I use an Eheim 3582 Twin feeder. Two compartments allow more flexibility in type of food and intervals. It's in constant use, both when I'm home and away. When home I supplement with frozen for the evening feeding, the remainder of the time, the feeder does it's thing. It's not inexpensive and also fairly large. I ended up building a bracket/holder out of acrylic to hang it on the rim. I needed a ramp to tilt it slightly in order for it to dispense larger flakes. The auger mechanism tends to favour smaller morsels and very large flakes can hang up. Other than that, it's a great unit. Here's a link with additional info.
http://www.aquariumproonline.com/Pro...3582_twin.aspx