Relay is not receiving full 5v from arduino

Other Hardware General Electronics
1

Hi everyone,

I have been puzzled over this problem for the past couple of weeks every time I come back to solve this problem. My knowledge in electronic circuity is very low (more of a software programmer).

The Problem:
I have this relay (5V Relay Module)

I have it wired up to my arduino and when I try to send a signal to the relay to turn on it isn't receiving the full 5v to "flip the switch". It is receiving about 4.8v according to my multimeter.

I have also tried PWM set to 255 with no avail.
How change I make sure that I am sending the full 5v?

2

The Problem:
I have this relay (5V Relay Module)
http://dx.com/p/arduino-5v-relay-module-blue-black-121354#.UuP19_vnZpg

Is that in itself a problem?

Please say how you are wiring this up. There are three inputs, what are you doing with them?

EDIT - Original post now modified answering this point.

3

Feed the 3 inputs: GND <-> GND , V+ <-> 5V, in <-> digital output
(do not use PWM. digitalwrite only)

4

Sorry I tried to tab over in the message box and accidentally hit 'enter' and it posted when I wasn't done typing.

But for wiring:

Pin 3 to Signal
Ground to arduino ground
5v to arduino 5v

Then
NC to Positive
COMM to Negative
NO to nothing

With is wiring I am not getting the full 5v

EDIT: I just re-read the forum and now I understand what I said was very wrong and didn't realize what I actually said. I NEVER put the following connections as it is written above. What I meant to say is I placed a positive to NC along with the other side of the positive to the COMM and had nothing connect to NO. For some reason I had positive and negative in my head as I was writing this. Sorry for the confusion.

5

I tried to tab over in the message box and accidentally hit 'enter' and it posted when I wasn't done typing.

See the "modify" word over the post, what do you think happens if you click that.

Then
NC to Positive
COMM to Negative
NO to nothing

WTF !!!!!!
Are you trying to melt your supply? That puts a dead short across the supply. What do you want to do with the relay?
Do not connect the relay contacts to anything yet, just get it to click first.

6

connect NOTHING to output (skrew terminals)
While toggle input you should hear switching on/off

7

In fact I see from the pic the module has an "on led" : even if you don't hear it click you should see that led.

But I'm thinking the problem might be taking the 5V from the Arduino; rather try a separate supply to the relay module, and join the module's -ve to the Arduino GND.

8

Grumpy_Mike:
See the "modify" word over the post, what do you think happens if you click that.

Ok. Thanks for the encouraging words. That is exactly what I did. You don't have to be mean about it. I was just explaining myself.

Are you trying to melt your supply?

No. Not in particular. Like I said before I have limited knowledge in this field and I have been trying to learn what I can on my own. So I was hoping to ask a question to some people do have knowledge in this field.

What do you want to do with the relay?

I just want to control a light.

Do not connect the relay contacts to anything yet, just get it to click first.

That is what I have been trying to do. I don't want to kill myself just yet.

9

That is what I have been trying to do.

OK so how have you been trying to do this?
Post the code you have been trying to use to turn on the relay please.

10

That is what I have been trying to do. I don't want to kill myself just yet.

That relay is intended for high current AC circuits. Please stay away from such circuits for now and just use the relay to turn on a LED (with a 220 ohm current limiting resistor). Otherwise you may just kill yourself.

11

This is code.

int lightPin = 3;


void setup()
{
  pinMode(lightPin, OUTPUT);
}

void loop()
{
  delay(1000);
  digitalWrite(lightPin, HIGH);
}

The Wiring is attached.

RELAY.bmp (1.2 MB)

12

OK
Make the loop:-

void loop()
{
  delay(1000);
  digitalWrite(lightPin, HIGH);
 delay(1000);
  digitalWrite(lightPin, LOW);

}

Now are you sure that those connections to the relay board are right. There was no way I could see from that link that the connections were in that order.

13

I am positive that is the right wiring.
Here is a better image for you via google http://i01.i.aliimg.com/img/pb/929/181/489/489181929_024.jpg

EDIT: The botom NC is actually NO

14

EDIT: The botom NC is actually NO

That is not important for the moment, let's concentrate in getting that LED to blink on an off first.

That looks right then so there might be a problem in translating that circuit into a practical circuit. Can you take a photo that shows the wiring. Try and make it less than 1000 pixels wide.

The other alternative is that it is broken.

15

I can get the LED to blink on the relay module, however, I don't believe that actual switch is clicking over. It doesn't take 5v to turn the LED on and OFF but as far as the switch I don't think I am getting enough current to the electromechanical switch.

16

In that case power your arduino through a wall wart through the power jack and connect the + on the relay to the Vin pin.

17

Try using 3-4 AA or AAA batteries (can provide plenty of current) as your source of 5V and signal, just connect + terminal of batteries to +5V and signal on relay board and negative terminal of batteries to neg terminal on the relay board (completely remove arduino from question at the moment to make sure your relay isn't defective), you should hear it click and un-click when you apply and remove the 4.5/6V from the signal pin.

18

No joy. I think it might be the relay, but I wanted to make sure before I tossed it.

19

Are you sure you connected the relay like this:
(the yellow wire (signal) can be connected to a digital pin, I'd go with pin 13 in this case, because you can see the onboard led go on at the same time, so you are sure that the program works... :slight_smile:

If that doesn't work, try just applying the 5V between - (GND) and + (5V) and then connect the S pin (signal) with your 5V pin. This should activate the relay. You should notice a 'clicking' sound whenever you change the status of the signal pin. There is even a red LED that shines as the relay is activated. (I have the same relay here with me, from DX) it's getting enough current from USB powered arduino. The clicking sound is very loud btw.

About that 4.8V signal, that should be plenty of voltage to trigger the relay. The current isn't coming from the signal pin, that's why you need to power this module separately (+ pin I mentioned earlier). There is a small transistor amplifying the signal current to trigger the relay coil.

I'd even espect that the accuracy of your multimeter is affecting this voltage. Even if it's 4.8V, that could be perfectly normal, PC usb ports don't even always give perfect 5V. We aren't living in a perfect world :wink:

20

Ok guys,

So I think it is a relay problem. I hooked up the relay like this:
(+) to 5v
(-) to GND
(s) to 5v
I turned it ON and OFF by removing the 5v from (s) and listened for the clicking with no avail, just the LED turned ON and OFF. So at this point I am going to try to get another relay. If anyone has anymore suggestions I am all ears. Thanks to everyone for the help.

@Ward123, Thanks for the help. I tried what you recommended with no avail.

@Grumpy_Mike, Thanks for all the help. I am sorry if I inconvenience you in any way. Thanks again.

@Everyone else, Thanks I tried most everyone's suggestions with no luck. Just going to try with another relay.