Syntherrupter - A Feature-rich, Polyphonic Interrupter

[Max]

Hello futurist,


Congrats to the mechanical part. I‘d love to see your finished interrupter!

It‘s been quite some time since I made that little print for the transmitter. Here is what I remember:
The transmitter is just an infrared LED. Three of the four center pins are cathode, one is anode. From the datasheet I determined Vf and If which gave me a resistor value of 60Ohm when using it with 5V. Again, thats what I remember, you should check the values. Current was around 60mA so a BC546C was sufficient. This transistor has enough gain and speed for this application. Many other standard transistors should work, too. Final schematic: Resistor to 5V, Anode to resistor, cathode to collector, emitter to ground, base to a 560Ohm resistor which goes to the pin with the interrupter signal.
I use the 5V instead of the 3.3V because the 5V come directly from the USB port. The 3.3V are provided by an onboard regulator where I don‘t know how much additional current it can handle.


Kind regards,
Max

[futurist]

Thanks!

Duty cycle is very low so it could probably be powered directly from processor, but in any case I'll use external transistor
I'm little short on THT components, but I managed to find four old 2N2222 transistors, I'll post some photos later today or tomorrow

[Max]

Duty cycle is low, but that doesn't help since the GPIO pins are current limited by their internal resistance (not short circuit proof AFAIK). Somewhere in the datasheet is described how the voltage drops if you draw more current than allowed. You wouldn't get much more than those 2mA and especially not the 10s of mA required to get a proper signal from the transmitter.
Therefore I'm glad you still had those transistors! 

Kind regards,
Max

[futurist]

I don't have enough space to connect microusb cable to debug port, is there any way to solder individual wires without desoldering microusb socket from dev. board?

edit: where do I connect LCD?

[Max]

Good evening,


@futurist:
You can see the PCB USB traces in the following documentation from TI, page 26: https://www.ti.com/lit/ug/spmu365c/spmu365c.pdf Hope this helps you.
Display connections and setup is described in the very first post of the topic, under "Replica with touch display".

Other news:
A new version of the Nextion Editor has been released (v1.61.1) which breaks the option to upgrade the Nextion firmware over USB. It's fixed in the source code but I didn't want to draw yet another beta release just for this fix.
The developper of SynthFont, the MIDI Software I'm using for years now, has offered to make SynthFont send MIDI directly to a serial port. No MIDI to USB converters, no MIDI serial bridges needed I really appreciate his support and initiative!


Kind regards,
Max

[futurist]

I managed to program everything but I didn't have enough time to test it on the coil




Turned out nice, can't wait for the next weekend

[Max]

Turned out nice

Agreed! I like those 4 transmitters in a row.
... and I didn't know that Broadcom, formerly Avago, once belonged to Agilent. Interesting how many companies are in some way connected to HP.

By chance I read about a MIDI feature called "running status", which is used by some MIDI devices to reduce the amount of bytes necessary to send. It is explained over here: http://midi.teragonaudio.com/tech/midispec/run.htm
While this is not important if connected to a computer (it's not used there since MIDI USB data rates make such tricks needless), it could be relevant for MIDI In which still operates at the slower 31250baud/s.
When reading about running status I realized that my code does not handle MIDI real time messages correctly. They would lead to missing or hanging notes. I didn't know that since I never used a MIDI program that sends them. However, i heard FL Studio does.
Support for running status and the fix for real time messages will be included in the next release.


Kind regards,
Max

[davekni]

Most of the MIDI computer files (.mid) that I've analyzed use running-status.  Perhaps that's due to some original keyboard 31250-BAUD source, or to reduce file size.  Either way, I needed to include running-status in my MIDI interpretation code to make it at all useful.  It would seem likely that some software reading .mid files and sending them real-time to a USB port wouldn't bother removing running-status.  (I have no personal experience with such USB MIDI output software.)

