Linear Actuators & Solenoids on Embedded Systems Development

Solenoid Drive Circuits

Mon, 01 Jan 0001 00:00:00 +0000

Solenoid Drive Circuits#

A solenoid is an electromagnet with a movable plunger — apply current and the plunger pulls in (or pushes out); remove current and a return spring resets it. The electrical interface is simple (a coil), but the drive circuit must handle the inductive energy stored in the coil when current is interrupted. A solenoid coil storing even modest energy (½LI²) can generate voltage spikes of hundreds of volts when the drive transistor turns off — enough to destroy MOSFETs, upset nearby logic, and weld relay contacts.

Linear Actuator Control

Mon, 01 Jan 0001 00:00:00 +0000

Linear Actuator Control#

A linear actuator converts rotary motor motion into linear push/pull motion — typically using a DC motor driving a leadscrew or ball screw inside a sealed tube. The external interface is two wires (motor+ and motor−), and the actuator extends or retracts depending on polarity. Stroke lengths range from 50 mm to 1000+ mm, with force ratings from 50 N (light duty) to 10,000+ N (industrial). From the embedded control perspective, a linear actuator is a bidirectional DC motor with end stops — the control circuitry is an H-bridge, and the primary challenges are knowing the current position and protecting the actuator at end of travel.

Proportional Solenoid Control

Mon, 01 Jan 0001 00:00:00 +0000

Proportional Solenoid Control#

Standard solenoids are binary — fully energized or fully off. Proportional solenoid control uses PWM to regulate the average current through the coil, producing variable force or variable plunger position. This technique is essential for proportional hydraulic/pneumatic valves, variable-force clamping, and any application requiring analog-like force control from a digital drive signal. The key challenge is linearizing the force-position-current relationship, which is inherently nonlinear in most solenoid designs.

Relay Drive Patterns

Mon, 01 Jan 0001 00:00:00 +0000

Relay Drive Patterns#

A relay is a solenoid that switches electrical contacts rather than moving a mechanical load. The coil circuit (driven by the MCU through a transistor) and the contact circuit (carrying the load current) are galvanically isolated — this is the relay’s primary value. Relays switch mains power, high-current DC loads, and analog signals that semiconductors cannot handle or where isolation is required. The drive considerations are identical to solenoid circuits (inductive coil, flyback protection), with the added complexity of contact management: bounce, arcing, and welding.