robot drummer arm

[squidmaster]

Hi. I'm going to build a robot drummer but am not sure where to start. I've been doing research but I am completely new to arduino and robotics so I'm asking for a little advice. I want to start the project with a robot arm that will bang on a drum. Add in new stuff till he can play a whole set. I'm pretty mechanically minded but don't know much about the electronic side of stuff. If anyone has any advice, what kind of arduino board I should get, books that would be helpful etc. I'd really appreciate it. I do a one man band show for a living. Now I need a robot band! You can check out what I do at jordpeck.com Thanks a bunch for your help. Jord

[corrado33]

I think it would be a LOT easier to have multiple "hands" beating on multiple drums.  You don't even need a hand, just something that will move back and forth quickly. 

I'm sure there are lots of videos of this out there.

[Soeren]

Hi,

Hi. I'm going to build a robot drummer but am not sure where to start. I've been doing research but I am completely new to arduino and robotics so I'm asking for a little advice. I want to start the project with a robot arm that will bang on a drum. Add in new stuff till he can play a whole set. I'm pretty mechanically minded but don't know much about the electronic side of stuff. If anyone has any advice, what kind of arduino board I should get, books that would be helpful etc. I'd really appreciate it.

If you aren't gonna take the hint below, at least give us the full details, you master of mech. 
What kind(s) of drum(s)?
Using regular sticks?
Using Whiskers? (totally different technique).
How great a range of power would you need to put into beats?
Just add any other metric you can think of.

The mechanical side is quite closely tied to the electronics side, as the exact electronics will depend on the interface - like using solenoid(s), motor(s), or whatever. The drum tehnique will influence it as well.

Like corrado33, I'd advice against using a "humanoid" arm, as that would just add tonnes to the level of complexity. A tubular stick holder with a set-screw or similar arrangement will allow for a quick stick change, and a simple arm mounted on the holder, hinged in the opposite end and pulled by whatever agitator you choose - a spring mounted holder will probably be the best way to get beats that isn't dampened by the stick itself.
Any way you do it, expect nothing more than very simple strokes - banging a drum is so much more than just banging and it is not possible to get a mechanical system, however well controlled, to get anywhere near what a human drummer can do (even the worst human drummer will be much better than your "Mechano drummer") - the only place where a "robot" has the upper hand is, that timing will be impeccable... Unfortunately, that can easily lead directly to a "mechanical sound", like most computer controlled music that sounds unnatural and "dead", due to the lack of timing errors (but this will be the consequence for any computer controlled system).
No wonder so many Ravers parties on E... Probably how they cope

I do a one man band show for a living. Now I need a robot band! You can check out what I do at jordpeck.com Thanks a bunch for your help. Jord

Heh, I had the same vision about thirty-some years ago, when working night clubs, either 4 single 'bots, or a single larger one that could handle all the instruments - but here's a hint that wasn't available back then... MIDI

And if you need a "physical representation", build some mechanical dummies that's controlled by the MIDI as well, but make sure to load the drums with cloth (or remove the skins).

Sound quality:
MIDI: As high as the rest of your sound system (and with acontinuous variable volume).
Homemade drummer: Low (unnuanced mechanical sound).

[squidmaster]

Gee thanks for the responses guys! I want to start simple. A stick that hits a small drum will be fine. Then during the show I can say something like "and if you tip a $20 betsy gets a new arm!". I will make things more complex as I go. I will need to send midi information, including notes & velocity, to the bot from ableton live. Also if I could put a head on the thing that can move around a bit and talk to me/the audience that would be awesome, probably a whole other ball game.

"What kind(s) of drum(s)?" - basic kit, normal sticks, snare, toms, cymbals, bass drum

"How great a range of power would you need to put into beats?"- I don't need to bang the heck out of things but a nice firm wamp will be good, and I want to play fast!!!

"like most computer controlled music that sounds unnatural and "dead", due to the lack of timing errors (but this will be the consequence for any computer controlled system)." You can get around this. When making computer music many times it helps to program little timing errors into the midi. I do this a lot when I'm making electronic music.

So you guys got an idea of what sort of board I should get? and actuators?(these need to be relatively quiet). And any resources books or on the web that will help me gain a better understanding of programming/the electronic side of things would be awesome.

I have already developed a variety of mechanical  actuators that do drum rolls a strike in different ways. I can play a drum set through a pedal board with these. As for the bots I just need to get some electric power behind them and all the programing side of things! Eventually I do intend to build more humanoid limbs and things for more of a presence on stage but that will be awhile off I know.

Thanks a lot guys, Jord

Thanks a lot you guys, Jord

[Soeren]

Hi,

A stick that hits a small drum will be fine. Then during the show I can say something like "and if you tip a $20 betsy gets a new arm!". I will make things more complex as I go.

That's a sound way of progress 

I will need to send midi information, including notes & velocity, to the bot from ableton live. Also if I could put a head on the thing that can move around a bit and talk to me/the audience that would be awesome, probably a whole other ball game.

I see you really want the physical banging and that you got your MIDI down. Perhaps there's a VST-plugin that could make your life easier here, but in essence, you need a box that receives the MIDI and translate the relevant commands into separate electrical signals, to get the velocity signal controlling the power fed into the whack.
Not a super hard task, but you'll need to learn to program whatever microcontroller you settle on.

"How great a range of power would you need to put into beats?"- I don't need to bang the heck out of things but a nice firm wamp will be good, and I want to play fast!!!

I was thinking on the range from a light "tap" to the loudest wham, but given the power for the max. the MIDI signal will be able to control the strength of each beat.
No problem with the speed - if made mechanically sound, it is just a matter of actuator selection. How fast do you need it to be?
300 BPM is likely around the maximum that you'll ever need and that's just 5 beats a second - nothing to sweat about at all.

