Video – LED Matrix

I’ll put a tutorial up for this if people are interested — there are no tutorials online for this kind of LED Matrix, the tutorial on the Arduino page does not work properly for most matrixes (also this has more software and thinking than the solar panel tutorial). On a side note, I’m selling the matrix for 3.5€ and I’m also selling an Arduino Uno for 20 €. I may also add some resistors as a gift.

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Solar Panel Direct Voltage Generator

Ever wondered why photovoltaic solar panels were so expensive? Me too. So I decided to try and build my own panel and I learned some things in the process.

Materials (unfortunately the company that made my cells and shipped has closed, but any quick search on google or ebay should get you quick results for the following):

-Sodering iron (pref. 100 W) – I assumed you have one, and some solder (you’ll burn through solder in this)

-Flux pen (mine looks like this):

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-0.5 V solar cells for 36 V maximum solar panel

-Frame (wood, steel, whatever)

-Tapping wire

I used also some meters of insulated copper wire to soder the terminal of the panel and make a long connection that can power stuff inside my house.

WARNING: These solar cells are fragile and should be handled carefully. I ordered a lot of them since they break easily. This is how they look:

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How-to:

Basically all you need to do is soder the tapping wire to the surface of the cells, using the flux pen (paint the white parts of the cell) and then put the tapping wire over than line and with the sodering iron press gently OVER the tapping wire and it will soder. Then turn the cell over and the cut the wire that is now protruding about the length of another cell. Put a new cell under the tapping wire and with a blob of solder, solder the tapping wire to the BACK of the new cell. Now the first cell and the new cell are in series. Now you just have to turn both over and keep doing this.

The front of the cells act as the negative terminal(anode) and the back as the cathode.

As you finish your setup, it should look like this (this example output a 9V voltage with a current of about 200 mA):

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Now you just have to encase the panel (I would advice a frame much like a painting with a glass or plastic cover), glue the solar cells to the wood panel and you have a 9V generator. Now what uses can this have?

Uses:

In series with a diode (I used a schottky diode much like this one: http://www.nxp.com/products/diodes/general_purpose_schottky_diodes_250_ma/ ,if you add more cells than mine be sure to use you amperemeter to check the current and get an adequate diode) the diode acts as a reverse polarity protection, which means you can use your solar panel to charge batteries without worrying about the batteries frying your solar panel.

I built an iPhone/iPod charger. The wire looks like this:

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The data wires of the charger need to be connected with a 10k resistor (green and white wires, this is used to bypass some software details with the devices), the ground is the black one and VCC is red and this takes in about 5V to charge. These small multi strand wires are fragile and you’ll need patience to take the insulation off and soder them. Also be sure to hook up two potentiometers in series with your solar panel input (after hooking the aforementioned diode in series) to act as a voltage regulator. Alternatively you can use two resistors as a voltage divider for a fixed voltage, in this case 5 V. Since my setup outputs 9V, I used 2 potentiometers in series and regulated it until I got 5V, and your iPod/iPhone will light up and charge!

A simple Arduino Alarm Clock

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This post is about a simple project that took me some hours to do: a simple alarm clock with an LCD display, reset button and buttons to set the alarm, plus the speaker obviously.

Materials:

-LCD 2×16 (with 16-pin interface and compatible with the Hitachi HD44780 driver)

-4 pushbuttons

– 4 10k resistors, a 1k resistor, a 220 resistor

-A potentiometer (I used a 10k mono one)

-An Arduino board

-A speaker (I used a 6 ohm one, but anything in the 5-10 ohm should be fine) mine was taken from an old radio

Schematic:

It should look more or less like this:

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The melody that is played is the Mario theme. The potentiometer is used to regulate LCD contrast, the three buttons are to set the alarm time and the other button is to activate or deactivate the alarm. The speaker needs the 1 k resistor as a pull down (which is the same function of the 220 resistor for the LCD).

The Arduino Code:

In this Code all the pins are according to what is shown above. Time.h and a library called pitches.h were used. You can download Time.h here: http://playground.arduino.cc/Code/Time and pitches.h is here: https://code.google.com/p/arduino/source/browse/trunk/build/shared/examples/Digital/toneMultiple/pitches.h?r=943

There isn’t much else, this is a simple project, I’ll leave you with a links to the code in case you want it (thanks to http://www.linuxcircle.com/2013/03/31/playing-mario-bros-tune-with-arduino-and-piezo-buzzer/ who had the trouble to actually write the melody). Also if you don’t like Super Mario, you can also play the Star Wars theme as your alarm clock: http://pastebin.com/E7GHLW4h, just create an array called melody and durations with the equivalent of what that guys plays in a loop!):

https://github.com/pedro-abreu/Code/blob/Arduino/alarm_clockmelody.ino

https://github.com/pedro-abreu/Code/blob/Arduino/pitches.h

Of course you could take this to a whole new level and make a more professional alarm which could play your favourite songs using an MP3 shield. Also you could get it all nice enclosed and sodered to a PCB, so people wouldn’t have to see the wiring.

Disclaimer: You are free to use the code, I do not own pitches.h, or any of the melody codes or any of the libraries.