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Phatline

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do you have some usefull input about:

how to get a drum trigger from a bongo drum (best would be velocity sensible) - with midibox?

 

i thougt about microphones... but when it comes to electronic amplified music, it could make fail-triggers...

then i thougt about to mount the microphones in the resonance body of the drum... but there mainly is the bass sound of the signal, while hi tones (outer ring or low velocity playing) are almost not hearable there...

but what to do with the mic-signal...

ok first make it simply take only 0-xV instead of -0+Volts...,

amplifie it to a range from 0-3,3V (stm32F4) a amp with built in Clipping?

connect to the 8 ain inputs onboard

write a program.

 

or is there any Bongo-Trigger-Crapper out there that could get connected directly to the Skin?

i dont know much of this, but i want to jam with an bongo player

 

Edited by Phatline
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Idea (good? false?better?)

The lower placed Electret Microphone (eg this: MCE-100 ) is reacting more on the bass sounds, because of its Location where are more low-frequency-signals, and because of its BANDPASS-Filter Settings. The Filter is needed because the AIN will react on Amplitudes... the more specific the Filter is set for a specific sound - the more accurate is this Amplitude methode - to get Velocitys...

The higher placed Electret Microphone is reacting more on the Direct Tap of the Skin or Wood, to avoid FALSE-Triggering from the Middle-Skin-Taps (Bass-Drum) it is place more near the Wood, and a Bandpassfilter that is set for MID-BandPass-Filter-Settings.... or so....

The Zener Diode should clip above 3,3V which is the max. Voltage for the Cores Analog Inputs

ndensator bestimmt die untere Grenzfrequenz, je grösser dieser ist, desto tiefere Frequenzen können übertragen werden.large.Bongo-Prinzip.JPG.51dd3856b7b96068Maybe there are better ways? - please tell me - i will draw a new shematic then.

 

Some Test for that Capsula...: http://www.loetstelle.net/praxis/elektretmikrofon/elektretmikrofon.php

The Output-Voltage goes ...from a few mVpp to over 100mVpp... you need a amplifier with a great dynamic bandwide....

 

hm to bad out of stock: https://www.adafruit.com/products/1063

Edited by Phatline
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Have you though about a piezo trigger? You may get a lot of feedback with a microphone. For this too you'd need a processing circuit as I think piezo elements can generate a high voltage (low current).

This one is very simple (open source):
http://musicthing.co.uk/modular/?p=933

It might be quite difficult to separate the rim and body sounds. 

The Zener (better Schottky) diode would be unnecessary if you used a rail-to-rail op amp powered at 3v3 and your scaling circuit was tailored to give a correct signal voltage. 

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very interesting link :happy:

i will try that  piezzo first, I already soldered the prototype AMP today.. piezos and krokos are ordered.

Schottky? did that work similar like Zener?

while Zener 3,3V exist: http://www.reichelt.at/ZD-5W-3-3V/3/index.html?&ACTION=3&LA=446&ARTICLE=145329&artnr=ZD-5W+3%2C3V&SEARCH=zener+3%2C3

i have real troubles to find a 3V Schottky?

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Good luck! I know a lot of professional drum triggers use this scheme. E.g. ddrum; they also have a "brain" which must be a simple ADC to MIDI. Bare piezo elements cost almost nothing, although you may need to experiment with the damping material e.g. a piece of foam.

Zeners have a fixed breakdown voltage (wide range available), whereas Schottkys have a lower forward voltage than a standard PN junction (4148). The normal idea with MCU pin protection is to use Schottkys as a shunt. The lower Vf is, the more range you have, as the clipping point is the reference voltage (upper limit) - Vf. To protect from overvoltage you connect the anode to the pin and the cathode to 3v3. This ensures nothing greater that 3v3 can pass, it's also normal to include one or two current limiting resistors. To protect from undervoltage you connect the anode to ground and the cathode to the pin. 

I would suggest using the op amp itself as a limiter, because it's impossible for the output to swing past the power rails. There are protection diodes at work here too, so you need a rail to rail op amp in order to maximise the signal transmission.

 

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Just now, latigid on said:

To protect from overvoltage you connect the anode to the pin and the cathode to 3v3. This ensures nothing greater that 3v3 can pass, it's also normal to include one or two current limiting resistors. To protect from undervoltage you connect the anode to ground and the cathode to the pin.

very clever

---the OP-Amp- as Limiter.... do the Shematic below that trick?... since i am not very good in analog basics

i found the EDRUM (DIY) Project which also uses Piezzos, here is the Analog Shematic

which is connected to the 4051ers on a Microcontrollerboard - so it is for 0-5V, when I use the multiplexer Midibox Variante I could use it 1:1 right?

http://www.edrum.info/schematics.html)

analog8_v06.gif

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I think for this circuit you'd get quite low range, LM324 is not rail to rail and the maximum output at 5V supply is 3.5V. So less for 3v3 -- 1.8V? MCP600x is more suitable and very cheap. 

