Is my Arduino Nano - Relay pin has not enough power?

Hi everybody,

Brand new noob in DIY world here. I did some research and investigations on my problem and I think I understand what's going on, but I'd like a confirmation (which I can't find precisely in other subjects).

So here is the thing.

I developed a small project using an Arduino Nano, a motion sensor, a Led Strip and a Relay.
The concept is simple : when we detect a motion, we switch on the relay, which gives power to the Led strip, and turn the leds on. And voila !

The relay is a 5V one.
The Led Strip supports 5V (it's a WS2812B). Not sure if they support more.
Therefore, mostly because of my choice of Led strip, I use a DC of 5V/2A.

My relay is powered directly by the wall DC (5V/2A). My Leds are powered by the same DC.
While developing the project, the Arduino Nano was powered by my computer.
I command the relay through D12 with a 1K resistor.

Until this, everything was working fine.

Now I wanted to move my project to the next step : get rid of the USB power from the PC, and power the Arduino Nano through the 5V / VIN pins.

1st. Not entirely sure if I'm doing things right here. I tried both pins. Since my DC is 5V I think (if I understood well) using the 5V is fine. I saw that VIN use 7 - 12V. So does using a 5V here means it doesn't have enough power?

Anyway...
So I power my Arduino Nano through the wall 5V/2A DC... The same that powers my Led Strip and Relay (and motion sensor).

In my setup() method, I wait for a few seconds, then switch OFF (LOW) the relay. (Yeah I realized that by default the relay is ON, not sure if that's normal too).

My problem =>
That works perfectly through USB. But since I got rid of the USB and power my Arduino through the wall power supply, switch OFF the relay doesn't work.

So I investigated a bit and read several posts on this forum. I followed some things here and there and here are my data:

  • The Arduino Nano doesn't seem broken. I can still upload my code on it.
  • My multimeter says that on D12, on my 1K resistor, the voltage is 2V when it's switch ON.

I have the feeling it's suppose to be 5V (didn't checked through the USB since I soldered...). Am I right?

If yes, does it just mean I need a 7-12V DC instead of 5, plug it to the VIN pin and voila?

If no, any idea of what I'm doing wrong?

Also, if the Arduino really needs a 7V DC, what about my Led strip that seems to use 5V and not more (disclaimer: not sure of this fact again...) ? Does it means I need 2 different power supply? (I hope no haha).

Thank you in advance.
I think I'm near to find the right answer but for once, even with everything I read, I prefer asking to be sure.

You’ll need at least 7v at the VIN pin, the circuit on the NANO goes through a small 5v regulator. I would suggest 9 volts or less. But, like you mentioned, the 5v for your relay card will need another regulator.

If you want to use your 5v supply, connect it directly to the 5V pin and then also connect that to the relay board.

Sir Michael

Hi,

Thanks for your reply.

I'm a bit confuse by this statement :

If you want to use your 5v supply, connect it directly to the 5V pin and then also connect that to the relay board.

Do you mean that I need a 7V supply connected to the VIN pin, then connect the 5V pin of the NANO to the Relay?

I'm still not sure of why I have this issue too.
From what I read in the documentation, a HIGH signal on the pin D12 is suppose to deliver 3.5V.
Right now, I have only 2V. For this, I understand that I need more power.
But why sending the signal LOW doesn't work, since the LOW signal is supposed to send 0V ?

Thanks

veler2:
So I power my Arduino Nano through the wall 5V/2A DC... The same that powers my Led Strip and Relay (and motion sensor).

In my setup() method, I wait for a few seconds, then switch OFF (LOW) the relay. (Yeah I realized that by default the relay is ON, not sure if that's normal too).

My problem =>
That works perfectly through USB. But since I got rid of the USB and power my Arduino through the wall power supply, switch OFF the relay doesn't work.

If you want to power a nano from a 5v supply then it must be connected to the 5v pin.

I presume you have a common GND between the nano and the relay.

...R

Is your relay stand alone or part of a module? Post a wiring diagram.

Hi everyone,

Thank you all for your answers.

I fixed my issue.

I'm still not sure of why, but I really had trouble to control the relay with the regular IN/OUT port.

My fix is a kind of cheat actually.
I plugged the GND of the Relay to the common GND of my project.
I plugged the IN of the Relay to the common GND of my project.
I plugged the 5V VC of the Relay to the Pin D12 of the Arduino Nano.
I plugged the 5V/2A DC to the VIN pin of the Arduino Nano.
I plugged the GND of the Arduino Nano to the common GND of my project.

And that's it. Sending a HIGH digital signal on D12 turns on the relay, where the switch is by default on the position I want.

It's like this for about 5h now and works like a charm. But I bet this is a bad practice. Isn't it?