Solenoid-protection circuit limits duty cycle

摘要

Several safety-critical solenoids in a laser-measurement system on an automotive-assembly line required protection from internal overheating during normal operation. After a 60-sec activation, the solenoids required 180 sec to cool before their next activation. One apparently straightforward protection circuit would comprise a timer based on a microcontroller, some support components, and a short program written in C+ +. However, the project would require evaluation and selection of a suitable microcontroller, purchase or rental of a device programmer, and considerable time in programming the microcontroller and evaluating its operational hazards.