Electronics > Projects, Designs, and Technical Stuff
Less noisy alternative to servo. Muscle / nitinol wire?
artag:
You can buy the CD steppers with leadscrew on ebay very cheaply - eg https://www.ebay.co.uk/itm/392331862778 (you will find cheaper ones than that). There are others with finer leadscrews if you need slower movement. Search for 'linear stepper'.
Steppers do need dual h-bridge drivers to operate them. If you use proper stepper drivers you will get all sorts of advantages but for a low-voltage stepper like the ones above you can still do them pretty cheaply with something like https://www.ebay.co.uk/itm/173044559728
I can't suggest any _cheap_ quiet servos - I'm afraid the only quiet servos I've seen are expensive ! But there may be other mechanisms like the CD sliders. For more powerful units, headlight positioners are worth considering. They're also stepper motors with a leadscrew. Mirror motors are more often just a geared DC motor and a cam.
If you have large numbers then pneumatics might be an answer : valves can be https://www.ebay.co.uk/itm/254229792066 rather than something expensive from Festo. Actuators might be syringes, or small balloons. Pump might be a fish tank aeration pump. The thing about pneumatics is that you'll typically have one pump and lots of actuators rather than lots of motors, so it doesn't get noisier - unless you need a bigger pump, or let the air out too noisily.
Muscle wire has quite a small extension with heat, so if used in extension mode needs to be wrapped around pulleys to get enough length. If used in a bending mode they will give more movement, but then you need thicker wire.
You might learn something from http://www.osloom.org/. I haven't seen updates for ages and I guess has been abandoned but they used muscle wire to avoid patents on many other forms of heddle actuator. It looks as though it had an acceptable level of performance but I don't know what happened to it.
Most of these aren't very accurate without feedback. But they're OK for pushing from one limit to another.
RoGeorge:
Another silent actuator is the wax piston. Slow and inefficient, but very strong.
https://en.wikipedia.org/wiki/Wax_motor
Twisted fishing line (only some types, not any line) can actuate, too, when heated.
beanflying:
--- Quote from: perik on November 10, 2019, 10:16:41 pm ---
--- Quote from: beanflying on November 10, 2019, 09:40:21 am ---Do you need no noise or just really low noise?
--- End quote ---
Ideal no noise but guess it is not possible :)
--- Quote from: beanflying on November 10, 2019, 09:40:21 am ---You could also take a look at things like the steppers used on CD drives or even the internals of a hard drive.
--- End quote ---
Good idea! But I need lots of servos so prefer buying instead av deconstructing :) Do you have an example of what kind of steppers this is?
--- Quote from: beanflying on November 10, 2019, 09:40:21 am ---Single gear reduction (standard servos are 5-8 reductions) only and even drop the motor voltage a touch to reduce the speed and noise. https://www.horizonhobby.com/helicopters/aircraft-servos/20-gram-performance-linear-long-throw-servo--15mm-lead-spmsh2025l
--- End quote ---
Sorry for stupid question but Single gear reduction - is that the same as Bearing that says single in the specs? At the moment I have got some cheap SG90 servos. They are pretty noisy though. If you know some other cheap servos in with lower noise you are welcome to recommend
--- Quote from: soldar on November 10, 2019, 04:24:34 pm ---3 cm is very doable with an electromagnet with a sliding nucleus. Also, you can have an arm that amplifies the travel range. Heat should not be a problem.
--- End quote ---
what is a sliding nucleus? I did some tests and to get a strong electromagnet the heat was actually a problem :)
--- Quote from: artag on November 10, 2019, 10:24:31 am ---As usual, it's a tradeoff of power, cost, speed, noise.
--- End quote ---
since in the project im working i need a lot of servos, around 100 or even more so will try to get a decent servo but with low cost. Because of the amount Im using at the same time I also need them to be more quiet. At the moment I have got some cheap SG90 servos. They are pretty noisy though. If you know some other cheap servos in with lower noise you are welcome to recommend
--- Quote from: artag on November 10, 2019, 10:24:31 am ---Steppers are noisy if the steps are large. Use small steps above audio frequency and they're a lot better
--- End quote ---
I understood first now that steppers cannot be controlled with pwm signal. Maybe also a more expensive alternative compared to servos ...
--- End quote ---
The SG 90's are among the noisiest ;)
The CD types Artag linked above are the sorts of stuff inside a CD drive so either wreck one to get a freebie or buy one for very little (fun to play with regardless). You just need a driver board to suit.
Look closely at the photo of the Horizon servo I linked it only has a single bearing at the oposite end to the drive. Not really an issue given the power but it will help it run more smoothly. I run the next size down and smaller in some of my indoor R/C toys (sub 2g servos).
A reason to go servo over geared steppers is micros like the arduino already speak servo but you need another board to talk stepper :)
CatalinaWOW:
Maybe put the garden variety servos in a soundproof box. You can extend the mechanical motion out through small holes in the box.
Implementing this approach will require attention to the paths of sound transmission. Much will come through the mounting points.
DrDisco:
Some small steppers with some trinamic drivers. Should work out. The trinamic drivers have a stealth chop feature. That will silence the motor right down.
They are quite expensive, but there are Chinese dev boards you can buy in the same form factor as the conventional a4988 Polulu modules:
https://www.aliexpress.com/item/32886021442.html?spm=a2g0o.productlist.0.0.479f50c2Xsl2fZ&algo_pvid=f8e16a04-8a46-4601-8c2b-a3339f76c234&algo_expid=f8e16a04-8a46-4601-8c2b-a3339f76c234-11&btsid=5e5ae011-27f9-44c6-8dcf-356585bc0018&ws_ab_test=searchweb0_0,searchweb201602_2,searchweb201603_52
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version