Khaleel123 has posted an Instructable on how he built a solar-powered FM radio/mp3 player using some leftover wood flooring, salvaged pc speakers, four ni-cad rechargeable AA batteries, and inexpensive FM Radio/mp3 player module and solar panels that he bought on ebay. The FM radio module cost him less than $3 and is capable to play mp3 audio through an SD card or USB drive.
Solar-powered FM radio and mp3 player
Wiring connections between the radio module, speakers, solar cells and batteries
The one I used has an operating voltage range between 5-12 and it is 4 ohm stable @ 3 watts rms x2. So knowing this its safe to use the following combination of components for the power source. Four rechargeable AA batteries in series which can be charged up to 5.8 volts but in our case will only get as high as 5.3 volts. Along with two 6 volt solar cells in parallel with a diode that drops the voltage .7v the total output of the solar cells is 5.3 volts at 300 ma. The diode is necessary to protect the cells from the power stored in the battery. The speakers are 4 ohms @ 10 watts so those are exactly within the recommended range for this type of module. The module did not come with any wires or antenna soldered to it, but was clearly marked and easy to solder to. Also the batteries had to be soldered to each other, as long as you scuff up the ends they can be soldered easily too. I just soldered on a around a foot of wire for the antenna then coiled it and hot glued it down. Hot glue was also used to secure the solar cells, speakers, and battery just because it was quick and easy to do it that way.
Sam Miller, Sahil Gupta, and Mashrur Mohiuddin built a 64×64 RGB LED matrix audio visualizer as their final project for the ECE5760 Microcontroller Design course at Cornell. The visualizer responds to a musical input in real time with a graphic animation on the RGB panel using vertical bars, balls, and particle to enhance the user’s listening experience. The RGB visualizer runs off of an Altera DE2-115 FPGA, which handles all the controls and processing of data for the 64×64 LED Matrix as well as the beat detection and audio output.
Functional block diagram of RGB visualizer
Our system starts with a musical input from the 3.5mm line-in input from the FPGA. This analog input is fed through an ADC to digitize the signal at a sampling rate of 48kHz. This signal is fed back through a DAC to the line-out port into speakers in order to play the audio. After the ADC, the audio signal is separated into its frequency components through our FFT module. These frequency components are used in a beat detection algorithm to detect large changes in signal energy, which correspond to beats in the song. The bars mode of the visualizer uses the frequency components directly, while the ball and the particle mode only use the beat of the song. Each of these 3 modules uses their inputs to calculate the coordinates and corresponding colors of each LED in the matrix. The outputs of the modules are muxed and written to two buffers (since the matrix writes to two LEDs simultaneously). From here, another module reads the contents of the buffer, and drives the LED matrix via the GPIO pins on the FPGA.
This project is a modification of my previous Bluetooth-enabled LED matrix display project, which used 8×64 monochromatic LED matrix (total 512 LEDs) for displaying scrolling text message. The original project used Bluetooth for display data transfer from a smartphone, but this one now uses Wifi. The display message is sent through web browser to a ESP8266 module that is configured as a web-server. No Arduino or any other microcontroller is used. ESP8266 alone works as a WiFi server and drives the MAX7219-based LED matrices.
Wifi-enabled scrolling led matrix display
Yesterday, I built a very simple DIY solar-powered USB charger for my TP-link 10400mAh USB Power Bank. All I needed was a 6V/3.5W solar panel and the TD1410-based 5V buck converter module. I bought both of them on Aliexpress for less than $8.
Simplest DIY solar-powered USB charger
It was one of the easiest projects I built. All I needed to do was to connect the input of the 5V step-down buck converter to the output of the solar panel using two wires.
Connections between the 5V buck converter and solar panel
From TD1410 datasheet,
The TD1410 is a 380 KHz fixed frequency monolithic step down switch mode regulator with a built in internal Power MOSFET. It achieves 2A continuous output current over a wide input supply range with excellent load and line regulation. The device includes a voltage reference, oscillation circuit, error amplifier, internal PMOS and etc.
Easy Pulse mikro is our new educational pulse sensor in a mikroBus form factor. Like our previous Easy Pulse sensors (Easy Pulse and Easy Pulse Plugin), it is also based on the principle of transmittance photoplethysmography (PPG) applied to a fingertip. The sensor consists of a pair of IR LED and photodiode to detect the cardiovascular pulse signal from the fingertip. The output of the sensor is passed through a necessary instrumentation amplifier to derive a nice and clean analog PPG waveform. The analog output is routed to the AN pin of the mikroBus connector. In this article, I will describe how to use the Easy Pulse mikro sensor with Microchip’s latest MPLAB Xpress development board for uniform ADC sampling of the analog PPG signal and sending the samples to a PC for post digital processing in order to retrieve the heart-beat rate. Currently, you can buy this sensor from our Elecrow Store.
Easy Pulse mikro