Slag-Werk

<Psch>

dr.Godfried-Willem RAES

2006/2015

[Nederlandstalige versie]

<Psch>

This pretty small robot was build in response to a question and request we had from many of our collaborating composers for an automated instrument that would be capable of producing the kind of 'reversed cymbal' sound and similar explosive noises so typical for techno musics. Our first idea went into the direction of precisely controlled compressed air exhausting in cavity resonators of different kinds. The first experiments were indeed very fruitful and convincing, but the problem was that we needed a steady supply of high pressure air at about 10 Bar. The compressor in our workshop fulfills this need very well, but every time it switches on to refill its reservoir, it produces an awful lot of noise (although it is labeled as ' silent compressor'...). Clearly unacceptable in concert situations. Of course we could use a tank of large capacity, say 500 liters, but that would be so bulky that we couldn't realistically take the resulting automate out on travels... Thus we went into investigations on electrically driven noise generators. Experiences with the automated thundersheet used and integrated in <Thunderwood> gained us some experience in this field. However, the brass sheet used in Thunderwood was way too large for a stiff and penetrating strong hiss sound. Also the solenoids used in thunderwood were way to sluggish for the sound we were after here. In earlier projects such as 'Hex' and 'Holosound' we used steel sheets (normally used as shims in precize metal construction) set into vibration and eventually into feedback using piezo disks both as drivers and as receivers. These projects however did not use the acoustic sound of the sheets directly but called for amplification. In our robot orchestra we very much on purpose avoid any kind of audio amplification, all sound being inherently acoustic. Thus the problem became to find a mechanism such that the sheets could be set into vibrations strong enough to produce an acoustic sound of the desired sound level and power.

For <Psch>, in the final design we ended up with 12 driving solenoids with individual metal sheets of different thickness. Stainless steel of the martensic kind was found to sound best. The maximum sound level is a function of the size of the sheets or foils used. The noise characteristics (spectral composition) are merely a function of material thickness (and related to it, stiffness). A steady noise can be produced by shaking the sheets at speeds exceeding the mechanical and very low resonant frequency of the pendulum system formed by the combination of sheet and solenoid anchor. Single strokes at high activation forces produce noise shots. With the thicker sheets however, flexatone-like sounds with clear sliding pitch content can occur.

Circuitry:

The midi in and buffer circuit is very straigthforward. We used a circuit board we had developed many years ago:

The circuit for the PIC processor is identical to the board used for automats such as <Vacca>, <Llor>, <Puff>.. So for details, we refer to those webpages. The mapping and functionality of the output pins however, is different.

Since the blue lites on <Psch> operate on 12V, (current 40mA) we had to lower the supply voltage (48V) and used a simple resistance voltage divider on a sepate board with power resistors:

The power supply is a Siemens Sitop SMPS type, featuring adjustable output voltage up to 52Volts. We adjusted it to 48V, twice the nominal working voltage for the solenoids, for this automate.


Midi Mapping:

Lights: for the lights, velocity nor keypressure are implemented. So they can just be switched on or off.

Details with regard to the selection and default disposition of sheet materials: (The note order is such that we have -on the ear- a scale of more or less ascending noise pitch bands).

Alternative available and tested sheet materials:

 

Technical specifications:

Pictures taken during construction:

 

Compositions for <Psch>:

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Nederlands:

