Week 5 Tutorial: Actuator studio

Wiring a motor, servo, LED or speaker to your board and closing the loop with last week's sensor

22 March 2027

Before the session#

Bring the sensor and board from week 4, still wired and working.

In the session#

1. Attend the lecture on actuators, then move into tutorial time. Last week’s board only read the world through a sensor; this week it writes back out to it, so the tutorial time is built around getting one motor, servo, LED or speaker moving under code before you worry about wiring it to anything upstream.
2. Pick a motor, servo, LED or speaker and wire it to your own board. Each of these actuators has its own wiring requirement, and skipping it is the fastest way to lose a part — or a session — to smoke rather than motion:
   • An LED needs a current-limiting resistor in series. Without one it draws as much current as the pin will give it and burns out in seconds — the resistor is cheap insurance, not an optional extra.
   • A small DC or vibration motor needs a transistor or H-bridge driver rather than a direct pin connection, because a microcontroller pin can only supply a few tens of milliamps and a motor wants far more. The driver lets the board switch a separate, higher-current supply instead of trying to push that current through itself.
   • A servo takes power, ground and a single PWM-capable signal pin — the width of the pulse on that one pin tells the servo which angle to hold, so once it’s wired correctly the code side is close to one line.
   • A piezo speaker can run straight off a digital pin through a small resistor, with no driver needed at all, which makes it the quickest actuator here to get making a sound if you want an early win.
3. Reconnect the sensor you wired in week 4 so it’s on the same board as the new actuator. You’re not starting a new circuit — you’re adding an output to last week’s input on the same board, which is what makes the loop in step 5 possible. If the sensor stopped working over the week, fix that connection now, before the actuator is also wired, so you’re only debugging one new thing at a time.
4. Before driving anything that draws more current than the board can supply, get a tutor to check your wiring. Power supply is the part that catches people out: a motor or a bright LED wants more current than the board’s regulator is rated for, and a driver wired backwards, or a ground shared incorrectly between the board’s supply and the actuator’s supply, is a fast way to damage a board. A quick check before power goes on costs a minute and saves a rebuild.
5. Wire the actuator so it’s driven by the sensor reading rather than a hard-coded value, closing a minimal input-to-output loop. A fixed value on the actuator only proves the wiring works; reading the sensor value in the same sketch and mapping it onto the actuator’s output — brightness, angle, speed or pitch — is what turns two separately-working parts into the physical-computing loop the spec actually asks for.

Afterwards#

You leave with a sensor-to-actuator loop running on your own board — the minimal version of the physical-computing pillar, and the base week 6’s bridging session connects to the digitizing and programming pillars.