DIY drum sequencer built with raspberry pi and launchpad

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noizehack
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DIY drum sequencer built with raspberry pi and launchpad

Post by noizehack »

I wanted a drum sequencer that did not require the use of a laptop or desktop computer and could easily be used with eurorack and other modular gear. I am also learning javascript programming so I wrote this node.js app that runs on a raspberry pi and uses a novation launchpad connected via usb as the controller and interface and uses the gpio pins on the raspberry pi to send out 5v trigger pulses. It also sends a clock out and can be clocked by an external clock and has a reset in jack.

I made a little video to demo how it works, will embed the video and some pictures in this post. Also the code is on github and the hardware part is pretty simple transistor buffers. The buffer circuits I got from the LXR drum synth and I will put up a picture of them, they are slightly modified.

I would love feedback on the design and if anyone would like to build their own let me know if you have questions about how to. I used a raspberry pi 3 and launchpad mark 2.

github with code and info on how to set it up and an instruction manual.https://github.com/noizehack/Launchpad-Pi-Sequencer

[video][/video]

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puzo
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Post by puzo »

thats cool, nicely done. will have a look into this, cheers
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kassu
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Post by kassu »

Looks nice!

For the trigger in circuit, I would recommend to put a diode in parallel to the 1M resistor, "pointing up" in the schematic. This makes sure it can take negative input voltages also.
noizehack
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Post by noizehack »

kassu wrote:Looks nice!

For the trigger in circuit, I would recommend to put a diode in parallel to the 1M resistor, "pointing up" in the schematic. This makes sure it can take negative input voltages also.
I was thinking you wouldn't need negative input voltages since it is for clock and trigger inputs. Or do you mean to protect the raspberry pi pin when a negative voltage goes into the buffer? I am not super well versed in ee theory, so I definitely could of gotten the buffers wrong. Thanks for looking at them and giving some feedback.
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av500
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Post by av500 »

kassu wrote:Looks nice!

For the trigger in circuit, I would recommend to put a diode in parallel to the 1M resistor, "pointing up" in the schematic. This makes sure it can take negative input voltages also.
I don't think you need that. -12V / 100k is 0.1mA of current.
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kassu
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Post by kassu »

That is true, I guess its overkill to put diodes.
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av500
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Post by av500 »

kassu wrote:That is true, I guess its overkill to put diodes.
the above trigger input is more or less the default on all Mutable Instruments modules, so I guess its good enough for real world use :)
puzo
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Post by puzo »

i quite like the look of the launchpad mini, but of a smaller footprint. This project has reqally peaked my interest, great littole set up. Will this work with the Launchpad mini
noizehack
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Post by noizehack »

puzo wrote:i quite like the look of the launchpad mini, but of a smaller footprint. This project has reqally peaked my interest, great littole set up. Will this work with the Launchpad mini
Right now it would not work with the mini since the mini has fewer colors and the way it gets midi messages to set the color is different. I would like to add compatibility for the mini and s launchpads, but I don't have access to either right now, so I would not be able to test if it works. some aspects might need to be simplified on the sequencer as well, since with only 3 colors there might be some confusion about which track you are on, with the mk 2 I was able to use a different color for each track.
puzo
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Post by puzo »

ok i see what your saying. I really would like to build one of these so will see if i can get hold of one cheap enough
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limpmeat
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Post by limpmeat »

this looks great
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