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  #21  
Old 03-25-2013, 01:28 AM
Jeff Jeff is offline
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Originally Posted by JohnnyRC View Post
This from the MIDI interface I am using, below: however I have had issues with this interface and has gone CW (continuous wave) and I've shorted several of my Bridge Rectifiers during the event. So perhaps another suggestion for firmware update would include some sort of protection?



Pulsewidth protection circuitry monitors each input modulator pulse and compares it to a user programmable maximum pulsewidth limit. If the modulator pulsewidth exceeds the preset maximum pulsewidth limit, the output pulse will be truncated to the maximum pulsewidth length. This ensures that the output of the controller will never operate at high or 100% duty (CW.) Specialized logic also ensures that the output pulse cannot be retriggered during a fault condition.
Maximum pulsewidth protection circuitry is done externally with discrete components and is independent of the microcontroller. This ensures that if the microcontroller locks-up or fails, that a CW condition is never seen at the output of the MIDI interface card.

Cool, another DRSSTC builder.

I don't want to take any business away from John, but the MD24 isn't a good choice for use in a DRSSTC driver application.

There isn't enough resolution in the MD24 MIDI controller commands to vary the on-time PW within the range needed for proper ring-up and safe operation. The MD24 works very well with servos, motors, solenoids and lighting. Although your feature description basically describes how a well engineered DRSSTC driver would operate.

I highly recommend you use a purpose built DRSSTC driver like Steve Ward's UD2, and a fiber linked MIDI controller that is available from a few different sources.
Component cost is very reasonable if you assemble it yourself. The 4hv forum has plenty of published information about the UD2, and related tuning/phase lead (if needed).

Here's an example of two large 12kva DRSSTC's operating with the Ward UD2.1 through a Goodchild DR MIDI controller, recorded a couple weeks ago:

http://www.youtube.com/watch?v=EMiblIS7sEI

Hope this helps, Jeff
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  #22  
Old 03-26-2013, 11:03 PM
JohnnyRC JohnnyRC is offline
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Quote:
Originally Posted by Jeff View Post
Cool, another DRSSTC builder.

I don't want to take any business away from John, but the MD24 isn't a good choice for use in a DRSSTC driver application.

There isn't enough resolution in the MD24 MIDI controller commands to vary the on-time PW within the range needed for proper ring-up and safe operation. The MD24 works very well with servos, motors, solenoids and lighting. Although your feature description basically describes how a well engineered DRSSTC driver would operate.

I highly recommend you use a purpose built DRSSTC driver like Steve Ward's UD2, and a fiber linked MIDI controller that is available from a few different sources.
Component cost is very reasonable if you assemble it yourself. The 4hv forum has plenty of published information about the UD2, and related tuning/phase lead (if needed).

Here's an example of two large 12kva DRSSTC's operating with the Ward UD2.1 through a Goodchild DR MIDI controller, recorded a couple weeks ago:

http://www.youtube.com/watch?v=EMiblIS7sEI

Hope this helps, Jeff

Hi, thank you, i love those BEAST's. i was thinking to use the MD24 as a MIDI controller/interface and send a fiber optic to my UD2 driver. but duty cycle could lend a problem with the MD24.

as far as i know UD2 is the only driver out to handle primary feedback switching.
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  #23  
Old 04-04-2013, 05:30 PM
Jeff Jeff is offline
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Originally Posted by Solenoid_nak View Post
It would be totally awesome if we could get PWM to work with solenoids rather than have them just on or off, but rather have midi note velocity converted to PWM to give solenoid a louder or softer hit.

So velocity value of 127 would be a harder hit
and velocity value of 65 would be half as loud etc

Would be great if we could get this in the next firmware!! Would be useful for anyone wanting to make a robot drummer to give it a more natural feel.

thanks

Look forward to it
John, I've strong interest in this capability as well. Although as I understand the processor, individual output channel velocity control is beyond it's capability, based on the existing timer structure. I'd be happy to be wrong.

A month ago, I began a project to convert a conventional grand piano into a player. Each of the MD24 note outputs are "anded" with the output of a PWM channel at the solenoid driver transistor. Delivering velocity control to each channel.
Individual PWM outputs are provided by six TLC5940's in series, driven by a host MCU monitoring only the MIDI velocity data. Although somewhat cumbersome, it's less complex than the commercial player systems.
A friend had recently given me a complete 88 key solenoid assembly for a Yamaha Disklavier, and that was enough enticement to dig into this project

Alternately, an MD24 piggyback PWM controller would open an entire new market if note output PWM cannot be accomplished with the existing MD24 hardware.