Sorry, I don't have real experience in trigger circuits, but these look quite simple to try out.

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A new concept:

The Piezzo take the Wood Hits

The Electrete take the Skin Hits

the software decide which one was hit, because of Amplitudes.

some first thougts about how to decode that 2 differnt Mics...large.basic-principle.JPG.d898cd27338858

How to Finetune the Amplitudes > Tune the Setup for your Bongos:

large.IMG_0965.JPG.ad0b2bda748a91598f2f1

1.Select Trigger-Input

2.Press AutoSet

3.Hit The Bongo HARDEST, and be Quiet

3a.On Skin for Electrete Inputs

3b.On Wood für Piezzo Inputs

4. >>> The Trigger goes now into an AIN which is set for to high Resulution > 1K... instead of 0-128, so Auto do what? > I got from ain e.g. Values from 45minAmplitude & 600maxAmplitude.

so 600 is peak Amplitude, and 45 is silence or better: the RoomNoise

now we have to scale that for a Note Velocity Value 0-127... so first

max-min=new max (600-45=555)

min=0 (instead of 45)

555/127=4,37

------ these are Settings----- Saved Variables on SD-Card (a Preset)

All Values coming from the Bongo now get calgulateted with -45 /4,37 to get 0-127 Velocity Values

-----

But I dont trigger them out now... now the "fun" or pain (ahh i like it) begin with, calculate - which one was hit now? Skin or Wood, is the Retrigger time over? Are the Amplitudes still fallin? Retrigger? or do Nothing... and so on

-the pain maybe will be to get exact AIN-Values... the AIN is more programmed for Controller is?t it? > avoid to much data mess and jumps and other (maybe) programmings... i will see

 

the "Dont-Retrigger" time has to be set by Hand... depending how fast you can play...

 

Edited by Phatline
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  • 2 weeks later...

The Test Equipment

large.572a2859eefc1_BongoTrigger-Prototy

 

This Kroko cand hold on surfaices up to 4cm (piezzo - clamp)

572a2859eefc1-large.572a284f1963c_BongoTrigger-Prototy

 

The Piezzos dont need Active components...large.572a2848871ab_BongoTrigger-Prototy

 

The Electrete Mic- Stands ---- the will be placed inside a bongo (since a bongo is open at the ground)large.572a2841262e4_BongoTrigger-Prototy

 

Midibox Stuff...large.572a283de4d11_BongoTrigger-Prototy

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  • 1 month later...

the piezzo mics are sensing weak on the ProtoBoard...to much noise to get some usefull out of it...> have to etch a PCB there...

the capacitor-Mic version turned out that on PA i have to much feedback... but i think will solve this by a concept that had used Grateful Dead

Grateful dead had a giant PA called: "The Wall of Sound" - this Wall was behind the musicans - so the head a good VIBE.

Wall of sound

With regular Microphones you had feedback³

They used 2 Microphones mounted together, but they speak only in one Mic.

Using two mics for noise cancellation. Combining outputs of both at equal gains, but in opposite polarities, will cancel ambient noise from each to a certain degree.

One of the 2 Mics got his Phase inverted, booth signals where summed then. so everything except the direct voice of jerry is terminated.

I will use this technology to AMP the bongos and get trigger out of it...

...here some background infos http://www.soundonsound.com/sos/jul10/articles/qa0710_4.htm

 

Edited by Phatline
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About the piezo it also depends on the mechanical setup . Some good pictures about how it's handled in "real" drum triggering ; http://edrums.info/acoustic_1-2/
I don't know about your noise issue , but i adviced by the past a model with Feedback loop : http://www.mouser.fr/ProductDetail/CUI-Inc/CEB-20FD64/ 
Maybe the feedback loop may provide some help ? What about amplifying the piezo out ? http://wiki.midibox.org/doku.php?id=electronics_basics#b-non_inverted_amplifier
regards,
Jerome

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edrums: yes good idea in there: they picked up a bit of waight (rubber foam)to the disc

14.jpg

Amplifieng piezzo: yes could give a try, but first i try that double mic thing -since it has more potential for splitting frequencys of the Skin (and piezzo-only body sound)

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