Closed Circuit Within Arduino Board

Development Boards Arduino
1

I am working with a Lilypad Ardiuno USB, and am building a circuit consisting of three buttons in parallel connected to one analog pin.

I currently have the Arduino disconnected from the circuit and have loaded the “Button” sketch.

When I touch the nominated “buttonPin” (tried for various values) the circuit becomes closed, and the

onboard LED turns on.

Is this a short circuit? Or is there something I can do to fix it?

For assistance, here’s is the steps I took to get to this point:

I have successfully completed the “Blink” and “Button” example sketches, on the A2 pin.

By inserting resistors in the appropriate locations, I am looking to identify each button while connected to the single A2 pin.

After inserting the resistors I performed two tasks which may have caused the unusual behaviour;

I connected LEDs to the 9, 10, 11 pins, but could not get them to work with the “Blink” sketch, so disconnected.

Then connected an LED to the A5 pin. (no resistors were used with the LEDs)

2

Your title describes the situation well; your finger made a closed, not short, circuit thus pulling the pin high. If you had the pull-down resistor connected then I doubt it would have worked.

PS- don’t connect LEDs w/o resistors to the output pins. That’s a good way to damage the pin.

3

Thank you for your prompt response!

The circuit should not have been closed as there is no circuit connected**, and is interfering with the button circuit when it is connected.

I have also now noticed that the charge LED is flickering rapidly, but cannot determine what is drawing power.

** I thought I had to be touching ground as well to actually create a circuit, which I was not doing.

4

Your body will pick up electrical signals from overhead lights and nearby wiring, and will inject these into circuitry.There does not have to be an obvious physical connect to “ground” as there is a capacitive one.

5

You are “in the circuit” but weakly via capacitive coupling. Akin to the touchscreen of a phone. But adding a pull -down or -up resistor to the input pin should overwhelm that weak coupling. So I ask what do mean, what are you seeing when you say …

and is interfering with the button circuit when it is connected.