Yourduino opti-isolated relay board

I just bought 2 no.s of "Opto-Isolated 2 Channel Relay Board" from Yourduino. I have used the instructions on their site and the wiki site to setup the relay. I have chosen to use the opto-isolator in my circuit (without jumper between VCC-JD and VCC).

The relay board when operated from the Arduino Uno works perfectly fine - I can see and hear the switching. The problem is that the power is not being transferred from the separate 5V DC source to the terminals. I have connected as per instructions as follows:
On power board:
JD-VCC to +ve of power supply
GND to power supply -ve

On relay board:
Vcc to 5v Vcc pin of Arduino
IN0 or IN1 to pin 13 or 12 of Arduino Uno

I measured the voltage coming in to the relays and I see that there is a 5 V drop across diode D1 (reference the image on Opto-Isolated 2 Channel Relay Board).
But as the relay switches on and off there is no voltage drop across either NC and COM or NO and COM.
I tested both boards that I purchased.

Am I doing something wrong? Or is there some known issue with these boards?

Never mind. I realized that I had to connect yet another power source at the relay outputs. Silly me...

Good to hear you solved it!