School of Arts



robotic chinese temple blocks by

  • Thomas Strypsteen
  • Stijn Smeets
  • Tim Duerinck

supervised by

dr.Godfried-Willem RAES


[Nederlandstalige versie]


Technical Description

Temple blocks are in origin Chinese percussion instruments used in religious ceremonies. The instruments can also be found in this context in Korea and Japan. It is a carved hollow wooden instrument with a large slit. In its traditional form, the wooden fish, the shape is somewhat bulbous. From an acoustic point of view they function much like a tuning fork and their cavity like a Helmholtz resonator. The pitch of both elements should be matched for a good hollow and resonating sound. As such it is a synergetic construction.

Temple blocks are often found in the percussion section of classical orchestras in a simplified (and generally poorly sounding...) rectangular shape. Most commonly one will encounter them in a group of five blocks of different pitches. The picture below shows such a set of five chinese temple blocks, arranged on a stand to comfort percussionists, dating from the interbellum.

The original chinese instruments can be found in widely varying sizes: from close to 1 meter for the very largest ones up to really tiny ones not larger than 3 cm. The very small ones have a sharp and very penetrating tone. A set of very small ones can be seen on this picture: They are hand carved from a single piece of relatively soft wood and covered with a thick layer of mostly red chinese lacquer. The lacquer not only protects the wood against moisture and the impact of the beater, but also changes the sound somewhat in making the attack sharper. The traditional lacquer is derived from urushiol, a substance from the toxicodendron vernicifluum and has the property to form a natural polymere in the presence of moisture and medium heat. Once cured, it is hard and stable but the fresh substance itself gives cause to quite severe allergic reactions when brought in contact with the skin. In China the temple block is usually placed on a cushion. Mounting them in a stand is a western adaptation. Although they produce a quite distinct tone and pitch they are never used as pitched percussion instruments. Each temple block has its own individual beater, as the weight and hardness of the beater head has to match the size and weight of the block to be struck. The original chinese beaters are rarely used by percussionists in western ensembles and orchestras. Medium hard cloth covered vibraphone or marimba mallets give a good sound. Using too hard mallets (drumsticks, hard nylon beaters...) lead invariably to destruction of the templeblock, first by cracking the lacquer, secondly by destroing the wood itself.

The idea of making an automated set of temple blocks arose from educational needs: In 2012 we were asked to teach a class on modern instrument building and automation for the students enrolled in the instrument building program at the School of Arts (Ghent University College). After discussing the topics to be treated, we decided with the students to set up a building project that could be finished within a single academic year. Hence the choice of a percussion robot, as this seemed to require the minimum of preliminary research, without being a trivial undertaking. The fact that it would constitute a most welcome addition to the robot orchestra and not merely an academic project seemed a challenge to the students involved. The building project was started in october 2012 and the first automated sounds came out in february 2013. By the month may, Temblo made his final entry into the robot orchestra and many composition students wrote a piece for the newborn robot.


Complete Midi Implementation table for <Temblo>:

Midi Channel: 12 (counting from 0)

Command meaning / effect


(+= implemented)

NOTE OFF (128 +12)

releases the hammers instantly for notes 60-65 and 72-77

switches off the lights for notes 120-127, switches off the ratchet motor.


NOTE ON (144+12)

note range 60-65 (low blocks) and 72- 77 (high blocks), velo implemented.

note 69: ratchet, velo steers the rotation speed.

note range 120-125: lights: here the velo byte steers the flashing speed

note range 126-127:lights: here the velo byte steers the dimming (light strenght)

POLY AFTERTOUCH (160_12) implemented for the lights only. (notes 120,121,122,123,124,125, 127) +
CONTROLLERS: 176+12 nr.66: Power on/off switch
nr 123: All notes OFF (emergency note off)
PROGRAM CHANGE 192 + 12 Not implemented


CHANNEL PRESSURE 208 + 12 Not implemented No
PITCH BEND 224 + 12 Not implemented No
SYSEX Not implemented


241 and higher Not implemented no real time msg's No


Compositions for the <Temblo> Robot:

Technical data and instrument passport:

name: <Temblo>

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Een nederlandse beschrijvende tekst is voorlopig nog niet beschikbaar. Het bouwdagboek daareentegen is -met het oog op de betrokken studenten- integraal in het nederlands geschreven.


Dagboek voor de bouw van <Temblo>:


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Naar Godfried-Willem Raes personal homepage... Naar katalogus instrumenten gebouwd door Godfried-Willem Raes Go to Godfried-Willem Raes' homepage

Last update: 2013-10-09 by Godfried-Willem Raes

Maintenance information:

Power supply circuit:

Pulse driver processor board:

Alternative circuit, using programmable 16-bit hardware timers:

Midi-Hub board:

Solenoids used for the small temple blocks: Lucas Ledex type 195203-234. Size: 0.5" x 1" . These are the essential specs, taken from the Ledex data sheet:

The operational voltage for 100% duty cycle operation is specified at 12.2V, climbing to 39V for a 10% duty cycle. We use them with pulses ranging between 500us and 3.75 ms on a voltage of 70V. Single note repetition rate at the longest pulselengths should be limited to 13.5 beats a second, yielding a duty cycle of 5%. Coil resistance at 20 degrees temperature is 37 Ohms. Thus the peak current during the stroke can be as high as 1.89 A. Acceleration can be calculated as 12.7 m/s^2

Solenoids used for the large temple blocks: August Laukhuff, kleiner trakturmagnet. DC coil resistance: 30 Ohms. Here again, we keep the duty cycle as low as 5% worst case. Nominal working voltage at 100% duty cycle: 12-14V. We use them with 70V pulses ranging between 1.5 ms and 8 ms. Note that these solenoids are always delivered with soldered-on surge supressors (VDR's). These have to be removed in any case as they contradict the way we are using these solenoids. The protection by the diodes on our pulse driver PC board provide ample protection.

Ratchet motor: Philips 24V DC, geared. Model MB15, 4 mm spindle. Order nr. 9904 120 52705. Current consumption: no load: 20mA, with load 40mA.