I did, but came to the conclusion that they'd be too slow, I think? My understanding is that they rely heavily on ambient temperature to return to their original shape, and as such can also have an unpredictable range of power/movement depending on the environment.On another tack. Have you looked into using memory/muscle type wire to activate you musical devices? The major problem is that they eat a lot of current but if you are not on batteries it does not matter. Speed can be hand by using several thinner wires etc.
Hank Fletcher said:For another potential project, I was wondering if there's any hobby-type product in terms of flexible axles? So instead of a pushrod going back and forth, it transmits rotary power like the flex cables that come with rotary tools? Is there such a thing?
Hank Fletcher said:...My recorder robot fingers need to react and operate fast, faster even than I think a normal servo will permit. But the fingers need only be either fully pressed or fully released, at least for the first prototype of the recorder robot.... Any ideas on what I might consider for the latching mechanism?
I started but then gave up on solenoids. I was just disappointed by how inefficient they were - lots of heat, energy suckers, and unreliable in terms of magnetically sticking in the activated position when energized too long. I thought about the car lock and the steppers, too. Trouble is, being a music application the amount of sound the motor/mechanism makes is a bigger factor than most other applications have to be bothered with.Ambient said:How about solenoids? Those are very fast. If you need strength as well then you can try out pushrods connected to a car door lock mechanism. But that would get kinda bulky I imagine. You could also use stepper motors and winch setup. But all in all I would just use some fast servos. You can use the long servo arms and that will give you a good amount of travel, at least 2'' I thin
Sorry, I'd forgotten that I'd already come to a conclusion as to what would be sufficient in terms of a "latching" mechanism for the recorder robot. If I'm using a geared servo, or geared motor, then I think that will be sufficient for keeping the finger securely pressed or left released with no power.Hank Fletcher said:I'm thinking some inexpensive DC motors connected to the pushrods, and some simple/efficient/fast way of latching the motors in either the pressed or released position if the finger doesn't move for longer than a second or so. This would limit the amount of power wasted in a stalled motor. Any ideas on what I might consider for the latching mechanism?
Hank Fletcher said:What do you mean by "fast" servos? I'm a little ashamed to admit that I've never worked with servos before, but I'd thought that all hobby servos only refreshed their position every 50ms (at 20Hz, or do I have those numbers backwards?).
Hank Fletcher said:Would it still be possible to get the servos at least coordinated so that they refreshed simultaneously?
Hank Fletcher said:What I don't want to happen is for the servo/fingers to get out-of-sync, as it were, so that the wrong fingers are going down at the wrong time. Or am I thinking about this all wrong, or too much?!
Hank Fletcher said:I did, but came to the conclusion that they'd be too slow, I think? My understanding is that they rely heavily on ambient temperature to return to their original shape, and as such can also have an unpredictable range of power/movement depending on the environment.
0123456789Hank Fletcher said:3v0, I've said it before: there's something cool about the muscle wire idea. I just don't think it's something I have the patience or funds to experiment with for this project.
I understand. It can be spendy. The stuff is much cheaper in bulk and even more so if you train your own wire but then there is that patience thing. I would like to play with it but the intro kits are not what I would call a value.
...
But how to transmit the power to the various joints? ... I wonder if even pulleys and strings might be the better way to, at least for keeping things light to the extreme joints, but I'm having a hard time getting my head around that solution, for instance, whether cases of various independent movement of the joints might interfere with that type of solution.
There are so many ways to go. Choice to some point would depend on scale.
The pulley string thing is fun to think about. In part it depends on how many joints you want in the arm/leg. The first two are easy.
Trivial for you, maybe! But still, I'm starting to get my head around it. Even if I went with servos over the gearmotors, I'd still want some method of feedback to know that the fingers are pressing firmly against the holes of the recorder. I figure measuring the current of the motor as it starts to stall would be a good way to do that?Pommie said:To get a pic to control 14 (18 pin pic) servos simultaneously and receive data from a PC is really trivial especially if the servos only have 2 positions. You should be able to get servos for less than $10 each.
Mike.
Hank Fletcher said:But while were on it, how do continuous rotation servos work? Does the difference in the PWM signal just change the speed, or is it control over 360 degrees of rotation?
No problem, and thanks for the ideas. Nice photos!Sorry for the length of these comment. John
Thanks for the tip. I don't know much about them, but now have something to do with my old hard drive that fried awhile back!blueroomelectronics said:What would be nice and fast; perhaps would be what hard drives use. A voice coil motor.
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