How to Connect Arduino Uno to Android via Bluetooth

Arduino is one of the most popular microcontroller-based electronics prototyping platforms available in the market. The area of applications of Arduino is huge ranging from simple LED driving circuits to complex internet-based weather monitoring circuits.

One of the in-demand concepts is communication between the Arduino board and Android-based smartphone or tablet. Even though Arduino can be configured to perform many complicated operations, it would be more beneficial if those operations are controlled using an Android phone.

In order to allow communication between Arduino and Android-based smartphone, we need to use Bluetooth communication. Almost all Android-based devices have built-in Bluetooth communication module. Hence, we need to use an external Bluetooth Module for Arduino board.

Arduino Android Communication Bluetooth

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555 Timer PWM Audio Amplifier

The ubiquitous 555 timer IC handles audio signals in its own pulse-width modulation (PWM) way. Here, the 555 IC works in astable mode. The switching frequency can be varied from 65 kHz to 188 kHz. Selection of PWM frequency depends on the amplitude of the input signal as well as the load impedance. By adjusting VR1, you can ensure comfortable listening with low audio distortion.
In pulse-width modulation, the carrier frequency’s pulse width varies as a function of the amplitude of the input audio signal. Feedback capacitor C2 ensures faithful reproduction of the audio signal. An output L-C filter is the common approach for a reasonable rejection of the carrier frequencies. For simplicity, it is omitted here. Moreover, the speakers cannot respond to the high-frequency signal. They respond to the average DC level modulated with the audio signal that we feed in from the input. Of course, the audio quality is not as good as that of a professional system, but it would be definitely an amazing experience to listen audio through a 555 chip with room-filling volume.

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IC 555 Timer Tester

This simple and easy-to-use gadget not only tests the IC 555 timer in all its basic configurations but also tests the functionality of each pin of the timer. Once a timer is declared fit by this gadget, it will function satisfactorily in whatever mode or configuration you may try it.
The two basic configurations in which a timer IC 555 can be used are the astable and the monostable modes of operation.
When the DPDT switch (S2) is in position 1-1, the timer under test automatically gets wired as a monostable multivibrator. In this case, the monoshot can be triggered by the microswitch (S1). The debouncing circuit constituted by the two NAND gates of IC1 (N1 and N2) produces a clean rectangular pulse when the microswitch is pressed. Resistor R3, capacitor C1 and diode D1 ensure that the trigger terminal of timer IC 555 (pin 2 is the trigger terminal) gets the desired positive-to-ground trigger pulse. This differentiator circuit also ensures that the width of the trigger pulse is less than the expected monoshot output pulse.

The monoshot output pulse width is a function of the series combination of resistor R8 and potentiometer

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World’s smallest transistor is just 1 nanometer wide

For more than a decade, engineers have been eyeing the finish line in the race to shrink the size of components in integrated circuits. They knew that the laws of physics had set a 5-nanometer threshold on the size of transistor gates among conventional semiconductors, about one-quarter the size of high-end 20-nanometer-gate transistors now on the market.
Some laws are made to be broken, or at least challenged.

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