This simple circuit was taken from a chinesse oven with conveyor belt, the conveyor speed can be regulated with a potentiometer in the front panel, the internal circuit board that control the DC motor it’s just a dimmer based on NTE5620 triac, .   The input voltage of the circuit is 220V AC, the circuit chop the ac wave and its rectified by a full wave bridge.

Download (it comes with proteus 8.1 project file, ready to test, simulate and modify).

Triac options: NTE5620 BCR8PM  MAC15

DIAC: DB3