DIY Midi to Trigger interface? Arduino?

oh, I meant the holes for the front panel. I got the ones with mounting holes, like in Sam’s 1007 midimuso midi2cv.

I did draw up the cutout for the din socket the other day, but its not been sent to manufacture to verify

Hi, looking at the schematic I wondered whether you have considered using a transistor (any small signal transistor will do) as a buffer for every output stage in stead of an op-amp?

Sounds also good! I have no idea what the pros and cons of that and the opamps are, I just saw the opamp on the kosmo midimuso and also some mutable instruments schematic (grids?)…

I can probably combine/modify some holes already in the library into a new one…
mine are with the center diameter of of 15mm and the mounting holes 22mm apart. Their diameter is 3mm if I remember correctly. Das that match yours?

Datasheet

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You would be using 1 transistor per output in stead of a few hundred (I’m not sure how many there are in a TL07x). But you need a few resistors to configure the transistors, so this may even take up more space, depending on your soldering skills. Both approaches would probably work nicely with only 1 (positive) power supply. The thought to use transistors struck me because I realized I have loads of small signal transistors laying about and not so many op-amps.

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Don’t know about TL07x but apparently there are 20 transistors in a 741 (ah, another fact to use up neurons in my brain).

It’d be quite a feat to get four transistor buffers inside the space of a DIP-14. Though of course there’s also routing to consider. I know I’d find the op amps a lot easier to assemble.

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You might want to check the DR-110 Midi Mod. It uses Arduino Pro Mini and sends the DR-110 Negative triggers. Might be a good source of inspiration for your drum machine?

I built this for my DR-110 and it works a treat. The Arduino code looks like it could be simplified but I uploaded it without changing and it works fine. I just use a Beatstep Pro as the sequencer.

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i searched for ages last week to try and find a datasheet. ended up just using the digital micometer… will see how close i got…

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This means that I can do the MIDI Thru just like this? Any idea why Sam has added a 74LS14 in his midimuso? because of the multiple outputs?

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It seems to be a common design.

My Midi Thru was designed based on a circuit found elsewhere but essentially the same.

I believe its just there as a buffer, its inverted by the first unit and then inverted back for the output.

Okai, this is my latest version:
I got rid of the shift register and used the 6N137 instead of 6N138. Also I connected the midi out (through) directly to the IN, as suggested in @Caustic 's diagram

Anything I missed? I did not use D13, because of the LED on this one, but that is probably not an issue right? Would be “cleaner” (and maybe faster?) with them all using the same ports? Are there more special pins to be aware of?

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The 6n137 is recommended to have a bypass capacitor of 0.1μF for pin 8, as per the datasheet. And pin 2 of the MIDI input could use a (DIY Midi to Trigger interface? Arduino? - #16 by Caustic). Both are mostly stability improvements.

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Use whatever works. :slight_smile:

Hey! I have the pcb soldered now and will test it soon! Your code looks very nice and tidy! I was wondering how drums are usually handled, because with simply changing your code I would end up with a gate that starts when the midi on message arrives and ends when midi off arrives. Does something like the beatstep pro sends the off message on the Release of the pad press? Or has it a preset length? Otherwise I might need to add some code to make short trigger signals from the gates, right?

Don’t know what you’re controlling, but the drum modules I have have a gate to pulse converter on the input, so the gate length doesn’t matter.

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So far I only have my own drum module which has this Input:

image

It should do the trick, right?

I think the whole thing is working! I am still missing more LEDs, because the ones I have are too short, but I tested with a single one and it blinked when I sent midi notes! I still need to figure how to use the right channel and match the midi notes to the jacks, but that should be doable! (Also: I need to check out how to do the midi thru in software, because I decided not to directly connect midi in and out for lack of space for a buffer(?, the triangle in the diagram posted by @Caustic ).
I noticed a thing though: when I don’t have the arduino inserted, the outputs default to ~10V, which seems quite high… Is there a good way to prevent that (in a future version)?
When I have the LEDs and software I will make a new thread with description and github link etc. :slight_smile:

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Kinda hard to answer without knowing what you have connected to the outputs… is there a schematic somewhere?

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