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Old 16th October 2003, 03:02 AM   #1
Optical is offline Optical  New Zealand
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Default Electronic drums

HI everyone, i am currently building an electronic drum kit, i thought i would start this thread to see if somebody has done anything similar or has ideas on the subject.
There are othe sites about that detail making the drum triggers but all of them either use a brought electronic drum sound module or make up a voltage to midi converter (midi brain) with some complication.

So heres what i've been doing: Firstly, i didnt want to bother making the midi brain, so thought i would buy a cheap midi keyboard and use the brain in that, much less hassle..
I had heard that under the keys of a keyboard there are piezo transducers to trigger the key touches, so i thought i would simply replace the piezos under the keys with wires leading to a drum pad with a piezo under it, simple.

When i got the keyboard and pulled it to bits i didnt find any piezos, problem, instead there were 2 switches, similar to the ones found under most calculator keys, one switch slightly above the other so as the key was pressed down on the keyboard one switch would trrigger then the second one shortly after where the micropro would process the time between closing switches and deduce the velocity of the hit from that..

So the problem i faced entailed taking a voltage spike from a piezo transducer placed under a drum pad of a voltage range 0~20V as this remained the best way to sense the drum hit, and change it into the 2 swicthes electronically..

I have drawn up a circuit which looks like it works ok and am currently testing it out, i will post up more details as i progress or i anyone wants to know anymore details.

Let me know what you all think anyway, the more interest the better!

Matt
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Old 16th October 2003, 03:27 AM   #2
Variac is offline Variac  United States
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Maybe the problem with cheap keyboards is that they might not be touch sensitive. It appears that yours isn't-that might be why it only has switches. Touch sensitivity varies the volume with how hard the key is pressed. I would think that with a drumset you have to have the sensitivity function, so I hope the keyboard was really cheap!

This is just a guess . i reallly don't know how keyboard work!
MArk
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Old 16th October 2003, 03:58 AM   #3
SY is offline SY  United States
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Matt: I've done some commercial drum trigger designs using force sensing resistors. You can get aftertouch, position effects, and even double the use of the zones as control buttons for programming. Normally, these are done as custom arrays (with expensive tooling costs), but I think you can buy discrete FSRs of various sizes and shapes cheaply, then do a paste-together- this looks like the way Futureman set up his triggers, and I know first-hand that this is how Mick Fleetwood did the cool effect of playing his clothes during a solo.

Interlink Electronics (Camarillo, CA) is the major source for FSRs.
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Old 16th October 2003, 04:41 AM   #4
Optical is offline Optical  New Zealand
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Hi, yes the keyboard is velocity sensitive, there are 2 switches under the keys, they close one after the other with the time between each one closing determining the velocity of the key press. i.e a light press might say have a 20ms difference between each closing, and 2ms for a fast hit


FSR's? ive heard of people using them, i havent ever seen one though, i shall look into it as they sound like they could be easier to deal with than a piezo..
I know all commercial designs use piezos tho (eg V-drums) so they must be reliable, but i'll check out these FSR's now
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Old 16th October 2003, 06:38 AM   #5
ir is offline ir  New Zealand
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i've had a similar idea before but no technical know-how (or more importantly money) to carry it past the thought stage

however, the drummer from my old band had an electronic kit (which is where my idea started). he busted one of the pads somehow and so we ripped it to bits and had a looky, just a normal piezo transducer. this got us thinking. he also had one of those cheap kiddy electric drumkits, you know thy're about PC keyboard size, have 4 or 5 usuallly hexagonal pads. anywayhs, we "carefully took it to bits" (i.e smashed) and even the kids toy had the same basic stuff as the $3000NZD kit!

anyways, my idea was basically to use the parts from a kids kit. mount the sensors in proper drum practice pads and somehow have an old Pentium133 act as the brains of the whole operation - most likely feeding it all thru the parallel port (8 inputs that way)

but thats as far as i got.
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Old 29th October 2003, 02:46 AM   #6
Optical is offline Optical  New Zealand
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Hmm, i may have to change my tact, the opamps dont want to be friends and work properly together, plus the amount of components needed to make everything stable was rapidly increasing and wasnt looking like a good option if i had to make several of these things..

so, im now looking at an atmel AT90S8535 microcontroller to process the piezo spikes with the ADC input they have and switch the digital pins accordingly..
code is pretty simple, it looks like there is already on of these chips in the keyboard! but it isnt labeled so i cant tell
i might have a closer inspection and see if i can read the code out from it, if so i could reprogram it!

anyway, thats my progress so far..
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Old 13th October 2004, 11:47 AM   #7
co1inr is offline co1inr  United Kingdom
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Default Electronic drums

Hi There,

I was just reading your thread from November 2002 and wondered how you got on building an electronic kit. I am considering building a kit myself (or at least modifying a practice kit) and there seem to be a lot of people who have had some success with kind of project on a low budget even using mousemats for pads!

It looks as though the Alesis DM4 or DM5 make ideal 'brains' and are available new for under 300 and second hand for less than 100. What did you use in the end?

Did you stick with piezo transducers or switch to force sensing resistors as suggested?

It would be great if you can offer any advice - even if it is 'never again'.

Regards

Colin
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Old 15th October 2004, 01:05 AM   #8
Optical is offline Optical  New Zealand
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Hi there
In the end after much trial and error, time and money spent, the whole project became over complicated to say the least, especially since as you say the dm4's and dm5's are so cheap (although they are still hugely expensive in new zealand)..
But i did stumble on this website: http://www.midibox.org/edrum/
which gives all the instructions needed to build a drum brain, took about 2 days to build up and get working, works perfectly *** is just what i need..
yes, im using piezo transducers for the drum head sensors.. it pays to glue them to a faily rigid material to stop vibrations from the resonating head causing false hits i found. but otherwise everythign is great
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Old 15th October 2004, 12:03 PM   #9
co1inr is offline co1inr  United Kingdom
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Glad to hear it worked out in the end. I think building the drum brain is a bit more than I'd like to take on (my hat goes off to you), plus I could do with a decent drum module to run from my sequencer anyway. However, midibox.org has some great links for building triggers which I am particularly interested in so thanks for the pointer.

What type of kit did you use? I have found recommendations for Remo and Pulse kits with tunable heads but none yet for rubber pads. I've yet to select a kit so it would be good to know what options are available.

I'm also keen to try building eCymbals rather than using drum pads to trigger cymbal voices. Have you tried this?

Colin
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Old 18th October 2004, 02:00 AM   #10
Optical is offline Optical  New Zealand
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so far i am still experimenting with pad designs and materials to see whats best, but so far most things seem to work adequatly (no missed or extra hits) ..
i got a stack of old fat rubber mouse pads that i use as the rubber layer on top of the 'drum' head which turned out to be quite good at what they do

I also built the drum rack from scratch using aluminium tubing and big D-clamps..

If i had the money i think id buy one of those smaller practice drum kits you can get with are like small racks with rubber practice pads on them..
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