[TMaxElectronics]

the running status is something that I have personally never seen in a Midi datastream from a pc. If I understand correctly, the way that the software midi layer works on windows, is that there is a single packet for each command and it is up to the output driver to decide whether to use running status or not (don't quote me on that though, my knowledge about that is very limited).
The midi out from hairless midi serial certainly does not use the running status (at least I have never noticed), neither does the USB audio implementation that I'm using for my interrupter (though the bandwidth of that is of course quite a bit higher ).

@futurist
Are those four tx modules all going to be used or are they just for future expansion? I'd love to hear some of the stereo effects with more than two coils.  If it sounds cool enough I might just steal coincidentally have the same idea for my midi stick

[Max]

Sometimes I hate it if I have new ideas... Because now I have enough stuff to release yet another beta. Too tired to make screenshots or videos of the differences but all of them are described on the release page. The fixes I mentioned in the previous replies are of course included. However, the running status feature and the real time fix are untested since I have no devices that use these features. The other features are tested and working as expected.

@TMaxElectronics: watching you...

@davekni: "running status" is not part of the USB MIDI specifications (at least that's what I read on midi.org). That's probably the reason why no MIDI program sends "incomplete" packages - which is more or less what TMaxElectronics said, too. A tool like hairless MIDI serial could reintroduce it, since it is "serial" MIDI and not USB MIDI anymore, but it doesn't.
My very first MIDI interrupter was able to parse MIDI0 files. I don't know where my MIDI0 files came from, but the few I tested didn't use running status... (Bad) luck I guess.


Kind regards,
Max

[futurist]

@futurist
Are those four tx modules all going to be used or are they just for future expansion? I'd love to hear some of the stereo effects with more than two coils.  If it sounds cool enough I might just steal coincidentally have the same idea for my midi stick

I have two coils, medium SKM400 halfbridge and small TO-247 halfbridge, so I'll definitely try the stereo option
Friend has CM600 coil and it would be great to test all three coils, but we have to find a place to do it

[Max]

It bothered me that the sliders "waste" a lot of space in the lower end of the range. Almost 10% of the range belongs to the value zero. I completely rewrote the math behind the sliders (math for a slider? yes!) and I think they work much better now. However, I have no access to an actual Nextion display; I'm limited to the simulator. Therefore it'd be great if someone* could test it and tell me, if it is easier to set values with the new version.
*actually only futurist could do it AFAIK... 

Nextion source file with new sliders can be downloaded here: https://github.com/MMMZZZZ/Syntherrupter/blob/v3.1.0-better-sliders/Syntherrupter_Nextion/Syntherrupter_Nextion.HMI
The compiled Nextion file is attached below.

Kind regards,
Max

[Mads Barnkob]

Looking forward to get this put together I must say that the Omni-mode is what I have dreamt about for years, I am really looking forward to use that feature (and not so much that I now have to build 6 identical coils)

I have just ordered all the parts I needed from digikey, since they are the only seller of the locking screw head opto parts with a good enough price to justify the import tax.

Here is the digikey order numbers if anyone else needs them

Dev board:
296-37267-ND‎
‎EK-TM4C1294XL‎
LAUNCHPAD TM4C129X EVAL BRD

Display:
‎1597-104990606-ND‎
‎104990606‎
NEXTION ENHANCED NX8048P070-011R

Optic transmitter:
‎FB162-ND‎
‎IF-E96E‎
LED FIBER OPTIC 645NM RED

Optic receiver:
FB124-ND‎
‎IF-D95OC‎
DETECTOR PHOTOLOGIC 5 TTL

[futurist]

*actually only futurist could do it AFAIK... 

I will, I didn't have any free time this weekend to play with the coil
I'm going on vacation Thursday and I'll try new firmware asap

[Max]

Good morning!


Today I tried some MIDIs and realized that it is pretty annoying to edit the MIDI files each time. It would be useful to enable and configure the stereo note mapping directly on the Syntherrupter. So I added a new page which allows exactly this: edit NRPs and generally send any MIDI command you want. Screenshot is attached below. Haven't yet created a release.

