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 Forum index » DIY Hardware and Software » Developers' Corner
sphereical midi controller with miditron?
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subjekt



Joined: Sep 25, 2006
Posts: 9
Location: london

PostPosted: Mon Sep 25, 2006 6:00 pm    Post subject: sphereical midi controller with miditron? Reply with quote  Mark this post and the followings unread

Hi there,

Not too sure if this is the palce to ask, but im currently in my final BA year of a music production, technolgy & engineering degree at uni, and i want to create a midi controller using a variety of sensors etc. for my final project.

I have just purchased a MIDITRON interface and am currently learning the basics of MAX/MSP, but i have an idea to use a ball or any sphere to trigger midi messages when rolled. What do you think the best way to do this would be? I was thinking having pressure sensors on the floor and rolling the abll around

Any ideas, comments, or previous experiences and suggestions are so so so welcome. It doesnt have to be complicated, can be dead simple. IT JUST HAD TO WORK!Im bloody excited about this.

Thanks, Subjekt
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jksuperstar



Joined: Aug 20, 2004
Posts: 2488
Location: Denver
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PostPosted: Mon Sep 25, 2006 8:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think this is the better place, since your not question isn't really in using MAX/MSP. I've deleted the double post in that section.

You could try accelerometers and/or gyroscopes. They are made very small & cheap these days. Check analog devices homepage at [url]analog.com[/url] or maybe Texas Instruments at [url]ti.com[/url]. The latest gyroscopes should be 5v, with varying output signal based on rotational acceleration. Your miditron and max patch would take care of the rest.

But this puts your electronics *in* the ball, which you may not want. Not sure were to send you for force sensors, especially if your looking for something larger. Switches might be your best bet in that scenario, especially if your just triggering sequences, not using the info for control change messeges.
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subjekt



Joined: Sep 25, 2006
Posts: 9
Location: london

PostPosted: Tue Sep 26, 2006 6:54 am    Post subject: gyroscopes! Reply with quote  Mark this post and the followings unread

Thanks for the great reply.

Gyroscopes sound intriguing, how would they work exactly? I was initially thinkikng of controlling data to change pitches etc, i take it these could do that, rather than your idea of triggering sequences. It does sound easier and a bit more simple though! Smile

Ive checked the analog.com website but dont really know what im looking for, just a cheap gyrooscope that can hook up to the miditron and be able to send midi data. any ideas?

your a lifesaver!

Subjekt
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subjekt



Joined: Sep 25, 2006
Posts: 9
Location: london

PostPosted: Tue Sep 26, 2006 6:57 am    Post subject: accelerometers Reply with quote  Mark this post and the followings unread

Iv also noticed accelerometers, could i use this to measure the accelration of the ball and thereofre cahnge midi data!? Im new to this but not stupid or proud, so tell me where im going wrong or what you think i should do!
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jksuperstar



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Location: Denver
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PostPosted: Tue Sep 26, 2006 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Soory, I read your "triggering midi messeges" as "triggering midi sequences". My bad.

THere's 6 basic axis of movement, x,y,z, and then pitch, roll, yaw. The first three are movement in a linear fashion, the last three are rotational. (If you know this, then consider that info for someone else reading this thread, or readers of lesser english skills).

The gyroscope can detect the one or more of pitch, roll, and yaw. They have small coils that detect this type of movement. So you could pick up the ball, and fake a throw to a friend, and the gyroscope wouldn't have any change. But, the gyroscope usually has to be near the center of the axis of rotation, and for a ball that means in the center of the ball.

The accelerometer will detect the xyz movements. IF the accelerometer were at the center of the ball, rolling it would create no signal, but throwing it to your friend would. If, you mount an accelerometer off center of the ball, though, you can use it to detect rotational movement. Picture your fingers as you wave. Depending on how you wave, the knuckles or your wrist is still (the axis of rotation), while your finger tips are moving...accelerating...in 1 axis of motion. Some accelerometers can do one, two, or three axis in one part depending on the model.
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subjekt



Joined: Sep 25, 2006
Posts: 9
Location: london

PostPosted: Wed Sep 27, 2006 5:49 am    Post subject: thanks again...a few more questions Reply with quote  Mark this post and the followings unread

you have no idea how much help your information is, i am so greatful.