<Psch>

Deze automaat ontstond in eerste plaats op vraag van vele komponisten en medewerkers aan de uitbouw van ons robotorkest naar een automaat die in staat zou zijn ook het 'omgekeerd cimbaalgeluid', zo typisch voor techno muziek, te produceren. Onze eerste ideeen terzake gingen in de richting van perslucht, gekontrolleerd ontsnappend in een of andere resonator. De proeven daarmee verliepen uitstekend en erg overtuigend maar, de perlucht diende wel een druk te hebben van ca. 10 Bar. Op zich geen probleem want de kompressor in ons atelier levert dat op zijn sokken. Echter, na enkele minuten geluidsproduktie was het voorraadvat leeg en schakelde de kompessor aan met een oorverdovend lawaai voor gevolg. De kompressor heeft nochtans een groot label 'silent compressor', maar wat zo'n slogans betekenen weten we onderhand natuurlijk ook wel. Het vooruitzicht op reis te moeten trekken met een op voorhand gevuld vat perslucht van minstens zo'n 500 liter, leek ons niet direkt een aantrekkelijk alternatief. Dan maar langs elektrische weg geprobeerd. Uiteraard hadden we reeds enige ervaring opgebouwd met donderblikken, onder meer bij de bouw van <Thunderwood> waarin een groot hard-messing donderblik werd geintegreerd, maar de besturing daarvan was veel te traag voor wat ons hier voor ogen stond. Hier hadden we behoefte aan uiterst dunne metaalbladen (veerstaal of inox) van relatief kleine afmetingen en erg snelle elektromagnetische drivers. Daarmee hadden we reeds heel wat ervaring opgedaan, lang geleden, bij de bouw ontwikkeling en kompositie van projekten zoals 'Hex' en later, Holosound. Daarin maakten we gebruik van heel dunne staalbladen opgehangen aan, of aangebracht tussen, twee piezoelektrische transducers. In de bladen konden we zo uiterst rijke en geschakeerde geluiden en klanken opwekken, mede door gebruik te maken van komputer gestuurde feedback (cfr. onze multidimensionele oscilatoren uit de jaren '70 van vorige eeuw). In die projekten werden de trillingen van de bladen evenwel elektronisch versterkt en zo naar de luisteraar gebracht. Versterking evenwel staat haaks op het koncept van het robot orkest zoals ons dat hier voor ogen staat. Alle robots in het robot orkest werken immers voor hun geluidsproduktie zuiver akoestisch.

In het uiteindelijke ontwerp, implementeerden we 12 trilplaten in inox van verschillende dikte en afmetingen, aangedreven door sterke elektromagneten met lichte hefbomen in licht aluminium. De geluidsterkte is een funktie van enerzijds de exitatie kracht maar wordt anderzijds begrensd door de totale oppervlakte van de folie. Hoe groter het oppervlak hoe groter ook het dynamisch bereik van de beschouwde plaat. De ruiskarakteristieke (bandbreedte en kleur) daareentegen blijken een funktie te zijn van de materiaaldikte en, daar deels ook mee gekorreleerd, de stijfheid of elasticiteitsmodulus. Voor wat dit laatste betreft bleek gehard martensitisch inox veruit het beste resultaat op te leveren.

<Psch> werd ontworpen om te worden opgehangen. Uiteraard dient de ruimte daarvoor mogelijkheden te hebben die aan de stevigheidsvereisten voldoen. Eventueel kan <Psch> ook op de bodem worden opgesteld, opgehangen in het daartoe ontworpen bijhorende statief. De klankprojektie is dan evenwel niet optimaal, tenzij de vloer zelf niet geluidsabsorberend is. Ter bescherming van de allerdunste metaalfolies (0.02mm is werkelijk flinterdun!), plaatsten we deze in het midden van de automaat en de dikste platen (0.3 en 0.4mm) aan de beide buitenzijden.

<Psch> beleefde zijn eerste publieke optreden naar aanleiding van het <M&M> techno en ambient koncert van 14.03.2006 in de Logos Tetraeder..


Midi Mapping:

Specifieke komposities voor <Psch>:


Bouwdagboek:


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Last update: 2016-09-27 by Godfried-Willem Raes


Servicing and spare parts information:

<Psch>:

Solenoids: 12 x Laukhuff, type 300810. Nominal voltage (100% duty cycle): 24V, 410mA. Resistance: 59 Ohm. Force: 10N. Displacement: 10mm.

Power Supply: Siemens SITOP. Polyphony is limited by the power of this supply. It will switch off and go in autoprotect mode on overloads. Voltage should be adjusted to 48V.

