can't activate relays of 4 channel 12v relay board

I have a 4 channel 12V relay board LOW triggered, which I wired as follows:
Arduino Digital pin to INI on relay board
Arduino 5V to VCC on relay board
Jumper VCC-JDVCC removed

12V external supply to JDVCC pin on relay board
GND external supply to GND on relay board
Relays work when powering them directly.

Sketch:
Arduino digital pin as OUTPUT and on LOW estate

When powering up Arduino and external supply and running the sketch the LED on relay board lights up, but relays don't actuate.
I rechecked the connections many times, used different external power supplies, etc.

Is there something I'm missing?

Arduino 5V to VCC on relay board

VCC might need to be connected to 12v instead of 5v.

Arduino only takes 5V. I would be afraid to put 12V into VCC. and connect the return to digital pin, the grounds are different? I might be ruining Arduino and the relay board.
On what grounds do you suggest this solution?

You really need to post a link to your relay board. Generally relay boards that are designated as 12v require 12v to operate the relay coils, so 5v probably won't work for operating the relays.

I'm not trying to operate 12V relays with 5V. The VCC 5V is only for the signal pin which operates the optocoupler, so I can keep 12V away from Arduino.
It seems to me that the optocoupler don't transfer enough current to the collector-emitter, to supply the relay circuit.
Any thoughts...?

If your relay setup is like the one in the below link, you might use a multimeter to troubleshoot your setup.

Yes it is similar to that. I can use a multimeter to check different things, although I'm not too proficient with that, (voltages, resistances, continuity, etc) but I would not know if the measurements are right.
I have done that with the board and discovered no apparent errors or shorts. There is no identification of the components. The information on the web, not too conclusive.
I got in touch with the vendor and provide me with nothing new.

If I look at the link above to the schematic that was posted and you are using separate 12vdc supply then yes...

Vcc on relay board to 5vdc Arduino, when the INO inputs on the relay board are grounded to Arduino GNd (or via your digital output pins) then this should "switch on" the relay as the opto isolated "trigger" circuit via the opco coupler is completed/activated and the ino led on the relay board is lit.

Do not connect GNd on relay board to GNd on Arduino but connect GNd on relay board to gnd on separate 12v power supply and make sure your 12 Vcc supply to relay board is connected to the right side of JD-VCC.
If you do it this way you will NOT be connecting either Vcc or GNd of either your circuits together which should be safe.

Overall, provided the schematic I saw is what you are using is correct then it seems your connections are o.k.
If you now touch each ino relay board input in succession to Arduino GNd each relay in succession should activate.
If this is the case then it is up to your code to do the switching to the right Arduino pins you chose to use.

..... If you are having more difficulty......

You mentioned you tested the relays manually and they worked so I am not sure if you may have possibly shorted something out, as it can't be ruled out I suggest the tests below.

Just do this test on each channel to see if anything is blown.

If you touch ino pins to the ground of Arduino, does the relays activate or just the ino led come on?
What is the voltage between pin 4 & 3 of the opto coupler when ino led is on?
What is the voltage between the collector and emitter of the relay switching transistor if the voltage between pins 3 & 4 of the opto coupler is 0?
If the voltage drop between pins 3 & 4 of the opto coupler are the same as the external voltage supply when the ino led is on it means the base emitter of the relay switching transistor is not forward biased and you have a opto coupler fault, if the pins 3 & 4 of the opto coupler are 0 or close to 0 volts when the ino led is on and the voltage between the collector and emitter of the relay switching transistor is same or close to external power supply it means you have a switching circuit fault.
Move to and test next channel.

The D1 diode is just for back emf protection when the relay switches off, but the diode should not be shorted, de solder one pin to check, if the diode is shorted your relay will not work.
Also check value R2, if open circuit the base emitter of the relay switching transistor q1 will not be forward biased, check value of R2 within tolerance.

Typically transistors, diodes and opto couplers are more suspect in fault conditions, either open circuit or short circuit, check for things that may get more than normal operating temperature.

..... tip.....

