Less noisy alternative to servo. Muscle / nitinol wire?

[perka]

I´m looking for a less noisy alternative to using servos for a project and I was thinking of using musclewires (Flexinol / nitinol wire) as an replacement. I havnt worked with musclewires before and wonder if this is possible or if they are very slow (I know they are driven by heat so slow cooling might be a problem)

Basically my project need to pull and push a small weight with a thin ironstick as arm. I need something that goes two ways. When I applies current to it I want it to pull and when I decrease the current again I want it to gradually go back depending on the current. Im using a pwm signal from my raspberry pi to control the current.

I wounder if anyone has some experience with doing the same? Basically replacing a servo with musclewire?

For example this one:

Flexinol® - 0.012" Diameter (1 foot) - COM-12096 - SparkFun Electronics

This 0.012" Flexinol® Actuator Wires (aka shape memory [Nitinol](http://en.wikipedia.org/wiki/Nickel_titanium)) is a one foot long piece of nickel-titaniu

www.sparkfun.com

I guess the thinner the wire the faster it reacts since it cools off faster?

 

[Nigel Goodwin]

As far as I'm aware it's very slow and very low power, I think your best option is to get some and try it on your exact application.

And of course it only pulls, you would need a spring (or something) to return it.

 

[alec_t]

my project need to pull and push a small weight

In choosing a servo alternative it would help to know :-
How much force is required?
How fast must the weight move?
How far must the weight move?

 

[perka]

In choosing a servo alternative it would help to know :-
How much force is required?
How fast must the weight move?
How far must the weight move?

Not much force. Maybe need to pull and push say 100 grams
It need to be pretty responsive. As close to the responsetime in a servo as possible
It need to move about 4-5 cm

Thanks

 

[alec_t]

I reckon the combination of the force and distance requirements rules out using a solenoid.

 

[perka]

I reckon the combination of the force and distance requirements rules out using a solenoid.

Yes i was first thinking of a solenoid but wont work

 

[alec_t]

Here's a concept I had ages ago but have never tried out. It might work for you.
Brushless DC motor turns a shaft which twists a pair of strings. The more twists the shorter the strings get, pulling the object against spring tension.

 

[rjenkinsgb]

Nitinol has a maximum contraction of around 5% and can be as low as 2%.

At best, for 5 cm movement, the the actuator would have to be a metre long!

 

[DrG]

Interesting topic. How noisy is noisy/quite?
Check out this little thread, including the video link. Is your servo "singing"?
What about a micro stepper? I have one something like this one that I have been meaning to play with.

 

[perka]

Nitinol has a maximum contraction of around 5% and can be as low as 2%.

At best, for 5 cm movement, the the actuator would have to be a metre long!

Maybe it is possible to gear it up through two wheels in different sizes since it is not that heavy

 

[perka]

Interesting topic. How noisy is noisy/quite?
Check out this little thread, including the video link. Is your servo "singing"?
What about a micro stepper? I have one something like this one that I have been meaning to play with.

This stepper motor is less noisy than a servo?

The thing is im going to chain about 300 of them so i need them to be pretty silent each one of them if its not going to be really loud. It is for an environment where you rather have no noise at all. Of course that is not possible but as close as possible would be nice

 

[shortbus=]

The thing is im going to chain about 300 of them so i need them to be pretty silent each one of them if its not going to be really loud. It is for an environment where you rather have no noise at all. Of course that is not possible but as close as possible would be nice

With that tidbit, maybe you should explain what your attempting to do. You may get so better ideas.

 

[hyedenny]

How about a piezo motor? Very quiet, very efficient, very small..

 

[perka]

How about a piezo motor? Very quiet, very efficient, very small..

That is interesting. Is there a stepper piezo motor that you can control through raspberry pi pwm signal. Or through a mosfet if needed ...

If you have a link it would be great

 

[hyedenny]

That is interesting. Is there a stepper piezo motor that you can control through raspberry pi pwm signal. Or through a mosfet if needed ...

If you have a link it would be great

Not exactly... They're controlled more simply than a stepper.
This is a question easily answered with a simple internet search.