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.