Servo motor

Turn an SG90 servo to an exact angle, hold it there, and then move on to the next block.

A hobby servo turns its horn to an angle between 0° and 180° and holds it there. Use one for a gate, a pointer, a flag that pops up, or a little robot arm.

In ArduinoStudio each Servo block sends one Angle, then waits for its Duration before the next block runs. It works in the simulator, over USB direct in Chrome, and through the Bridge, so you don’t need the desktop app to drive a servo on a real board.

Wiring

Pin 9 is the block’s default, but any digital pin works: Firmata makes the servo pulse itself, so you don’t need a PWM (~) pin. Wire colours vary by brand. Signal is orange or yellow, power is red, ground is brown or black.

The Arduino’s 5V pin is fine for one SG90 with a light load. Bigger servos, or more than one, need their own 5 V supply. Join that supply’s GND to the Arduino GND.

Block settings

Step by step

1. Wire the servo

   Connect orange or yellow to pin 9, red to 5V and brown or black to GND. Press a horn onto the shaft so you can see it move.

2. Add the first Servo block

   Click + on the sequence, open the Components tab, open Motion and choose Servo. Keep Digital pin 9. Set Angle to 0 and Duration to 600 ms. Mode shows “Coming soon” and stays at “to”.

3. Add a swing to 180°

   Add a second Servo block with Angle 180 and Duration 1000 ms. Duration is how long the sequence waits before the next block. An SG90 needs about half a second for a full swing, so leave some margin.

4. Come back to the middle

   Add a third Servo block with Angle 90 and Duration 600 ms.

5. Repeat it (optional)

   Right-click the sequence name (long-press on a touchscreen) and tick Infinity Loop. The servo now repeats 0, 180, 90 until you press Stop.

6. Try it in the simulator

   Press Play with no board connected. In the Virtual Board panel, pin 9 is listed as SERVO and its value steps through 0, 180 and 90 while each block counts down its Duration. The Servo block itself shows a red OFF while it runs. That is a display quirk; the Virtual Board shows what is really happening.

7. Run it on the board

   Plug in the Uno, click USB direct in the toolbar, press Connect on the USB direct row and pick the board. Press Play. The horn swings to each angle and pauses for that block’s Duration. See Getting started if the board doesn’t show up.

Mini-project: push-button gate

Press a button and a gate opens, stays open for two seconds, then closes. Keep the servo wired as above and add a push button between pin 2 and GND, across its diagonal legs. No resistor is needed. The button guide explains why, and the idea comes from the servo gate project.

1. Start with the button

   Build one sequence and turn on Infinity Loop. Add a Button block from Inputs, with Digital pin 2.

2. Add a Check

   Add a Check right after it and keep its defaults (If =, To On/Off, Choose on). For a button, that means “pressed”.

3. Open, wait, close

   Add a Servo block with Angle 90 and Duration 500, a Wait of 2000 ms, then a second Servo block with Angle 0 and Duration 500.

4. Test it

   In the simulator, click pin 2’s toggle on the Virtual Board to 0 to press the button. On the board, use USB direct and hold the button down until the gate moves. The Check reads the button once per pass, so a quick tap can fall between readings.

Use USB direct for this project rather than the Bridge. The Bridge doesn’t turn on the button’s internal pull-up yet, so the gate can open by itself.

Questions