Now there are three judgments in the mechanical or electric coin mechanism , involved shapes , materials and weight . Mechanical coin mechanism usually measures by slits and cradles . Slits are constructed by slanting channels , they are like the arranging mechanisms of automatic productions . Electric coin mechanisms differentiate from the different coins by examining the variation of voltages when coins pass through electric coils . Actually , the traditional coin mechanisms still have many disadvantages , so we will adopt the multi-function way to raise the identifying ability . This research uses the TRIZ method during the design process and operates the contradiction matrix to find out the feasible and requisite design . We believe that this research could be good for the market development of coin mechanisms .