Relay guidance

Other Hardware General Electronics
1

Hi,

Am fairly new to all this, so hopefully this is a simple question. I have bought a small relay board to allow me to use the Arduino to switch AC power (see photo). A couple of basic questions:

  1. What is the little plastic jumper for in the bottom left?

  2. You will see that I have connected the middle and lower connectors of the switched side of the relay to my high load circuit. I don't have the connectors yet to connect the relay to the Arduino, so just connected this to power to test my wiring. The load (a bulb) came on, which is not what I expected.

I am wondering whether I am using the wrong 2 connectors on the output side of the relay, or maybe the jumper controls whether the relay defaults to on or off? Or both??

I can't find any useful documentation online, so wondered if anyone else has such a board and can advise?

IMG_1101.JPG
IMG_1101.JPG2448×3264 1.43 MB

2

Leave the jumper where it is!
The connection you have done til to the contacts "normallt closed"/NC.
Use center contact, move the other wiew end to the oposite side. This will be connectet to the "normally open"/NO

There is a schematic where you can see the actual connections on the board. This will explain the jumper..

3

Excellent - thank you. Of course, NO and NC now make sense!!

I can't find a description of what the jumper does though. It just seems to connect two VCC pins together - what is it for?

4

see the schematic here..
The jumper connects power to the coil from your 5V input.
If you remove the jumer you must supply power to coil from other source
Jumper shall NEVER connect to GND. (leave it where it is or remove)

http://www.ebay.com/itm/2-Channel-Relay-Module-for-Arduino-PIC-ARM-DSP-AVR-Electronic-5V-/131111440646?_trksid=p2054897.l4275

5

I have a couple of those somewhere, but I have not used them for anything yet.

There is a funny detail as far as i remember:
It will energize the relay as default, when the pin supplying signal to the relay board is LOW.

It is called "active low" and there is a post about it here:
http://forum.arduino.cc/index.php?topic=79745.0

6

Whithout having read 328s datasheet, and not tried.
Try digitalWrite HIGH before pinMode OUTPUT.

7

Many thanks - that's great.

And thank you for the extra tip about active low - that would definitely have caught me!

Nick.

8

OK so this is all working fine, now that the required connectors have arrived. The relay switches on and off as expected. However, a question related to the active low point raised already. Here is the simple code:

void setup() {
  digitalWrite(13, HIGH);
  pinMode(13, OUTPUT);
}
 
void loop() {
  delay(2000);
  digitalWrite(13, LOW);
  delay(2000);
  digitalWrite(13, HIGH);
}

With the Arduino connected to the relay board, when the Arduino is powered up via USB the relay clicks on and off about 5 times very rapidly before running the Sketch code. I have included the digitalWrite(pin, HIGH) as suggested earlier.

Whilst this is not the end of the world, it feels unhealthy depending on what is connected to the power side of the relay - at the moment only a light bulb, but if it was something like a pump or fan that would not feel like a good thing to do.

Any suggestions on how to suppress this behaviour?

9

nickdrums:
...
Any suggestions on how to suppress this behaviour?

Have you tried another pin than 13?

13 is a bit funny.