I make sweet potato chips for myself and dog treats by drying them in an oven set at 125 F.  It usually takes 15 hours to do two baking sheets worth.  I slice them very thin on a mandoline and spread them out 1 layer thick.  I might invest in a dehydrator if I did more than this but in the meantime the oven works well and my oven has a 20 hour safety cut off so even if I forget about the potato chips, it isn't a problem.
				
			 
			
		 
			
				
			
			
				marni
Katy, Texas
Trek Madone 6.5-  "Red"
Trek Pilot 5.2- " Bebe" 
"easily outrun by a chihuahua."