With my controller, my smoker has temperature swing of 3 F and occassionally 5F.
Other users of my controllers report a little bigger temperature swing. It is due to the fire box.
In my burner it can hold 10 lbs pellet, but the fire pot is very small, only a cup of pellet is on fire. It is very easy to control.
In a common fire box, you may have 10 lbs charcoal, all 10 lbs is on fire at same time. It is harder to control 10 lbs.
You can buy my burner directly. 6"x6"x20", made from 3 mm stainless steel. Ex-works Beijing US$130, Surface mail cost US$70, total US$200.
Or you can build it by your self according to my sketch and you need to pay me patent fee of $1.00, one dollar
With my burner and controller your smoker will become to an automatic pit. You can sleep all night without babysitting your pit and temperature swing is under 3F.
You need also controller, please check http://www.allchinas.com/probe