Detecting Retraction of Stabilizer Legs of Mobile Cranes via Inductive Sensors

Mobile cranes, ladder trucks, bucket trucks, and others are equipped with extendable stabilizer legs. The position of stabilizer legs must be figured out. 

Existing customers' verification systems are dependent on mechanical contacts. But, the long-term maintenance and replacement costs for these vehicles are relatively high. Hence, we need a contactless solution.

Normally closed two-wire inductive sensors are designed for this application. Several sensors (one for each stabilizer cylinder) are installed and linked in such a way that each sensor to be satisfied that a target is either present or absent, thus ending the logic circuit.

At first, the simplest approach seemed to be to wire these devices in series, as would be done with mechanical contacts. But, when sensors are used, series wiring has the problem of voltage dropping. This challenge is solved by choosing 2-wire sensors with a ‘normally closed’ output, then wire them in parallel to make a reasonable NAND situation.