Right, ive got a basic idea now, i want to use a spherical object (ball) to trigger a synth via max/msp. So rolling, throwing or moving teh ball would trigger differnt pitches or sequences. Am i right in understanding that if i were to roll a ball along the ground neither a gyroscope or accelerometer would detect this (unless off axis-)?
But throwing the ball would.

I take it the two could be used in conjunction. What one would you reccomend for ball rolling etc.

thanks again, you are in my project already as a huge help.

Subjekt
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subjekt



Joined: Sep 25, 2006
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PostPosted: Wed Sep 27, 2006 7:19 am    Post subject: Gyro found? Reply with quote  Mark this post and the followings unread

Me AGAIN

You must be getting sick of me, but i ahve to complete this in 6 months!

I have been browsing analog devices and have found this gyro:

http://www.analog.com/en/prod/0,2877,ADIS16250,00.html

Would this interface with my miditron? Also would it do the job!
thanks again!
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Blue Hell
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Joined: Apr 03, 2004
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PostPosted: Wed Sep 27, 2006 8:30 am    Post subject: Re: Gyro found? Reply with quote  Mark this post and the followings unread

subjekt wrote:
Me AGAIN


I can understand you being excited and all but I don't think there is a need for posting duplicate messages. I deleted the one in the new thread as I think the one in this thread is the appropriate one to keep.

_________________
Jan
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subjekt



Joined: Sep 25, 2006
Posts: 9
Location: london

PostPosted: Wed Sep 27, 2006 8:44 am    Post subject: apologies Reply with quote  Mark this post and the followings unread

I didnt actually realise i had posted duplicate messages. Sorry!
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jksuperstar



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PostPosted: Wed Sep 27, 2006 9:58 am    Post subject: Reply with quote  Mark this post and the followings unread

The gyroscope WILL detect the rotation. Which I think you've figured out, but your post stating neither would made second guess.

Anyway, that gyro has a digital interface, and it may be alot of extra work to get info out of it. Also, now that I look, gyros are pretty expensive, compared to accelerometers. I'd use a 2 axis accelerometer, and mount it so the the two axis are parallel to the outside of the ball. It couldn't hurt to use a 3 axis controller, not that the 3rd axis would help detect the ball rolling, but you might get really strange signals out of it as the ball is rolling. Or, it might be used to detect centripital force.

Make sure you pick an accelerometer that uses the same voltage levels that your miditron does (probably 5v), and has analog outputs, NOT SPI or some other digital format. Probably anyone of the ADXL3nn series will work...just choose one based on the sensitivity to g's you want (don't ask me that!). They all seem to be within an order of magnitude, and you go with 3-D, you only have 1 choice anyway. I'd err on the side of less sensitive/more robust, since you can always amplify a signal up, but you can't bring it down once it's clipped.

I have no idea how you're going to get the signals *out* of the ball, put everything inside the ball, then wireless transmit out? or just accept having a tether on the ball?
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subjekt



Joined: Sep 25, 2006
Posts: 9
Location: london

PostPosted: Wed Sep 27, 2006 11:48 am    Post subject: cheeers....more post to come Reply with quote  Mark this post and the followings unread

thanks again for that, il have a look at them. But be sure i WILL be getting back to you! Youve been an invaluable source.
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subjekt



Joined: Sep 25, 2006
Posts: 9
Location: london

PostPosted: Wed Sep 27, 2006 4:34 pm    Post subject: magnitude? Reply with quote  Mark this post and the followings unread

Right, had a big read up on accelerometers and gyros, your definately right about the cost of gyros with analog outputs. but im still trying to look for one! One thing i didnt quirte understand from your post was

"they all seem to be within an order of magnitude, and you go with 3-D, you only have 1 choice anyway."

What do you mean by 3D? I think nearly all of the adxl3xx series would work. Also, i know you said not to ask, but the range of g's is perplexing me also.

Nearly there though, just dont want to purchase the wrong one!
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