Modified Velocity Sensing Keyboard
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- Опубликовано: 5 янв 2011
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Alan @vk2zay / vk2zay sent us a question via Twitter:
@tymkrs oh yeah, your keyboard interface got me curious... Do you know how they implement velocity sensing keys?
We just happen to have one already taken apart (it's being modified for another project). So we decided to take a few minutes to show how these actually work under the hood. If you have any more information, please leave a comment or video response.
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Awesome, thanks for taking the time to pull that apart to show me how it works!
Now you've got me even more curious about how the scanning logic works, it must poll them relatively quickly to get accurate acceleration sensing, with those diodes and the bit of the traces I can see it looks like it has a scanning matrix, either grid or a charlieplexing graph topology...
@vk2zay Addie @atdiy said she might do some more detailed research and post an article to the tumblr feed.
The modification was to break the circuit for the back switches at each diode, tapping in there with the ribbon cable, and to wire the header together a source for all of the switches. I wasn't too interested about how it originally functioned for my purposes.
Look for our SidCog organ (which uses a hammond keyboard) and Protosynth videos for more interfacing material. I prefer interfacing with the existing switches, but that gets tricky when the organ is still functioning in it's original function.
There is room under the keys that you might be able to make use of too.
Hi, I would like to get in touch with the author of this specific video above , about keyboard sensing, to ask a few questions. How could I get in touch?
I'm trying to figure out a simple way to add midi to my Hammond and Wurlitzer organs by creating an ultra thin strip that can slip into the area between the back of the keys and the black steel panel behind the keys. Since all keys have a long mounting base it would be fairly simple to use the movement of this base ( as a key is pressed so moves the base) to make contact with a spring loaded movable pin, one behind each key. Midi triggering could be done easily using this. Ideas for interfacing?
The diodes are there to allow for some kind of charlieplexing or matrix, think an X Y grid. They allow the midi controller circuit to scan through all of the switches on just a few wires (over and over very fast). I just wanted the keys to act like switches, so I threw out the matrix and the midi circuit. But if you want your hack to generate midi signals to control a computer or something then you'll need to leave those diodes in place!
I just got an oxygen 8 midi controller keyboard and wish to make the velocity sensitive keys into an on/off configuration like you have it in the video. I'm actually going to convert the controller to an arcade push buttons setup instead of the black and white keys. Can you provide any guidance on which diodes to remove and the role of the ribbon ? Thanks in advance !
Where the ribbon cable is soldered to the midi circuit, I connected each combination of pins (using a single wire) to test each note and made the sounds come on and off. All mapped now ! So if I understand this right, I can just toss the midi circuit and connect my switches straight to the ribbon cable, right ? I'm curious why did they go through the hassles of adding all these diodes ?
I cannot thank you enough for the tips, I'm new to modding and this is incredibly helpful. Cheers
Hii , i have Korg microkey 2 :( i want to switch velocity off , i don't need it :( please help me :(🙏🙏🙏
I am not using the midi part of the circuit at all. What you need is to tap into the traces that lead up to each of the switch pairs (two leads for each of the two switches for each key). Add your switch between these two sides, connecting both together simultaneously (which says full velocity to the midi controller). Repeat for each key.
how to find out the scan matrix looking at the ribbon . I have a 25 key midi keyboard which is not sending out midi . hence wan to fix it using arduino. but i'm unable to find the scan matrix for the same.. plz help.
Multi-meter continuity check to find out which ribbon line becomes connected to which ribbon line when each key is pressed. Looking over the traces first can give you hints.
thanks, will try that
i'm getting duplicates highs while scanning key rows and columns.. my 25 key keyboard has 16 pins an I assumed 4 rows and 8 columns . i'm having some success identifying keys . but I'm getting high for both 1,1 and 1,2 for C note.. like this i'm getting a few duplicates..am i doing anything wrong ?
Working out exactly how the matrix is laid out can be troublesome, sounds like you are on the right track to victory!
I didnt understand how to resolve the velocity problem when i hit some notes they go from 0 to 127 velocity with out any middle velocity pls help
Parigos Ziemprod How are you calculating it? Just time how long it takes to measure the first button press to the second. Measure the distance between the keys, divide distance by time.
athf226 i dont calculate i just see it on the daw ... When i hit the key it automaticly go to 127
Parigos Ziemprod if you are doing it this way as in 2 contact points, you need to calculate from rising edge of the first switch to rising edge of the second
athf226 no bro i dont have voltmeter so i know by my daw that the key is dead ... i dont know what to do to resolve it :/
Can I repair the touch sensor if it's not working
If you can diagnose why it is not working, then yeah. Cleaning the board and rubber with a mild detergent can sometimes fix a spotty connection. Sometimes adding a bit of pencil carbon can help make one of the connection points connect more strongly.