Regards, Jeff
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  #24  
Old 04-04-2013, 10:11 PM
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Quote:
Originally Posted by Jeff View Post
John, I've strong interest in this capability as well. Although as I understand the processor, individual output channel velocity control is beyond it's capability, based on the existing timer structure. I'd be happy to be wrong.

A month ago, I began a project to convert a conventional grand piano into a player. Each of the MD24 note outputs are "anded" with the output of a PWM channel at the solenoid driver transistor. Delivering velocity control to each channel.
Individual PWM outputs are provided by six TLC5940's in series, driven by a host MCU monitoring only the MIDI velocity data. Although somewhat cumbersome, it's less complex than the commercial player systems.
A friend had recently given me a complete 88 key solenoid assembly for a Yamaha Disklavier, and that was enough enticement to dig into this project

Alternately, an MD24 piggyback PWM controller would open an entire new market if note output PWM cannot be accomplished with the existing MD24 hardware.

Regards, Jeff
Jeff, thank you always for your input.

I am going to see what I can do to make the PWM functions as useful as possible. I think that independent PWM by note velocity is quite possible. Naturally, the question is that of precision and accuracy. The code will be written in assembler for efficiency and the highest possible precision, given the microcontroller's clock speed.
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  #25  
Old 04-05-2013, 03:11 PM
Jeff Jeff is offline
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Quote:
Originally Posted by John View Post
I am going to see what I can do to make the PWM functions as useful as possible. I think that independent PWM by note velocity is quite possible. Naturally, the question is that of precision and accuracy. The code will be written in assembler for efficiency and the highest possible precision, given the microcontroller's clock speed.
John, that's Amazing. I had no idea it would be possible using the existing MCU.
Thanks for considering PWM by note velocity as a possible feature in the future.
Please include me as a beta tester when you have something needing a good shakedown. I'd be daisychaining four MD24's.

Regards, Jeff
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  #26  
Old 04-05-2013, 03:35 PM
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Jeff, what do you suppose is the ideal frequency for a PWM signal in your application? What would be the slowest useful signal?
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  #27  
Old 04-06-2013, 06:43 PM
Jeff Jeff is offline
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Jeff, what do you suppose is the ideal frequency for a PWM signal in your application? What would be the slowest useful signal?
Hi John, that is a very important question, and I don't have an answer for you yet.
I need to test a few different solenoids to determine what the lowest PWM frequency is before it becomes audible, or rattle is detected.

I'll have this information in a few days. I'll be testing high mass/low voltage Ledex coils, and low mass/high voltage piano coils with a signal generator/ precision power supply.
Thanks again, Jeff
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  #28  
Old 07-22-2013, 11:07 PM
Jeff Jeff is offline
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Hi John, it's taken me awhile in working with different solenoid types, and drive voltages, to report something tangible.

To start off with, MIDI supports 128 steps of velocity resolution. Various apps allow the user to define the note velocity.

These same apps also support volume in a range of 128 steps. A variable voltage power supply could also be used to control note volume. I decided to use a fixed voltage in order to keep the testing simple, considering pulse width and voltage are entirely interactive and would only muddy up the testing.

In my testing, I used a programmable pulse generator capable of 0-100% duty of an assigned 100ms pulse. The variable pulse width is considered the velocity value. Both solenoids tested were considered "high speed" and had what I'd consider to be low mass strikers.
Drive voltage was 50vdc in the first test. Solenoid current was 800ma.

First tests were made using a Yamaha "Disklavier" solenoid rail. This is an OEM player unit manufactured by Yamaha for installation into their pianos. The solenoids (88 of them) are very compact and were designed for 50vdc operation. We have a Yamaha G2 Grand Piano, and this Disklavier solenoid rail was installed into the piano for this test.

I chose 100ms as a timing value because a full 100ms pulse at 50v was approximately equal to the highest force (volume) the G2 grand key mechanism can tolerate. Very loud on middle C. A greater pulse width did not produce a louder strike, it only held the key down longer.

1-25ms unable to lift the jack.

30ms, very light touch. When tested on lower note scale it was almost inaudible (C1).

50ms, light to very moderate, depending on the note being struck.

75ms, moderate to loud. This would be a normal piano volume.

90-100ms, blasting loud. Obviously there will be heavy wear on the mechanism if this continued for very long.

