Hardware - Actuator Groves

Seeed lists some optical output devices (e.g., LEDs) as Actuators and others as Displays. Also, they (incorrectly) list the Button as an Actuator. We attempt to be both compatible and correct, but obviously, YMMV.


The Seeed wiki (incorrectly) lists the Button as an Actuator. However, it is actually a Sensor.



The Servo Grove uses a small servomotor, as used in radio-controlled models (e.g., airplanes, boats, cars). It responds to a train of pulses that have a varying duty cycle (i.e., time spent in the HIGH vs. the LOW state). The servo attempts to maintain its shaft in the corresponding angular position.

This Grove is normally cabled to a digital port (e.g, D3) whose "lower" line (e.g., D3) is capable of generating a Pulse Width Modulated (PWM) signal. Typically, the signal's pulses are integrated (summed) inside the servo to produce an appropriate analog control voltage.

This kit doesn't have a Grove card, just a servo motor with a cable and plug. The motor comes in a small, zip-lock baggie. An even smaller baggie contains four stiff plastic objects, along with screws for attaching them to the end of the motor's shaft:

  • bar (2.1" long), attached in the center
  • bar (0.7" long), attached at one end
  • cross (1.0" wide), attached in the center
  • disc (0.7" wide), attached in the center


LCD RGB Backlight

Per the Seeed wiki, we cover this as a Display.

LED Socket Kit

Per the Seeed wiki, we cover this as a Display.



The Buzzer Grove is actually a piezoelectric speaker, so it can be hooked up to an analog (e.g., integrated PWM) signal to produce arbitrary tones (i.e., sound waveforms). However, it also has the ability to buzz when driven by a fixed-frequency (e.g., square wave) digital signal.

The active component is a squat cylinder, mounted on the top surface of the Grove. It is about 0.2" tall and 0.4" in diameter, with a 0.1" hole in the top center. The buzzer and port socket are on the top of the Grove.


Relay (modified)

The Relay Grove is an electrically-operated mechanical switch that can close (i.e., connect) or open (i.e., disconnect) a pair of contacts under computer control. The contacts are quite substantial, handling several amps at up to 250 VAC or 30 VDC.

This Grove is normally cabled to a digital port (e.g., D2); the lower line is used as the driving signal. It is a bit bulky, because of the relay component (a plastic box, about 0.6" high, 0.7" wide, and 0.6" deep). A "normally open" (NO) pair of relay contacts is hooked up to a plastic-cased pair of screw terminals, located between the relay and the socket. (We attached a pair of clip leads to these terminals, for convenience.)

Specifically, the boards we have use the following relay:

He Li Shun HLS8L-DC5V-S-C
Subminiature SPDT Relay 5V - 10A/120VAC HLS8L-DC5V-S-C

Because this is an SPDT (single pole, double throw; i.e., form C) relay, it can switch a signal line between a pair of contacts. Although the Grove only provides access to one (normally open) contact, the pins from the relay are available on the bottom of the board. If you need access to the third (normally closed) contact, an additional wire could be soldered to the appropriate lead.


This wiki page is maintained by Rich Morin, an independent consultant specializing in software design, development, and documentation. Please feel free to email comments, inquiries, suggestions, etc!

Topic revision: r4 - 17 Apr 2017, RichMorin
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