Compatible Relays

Other Hardware Motors, Mechanics, Power and CNC
1

Hi, I've been reading the forum all day but still is not clear to me if the statement "Arduino Compatible relay" means that there is no need for flyback diode and transistor

More precisely I bought the following:

And I am succesfully controlling a 220V AC 0,03 mA water pump through its 5v "IN1" trigger, If I want command the relay with my arduino yun do I need something like this scheme?


or this in case of separate 12v supply for the relay coil?

http://i1.wp.com/tronixstuff.com/wp-content/uploads/2010/04/examp3p11.jpg?resize=500%2C293

Or the compatible relays don't need it?
excuse me if this is too obvious a question, I'm studying the documentation but didn't get this clear yet.
Thank you in advance
Frenk

2

Hi dannatofrenk,
I have used a similar relay module with good results, (in fact I have a spare) all the driving componets are on the PCB including the flyback diodes, etc. The only slightly odd thihg for me is that some require a LOW input to activate the relay, inverted logic almost.

If I can lay my hands on it quickly here's a picture of my relay module in use in my seed propagator, where it switches the heating cable. I used both relays(5v) to totally isolate the mains...

Hope it helps, Regards.

Mel.

Sprop-1.jpg
Sprop-1.jpg600×800 113 KB

3

Hi, the relays that are quoted as arduino compatible, are actually and assembly of opto coupler , and flyback diode and relay in one.
They have all the components required to make relay interfacing easier, I have a few of them to and they make prototyping a lot easier than using discrete relays and associated components.

Tom...... :slight_smile:

4

See more info on using this type of relay here:
http://arduino-info.wikispaces.com/ArduinoPower#4-8

5

Sorry for the slight redirection, but is a relay rated for 10A @ 250VAC, then rated for 20A @ 125VAC?

6

Sorry for the slight redirection, but is a relay rated for 10A @ 250VAC, then rated for 20A @ 125VAC?

Those are contact ratings. Unless otherwise specified, the 10A would be the maximum switched current and the 250VAC would be the maximum switched voltage. There would be different (lower) ratings for switching a DC load.

If the switched current was specified separately with at least 20A maximum AC, and the maximum VA was specified as being at least 2500VA, then the contacts could safely switch 20A @ 125VAC.

7

dlloyd:
Those are contact ratings. Unless otherwise specified, the 10A would be the maximum switched current and the 250VAC would be the maximum switched voltage. There would be different (lower) ratings for switching a DC load.

I was trying to understand how the ratings apply to USA standards as we only use 125 VAC and I have two 600 watt loads, and was hoping to put them both on the same relay. However, because ratings are always given in the highest Ac or DC voltage, I was inquiring if the ampere threshold would then increase as the voltage is lowered down from 240 to 120. From my perspective, a 600 watt load consumes twice as many amps on a 120v circuit as it would on a 240v circuit.

8

Found the datasheet ... It's worse than expected.

This is a Form-C relay (it has normally open, normally closed and common contacts)

For a resistive load: 7A @ 240VAC, 10A @ 125VAC

For an inductive load (0.4PF): 3A @ 120VAC

https://www.ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf

9

Mine is the same brand and similar ratings, but I only have 2 terminals in normally open position.

How do ascertain which form the relay is? Is there a distinguishing mark?

10

How do ascertain which form the relay is? Is there a distinguishing mark?

The last letter of the part number on the relay is the form type.

Form A: Form B: Form C:

11

Hi all,
thank you very much for your information and documentation, this is precious really. Arduino has lots of documentation, o and a steep learning curve so many aspects to control.