I'm an electronics noob, learning, and would appreciate some input from bigger heads.
I've got this project in mind, involving using electric motors to drive pistons to quickly strike a static surface then rapidly retract to await the next event. Each must be independently controllable and operate quickly.
If you just want to drive a hammer to strike something, servo control seems overly complex. You don't need any feedback or precise positioning, so I'd say go with a solenoids. They don't need as complex a control system and cost a fraction of what a servo does (and an even tinier fraction of a linear actuator's price). You'll probably also get more speed and power from a solenoid.
My whole thing with this controller unit is that they have a version that takes MIDI as input, allowing me to control these solenoids with a MIDI device (sequencer, keyboard, drum controller, knob box, whatever).
I did a bit of googling one night and found a few MIDI to motor control boards using PIC's that others had made, but they did all the programming themselves, etc, and at anyrate have yet to respond to my emails. So I settled on this one.
It's overkill, but it should do what I want it to do out of the box and doesnt cost a lot.
Solenoids aren't good at 'dynamics'..you'll need to go with servos if you want your mechanism to be able to respond to Midi velocity or aftertouch data.
Huh...at the Maker Faire Brian Jepson had me all revved up over a Make branded Midi controller card kit...there's no sign of it at the Make store though.
The controller you linked looks pretty cool ( and RS-232 to 16 servos for less than $50 is a steal, I'm buying one). However, you might want to look at this:
In the column on the left of that page you'll need to look at the "Core Module" and the "DOUT Module". Together they will give you a MIDI-to-32 digital outputs. It would be pretty simple to go from there to drive solenoids or what have you.
As far as servo vs. solenoid vs. linear actuator, everything said above is correct. Additionally, you have to take into account two things: How big is your striker, and how fast do you want it to go....
Hobby Servos = slow and weak Solenoids = fast (unless damped) and can be pretty forceful if large. Linear Actuator (lead screw type) = slow and very strong Linear Actuator (linear motor type) = fast, strong, and insanely expensive Hydraulics = slow and VERY strong but needs pumps and stuff Pneumatics = fast and strong, but requires compressed air
So ... what exactly are you wacking, and what are you wacking it with?
To strike a surface and quickly retract, sounds like a solenoid driving something like a piano-hammer would work well. Hobby servos, like what the first product uses, may be too slow to "quickly strike a surface and retract".
Another thing you can do is take a regular DC motor and attach a hammer to the end. You can then drive the motor hard and let it recoil off the surface you are whacking with the hammer.
To drive 12V DC solenoids or 12V DC motors, you may want to consider this product my company makes:
Our IOPoint-USB product may be used to drive 16 12 volt solenoid hammers, motors, steppers etc. from your computer. However it uses USB, not MIDI. If you are driving the MIDI data from the computer, you can probably patch into the MIDI stream via software to keep the 16 hammers in sync with any music you are generating.
Steppers won't work for the speed reason.. Plus it would consume 4 of 16 output channels to drive one unipolar stepper.
Mark http://www.bibaja.com Web based Irrigation and Landscape Lighting Control (and various other gadgets...)
Thanks for the tip. Indeed I do own the company, design and build everything, test it, write the software... Chief cook and bottle washer. :-) Bibaja is my own make hobby turned semi-pro.
I sometimes recommend other products like LabJack and Phidgets when they are a good fit for an application. I'm not *completely* biased. ;-)
Sorry to hear you aren't a LON fan. I do like the power line communications (physical layer, anyway). I prefer TCP/IP to LON, however. In all my products that use LON, I bridge to TCP/IP and hide the LON when possible.
Back to topic, I'm interested in ENDIF's answer to your question about what ENDIF is wacking and wacking it with. Since we're talking about MIDI, the Orchestrian Player Piano came to mind. It would be really cool to get an assortment of bells, or an old Xylophone, and build up a little mini-Orchestrian.
If only there were more hours in the day (and I could stay awake that long...)
Congrats and best wishes for your biz Mark. I guess that you're the guy to talk to about my 'dream' irrigation controller that doesn't exist. 8-)
I guess that there's nothing wrong with LON as a technology, it's the cost of the tools, non-open nature of the protocol, cost and availibility of neurons, licensing fees and other issues. In the stuff i've done, it doesn't out perform RS-232/422/488 or TCP/IP.
I was guessing the same thing, that ENDIF's building some sort of carrilon. I've had a back burner project like that for some time. I've bought the MIDI board set I linked above, and snagged a few dozen nice little Ledex rotary solenoids from ebay. Just yesterday I found a source for really inexpensive metal tone bars so the project might get moving again.
