Driver Offers Proportional Solenoid Control Without PLC, Microcontroller

摘要

The proportional-control solenoids used in some industrial hydraulic systems are usually driven by microcontrollers or programmable logic controllers (PLCs). Such complex drivers typically require several different supply voltages for logic and control. (The purpose of proportional control is to move the solenoid plunger to an arbitrary position and leave it there.) A set-and-leave solenoid driver, however, should not require a costly PLC or the processing power of a microcontroller. Ideally, it should operate from the solenoid's own supply voltage. The circuit in Figure 1 meets these requirements while occupying only a small surface-mount footprint. U2 is a 350-mA driver with built-in analog and pulse-width-modulation (PWM) dimming control. It's typically used to drive high-brightness LEDs, but in this application, its open-drain output (OUT) and current-sense terminal (CS+) connect directly to the solenoid terminals. R6 sets the maximum solenoid current. The circuit drives solenoids ranging from 6 to 40 V dc, using only the solenoid's 6- to 40-V dc source. The circuit was tested using a LEDex 24-V pull-solenoid rated for currents up to 290 mA.