<PlayerPiano>

I & II

Godfried-Willem RAES

1994/1995/2005/2007

Technical Description Player Piano I

 

This instrument requires a normal 230Volts / 1300Watt mains connection. The control computer should always be setup centrally in front of the keyboard and connects to the playing mechanism with four thick bundles of flatcables. The module accepts normal midi input, but files considered for playing should always be passed to our staff prior to being played. There should be no controllers in the files and any note-on command should be strictly followed by a corresponding note-off command. The instrument is fully polyphonic (88 notes) and has a 7-bit velocity control for each individual key. Velocity scaling is not linear and depends both on the type of piano and on the hammerweigth for the notes to be played.

Musical range:

 

Note for organizers:

the player pianos I and II will always and only be operated by a qualified technician or musician from the Logos Foundation. So, the instruments will not be rented out on their own. (Don't even ask). The insurance value for these instruments is 12.500 €. The grand piano itself has always to be provided by the organizer. No modification on the piano itself is required. Placement of the instrument on the piano is absolutely harmless to the instrument. Note that the music requires the piano to be in top condition and well tuned.

Transportation of the robot is possible with any normal sized car. The case of the mechanism measures 1400mm x 200mm x 200mm for <Player piano 1>, and 1320mm x 150mm x 150mm for <PP2>. The control computer for player piano I is build into a 6 unit 19" rack. For <pp2> it is a much smaller module containing only the hefty power supply. The Vorsetzer case is very heavy (47kg) and requires 2 people to be lifted up and carried. Installation on the piano takes less than five minutes.

Please note the technical requirements with regard to the piano: 88 keys grand piano and a free flat space on the left and on the right side of the keyboard of at least 31mm.

  Player Piano 1 Player piano 2 ( <PP2> )
Weight with case 47kg 49kg + power supply
Netto weight   30kg
Case sizes

1310mm x 155mm x 150mm

stainless steel

1320mm x 155mm x 160mm

stainless steel
Pedal module   35kg
Power Supply/ control unit 6 unit 19" Rack in flight case 370mm x 250 x 70mm, no case
Insurance value

12.000€ + 500€ (flight case)

total: 12.500€

12.000€ + 1.000€ ( flight case) + 1.500€ (pedal) + 500€ (flight case pedal)

total: 15.000€

 

Technical Description <Player Piano II>

In this model, <pp2>, the key controlling electronics could find a place in and on the Vorsetzer chassis itself. Only the hefty power supplies (24V and 12V 1200Watt) remain in a separate box to be placed under or inside the piano. Therefore, the mechanism is slightly heavier than the first model. The power supply is a lot lighter (ca. 5kg) than the control computer used for player piano 1. The new power supply fits in a normal attaché case. A mechanism to operate the right pedal is available as well and is conceived as a separate robot. (Insurance value: 1.500€, weight 35kg) For detailed specs, click on the link above). This pedal can be used both with the first model as with the newest model of our player piano.

The circuit for the control of 10 piano keys came out like this:

A single vorsetzer mechanism needs nine of these circuit boards. The midi input board, with 9 TTL midi output signals to feed the boards above and incorporating a simple +5V dc supply for them look like

The 5V dc voltage is derived from the positive hold power supply. This introduces a small risk: in case of power supply overload due to a too large amount of keys pressed together, this power supply may go in safety shut down, leading to a reset cycle on all the PIC controllers.

A separate pedal robot was designed between 1994 and 2005 to be used in combination with both models of player piano. It is documented in a separate webpage: Piano Pedal Robot.

Collaborators on the design and realization of player piano II:

Construction log for Player Piano II:

 

Notes on the calculation of the power supply capacity:

If we take solenoids with a DC resistance of Rdc = 19.1 Ohm and we want full polyphonic (88 notes!) playing capability, the maximum current the hold-power supply (here nominal specified at Uh=12V) should be capable of delivering is: Imax = 88 Uh / Rdc = 55A, or in power terms: 660Watt.

If the automate should not be capable of surpassing human polyphony on the piano, we can content ourselves with 20 note polyphony, including fist and clusterplaying by humans. In that case the power supply requirements become Imax = 12.6A and Pmax = 151Watt.

