robodatech.Current feedback
A device such as the TI DRV8876 integrates current sensing and regulation. Current can help detect a jam, but normal acceleration also produces peaks; use limits and timing together.
Actuators
Turn a command into movement.
Match motors, servos, and linear actuators to the load. Understand torque, speed, current, feedback, and the driver between your code and the mechanism.
Try it yourselfChange an input.
Change an input.
See what follows.
A simplified learning model. Values describe the model, not a connected robot.
The controller signals. The driver supplies power.
A GPIO carries a logic signal. A driver switches energy from a suitable supply into the motor windings. Motor startup and stall currents can be much higher than normal running current. Size the driver, wiring, connector, fuse, and supply for the actual load and thermal conditions, rather than a headline peak-current rating.
Pick a movement technology
| Actuator | Best suited to | How it is controlled | What to check |
|---|---|---|---|
| Brushed DC gearmotor | Wheels, conveyors, pumps | H-bridge direction and PWM; encoder for speed feedback | Stall current, gearbox backlash, continuous duty. |
| Positional hobby servo | Small joints and steering | Pulse width requests an internal position loop | Rated voltage, travel limits, peak current, loaded torque. |
| Stepper motor | Repeatable indexing and screw axes | Current-regulated phase driver with step/direction | Acceleration limits; open-loop steps do not prove position. |
| BLDC / PMSM servo | Efficient continuous motion and strong joints | Commutation drive; encoder for precise servo control | Motor-drive compatibility, current limits, tuning. |
| Linear actuator | Push, lift, extend | DC or stepper drive plus limits/position feedback | Force, stroke, speed, duty cycle, and end stops. |
Work through the load
For a horizontal joint holding 0.5 kg at a 0.12 m lever arm, gravity alone needs τ = m × g × r ≈ 0.59 N·m. The real selection must also cover linkage weight, acceleration, friction, and a design margin. A stall-torque figure is not a continuous operating rating.
For a wheel, ideal tractive force is F = τ / r. Gearing trades speed for torque and adds losses. Mechanical power is P = τ × ω, with angular speed in radians per second.
Modern driver features
Feedback and faults
Use an encoder when you need actual motion. Monitor driver faults and temperature where available. A command sent successfully is not evidence that the shaft moved.
Commission gradually
Start with the load supported, conservative current limits, and low speed. Verify direction and limit switches before allowing a longer move.
What the PWM experiment means
The square wave illustrates duty cycle: the fraction of each period that the command is high. Motor speed is not simply duty multiplied by a universal RPM number. Supply voltage, back EMF, load, friction, and driver losses determine the actual response.
Go to the source
Manufacturer and project documentation. Reviewed 20 September 2026; check your exact board revision and software release.