This heat gun coffee roaster is constructed primarily of off the shelf iron pipe, complimented by a flour sifter, motor, and a handful of customized components.
Only the motor mount must be constructed carefully to align the bolt holes with your motor. A few other components need to be cut and/or shaped, but the dimensions of those are not tightly constrained – close is probably good enough.
The roaster functions similar to other hot air gun coffee roasters, accessorized with a motorized stirring paddle action in this case using a stepper motor controlled by an arduino pro mini and a DRV8825 stepper driver.
A practical aspect is that the iron flange and “L” do get very hot, basically as hot as the hot air gun. As such, the coffee is roasted not only by the forced hot air, but the radiant heat acting like a stove top from the iron floor flange that makes up the base for the flour sifter.
Note: The frame remains at a moderate temperature during a regular roasting period.
* Hot air gun heat supply
* Minimal custom or modified parts: motor mount, paddle, shaft, cylinder mount adapters (2), Optional stepper controller (you could use a simple motor)
* Integrated Cable management
* Very stable – it won’t tip over, or blow away.
* power supply magnetic storage
Parts list with approximate per component price:
* Springs (2) @ $2.80
* 1 1/2″ floor flange (1) @ $9.50
* 1 1/2″ to 2″ street ‘L’ (1) @ $6.20
* 1/4″ x 2 1/2″ galvanized nipple (4) @ $1.10
* 1/4″ x close (no gap between threaded ends) (4) @ $0.72
* 1/4″ x 2″ nipple (4) @ $0.93
* 1/4″ x 3 1/2″ nipple (4) @ $1.40
* 1/4″ tee (4) @ $1.65
* 1/4″ 90 degree ‘L’ (8) @ $1.25
* 1/4″ coupling (2) @ $4.58
* 1/4″ cross (4) @ $3.07
* 1/2″ wire rope clip (i.e. ubolt feet) (4) @ $1.65
* Hose clamp (2) @ $3.00
* Conduit hangers (motor mount bolts to these) (2) @ $2.50
* Flour sifter (walmart 3 cups) (1) @ $4.34
* Stepper motor (1) 36.8OzIn, 0.4A, Nema 17 (1) @ $9.99
* Pipe ground clamp (i.e. cable management) (2) @ $3.50
* Motor mount (i.e. customized 1/8″ x 2″ customized aluminum bar) (1) @ $3.50 (pro-rated from larger stock)
* Flexible shaft coupler (1) @ $2.50
* Shaft 3/16 steel (1) @ $2.25
* Controller (Arduino pro-mini + DRV8825) (1) @ $5.00
* Wall-wart power supply (1) @ $10.00
* Misc nuts, bolts, washers @ $5.00
* Heat shrink for cable management @ $0.50
* Magnets for wallwart (3) @ $0.50
* Switch for power management (1) @ $2.00
* Motor mount – spec out a bolt pattern for a motor of choice
* Conduit hangers which hold the motor mount – cut the loop portion, and slot each side to allow the hose clamps to slide through with minimal deviation from the cylinder.
* Shaft – cut to length.
* Flexible coupling – get one that matches your paddle shaft diameter, and motor shaft diameter. Other examples on youtube may offer a looser coupling.
* Controller tutorial and code here:
* UBolt feet are completely optional – to protect surfaces.
* This build is not square – not all the pipes are tightened exactly the same. There is no functional impact as built.
* The pipes are all right handed, consequently they do not naturally succumb to a 360 degree continuous set of connections (i.e. a loop). You can accomplish a full loop as this design requires by perhaps creating custom pipes and threading, or as I have done tightly screw a pipe into a receiving component, position the opposite side receiving component and unscrew the pipe about half way from the first as it screws half way into second (for example you would tightly screw the galvanized nipple into the center coupling, position the corner “L” on the other side of the nipple, then unscrew the nipple from the coupling as it screws into the “L”)
* With the motor attached to the flour sifter, the sifter is weighted to one side and will fall if not supported – thus the springs.
* The flour sifter comes with a mixing wire loop thingy. It is easily removed without damaging it or the sifter.