The Relay is : Blue PCB Type DC 24V SPDT 5 Pin Mini Power Relay SRD-24VDC-SL-C
There are FOUR pins
Ground
Vcc
IN+
IN-
How do I program such relay ?
Do I have to provide extra components to make sure that Arduino UNO can handle it
Wiring tip will be greatly appreciated ( I mean how to wire it to talk to Arduino)
This datasheet, using the part number SRD-24VDC-SL-C you gave, shows the 5 expected pins: 2x coil, Common, NC/NO....
here is a pretty good guide, you will need the higher voltage for the relay
another good guide, its near the bottom of the page
http://rouvelle.com/ramm_fa_12/
4 pin relay...?!
Either you have broken a pin off, or... is this relay mounted on a PCB...?
Hi, I think you have a PCB mounted relay, the Gnd, Vcc,+IN and -IN, sound like the relay PCBs you can get on abay and elsewere.
A picture of the relay would help. The other end of the PCB would have three terminals for Com,NO and NC.
I think you haven't given us the whole story.
So to prevent confusion a picture or a better complete description would help, if we do not have accurate info, we cannot give you accurate and correct advice.
We are here to help.
Tom.... 
Edit, good you posted as I posted.
Tom,
I just did
That's not the part number you gave in your first post...., on which I based my previous answer.
I Googled the part on your pic, and it looks to me as if there are two COM pins... on between the coil pins and one by iteslf middle bottom.
OK that's irrelevant since the relay in question is actually a relay module, not a relay on its own.
We are all stabbing in the darks here.
Can you provide a link to where you obtained the relay in your picture as it is impossible to see the details in it such as what the jumper is for ?
Those pins pertain to the opto isolator.
So I'd guess 2 of the 4 are the coil as always, and the other 2 are the isolator.
Either
Vcc and Gnd are the coil, +- are the isolator
Or
Vcc and Gnd are the isolator, +- are the coil....
But what their naming convention is I would be reluctant to guess.
EDIT but you may be able to see the traces on the board, or beep the connections out with your meter to see what's what.
here goes
gnd to gnd
In to your auduino output.
Vcc to 5v
relay contacts (5v relay not a 24v)
com common contact
no normally open contact
nc normally closed contact
here is a better picture, the modual you have looks confusing the common isnt present ie not soldered
http://www.ebay.com/itm/5V-30A-C-type-OPTO-Isolated-Relay-Module-/201052182388?pt=LH_DefaultDomain_0&hash=item2ecfa4d774
Here is a better picture of the mysterious TWO pins
I hope this will help in wiring this thing
I can do any testing you want me to perform on the module
jonisonvespaa:
here goes
gnd to gnd
In to your auduino output.
Vcc to 5vrelay contacts (5v relay not a 24v)
com common contact
no normally open contact
nc normally closed contacthere is a better picture, the modual you have looks confusing the common isnt present ie not soldered
http://www.ebay.com/itm/5V-30A-C-type-OPTO-Isolated-Relay-Module-/201052182388?pt=LH_DefaultDomain_0&hash=item2ecfa4d774
That's not the same one: the OP's has 2x INs, one + one - which is the point of his question I think.
it is almost, the one he has doesnt have the common connected really not sure how that one would work
right on......
The ebay picture is NOT what I have......
jonisonvespaa:
it is almost, the one he has doesnt have the common connected really not sure how that one would work
The boards are different- your post has only one IN, the OP's has two
As I mentioned earlier in the post . I saw a sample connection using the two IN+ and IN- connected to a sensor.
That of course will not help me CONTROLLING the relay using Arduino......Hence my post
this is how to connect to your module, my advice is to have a look at a few relay circuits and learn how they work
gnd to gnd
In to your auduino output.
Vcc to 5v
relay contacts (5v relay not a 24v)
com common contact
no normally open contact
nc normally closed contact
jonisonvespaa:
Which IN? I have TWO
