9 replies to this topic

[Tim]

Hi community! I'm completely new to micro-controllers, and relatively new to programming. I've been lurking around the forums for a while now and have finally decided to dive in and see what I can accomplish. For my first project, I'm hoping to play around with some 'air circuits' for use in an electro-mechanical musical instrument, but I'm really not sure where to start as far as parts are concerned. Obviously, I need a netduino, but what else? The parts I'm emulating are just simple buttons and levers that lift a pad (from which air will escape). My initial thought was to use a servo to simply lift the pad, but then it occurred to me that I could replace the whole system with a solenoid. In a perfect world, whatever mechanism/setup would be (in order of priority) very fast, very small, and low power. Speed is the most important, since it needs to feel as immediate as pushing a lever would. Size comes from my desire to keep the entire instrument portable. For my idea to ultimately work, I'd need anywhere from 40 (best case) to 120 (worst case) 'lever-replacement systems'. Power comes mostly from the size and portability standpoint. It would be unfortunate to have to plug the thing in to use it. Ideally, it could be battery powered. I suspect that one of these priorities will have to give (i.e., speed means more power-hungry, etc.), but that's my pie-in-the-sky. Any suggestions on specific parts? (links would be very, very helpful). I've tried to do some poking around, but I'm a bit lost in everything. Looking at some of the solenoids, for example, all I could find was high-pressure stuff (hydraulics, pneumatics, etc.), or really tiny stuff (the pads I'm replacing are about 2-3 centimeters in diameter). Servos seem even wackier, since all I really care about is opening and closing as fast as possible (partial opening and closing is undesirable even on a 'normal' instrument). Also, is the netduino mini something I should consider for such a project? Thanks for the consideration!

[CW2]

The parts I'm emulating are just simple buttons and levers that lift a pad (from which air will escape). My initial thought was to use a servo to simply lift the pad, but then it occurred to me that I could replace the whole system with a solenoid.

Could you share more details on how the mechanism is supposed to work? Is it similar to (for example) one inside an accordion? Could you replace lifting the pad with pushing the button (i.e. servo with a cam)? How about using solenoid air valve?

[Tim]

Could you share more details on how the mechanism is supposed to work? Is it similar to (for example) one inside an accordion? Could you replace lifting the pad with pushing the button (i.e. servo with a cam)? How about using solenoid air valve?

All the mechanism needs is a button and a pad that lifts. Accordions, I believe, have very similar mechanisms, but I've never popped open one to check it out. The instrument I'm considering would be a member of the accordion family, but these instruments can be crazy-complex or just down-right simple; I'm going for something very simple (hopefully). If you've ever looked at a woodwind instrument (e.g., saxophone, clarinet, flute), then just about any key should demonstrate what I'm aiming for: a simple 'button' that when pressed lifts a pad (opening a hole from which air can escape). Does that help?

I'm really open to any mechanism that accomplishes the above feat. I imagine that a servo/cam option would certainly work, but I am concerned with the weight. Solenoids seem very promising, but I can't figure out where to start. The simpler and faster the better!

Thanks for the comment!

[CW2]

If you've ever looked at a woodwind instrument (e.g., saxophone, clarinet, flute), then just about any key should demonstrate what I'm aiming for: a simple 'button' that when pressed lifts a pad (opening a hole from which air can escape). Does that help?

I see, thanks for the clarification. Accordion has similar mechanism, a pallet that covers tone hole is lifted when a key is pressed.

Solenoids seem very promising, but I can't figure out where to start. The simpler and faster the better!

You'd probably need a linear solenoid actuator, which can be also made from a relay coil - usually, you can get them in amounts on various bargain sales and you could even reuse some of their mechanical parts. Netduino cannot drive coils directly, please refer to previous links for sample schematics how to switch inductive loads with a transistor. You can also use specialized drivers (integrated circuits) instead of discrete transistors, like Darlington arrays, power shift registers, etc. The selection of an actual device depends on coil voltage, max. current, communication interface etc.

[Tim]

Thanks CW2 for the great responses!

I see, thanks for the clarification. Accordion has similar mechanism, a pallet that covers tone hole is lifted when a key is pressed.

Excellent example of what I'm trying to get at!

You'd probably need a linear solenoid actuator, which can be also made from a relay coil - usually, you can get them in amounts on various bargain sales and you could even reuse some of their mechanical parts. Netduino cannot drive coils directly, please refer to previous links for sample schematics how to switch inductive loads with a transistor. You can also use specialized drivers (integrated circuits) instead of discrete transistors, like Darlington arrays, power shift registers, etc. The selection of an actual device depends on coil voltage, max. current, communication interface etc.

Wow, that's only a little bit intimidating. Any chance there are off-the-shelf options? If this is the only way, then I'll certainly start trying, but my project likely just got much harder and bigger than I had anticipated.

Upon reflection, really all I need is a way to 'instantly' allow and stop low pressure airflow. The idea of levers and pads seems like just one way to solve the problem... but I'm just not well-versed enough in mechanics/engineering to know where to start. I'm half tempted on just buying some random solenoids online and just trying to get them working. If I could at least get to a prototype stage, then I might have a better idea if I'm way over my head or not. Any suggestions on a basic solenoid that would work with the Netduino?

Also, just generally speaking, what suggestions do folks have for tools and parts for getting started?

[CW2]

If I could at least get to a prototype stage, then I might have a better idea if I'm way over my head or not.

I have just spotted Robotic Xylophone - you probably wouldn't want to make solenoids by yourself, but there are some useful ideas demonstrated, like interfacing with shift registers over SPI. You can use 74HC595 that can be easily chained to increase number of outputs, or even TPIC6B595/TPIC6C595 power version that has built-in output transistors and protection diodes.

[Tim]

I have just spotted Robotic Xylophone - you probably wouldn't want to make solenoids by yourself, but there are some useful ideas demonstrated, like interfacing with shift registers over SPI. You can use 74HC595 that can be easily chained to increase number of outputs, or even TPIC6B595/TPIC6C595 power version that has built-in output transistors and protection diodes.

That video was genius! That's precisely the kind of thing I'm looking for, and I'm sure I can modify the concept easily for what I'm trying to do. I'll look into the parts you've mentioned.

Why would making my own solenoids be a bad idea? They seem pretty straight forward from the video. Any suggestions for an alternative, off-the-shelf option?

Thanks again!

[bill.french]

my first instinct is to google pinball machine replacement parts, they tend to have lots of inexpensive solenoids...

[bill.french]

actually a netduino driven pinball machine would be a pretty cool project!! TO THE LAB!!

[Tim]

my first instinct is to google pinball machine replacement parts, they tend to have lots of inexpensive solenoids...

ooo, excellent idea!