Using current limiting resistors on AVR I/O pins

Today I want to talk about protecting digital Inputs of AVR or any other microcontroller from over-voltages. When you look at majority microcontroller circuits found on internet shared by hobbyists you don’t find any input protection. Some argue that in most cases this is not needed, or simply don’t understand how it works. Lets see how simple resistor can save a day. Lets see at simplified version of digital input of AVR microcontroller. We can see there that input uses CMOS logic where transistor is switched by voltage. According to AVR datasheet, gate control voltage should stay within -0.5V to VCC+0.5V range. If we power our device with 5V supply, we need to make sure that pin input voltage stays in range -0.5 to 5.5V. When input voltage source is taken from same power supply, then we don’t have to worry much about it. But what if AVR is accepting…

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The Compact ATtiny Breadboard Headers

If you have to spending endless times to start prototyping with an AVR ATtiny, then you can make it becoming easier. Yep, all you need to do is build the headers that can carry the 8 and 20 pin chips, where it can be plugged directly into breadboards. Technically, these controller boards are building to provide a quick start for projects with 8 and 20 pin AVR microcontrollers, such as ATtiny13, ATtiny45 and ATtiny2313. Since they didn’t include any fancy stuff, and they keep it as simple as possible. By using this cute yet compact ATtiny breadboard headers, the Arduino projects becoming much easier. As you can see from the above figure, this little breadboard headers is very handy, where it occupy only one more row on each side as a controller would need. This breadboard headers already included the following components: 6 pin ISP header; 8 MHz resonator; Reset…

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IR remote control signal receiver using AVR microcontroller

IR remote control is a device you can find everywhere where you can find TV, VCR or home theatre. Why not to use one of them for controlling your own devices like light, air conditioning etc. As we know remote control devices uses IR light. This is invisible light about 950nm wavelength. One biggest problem in using IR light is that there many other sources of it like sun, light bulbs, fire. In order to exclude other sources, IR signal is modulated by some frequency. Receiver has to be tuned for this frequency. Mostly remote controls transmit IR signal using 36kHz frequency signals. Transmitting and coding is one part which can be done more easily than receiving and decoding. Decoding is usually performed by using microcontrollers. Firs of all receiver has to get rid of 36kHz carrier frequency. This is not simple task to demodulate signal, this is why special…

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