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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 the hobbyists you don’t find any input protection, some argue that in most cases this is not needed, or don’t understand how it works. Let’s see how simple resistor can save the day. Lets see at simplified version of digital input of AVR microcontroller. We can see there that input uses CMOS logic where the transistor is switched by voltage. According to AVR datasheet, the gate control voltage should stay within -0.5V to VCC+0.5V range. If we power our device with a 5V supply, we need to make sure that the pin input voltage stays in the range -0.5 to 5.5V. When the input voltage source is taken from the same power supply, then we don’t have to worry much about it. But what if AVR is accepting digital signals from other sources like sensors, other devices that are powered with their power supplies. Can we be sure that voltage will always be within safe limits? This is why there are two clamping diodes (sometimes called ESD protection diodes) used. They…

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The Compact ATtiny Breadboard Headers

If you are willing to spend endless times prototyping with an AVR ATtiny, then you should make it 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 more comfortable. As you can see from the above figure, this little breadboard headers is very handy, where it occupies 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 pull-up resistor and reset switch; Blocking capacitors; Serial connection header. These ATtiny Breadboard headers not only small and compact, but it’s equipped with all the essential electronic components that you’re needed. Just plug them in your breadboard and connect your programmer with it! Voila, it works like magic.

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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 most significant problem in using IR light is that there many other sources of it like the sun, light bulbs, fire. To exclude other sources, the IR signal is modulated by some frequency. The 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 efficiently 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 a simple task to demodulate the signal; this is why particular IR receiver IC’s are produced. One of them is TSOP1736: This receiver simply removes 36KHz carrier signal and gives clean pulses that are used for device control. I won’t go too deep in how it works – you can find this information in datasheets. This module…

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