If you want to "invert" the on state of your relays to when the digital pins on the Arduino are on or "high", which is a better safety condition or "safe fail state", then use of 2 resistors and a transistor to ground Opto ino would be better, just search my name for my posts and you will find the circuit I Posted.
Or, located on the URL below.
http://www.ipcamtalk.com/showthread.php/4201-Arduino-amp-Blue-Iris-Integration

Thank you Kevern, I was able to check the resistance value of the LED side of the optocoupler and notice something odd. The resistance is 10k, and doing some maths the current would be only 0,5mA, which I believe is the problem. The information I have from all the webs I visited is that the optocoupler needs about 5mA to operate, so it should have been a 1K resistance to the optocoupler . I put a 1K (2K) in parallel with this (Lower resistance, increase the current) with this and the relays now operate. Judging for this there must be a "faulty" board. As I 'am not going to return this low priced board for a replacement, I would solder resistances in parallel on the board and use it.
Does anybody knows which are the components: Optocoupler, Q1 transistor, diode.

Thanks to all.

Aaah yes, maybe not a faulty board at all, maybe just designed to work with 12Vdc tolerances on the opto trigger side as well, which Although unusual and unlikely is not impossible.

If you mathematically calculate the opto led side of the circuit current as if you were using 12Vdc then recalculate the required resistor to deliver the same current as the 12v calculation for the same circuit but using 5 or 3.3 Vdc then you may well have solved the problem, well done!

However, I suggest you also take the chip number off the opto DIP IC and run a specifications check just to be sure.

Typically the diode is in parallel to the activation coil of your relay, the opto coupler has 4 pins (IC) DIP, and Q1 has one of its 3 pins (collector) connected to the relay coil.
I could be of more assistance if you were able to post a link to a picture of your relay board.

Regards,
Kevern.

I got in touch with the vendor and provide me with nothing new.

Why haven't you posted the link to your vendor? Maybe others can better get info there to understand what relay board you have.

Sorry about the delay. This is the link:
http://www.ebay.es/itm/281370627777?euid=f9d74ed25e5f4eefa1a7b2c18362137d&cp=1

josegg:
I was able to check the resistance value of the LED side of the optocoupler and notice something odd. The resistance is 10k, and doing some maths the current would be only 0,5mA, which I believe is the problem. The information I have from all the webs I visited is that the optocoupler needs about 5mA to operate, so it should have been a 1K resistance to the optocoupler...

The current limiting resistor on al the boards I have seen is 1k. It should read 102.
If it reads 103, then that's the problem.
If that's the case, just piggyback a 1k on top of the 10k.

The primary side of the opto has usually three components in series.
A 1.2volt IR LED inside the opto, a 1.8volt indicater LED, and a 1k resistor.
The opto current with these parts is ~2mA (5volt Arduino).
Leo..

I just received another relay board, I channel Hi/Lo triggered, which had the same problem, the current resistor to the optocoupler was marked as 103, that is 10K Ohm. The solution was to piggyback a 1K, this time much more difficult to do.
This is a warning to the users of this type of boards.

First, everyone, the OP is talking about a 5v relay board so that is what VCC is.
Second, funny, I have a problem like you, except my relays work, but the lights on the relay board don't!

amarotica:
First, everyone, the OP is talking about a 5v relay board so that is what VCC is.
Second, funny, I have a problem like you, except my relays work, but the lights on the relay board don't!

The actual specs for that board need to be sorted out. The optical isolator may operate at 5v (or may require 12v), and the relay coils may require 12v.

4 Channel 12V Relay Module Board Optocoupler LM2576 Power Supply Arduino

12V 4-Channel Relay interface board, and each one needs 50-60mA Driver Current.
Equiped with high-current relay, AC250V 10A ; DC30V 10A.
Standard interface that can be controlled directly by microcontroller (Arduino , 8051, AVR, PIC, DSP, ARM, ARM, MSP430, TTL logic).
Indication LED’s for Relay output status.

Package Included:

1PCS*12V 4 Channel Relay Module With optocoupler For PIC AVR DSP ARM Arduino

i want to operate relays of 4-channel relay board can any one help me on this.thanks