Electronic – arduino – Fluctuations in 7805 Regulator IC Output

7805arduinodecoupling-capacitor

I built an Arduino using ATmega328 on perfboard. To power it, I used an 8V adopter with a 7805 IC. But the ATmega328 IC started to reset randomly. After some efforts I figured out that the problem was not using decoupling capacitors. So I used a 100uF and 10uF electrolytic capacitor at the input and output respectively. Though it helped to solve the problem but the IC still sometimes gets reset. I tried to look online but they do not tell anything except using the decoupling capacitors. I would be grateful if someone could explain:

  1. What other measures can I take to prevent this fluctuation
  2. Which capacitors are best for this purpose of AC filtering
  3. What specific values are good and is there any method to
    calculate them based on the load requirement

I hope this would not turn out to be a duplicate question!

Best Answer

You're probably seeing short transient dropouts. Use 0.1uF ceramic caps across the power and ground pins of all your ICs, and keep the leads/traces as short as possible.

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