Other ideas I'll implement sooner or later:

• Make ADSR parameters editable. Together with this change I'd probably add some other features to ADSR like exponential decay.
• Create NRPs or SysEx Commands for all settings of the Syntherrupter. Allow import/export from/to PC. Instead of modifying ontime, channel assignments, etc for each MIDI by hand it will happen automatically.
• Make volume logarithmic as described by the MIDI standard.
• Allow to compensate the non-linear volume behavior of a tesla coil. This is independant of ADSR exponential decay and the logarithmic volume.
• Firmware version check. Enable/Disable functions based on firmware combinations.
• Something something I probably forgot.

I'll try new firmware asap

Great! Thank you.

I'm going on vacation Thursday

Since you're currently the only one who could have played with real tesla coils, I don't like this for sure. However I hope you'll enjoy it!

Looking forward to get this put together I must say that the Omni-mode is what I have dreamt about for years, I am really looking forward to use that feature (and not so much that I now have to build 6 identical coils)

Honestly it already works pretty well with only 4 coils. However, having played with those features myself, I have to build 6 identical tesla coils, too. One day...  Maybe smaller SSTCs. Then I could even build 12 coils  Oooh so many ideas, so little time...


Kind regards,
Max

[futurist]

I'll try new firmware asap

Great! Thank you.

I'm going on vacation Thursday

Since you're currently the only one who could have played with real tesla coils, I don't like this for sure. However I hope you'll enjoy it!

By vacation I meant going home Now I have two tesla coils to play with

[Max]

... and suddenly your post makes quite a bit more sense.
Once I have the feedback for the sliders I'll throw out another beta release so that you can play with the NRP editor, too. It should make experimenting a lot easier.

While I give my best to keep the user interface as intuitive as possible I'm starting to think that I'll have to write a serious manual sooner or later... Again, any feedback is highly appreciated. Especially since you can play with the UI without buying any hardware


Kind regards,
Max

[futurist]

It was quite windy these days so I couldn't test both of the coils, I played a few midis on my smaller coil

/>
Duty cycle max. 5 %, max. on-time 300 us
I'm still getting used to UI, polyphony will probably sound nicer if I increase max. duty cycle

Sliders (unfortunately youtube rotated video)

[Max]

@futurist:
Thank you for the video. Unfortunately my timing is horrible: Today I finally got access to my interrupter, so I could play around with the sliders, too. Feels okay to me, but I added a rounding feature (value only increases in steps of 5 or 0.5), which gives a more "stable" feeling. How do they feel to you? Do you find it difficult to set the values you want?

You made me realize that the name "Max. Ontime/Duty" on the MIDI Live page is rather confusing, so I renamed them to "Note Ontime/Duty", which should be clearer.

Now concerning the strange behavior in your first video: I couldn't really find a combination that reproduced the behavior, therefore I'd ask you to tell me

• Which values you set on the MIDI Live page (Note Ontime/Duty) ("Screenshot" might be fastest)
• Which values you set on the "Settings->Coil Limits" page (Coils min/max settings) ("Screenshot" might be fastest)
• Link to the MIDI file
• List of the channels passed to the interrupter, and, if not saved in the MIDI file, the program number of each of these channels.

I suspect the duty cycle limiter in combination with a rather high minimum ontime required by your coil to be the cause of the problems.

Since I was able to test everything today, I published Beta 6. It includes the NRP editor, and the sliders futurist already played with. Oh and I kinda verified the running status feature, and it worked as expected.


Kind regards,
Max

[futurist]

As I said I'm still getting used to UI but for now everything works nicely and it isn't difficult to set the exact values I want

You're right about min. on-time, I have 30 us min. on-time on onetesla interrupter. Do you plan to add min. on-time setting?

Can you suggest max. duty cycle and min. off-time?
Onetesla interrupter doesn't have duty cycle limiter and I didn't blow up the bridge. Here is same MIDI played with onetesla interrupter

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Currently I have max. on-time 300 us, min. off-time 0 us and max. duty 5 %. I'm waiting for wind and rain to stop to test it further