You can get around this. When making computer music many times it helps to program little timing errors into the midi. I do this a lot when I'm making electronic music.

Yes of course, or you can make a plug-in that inserts random short delays - I wouldn't be surprised if there's already a VST for that.

So you guys got an idea of what sort of board I should get? and actuators?(these need to be relatively quiet). And any resources books or on the web that will help me gain a better understanding of programming/the electronic side of things would be awesome.

For the board that will receive the MIDI and control the hardware, there's lots of choices.
To be able to get a lot of example code from the net, the Arduino, or rather one of the cheaper clones may be the best start, as there's plenty of MIDI code floating around.
If you need more speed later, there's Arduino compatible board with faster microcontrollers (PIC, ARM etc) which still behaves similar to the original Arduino.

You'll need some interface to the actuators as well, but that comes after actuator selection.
To get silent actuation (any sound  concurrent with the beat would be drowned), solenoids would be best, as a motor will have some lvel of mechanical noise/sound when running (might be dampened by careful construction and a sound "shell" around it, or perhaps drowned by the music).
A motor might seem easier to control in respect to velocity, but I'd go for solenoids, as they can be smaller, which matters if you are planning an array of actuators and they can be controlled by PWM for the velocity, reducing the driver/interface to a simple power stage, with the controller handling both timing and velocity and just output on a single line to each driver.

I have already developed a variety of mechanical  actuators that do drum rolls a strike in different ways. I can play a drum set through a pedal board with these. As for the bots I just need to get some electric power behind them and all the programing side of things! Eventually I do intend to build more humanoid limbs and things for more of a presence on stage but that will be awhile off I know.

For speed and least power needed, I'd use carbon fiber for the arm holding the stick. Either round stock, or if you can get triangle stock (for added stiffness). A round piece, 6mm in diameter or lightly larger should have the needed strength.
I imagine an arm, hinged in one end and a solenoid pulling it (via a wire for placement out-of-sight) at a small distance from the pivot point. The distance will be determined by the actual solenoids parameters (power/distance of pull). A spring in between solenoid and arm will help if it bangs onto something when prototyping.

[squidmaster]

Thanks Soeren. I'm researching the micro controllers and solenoids right now. What would you recommend?

[squidmaster]

So I think ive settled on the arduino mega. Still trying to figure out these solenoids. There are a lot out there and I'm having a difficult time figuring out what does what how hard how fast. How do I read the numbers Aaaah?!?

[corrado33]

So I think ive settled on the arduino mega. Still trying to figure out these solenoids. There are a lot out there and I'm having a difficult time figuring out what does what how hard how fast. How do I read the numbers Aaaah?!?

Post exactly what you're looking at and we'll try to help you.  A link to a datasheet would be nice. 

[squidmaster]

Thanks Corrado. Basically I'm just jumping on google lookin up linear solenoids. There are a lot of places to buy. Is there a good place for solenoids you guys shop at??? It's hard for me to compare because I don't really know what I'm looking for, don't understand the specifications. If you could tell me a source to buy from and how to read the specifications that would be most helpful!

[Soeren]

Hi,

Basically I'm just jumping on google lookin up linear solenoids.

I got this thought... Drumming power is mostly coming from the wrist and if you make a wrist joint instead o a longer arm, you will have less mass and that will help a lot.

To take this a step further, rotary solenoids do exist, although I'm not sure how easy they are to find, and there'll be much less to choose from, but if a rotary solenoid was mounted with a springy stick-holder and placed at the right height and distance relative to the drum (on a heavy mount, or bolted to the drum itself by a bit of metal), it would srely work (provided you can find a solenoid with enough power of course).

Either way, keeping the stick close to the pivot point will enhance precision and lower the power needed.

[...] how to read the specifications that would be most helpful!

What specs are you thinking off?
The most important specs are the length of the stroke and how much pull it has at that length.
The same solenoid will have more pull strength if used with a shorter travel, so these two parameters are closely symbiotic. Besides this, you need some that you have a supply for (Volt/Ampere-vise).

[squidmaster]

I guess those are the specs just how hard how fast. I wish I could see how they perform though. I guess I'll just buy a few I think will work and see what happens. How much should I pay for a solenoid?

[Soeren]

Hi,

I wish I could see how they perform though.

In your shoes, I'd rig up the joint and a stick holder, set it up with a drum and use a luggage weight or similar to find out what's needed. I have no idea what's needed, but an hour of serious drumming does tire you out some, so it probably need more than what I'd initially guess.

You can recalculate your measures for whatever stroke length of a solenoid.
Say, you pull at 1 inch from the pivot center and need a single pound of pull for a reliable bang, then you'll get the same power by eg. pulling at ½" with 2 lb.

A piece of wire or string and a pulley will help changing the direction of the pull for easier reading of the weight if needed.

I guess I'll just buy a few I think will work and see what happens. How much should I pay for a solenoid?

Find out what you need in terms of pull (or push) power first and then get them as surplus. But beware, surplus solenoids can be a few bucks or a hundred (or even more). Depends on where you get them.


Some that may or may not be usable:

$4.50 and $2.75
http://www.sciplus.com/category.cfm/subsection/14/category/144

$4
http://www.surpluscenter.com/item.asp?item=11-2069&catname=electric

$6
http://www.alltronics.com/cgi-bin/item/04N019/search/12VDC-Pull-Solenoid

Various (some cheap, some not so)
http://www.surplussales.com/Motors/Motors-6.html

Various
http://www.electronicsurplus.com/LeftNav/ProcessControl/Solenoids.cat