voltage on output pin when "LOW"

Using Arduino General Electronics
1

While troubleshooting some problems I noticed that my Arduini Uno shows a voltage even when the output pin is set to LOW.

I am feeding 12v to the vin pin for power. When I measured an output pin while on HIGH I get about 11.8v, when the pin is set to LOW I measure about 5.6v. If I feed it 5v then the output pin is 2.6

Why is that?

2

I am feeding 12v to the vin pin for power. When I measured an output pin while on HIGH I get about 11.8v

If that is really the case then your Arduino is on steroids and/or has mutated into something else. Which 2 points are you measuring between when you see this voltage and which Arduino board are you using ?

3

I am using the R3. Measuring voltage between ground and the output pin. There was nothing connected to the board when I measured the voltage and it is consistent.

Anyone want to buy an UNO on steroids? hehehe

4

12volt on the Vin (better use the DC jack) is pre onboard 5volt regulator.
The regulator makes 5volt for the whole board, so you should not see that voltage anywhere else anymore.
Output pins should switch between 0volt and 5volt (unloaded).
If your Arduino works, your meter is probably stuffed.
Leo..

5

Confirm exactly how you are making your measurement.

6

Hi,
What sort of 12V supply are you using?

Tom..... :slight_smile:

7

The voltage on an output pin depends on its load. The output FETs in the ATmega
chip have roughly 40 ohms Rds(on), so if you draw enough current (10's of mA) you'll
see significant voltage drop across the output FETs. This is one reason not to overload
them (20mA is plenty, enough to lose nearly a volt of output).

8

I have an old arduino Duemilanove and when I connected 12v to the external barrel jack, I noticed the onboard LED appearing brighter. I checked the arduino 5v pin and the voltage was 8v+. I then skipped using the external power jack and used a 7805 regulating chip directly connected to the 5v pin to externally power the arduino. The power auctioneering circuitry seems some what tuti-fruti. Using a multimeter, check the 5v pin voltage when USB powered, then again when externally powered with 12v.