8 Channel Relay

Hi everyone. Long time reader, first time poster…

I have an 8 channel sainsmart relay that is powered by an Uno. I am trying to get the relay to light a string of Christmas lights. The relay clicks on, the led illuminates, but the Christmas lights do not light up. I have tried another relay, and have measured the both relays with a multimeter.

My setup has a wire from 5v, a wire from gnd, and a digital pin to the relay. I have no power to the seperate vcc, jdvcc, or ground.

Any help would be much appreciated. Thanks!

Draw us a diagram they way you have things wired.
Maybe take a picture and attach it.

If it clicks you are 99% there!

Thanks for getting back so quick. Here's a picture of my setup

Here it really is.

You MUST power the relays with an external power supply.

Make sure you have a gnd to gnd connection

Are you wired as in the image?

2014-11-11_12-40-52.jpg

To take advantage of the opto-isolation feature, try this for your digital control and power connections:

No, that unused ground, should be used. If you are using an external power supply, you need to make sure the ground from the power supply is connected to the ground on the Arduino.

Its called a Common Ground

HazardsMind:
No, that unused ground, should be used. If you are using an external power supply, you need to make sure the ground from the power supply is connected to the ground on the Arduino.

Its called a Common Ground

Yep, it's a common ground on the relay board. If used, it would still work, however it would defeat the purpose of opto-isolation.

For complete isolation, the control signal already has a complete path (source VCC and return through the I/O pin).

This relay board uses the “sink” capability of the Arduino’s output pin. Logic 0 (LOW) will illuminate the IRLED and visible LED and energize the relay. For driving 1 relay, only 2 wires are required, VCC and IN.

The main problem that can be seen from Picture1.jpg is that there is no separate supply as pointed out by HazardsMind.

Note: Possibly one relay would work this way (Picture1.jpg) if powered by USB, however if powered through the power jack and VIN is 12V, then there may not be enough current available without thermal overload kicking in. Each relay and driver requires 100mA, so the max load would be 800mA with all relays energised.

The main problem that can be seen from Picture1.jpg is that there is no separate supply as pointed out by HazardsMind.

Should be no problem using a main common power supply as long as it has sufficient power and the voltage is appropriate for the relay coils and powering the arduino.

Is there a reason why these relay modules on the market do not have power adapter components built right into the circuit? If mains AC voltage is flowing into the unit, why not use some to power its own higher voltage and current needs, then the arduino need only power a single LED?

It's called design flexability, and the reason is the many end-user possibilities.

You have the wrong wiring at relay output.
Read your Christmas light instruction.
Pin power line to the COM pin (at the center), and wire the NO to the light driver. GRND direct to light driver. Then you can command the relay from arduino to energize through IN pin.

If you wire the NC to the light then the light will ON directly. You turn it OFF from Arduino.

At the wiring.jpg you send, it show that only 2 wire connected to NO and NC at the relay outlet.
There is no power in at COM pin.
Please be careful to wire the light because may be it is high voltage. Read the instruction.