types of smart bulbs are available form price $10 to $100. But, can you think you can convert a low price led bulb to a smart bulb easily? Today I will show you how I converted a cheap Chinese led lamp to a Smart Lamp.

Convert $2 LED Lamp to $50 Smart Lamp – [Link]

Laser for sending music over a distance

Light is a very popular means of communication. Today, optical fiber communication is the backbone of telecommunication and internet. Light is guided through a fiber optic cable in such systems to achieve low-attenuation and high speed data transmission. Question is: Is it possible to use light for communication without a guiding medium? The answer is positive. Because of the highly collimated nature of the laser beam, it is feasible to use a laser output to transmit information without a guiding medium even in daylight, provided that the line of sight occurs between the sending and receiving units.

Armand & Victor from DIY Experiments Youtube channel illustrates a very simple example of modulating a laser diode output with an analog audio signal and sending it over a distance of more than 400 meters. The laser diode used in this project was of 250 mW capacity, which is ~ 100 times more powerful than a regular laser pointer. A single-transistor class-A amplifier circuit was used to amplify the audio input signal prior to use it for modulating the laser output light. A 1:25 turn ratio transformer is used as a coupling device between the audio and the laser module. The transformer is necessary to ensure only the AC variations (and blocks any DC component) in the audio signal will modulate the laser beam.

Circuit setup for modulating Laser with an audio signal

Circuit setup for modulating Laser with an audio signal

On the receiving end, the audio is reconstructed back by aiming the modulated laser beam at an array of four mini solar panels. The solar panel output voltage varies according to the signal variation contained in the laser and is directly fed to a high power (250W) guitar amplifier. The audio quality was quite remarkable for such a simple setup. Check out the following demo video of this project:


DIY USB 5V Solar Power Bank

Abdulgafur tipped us with his latest project, a 5V solar powered power bank. The circuit consists of two stages, the first stage is the battery charger stage based on MCP73831 and the second stage is the step up converter based on LT1302-5 which converts the battery voltage to 5V.

Solar energy is renewable, free, widely available and clean form of energy. It is considered as a serious source of energy for many years because of the vast amounts of energy that is made freely available, if harnessed by modern technology. Many people are familiar with so-called photovoltaic cells, or solar panels, found on things like spacecraft, rooftops, and handheld calculators. The cells are made of semiconductor materials like those found in computer chips. When sunlight hits the cells, it knocks electrons loose from their atoms. As the electrons flow through the cell, they generate electricity. In this project, we are building a power bank which harvests energy by using a solar panel.

DIY USB 5V Solar Power Bank – [Link]

LipSync – An Assistive Device For Smartphone Use

Smartphones and mobile devices are diving deeply in our lives and make a lot of things much easier than before. So, having a smartphone or a mobile device became one of life’s necessities for everybody. But unfortunately, there is still a big challenge for people with limited use of their arms to use and benefit from these devices.

A group of developers tried to help these people and increase their accessibility to the smartphones through “LipSync”. It is an Arduino-based assistive device which aims to increase the ability to use touchscreen devices through a mouth-operated joystick with sip and puff controls.


The developers team, as they mentioned in the project page, focused on creating a robust and easy to build device, designing a device housing which can be 3D printed, and making it flexible for a variety of wheelchairs.

LipSync is based on Arduino Micro, a microcontroller board based on the ATmega32U4 equipped with a Bluetooth module for connecting with the smartphone and send the appropriate instructions.

Arduino Micro - Image courtesy of
Arduino Micro – Image courtesy of

Two main sensors were used in this project. An Analog 2-axis Thumb Joystick used to manipulate a cursor on the device screen, and a Pressure Sensor to catch sip and puf controls and simulate the actions of “tap” and hitting the back button, respectively.

MPXV7002DPT1CT-ND Pressure Sensor - Image courtesy of Digi-Key
MPXV7002DPT1CT-ND Pressure Sensor – Image courtesy of Digi-Key


In addition to the main control functions, move the cursor, tap, and go back, this device can simulate additional secondary functions such as “tap and drag” and “long tap and drag”.

LipSync is an open source project. Schematics and PCB files are available here, but the 3D printer files and arduino code will be made public later.


To read more details about LipSync visit the project page on, where you can follow it and join the development team.