3x4 Analog Keyboard for Microcontroller

This is a simple analog keyboard, hundreds of possible aplications, all you need is a ADC port in your controller, and some patience for get the right values for each button. Better the resistors you use, more precise the circuit will work and you can make one with hundreds of buttons if is needed.

Here is the PCB layout. (500dpi)

Click to Enlarge

And here's the solder mask and silk screen. (500dpi)

4 Channel Relay Module

this is a little PCB i made yesterday, it is a simple relay control module for micro-controllers, in this PCB i put together 4 channels, but the design accepts much more.

Here is the schematic:

Click to enlarge!

Here is the copper side printable image. (300dpi)

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• Technical Explanation:

1. This board was initially designed for 4x 5v Relays but it is pretty flexible, its blocks are well defined(Resistor, Led, Transistor, Diode, Relay), so you can add or remove how much relay blocks you want.
2. You may replace the leds for a jumper if you do not need them.
3. If you want to use relays with any other pull-up voltage, all you have to do is change the supply. Make sure you have connected the controller's GND as well.
4. The resistors values are not critical, for my prototype i used 470R but can be high as 2K2.
5. The transistors can be any smal signal npn like 2n2222, bc548, 2n3904 etc.

Click to download Eagle Files.

Hello World!

Hello guys, you will find here some interesting things about eletronics development and open source hardware, the plan is share with you people some open source hardware projects i found and some i've designed myself. There's no much to say, so come back latter for cool stuff. Thanks geeks!