How To See Signals From Sensors On The UNO

For reference I'm trying to upload pictures from my iPhone, but the post errors out with a message saying it can't upload the pictures.

I'll try to post later from a laptop, but hopefully someone can chime in with a solution in the meantime.

You can use Serial Plotter

If the Uno doesn't see the signal from your "PCB board" how do you know that it's working?

And what is this PCB board? In my world PCB usually means Printed Circuit Board. Can you post a link to whatever you're talking about?


First is all I should note that just I changed my code to have the led always on (it's connected to ground and pin # 13 which is always HIGH) until the sensor is tapped, then it turns off (pin # 13 goes LOW) because this works better for my application.

I know the separate sensor reading PCB board is working because it's light changes from green to red when I tap on the Piezo disc attached directly to it, but the LED light attached to the UNO does not go out indicating the UNO did not recognize the signal from the PCB. Also, I have a separate computer that recognizes the signals coming from the PCB so that it is working is indisputable.

Unfortunately the serial monitor does not show that a signal was received because the UNO doesn't recognize the signal coming from the PCB. Thus the serial monitor shows all 0's for the signal strength (see pic)

I have other sensors that I hooked up to the UNO and they register the taps on the Arduino with the red light going off and the serial monitor displaying tap values.

Back to the drawing board.

Any other suggestions on how I can get the Arduino to recognize a signal from the PCB shown in my pics?

How about posting your code here so we can see what you're talking about.

And please post a link to the "PCB board" because I still have no idea what it is.


Here's the code:

int led = 13;
int vs =A0; // vibration sensor

void setup(){
pinMode(led, OUTPUT);
pinMode(vs, INPUT); 

void loop(){
long measurement =vibration();
if (measurement > 50)
  digitalWrite(led, LOW);
  digitalWrite(led, HIGH); 

long vibration(){
long measurement=pulseIn (vs, HIGH);  //wait for the pin to get HIGH and returns measurement
return measurement;

Here's two pics of the piezo sensor board. It picks up fainter signals from piezo discs when I tap them than the Arduino Uno board does which is why I'm using it.

Notice before I tap the piezo disc the light on the piezo sensor board is red and the red LED on the breadboard is lit:

After I tap the piezo disc the light on the piezo sensor board turns green, but the red LED on the breadboard stays lit and it should turn off briefly.

I can hook up the piezo disc directly to the UNO and tap it hard and the red LED on the UNO turns off briefly so I know I set up everything correctly; however the UNO is not sensitive enough to catch the fainter taps on the piezo disc and it cannot pick up the signal from the piezo sensor board.

What do you think I need to do to get the UNO to recognize the signal coming from the Piezo sensor board and to pick up fainter signals directly from the Piezo discs? Thank you.

Please learn how to post code and pictures here properly and fix your posting...

Done, thanks. Any idea how to get the Arduino to read the signal from the Piezo Sensor Board?

Some of my pictures disappeared. What could cause that?

All four of the pics I placed in my post yesterday show on my laptop, but two of the four pics don't show when I look at my post on my iphone. Not sure if it's an iphone issue or something further upstream. Regardless, my post is fixed. I look forward to any help you can offer.

I checked voltage across ground and signal and noticed it was low. I jiggled some wires and played with the potentiometer on the Piezo PCB and Presto now I measure proper voltage across ground and signal AND triggering the Piezo PCB also turns off the red LED.

Case closed.