It appears that up to 30ms (about 1/3) of the velocity value was unusable. The remaining appeared somewhat linear until it reached about 90% and then was over driven.

What this told me: since a piano uses a key mechanism, there's mechanical overhead that must be overcome before the hammer will strike the string.


IMHO, if you were able to provide 15 steps of variable pulse width to an assigned
note strike length of say 100ms, beginning with a 30% (30ms) minimum with steps divided equally, the resulting velocity could easily mimic a current technology player piano with 128 steps of velocity control. Perhaps it might help to support 128 steps in the note velocity register, and then do a fit to the closest 16 step value that you support. The user will have to define the starting note pulse width, like what is already done with rev 1.4 beta.

The second test was made using the robot vibraphone, having direct strike solenoids (no mechanism overhead).

I used 100ms as the full pulse period. Power supply was 25vdc. Current 600ma.

Interestingly, the results were nearly the same as the piano, up to 40ms the solenoid barely struck the bars trying to overcome the mass. From 50-100ms the volume varied almost linearly. I decided to skip taking note of the volume increase since the results were so close to the piano.


I'd be happy to take this further if you have other tests you'd like me to do.
Hope this helps.

Regards, Jeff
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  #29  
Old 07-24-2013, 11:44 AM
Jim U Jim U is offline
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Most of the MIDI organ controller companies (MGB, Artisan, etc.) offer pipe magnet drivers. How about a feature to load arrays of addressable latches 8 X up to 16. Someone will probably offer the companion note driver later on.

Jim U

Last edited by Jim U; 07-29-2013 at 06:13 PM.
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  #30  
Old 08-23-2013, 05:03 PM
dJ dAb dJ dAb is offline
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Hey John, now that summer is winding down I wanted to do some studio maintenance. I was curious what the most recent MD24 firmware, etc. might be? Curious what has been implemented since my last login. Thanks, Sean
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  #31  
Old 09-05-2013, 02:03 PM
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Originally Posted by dJ dAb View Post
Hey John, now that summer is winding down I wanted to do some studio maintenance. I was curious what the most recent MD24 firmware, etc. might be? Curious what has been implemented since my last login. Thanks, Sean
Hi Sean,

Based on the continued problems many users have sending sysex messages (due to MIDI interface bugs, driver bugs, etc). I'm considering changing the configuration paradigm to use MIDI NRPN, which involves only "vanilla" CC messages that should be reliably transmitted by any interface.

Ease of configuration is clearly an issue with all HL products, so I'd like to build a configuration utility to make everything easier.

I'm also beginning to reevaluate the hardware platform...

In short, things are "on pause" for the moment.
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  #32  
Old 09-09-2013, 10:22 PM
dJ dAb dJ dAb is offline
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Gotcha, still wouldn't mind knowing what the latest firmware was or, links to existing firmware. I need to make a minor change and forget what firmware used. Thanks, Sean

btw, never had problems with my two units ;o)
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  #33  
Old 10-08-2014, 07:06 PM
flyweight flyweight is offline
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Smile midi CLOCK as slave

I would like to see a good implementation of midi
CLOCK as slave
sync from midi clock

Selectable Divisors (1-4-6-8-16-24-32-64)
lets say that you could have 4 different chanels generating clocks at different divisions from the incomming master clock

for example 1/4, 1/16 1/3 and 1/8th of the master tempo

reset (send on midi stop command), maybe alreay present not sure
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  #34  
Old 10-31-2014, 03:33 PM
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Quote:
Originally Posted by flyweight View Post
I would like to see a good implementation of midi
CLOCK as slave
sync from midi clock

Selectable Divisors (1-4-6-8-16-24-32-64)
lets say that you could have 4 different chanels generating clocks at different divisions from the incomming master clock

for example 1/4, 1/16 1/3 and 1/8th of the master tempo

reset (send on midi stop command), maybe alreay present not sure
Hi Flyweight, welcome to the forum. Clock output with selectable clock division and start/stop/reset has already been implemented and will ship in the Rev H beta!

https://www.trycelery.com/shop/md24revhbeta
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  #35  
Old 12-08-2014, 07:57 PM
flyweight flyweight is offline
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Wow thats great Jonh!
thanks for the quick reply and support

Tim
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  #36  
Old 12-10-2014, 03:18 PM
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To follow up: the Rev H MD24 is now called the MIDIWidget. More information can be found here:

http://midiwidget.com
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