Simple chain extension indicator

With the link extension the summar radius of the sprocket with chain increases as seen in the added to challenge picture. Therefore, to detect extension must somehow determine the radius increasing. The simplest solution is optical slot sensor (optical switch, optocoupler etc): The combination of transmitter and receiver, the sensor responds to interrupt of the beam by external opaque object. Sensor signal processing: Can be quite a simple process: the beam is interrupted or not with a certain threshold (determined by the characteristics of hardware) and as result wear indicator activated or not - Ladder logic only, without microprocessors. More thorough signal processing: the timing and amplitude of the dip, the collection and processing of statistical information, the determination of incidental triggering etc. In addition to the optical sensors can use magnetic or capacitive sensors, but the very small changes of the distance leads to the very little changes in output signal, and this changes will be very difficult to detect. Therefore, their use may be impractical. It’s possible to use mechanical sensors too, but the chain extension process very slow, and for one micron movement in triggering direction corresponds to thousands links movements in tangent direction that leads to very intensive wear of mechanical contact. Exception is limit switch with rolling contact, but it will be weared too, simply not so intensive. Therefore, their use may be impractical too.