external HD not showing up when connected via Time Capsule

Pardon my ignorance, but I've searched for the answer but cant find someone with my same issue. It might be a bit remedial. ANyway, I recently got a new external hard drive so that I could store my iTunes and iPhoto librabries without taking up space on my macbook air. It's an Iomega something or other. I set it up properly and when its plugged directly into the computer, it shows up fine. However, when I plug it into the USB on my Time Capsule, I can't find it anywhere. I thought I read somewhere that the Time Capsule doesn't have enough power the external hard drive, but I have no idea. Is there something I missed? is it a hardware issue? Any help would be great....