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MIDI Interrupter Software

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JayJayJay

Tue Feb 05 2013, 10:17PM

Registered Member #10023 Joined: Tue Feb 05 2013, 05:27AM
Location:
Posts: 4

Guys: In regards to the MIDI Interrupter Software question, I am using MIDI over wifi to connect to my computer's MIDI interface (MOTU MIDI Express) from my iPad! There are several free apps (search app store for MIDI) that work just fine. I haven't experimented with loading existing MIDI files onto iPad yet, as I am using software (Pro Tools) on Mac for that. Will provide an update once I get a chance to see if that also works.

Fish

Thu Feb 07 2013, 04:55AM

Registered Member #8265 Joined: Thu Nov 22 2012, 11:19AM
Location: Australia
Posts: 6

Out of interest, has anyone got any midi interrupter to work with either a usb->midi box from a laptop or a midi device without batteries? I built my own midi interrupter http://4hv.org/e107_plugins/forum/forum_viewtopic.php?150253 which works perfectly with a speaker but dies when attached to my coil (also evr mB). If you get your usb->midi to work with a speaker ill be interested to know if you can then get your coil to play from a laptop.

Physics Junkie

Thu Feb 07 2013, 05:14AM

Registered Member #7267 Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407

Fish wrote ...

Out of interest, has anyone got any midi interrupter to work with either a usb->midi box from a laptop or a midi device without batteries? I built my own midi interrupter http://4hv.org/e107_plugins/forum/forum_viewtopic.php?150253 which works perfectly with a speaker but dies when attached to my coil (also evr mB). If you get your usb->midi to work with a speaker ill be interested to know if you can then get your coil to play from a laptop.

I use mine with my laptop. Ive tested it with the circuit I am building now with success. But im not done yet building the rest of the coil. I assume it works fine because I can hear my MIDI songs humming from the GDT's.

Goodchild

Thu Feb 07 2013, 06:50AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Something I failed to do for some time is to build a "dry test" rig for testing my MIDI controllers. I finally made one and it made my life a whole lot easier, not just for testing new software but for also checking new songs without hooking up a coil.

It's not supper complex rather just a fiber RX unit and output for your scope and and output for a speaker! In the long run it will save you a lot of fuses and IGBTs!

Here is one I just built

Fish

Thu Feb 07 2013, 11:26AM

Registered Member #8265 Joined: Thu Nov 22 2012, 11:19AM
Location: Australia
Posts: 6

Here is one I just built

wow, did you build that box by hand or CNC, looks very professional!

Playing with the coil all afternoon with no f***ing improvements to my midi player. I even ran my piano off some D cells and pulled apart an old receiver and used the toslink for a bodgied up fiber link - to no avail(link works fine, still interference with piano though). My RTTTL is still flawless so its not interference (e?)affecting the ucontroller directly, it has to be my piano.

-Making my midi controller I found that Yamaha has a *funny* MIDI stream-always sending signals regardless of note on/off event, so maybe Yamaha midi is somehow more sensitive than other brands. Pretty sure this hypothesis is ridiculous but I can't figure out what else it could be??

Has anyone had a midi player suffer ridiculously from a TC but at the same time have a ucontroller work fine?

Goodchild

Thu Feb 07 2013, 04:23PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

Whenever I had trouble with the coil interfering with the piano it was because of one of two things:

1. you are too close to the Tesla coils with the keyboared

2.the coil is not grounded properly.

Both of these thing will cause extra interference to get to the keyboard and trigger keys.

The box is just a hand made thingy, thanks for the compliment!

Fish

Fri Feb 08 2013, 11:34AM

Registered Member #8265 Joined: Thu Nov 22 2012, 11:19AM
Location: Australia
Posts: 6

Thanks Goodchild, sanded my ground stake, replaced the clamp and got some multi-stranded(more stranded than the house wiring i was using anyway) cable for my ground lead and found a 10m toslink cable. Finally some success!

Sorry for hijacking this thread, I'll start a new one for MIDI controller design problems if there are any objections?

My velocity 'handling' for my midi is very crude, PW is literally set to the velocity so 0-127uS. I was wondering what math people employ to get the maximum PW while taking into account the frequency and pw of other tone generators? Are there any good sites (wiki etc) that explain overlayed signals and the effective properties of the new signal? Unless I'm missing something simple I think that this must be fairly complex in order to get max PW while keeping duty cycles within limits??

Have people set PW way down in order to get a larger band width for their coils? I did not design my coil (minibrute) so I'm not 100% sure that this is entirely feasible? Thoughts

Goodchild

Sat Feb 09 2013, 07:03AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

A lot of people ask me how I handle velocity, well the simple answer is I don't. I ignore the velocity from the incoming MIDI.

Rather what I do is let the user set a base value on the interrupter and then the software calculates pulse width based on this base number, how many notes are playing, and how high in frequency the notes are.

It reduces PW on a logrithmic curve as frequency increases PW goes down. It's very similar to the response of human hearing. However I do it to get a handle on input power so that high notes don't draw excessive current from the mains.

...

Sat Feb 09 2013, 07:47AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

see

the interrupter is connected via fiber to deal with the rf from interfering with the usb-midi cable, other than that everything is pretty strait forward, all of the details are on the kickstarter page under downloads.

koolksmart

Mon Feb 11 2013, 01:08AM

Registered Member #5300 Joined: Thu Jun 14 2012, 12:00AM
Location: California
Posts: 31

JayJayJay wrote ...

Koolksmart: Also, I was able to verify the short by plugging in RCA cable to female RCA jack and test continuity between tip/ring on cable and solder points. The tip on the cable side beeped out with both solder points at PCB which verified short. The output to speaker worked regardless of short.

I did your short test, and it didn't appear shorted. But I decided to buy a BNC-RCA adapter...It worked! The coil is firing as instructed.
The only issues I'm having now are: 1. The overcurrent LED is almost always tripped when using it, and I can tell that it's a pretty high current spark and 2. Sometimes the coil will just keep playing a note even after I've stopped, and the only way I can get it to stop is to play other notes...That may be an issue with the piano I was using. 3. I blew out the wall socket power supply that I got with the kit almost immediately, so I had to move on to a 9-V battery...Any idea why that may have happened?

Thanks to everyone who helped!

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