Metal sheets: different brands and materials can be used: Hasberg, Lamifol, polyacrylate or polycarbonate sheet etc. Stainless steel and/or brass recommended. Maximum thickness: 100µm. The mounting hole should be 5mm. (Clamp the sheets between stronger material during the drilling operation for this hole). Stainless steel hex inbus bolts (M5 x 12) and nuts with washers are used for mounting. Lamifol as a brand name ceased to exist in 2015 and is now replaced by Georg Martin Gmbh material under the name M-Tech.

Optocoupler: 6N138 (on midi input board)

PIC-processor board: MidiPulse Rev.2, 2004. ( same board as used for <Vacca>)

PIC-firmware:

LED-spots 12V / 40mA

Midi in and buffer board design, including the 5V dc power supply also used for the PIC board:

Lookup table for the repeat frequencies as implemented in the firmware version 2.1:

Key pressure or

CC#30 value:

Repeat frequency in Hz:

Dur[1]= 41667

freq= 1.0000000000000

Dur[2]= 39494

freq= 1.0550125757499

Dur[3]= 38450

freq= 1.08365843086259

Dur[4]= 37434

freq= 1.11307011451265

Dur[5]= 36445

freq= 1.14327525495038

Dur[6]= 35482

freq= 1.17430434210774

Dur[7]= 34544

freq= 1.20619113787247

Dur[8]= 33631

freq= 1.23893629885126

Dur[9]= 32743

freq= 1.27253662360403

Dur[10]= 31877

freq= 1.30710752789367

Dur[11]= 31035

freq= 1.34257021642232

Dur[12]= 30215

freq= 1.37900601246621

Dur[13]= 29416

freq= 1.41646269603844

Dur[14]= 28639

freq= 1.45489251254117

Dur[15]= 27882

freq= 1.49439303732396

Dur[16]= 27146

freq= 1.53490999287802

Dur[17]= 26428

freq= 1.57661066545583

Dur[18]= 25730

freq= 1.61938074880166

Dur[19]= 25050

freq= 1.66333998669328

Dur[20]= 24388

freq= 1.70849051446066

Dur[21]= 23743

freq= 1.75490319953951

Dur[22]= 23116

freq= 1.8025033166061

Dur[23]= 22505

freq= 1.85144042064726

Dur[24]= 21910

freq= 1.90171915411532

Dur[25]= 21331

freq= 1.95333864641445

Dur[26]= 20768

freq= 2.006291730868

Dur[27]= 20219

freq= 2.06076792455941

Dur[28]= 19685

freq= 2.11667090000847

Dur[29]= 19164

freq= 2.17421554303207

Dur[30]= 18658

freq= 2.23317969057062

Dur[31]= 18165

freq= 2.29378842095605

Dur[32]= 17685

freq= 2.35604561304307

Dur[33]= 17218

freq= 2.41994811631239

Dur[34]= 16763

freq= 2.48563304102289

Dur[35]= 16320

freq= 2.5531045751634

Dur[36]= 15888

freq= 2.62252433702585

Dur[37]= 15469

freq= 2.69355916133342

Dur[38]= 15060

freq= 2.76671093404161

Dur[39]= 14662

freq= 2.84181330423316

Dur[40]= 14274

freq= 2.91906029610948

Dur[41]= 13897

freq= 2.99824902257082

Dur[42]= 13530

freq= 3.07957625030796

Dur[43]= 13172

freq= 3.16327563518575

Dur[44]= 12824

freq= 3.24911624038262

Dur[45]= 12485

freq= 3.33733813910025

Dur[46]= 12155

freq= 3.42794460441519

Dur[47]= 11834

freq= 3.52092839840009

Dur[48]= 11522

freq= 3.61627032343922

Dur[49]= 11217

freq= 3.71459986330272

Dur[50]= 10921

freq= 3.81527943106553

Dur[51]= 10632

freq= 3.91898670679709

Dur[52]= 10351

freq= 4.02537597011561

Dur[53]= 10078

