A couple weeks ago I received some sample products from Dorji Applied Technologies, a china-based company that make varieties of RF and sensor modules. One of the products I received was their latest DSTH01 sensor module that carries Silicon Labs’ Si7005 digital relative humidity and temperature sensor on board. Things I liked about it are it is inexpensive (available on Tindie for only $6), compact, and most importantly it supports I2C host interface for communication.
DSTH01 module with Si7005 sensor onboard
Pin diagrams of DSTH01 sensor module
A person suffered from high-frequency hearing loss has reduced ability to hear high frequency sounds. This has direct impact on his/her ability to understand speech because most of the commonly used consonants like s, h, and f, are spoken with high pitches. Other examples of high frequency sound are a woman’s or a child’s voice. Studies have shown that by simply amplifying the high frequency notes through a hearing aid does not help too much. Latest hearing aid technologies use a technique called frequency lowering where the high frequency notes are captured, processed, and delivered to the person in lower note frequencies, which are much easier to hear. I found this nice instructable that describes a DIY frequency shifting hearing aid project as a simple solution to the above problem. The project uses low pass and band-pass filters to isolate low and high frequencies in the original audio signal. The so-isolated high frequencies are shifted down by passing through a modulator with a 2KHz carrier signal. The down-converted frequencies are then summed up with the isolated low frequencies to regenerate the original sound.
Hearing aid for high-frequency hearing loss
A variable bench power supply is an important equipment in electronics lab for conducting experiments, prototytyping, and testing. This cool-looking DIY bench power supply provides fixed 5V and 12V outputs along with a separate variable DC output ranging from 1.2 to 25V. The on-board LCD display shows instantaneous output voltage, current, and power drawn, which are very important parameters during prototyping of a new project. The power supply can also be connected to a PC through RS232 port to visualize and monitor these parameters graphically on screen. The project uses Atmega8 microcontroller for measuring and displaying the electrical output parameters.
DIY variable power supply
Here is a nice instructable on building a Bluetooth-controlled dual channel relay switch using Atmega328 MCU and a cheap HC-06 Bluetooth module. You can use this device to control various appliances and devices in your home by sending commands through any Bluetooth device.
Bluetooth-controlled relay switch
The easiest way of producing a sound using an Arduino board is by bit-banging its I/O pin driving a buzzer or speaker. However, if you want to go beyond simple beeps and synthesis complex and more interesting sounds, you need a better understanding of the Arduino hardware as well as the theory behind wave synthesis. Here’s a wonderful tutorial from Makezine that describes the fundamental concept of synthesizing waveform and how to manipulate it in real time.
Arduino sound synthesis