When I connect the Vcc and GND of my circuit to the 5v and GND in my Arduino, it is powered off and stops working. What is the reason and how shall I fix it?

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Reference: Serial to Parallel Shifting-Out with a 74HC595

  • 1
    It sounds like you're short-circuiting the power supply. Can you show a diagram of the circuit you connected? Commented Sep 11, 2014 at 13:11
  • @PeterR.Bloomfield : Ok sure Commented Sep 11, 2014 at 13:17
  • That diagram is from the shift register tutorial at Arduino.cc, so I think it's safe to say it's OK. You've most likely made a mistake in the wiring. You'll need to check all your connections to ensure nothing is hooked-up wrongly. Commented Sep 11, 2014 at 14:02
  • @PeterR.Bloomfield : how does short circuit happens to a power-supply any way ? Commented Sep 11, 2014 at 15:34
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    @AbdelrahmanTarief: Maybe the series resistor value before the LED is too low and therefor the LED is drawing too much current, more than the AVR can source? Commented Dec 10, 2014 at 23:58

1 Answer 1


Note: if you are changing something have the power off.

The first thing to try is unplug the IC. If it powers up after the IC is removed it is Possibly the IC is bad; However measure the Voltages on the proto board where the IC is inserted, be sure Pin 16 is +5V when referenced to pin 8. Check the data sheet for the correct pinout, I do not know what IC you are using. If the voltage is correct it is pointing more to a bad IC.

The final check for the IC is to insert the IC and remove the ground lead to the LEDs. If the system comes up then the problem is not enough power to drive the LEDs as is. If it does not come up replace the IC. Even a momentary reverse voltage or a ESD (Electro Static Discharge) incident will damage the IC, we know is is going to fail, we do not know when.

Be sure your resistors are at least 300 Ohm or higher, with that resistance the LEDs when all on will draw a total of 80mA. If you want to do the calculations try this link: "http://www.onlineconversion.com/ohms_law.htm".

If you want to check the LEDs, remove the IC and connect +5V one at a time to the wire that goes to the resistor from the IC. Good Luck, Gil

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