freq= 4.13441820467024

Dur[54]= 9811

freq= 4.24693371385859

Dur[55]= 9552

freq= 4.36208821887214

Dur[56]= 9300

freq= 4.48028673835125

Dur[57]= 9054

freq= 4.60201752448273

Dur[58]= 8815

freq= 4.72679145396105

Dur[59]= 8582

freq= 4.85512312592247

Dur[60]= 8355

freq= 4.9870337123479

Dur[61]= 8134

freq= 5.12253094008688

Dur[62]= 7919

freq= 5.26160710527423

Dur[63]= 7710

freq= 5.40423692174665

Dur[64]= 7506

freq= 5.5511146638245

Dur[65]= 7308

freq= 5.70151432220398

Dur[66]= 7115

freq= 5.85617240571562

Dur[67]= 6927

freq= 6.01510995621

Dur[68]= 6744

freq= 6.1783313562673

Dur[69]= 6565

freq= 6.34678852500635

Dur[70]= 6392

freq= 6.51856487275761

Dur[71]= 6223

freq= 6.69559162247576

Dur[72]= 6059

freq= 6.87682235792485

Dur[73]= 5898

freq= 7.06454165253758

Dur[74]= 5743

freq= 7.25520924023449

Dur[75]= 5591

freq= 7.45245334764204

Dur[76]= 5443

freq= 7.65509216730969

Dur[77]= 5299

freq= 7.86311882745172

Dur[78]= 5159

freq= 8.07650061381405

Dur[79]= 5023

freq= 8.29517552591413

Dur[80]= 4890

freq= 8.52079072937969

Dur[81]= 4761

freq= 8.75166281593503

Dur[82]= 4635

freq= 8.98957209636821

Dur[83]= 4513

freq= 9.23258734027624

Dur[84]= 4393

freq= 9.48478640261021

Dur[85]= 4277

freq= 9.74203101862676

Dur[86]= 4164

freq= 10.0064040986231

Dur[87]= 4054

freq= 10.277914816642

Dur[88]= 3947

freq= 10.5565408326999

Dur[89]= 3843

freq= 10.842223956978

Dur[90]= 3741

freq= 11.1378419317473

Dur[91]= 3642

freq= 11.4406004027091

Dur[92]= 3546

freq= 11.7503290092122

Dur[93]= 3452

freq= 12.0702974121282

Dur[94]= 3361

freq= 12.3971040364971

Dur[95]= 3272

freq= 12.7343113284434

Dur[96]= 3186

freq= 13.0780498012136

Dur[97]= 3102

freq= 13.4321942832581

Dur[98]= 3020

freq= 13.7969094922737

Dur[99]= 2940

freq= 14.172335600907

Dur[100]= 2862

freq= 14.5585837409737

Dur[101]= 2787

freq= 14.9503647889008

Dur[102]= 2713

freq= 15.3581521071385

Dur[103]= 2641

freq= 15.7768522024486

Dur[104]= 2571

freq= 16.2064047711656

Dur[105]= 2504

freq= 16.640042598509

Dur[106]= 2437

freq= 17.0975242784845

Dur[107]= 2373

freq= 17.5586458772299

Dur[108]= 2310

freq= 18.037518037518

Dur[109]= 2249

freq= 18.5267526307989

Dur[110]= 2190

freq= 19.0258751902588

Dur[111]= 2132

freq= 19.5434646654159

Dur[112]= 2076

freq= 20.0706486833654

Dur[113]= 2021

freq= 20.616856341745

Dur[114]= 1967

freq= 21.182850364345

Dur[115]= 1915

freq= 21.7580504786771

Dur[116]= 1865

freq= 22.3413762287757

Dur[117]= 1815

freq= 22.9568411386593

Dur[118]= 1767

freq= 23.5804565176382

Dur[119]= 1721

freq= 24.2107301956227

Dur[120]= 1675

freq= 24.8756218905473

Dur[121]= 1631

freq= 25.5466993664418

Dur[122]= 1588

freq= 26.2384550797649

Dur[123]= 1546

freq= 26.9512721000431

Dur[124]= 1505

freq= 27.6854928017719

Dur[125]= 1465

freq= 28.4414106939704

Dur[126]= 1427

freq= 29.1987853305302

Dur[127]= 1389

freq= 29.9976001919846

Note that if using vel=127, the fastest possible repeat speed will be limited to 19.2Hz.