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Power sources for AVR

Power sources for AVR microcontrollers are a crucial part. Every circuit has to be powered from some source like a battery or AC adapter 110V/220V. Using batteries is a more convenient way to power the microcontroller projects as the circuits are simpler and constructed devices become portable.

There are many types of batteries in shapes and sizes or capacities. So when choosing a battery you should consider many factors:

  1. Capacity is a critical parameter measured in mA/h. This parameter defines how long your microcontroller project will be working before recharging or replacing batteries. The rule is simple – as bigger battery capacity, as long your circuit will be working. Still, on the other hand, your project may become more expensive or even heavier because of bigger batteries.
  2. The second parameter is the battery Voltage. If the battery’s voltage is too small for your circuit, you’ll have to connect several batteries in series.
  3. Another is the Expiry date. You don’t want your battery energy leakage or become obsolete because of this.
  4. Working temperature. If your project is working in more extreme temperatures – heat or cold, you should consider this.
  5. And the last parameter would be chape, size, and weight. If your project is flying model control, you will look for a light, small and capacious battery.

If you decide to power your Atmega project from the AC line, you need to transform your line voltage to near 5V and stabilize it using a voltage regulator like 7805.

This regulator outputs stabilized 5V up to 1A. If you don need more than 100mA, you should choose the 78L05 chip.

In some cases, if your project is connected to a computer port and the circuit requires a small current, you can power the circuit directly from the port. For instance, usually, the circuit connects to LPT using 3 wires, and other lines as outputs can serve as a power source by writing to these lines value “1”.

A similar situation is with RS232. Just there, you need to put a voltage regulator or Zener diode as voltages are not in the 0 – 5V range. You should connect more than 10uF capacitors in parallel to the Zener diode.

Just remember that regardless of the power source you use, you should connect like 0.01 to 0.1uF capacitor between the power line and ground to filter noises. This applies to any digital IC in the circuit.

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