Thanks for the well wishes. I would be happy to hear about your dream irrigation controller. Who knows, I may have already designed it. :-) Feel free to contact me directly through my website's contact form:
I agree that the LON tools cost and product availability are a problem. It is one I would like to change and I have something in development that I hope will help make it more accessible.
A computer controlled Carillon would definitely be a cool project! I wonder if Berkeley has their Carillon under computer control already... I'm surprised how few Carillons are in the US according to Wikipedia:
Basically, my idea is for a simple man-portable beat-bot about the size of a brief case.
The whole thing's really just a visualization tool - electronic music performances can be sooo boring to watch, regardless of how awesome the music may be..
So:
- Strong but light metal shallow box frame.. think of a 4 inch deep metal window frame.
- Box frame has a handle on the outside, and faceplates that detach completely on the large open sides, allowing the assembly to travel safely. I wonder if they'd let me take it on a plane?
- MIDI to Motor controller + power supply + motors, etc, all mounted inside.
- motorized strikers lined up side by side, facing one inside face of the metal box frame, using it as the striking surface.
- inside face of the frame being struck is covered with corresponding piezo triggers that then send trigger pulses
- LED's that light up with the piezo for additional visualization or light-passing heads on the striker tips that pass through a frame-mounted laser
- these trigger pulses could be used to trigger a drum brain, or send CV for a modular synth (think, worlds most heavy, inefficient and loud but fun to watch MIDI to trigger/CV converter ;] )
I have other variants of this idea, but this is the most fleshed out and easiest.
The reason I chose linear striking instead of rotational motion is reducing lag time between MIDI event and striking event, size constraints, plus there's just something more visceral about a piston like motion.
I don't really need the motors to respond to MIDI dynamics, as the parts assigned to the bot would either be dynamics-irrelevant or dynamics could be added in 'after the fact' with LFO's, etc.
It's pretty damn ambitious for someone starting out, possibly even ridiculous, but I'm determined. =]
Check out this guy's <A HREF="http://home.comcast.net/~rblang/index.html" TARGET="_blank"> website </A>and click on the xylotron link. He's pretty much done what you're talking about.
Sorry for re-raising this topic but I found it on a search and this project is very close to what I am attempting to do. I want to automate an acoustic plucked (as opposed to strummed) stringed instrument for a show-type performance. I would like to use a MIDI file to control the solenoids used to pluck and depress the strings. My ideal set-up is that I would have a number of MIDI files stored locally on a controller and would use DI's (switches) to select and start and pause the required MIDI file. Failingf that I would use a computer to select start and pause the files and feed them through the controller. In either design, the controller would trigger the required DO's (I need about 24) which would then use a bank of relays to drive the solenoids. the idea is that the solenoids would enable the instrument to play the MIDI file notes in real time to the tempo defined in the MIDI file.
Would you say that the MiniBox Hardware Platform ("Core Module" and "DOUT Module") have the functionality I need in a controller? I am a musician and a mech. eng. with some exposure to PLC's but a newbie to electronics and particularly microcontrollers and so any advice you can give would be much appreciated.
Some of you might be interested in the carillon (automatic-bell playing machine) I made last summer. It ran for a few weeks in a garden shed, outside the South Bank Centre, London:
...if you watch the video for a minute or so, you'll see the bells.
For those of you interested in the details: I percussed the bells using cheap servos (under ten quid), rather than solenoids. This may seem like overkill as a solenoid would do the trick but all those solenoids in a tightly-packed space would create a lot of clicking - I was worried would seriously undermine the sounds of the bells. Also, servos were good because this carillon was thrown together very quickly - I only had a month to source everything, make it, programme it an test it. With servos, it was very easy to adjust the swing at the last minute, when the wooden frame arrived (the day before the show opened).
I controlled the servos using an SSC-32 from Lynxmotion, controlled from the fakey serial out of my Mac (via a USB-serial converter) and I wrote a simple Max/MSP patch that let me control the bells directly from midi files, making it easy to work with them musically.
In the video, they're playing Poulenc's Perpetuum Mobile. I'm now in the process of making the whole system wireless, so each bell is in it's own little box and the bells can be widely scattered across a venue. I'm also writing my own music for them. I'm in the throes of working out the best way to control them wirelessly, without introducing latency (am currently experimenting with an xbee mesh and a simple ir-based mesh). Each bell box will have its own little bespoke circuit, with the recycled servo motors, a pic chip-based control circuit.