Seeking advise on miniature pneumatic actuators and solenoid valve for a percussion player mechanism

Hello,
I want to experiment (just for fun) with a PC controlled percussion player mechanism. Initially I want to play with a small solenoid valve connected to a
small pneumatic piston. Piston will drive the hitting arm. I think max actuation/hitting rate would be around 20Hz. (Is this rate reasonable?) (I do not have any hands on pneumatic experience. That's why I've considered starting with pneumatic, so I can learn more)
How to control the hitting force in pneumatic system ? Can you recommend (low-cost) small/miniature solenoid valves and pneumatic pistons etc for this experiment? Any other suggestions?
Roberto
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Putting the pneumatics in the circuit introduces delays that might be hard to compensate, since they depend on manifold pressure. Why do you feel they are necessary? Why not hit the surface (or the far end of a lever with a striker on the other end) directly with the solenoid?
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On Mar 12, 12:20 pm, snipped-for-privacy@gmail.com wrote:

Hello zwsdot,
Yes, I think you are right. Just a solenoid (an electro magnet with long enough stroke length) would do the trick. Probably a PWM ignal may also control the applied force. What do you think? How to select solenoid? (Probably the selection parameters size diameter/length, stroke length, operating voltage/current,...) How to find out how much force required? (I think answer is the do some experiment?) Is there any application that you are aware of for the force control with solenoid?
Roberto
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Roberto wrote:

IIRC, Hanon's piano finger exercises are often played around 108 beats/minute, 4 quarters per beat. A Czerny exercise might go twice that. 120*8 keys/minute = 16 Hz. Yes, 20Hz is reasonable. On the percussion side, I'd guess that's near the max speed a snare drummer could perform.

As ZWS noted, pneumatics are not known for speed or precision...

Pneumatic force is proportional to the supply pressure. Solenoid force is proportional to the drive voltage. No good ideas for supply.

If you have trouble finding "the right parts", then get a single, cheap actuator moving first... If you have some servos modified for continuous rotation or similar motors handy, you might try attaching a spoked striking mechanism and spinning them at different speeds...
- Daniel
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D Herring wrote:

108 beast/min < 2 Hz, twice 108 beats/min < 4Hz. It is impossible to get 16 Hz using *ONE FINGER* (You can try :-) BTW, 20Hz accepted as continual sound, not as sequence of beats.

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Nick wrote:

Correct; I was quoting exercises where the pianist plays successive notes with different fingers. For "single-finger" speeds, Hanon's exercise 51 has the player play sixteenth-note octaves at 40-84 beats (quarters) per minute. That's 2.6 to 5.6 Hz per finger. The trick is not to move the fingers much; the wrist bounces much faster.

Yes, I've heard 20Hz quoted as the lower threshold of "sound", though most people's ears have a higher frequency cutoff. But I still maintain that any competent pianist can strike 12 or more keys in succession within a second. Horowitz did much better. Since the snare drummer uses two sticks, a combined rate of 2*5 Hz still seems easily achievable.
- Daniel
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Roberto wrote:

Not yet... 5 Hz is pretty enough.

Nick
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Hello,
In addition to the force applied by the striker to the percussion instrument's skin, there are more parameters to select and control;
Stirker Material: The striker material is important. Hitting to a drum, to a tabla, a darbuka etc by hand or with a wooden striker produce different sounds. Human player use different sections of their hands. They also chance the shape of their hands. How to do this on a robotic player?
Duration of Contact: The duration contact of the striker and with the instrument's skin produce different sounds. How to control this on a robotic player?
Location Of Strike: Location where the striker hits to the instrument surface produce different sounds. How to move the striker to different locations over the instrument on a robotic player?
Any comments?
Roberto
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People are scared of electric solenoids ,
so they opt for pneumatic .
But at 20 hz , solenoid is far more
controllable and effecient and lower
cost .
The trick to solenoids , is using switch
more techniques . Even a stepper motor
H bridge can be digital driven !
It actually simplifies circuitry .
Its fortunate , solenoid has high inductance.
Simply use current feedback to tell the
300khz driver when to on/off , and the inductance
limits the current rise , to allow enuf time for the
feedback to get to the controller ..
PWM'ing is another digital method that needs
inductance to create the analog result . -------------------------- The LM494 controls power supplies , but it needs to control dead band ( obsolete ) . More modern ,, is to use an oscillating ,, 2 transistor half H bridge . Like used on all elctronic ballast , flour' lites . First PC power supplies used LM494, now they oscillate , and i just bought a new PC p.s. that has only one NPN driver !
BTW My 93C66 serial EEPROMs are blank and i need to know if they will boot . Has anyone ever tried to boot ? 1) no address input 2) apply power 3) clock out data ,starting at 4) address 0000
__________________________-

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