In our practical design for pp2, we went for a Sunpower 12V/50A power supply and trimmed the output voltage down to 10.5V. This value should should ideally be chosen such that when a key is depressed with velo=1, we hear nothing. Unfortunately, this value is greatly dependent on the adjustment of the piano itself. On worn out pianos one would need a specific voltage for every single key in order to allow for reliable silent depressing of keys. With the abovementioned practical values, we can depress all keys together without going over the ratings of the power supply, since it will draw just 48.4A.

The calculation for the requirements on the velo-power supply are a little more complicated. A first limiting factor is due to the fact that data are transmitted to the player piano in a serial (midi) format. If the note-on messages flow in neck to neck at the full midi baud-rate of 31250b/s, the minimum time between the starts of any two note-on commands will be 952 microseconds. Thus a command to play all 88 notes at once will take a minimum time of 83ms. We will hear this as a fast arpeggio. This is unavoidable although the effect can be greatly masked by sending all the notes in such clusters out of order.

If we scale the duration of the 1-127 velocity range from midi on pulse-times in the range 156 microseconds to 20ms, the consequence is that given the limitations of midi, we can have a maximum of 20ms / 952µs = 21 overlapping velo-pulses. If we use a 24V power supply, the current required from it is thus reduced to: 21 . (24V / 19.1) = 26.4 A, or in power terms : 633Watt.

The total peak power required for the automate becomes thus 660W + 633W = 1293W.

Practical SMPS selection:

Both power supplies need modifications in order to make them silent. As they are, they are well enclosed (understandable for safety reasons...) and cooled with a small 'made in Taiwan' but strong and extremely noisy fan. Completely unacceptable for concert use of course. The fan is connected internally to the main PC board with a small 3-pin receptacle. The black wire connects to the negative power output, the red one feeds the 12V rated (140mA) fan motor and the yellow one seems to be some kind of sensor. In the way this operates, both power supplies are quite different. On the 12V/50A model, if you mechanically block the fan or unplug the connector, the power supply shuts down. It needs to see a voltage no smaller then 50mV on the yellow connection. So we replaced the fan with a resistor of 100 Ohms / 2Watt in series with 0.47 Ohm.

On the 24V/25A power supply, it seems one can disconnect the fan connector without replacing it by any kind of dummy. The voltage we found here on the yellow sense wire is 22.9V. For cooling we removed the top covers of both power modules and constructed a new cover from perforated metal sheet, for natural convection cooling.

Power Mosfet types used:

IRF540: for velo pulse: Specs: 27A/100V, Ron = 0.085 Ohm,k Ci=1.45nF, ton delay= 15ns, ton risetime = 70ns, toff = 50ns.

IRL640: for key hold: Specs: 17A/200V, logic level mosfet. (Ug=5V). No cooling applied. IRLZ44N can be used as an alternative.

Solenoid type used for <pp2>: Lucas Ledex (now distributed by Saia-Burgess) STA type 195207-228 (13.8V DC @ 100% duty), 10Watt, 7.8N @ 5mm with 60degree plungers. 26mm diameter, height 52mm.

Repertoire:

Contemporary Music Player Piano Repertoire available at Logos

Conlon NANCARROW (1912-1997)

Godfried-Willem RAES (1952-)

Hans ROELS

Kris DE BAERDEMACKER

Joachim BRACKX

Barbara BUCHOWIEC

Francesca VERBAUWHEDE

James TENNEY (1934-2006)

Kristof LAUWERS

Sebastian BRADT

Mauricio KAGEL

Caroline WILKINS

Claude COPPENS

Cornelius CARDEW (+)

Moritz EGGERT

Gyorgy LIGETI (+)

Peter CASTINE

Siegfried KOEPF

Klarenz BARLOW

 

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Last update: 2008-01-13 by Godfried-Willem Raes

The circuit boards, each controlling 10 piano keys, were designed by Johannes Taelman and look like:

The newest boards use a more advanced PIC (an 18F4520) and can control 14 notes each. With this board, only 7 boards are required for a full 88 keys keyboard. The boards are available from the logos foundation. Detailed descriptions can be found on our page on <Qt>, since this 6-octave quartertone organ robot uses the same boards.