Currently I am using a dip Atmega328p-pu with a breadboard built circuit. The problem is when i am supplying the circuit from Arduino Uno's 5V it is working perfectly fine, but it's not working when I supply it from power supply. When I mean not working, it has the typical blink code in it and it works perfectly fine with uno's 5v, but it keeps resetting or freezing in one part of code -the led just lights instead of blinking-

The circuit has 10k resistor in first pin, 16 mhz crystal, 2x22 pf capacitors near it and all power connections are also connected

Thank you

  • \$\begingroup\$ You make no mention of decoupling capacitors, you really want a 100 nF to 1 uF cap between Vdd and ground, right on top of the ATmega. It might work without one but it won't be reliable or tolerant of interference, especially with longish wires to the 5 V supply. Do you have a pull-up resistor between the ATmega /RESET pin and Vdd? If not, the chip might reset itself from any noise or not work at all. What are you using as input for the regulator? If you really want help, post a schematic and/or a picture of the setup. \$\endgroup\$
    – jms
    Sep 23, 2016 at 9:21

1 Answer 1


You should first measure the output of the power supply. It looks like a brown-out reset issue. (Would like to comment instead of posting reply but my rep. isn't enough yet)

  • \$\begingroup\$ But I also powered it with using a regulator circuit with 7805 and capacitors with 12V. It still had the problem. It seemed more stable But i still had the reset \$\endgroup\$
    – Hallo Welt
    Sep 23, 2016 at 8:39
  • \$\begingroup\$ Make sure you applied +5VDC to both reset pin with pullup resistor and VDD pin. Also, don't forget to place 100nF decoupling caps near the MCU. \$\endgroup\$ Sep 23, 2016 at 9:25

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