How to prevent Arduino's digital pins goes high on bootup?

Question

I have done my project finally :) , but i noticed that the arduino board on startup it's some digital pins goes high for a bit time 1 seconds or little more! and this causes problem in my project because i'm using it in starting dc motor. I forgot to mention that i have 2 relays connected with arduino and they are triggered on arduino startup or with resetting it, then my code works perfectly. I tried doing pull up resistor and pull down resistor but it seems same situation. Also tried (INPUT_PULLUP) and no result.

Any suggestion please?

Do you initialize the pins at the beginning of setup with `digitalWrite(pin, LOW)`? — George, Aug 18 '15 at 14:37
Yes, it solved by reverse all output values from HIGH to LOW because the relay works in active low — Mahdi Alzubaidi, Aug 18 '15 at 16:05

score 1 · Answer 1 · answered Nov 28 '19 at 12:29

I had the same problem when booting the arduino/connecting to a power source. Only using digitalWrite(pin, LOW) in void setup() did not work for me. Every pin needs to be connected to a physical pull-down 10kOhm resistor in parallel to whatever you're controlling.

How to prevent Arduino's digital pins goes high on bootup?

1 Answers1