Servos

A hobby servo turns to an angle and holds it. It is the classic choice for a skull jaw, a turning head, or a lid that lifts.

Wiring

A servo has three wires:

Servo wire	Goes to
brown / black (ground)	the servo supply’s GND and a board GND
red (power)	a separate 5 to 6 V supply
orange / yellow / white (signal)	a board pin

Give servos their own power

Don’t power a servo from the board’s VIN or 3V3 pins. When a servo starts to move it pulls a burst of current, the board’s voltage dips, and the board restarts, usually in the middle of a scare. The fix is a 5 V supply of 2 A or more, with its ground joined to the board’s.

Which pin? The board pages mark the best servo pins with ★. Those pins stay quiet while the board starts up, so the prop doesn’t twitch every time it gets power.

Setting it up in the console

Assign the pin to Servo. Its options are:

• min / max (µs): the pulse lengths at each end of travel. The defaults are 500 and 2500. Most props only want part of the servo’s range. A jaw might only need to open a little.
• reverse: swaps the direction.
• smoothing: how the servo gets from one position to the next. Choose Off (it snaps), Snappy · 250 ms, Smooth · 600 ms, Gentle · 1000 ms, Slow · 1500 ms, or Custom….

Finding the end stops

After Save to node, press Calibrate in the TEST column. Move the slider until the jaw is just closed and press Set as min. Move it until the jaw is open as far as it should go and press Set as max. Then press Done and save. From now on, 0 % means “closed” and 100 % means “open”.

Tip

Start from the middle and move toward each end slowly. A servo pushed past the prop’s real limit buzzes and gets hot.