OUTPUT not ouputting 5v

Using Arduino General Electronics
1

I am having issues getting a full 5v out of a OUTPUT, HIGH digital pin. When measuring with a multimeter I only get 2.8v. After soldering to the 5v (because the LCD covers it), I properly get 5v now. Are digital pins set as OUTPUT, HIGH not supposed to do 5v?

int HOT_WIRE = A8;
void setup()
{
// Initial setup
myGLCD.InitLCD();
myGLCD.clrScr();

//Make 8 hot for 5v
pinMode(HOT_WIRE, OUTPUT);
digitalWrite(HOT_WIRE, HIGH);
}

2

Which Arduino board are you using ?

3

Are digital pins set as OUTPUT, HIGH not supposed to do 5v?

No they are not.
According to the data sheet a logic HIGH can be anything above 4.2V.
Of course it depends on what it is connected to. A load greater than 20mA will reduce this.

4

I am using a Mega 2560.

When testing the voltages, the only items hooked up were an LCD/Touch shield (not the actual LCD though). I had the hot wire going to a breadboard and made my measurements off of that, nothing else was hooked up to the breadboard.

2.8 still seems low, but it does get the job done with my relays....

5

mginster:
I am having issues getting a full 5v out of a OUTPUT, HIGH digital pin. When measuring with a multimeter I only get 2.8v.

You'll only get 5V if you're not overloading the pin (ie. not trying to use it to power other devices).

If it's dropping down to 2.8V you're drawing too many amps and your pin is about to die.

6

Are you trying to power the LCD with the pin?

7

Nope, it is an unused pin from the LCD shield. Its just a pass through hole on the shield.

8

An unloaded pin that's set HIGH should be millivolts away from the 5V supply - its being pulled high by a FET
with an on resistance of around 50 to 100 ohms. If its reading 2.8V it suggests its either not set as an OUTPUT
(ruled out by the code snippet) or there is too heavy a load on it or the pin is burnt out.

9

mginster:
Nope, it is an unused pin from the LCD shield. Its just a pass through hole on the shield.

Either something is connected to it that you don't know about or it's damaged (from a previous overload).

Try removing the shield and test it again.

10