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So i'm looking for a device that can exert variable amounts of force on command. Like say from 1N-12N. I was thinking a linear actuator might be able to do the job but im not sure. Is there a variable force inducing device of some sort? And it needs to be able to change the force rapidly.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
scrooch, apply a force of 1 to 12 Newtons - over what length of travel - uni-directional or bi-directional - how rapidly does it need to change - any other requirements
scrooch, apply a force of 1 to 12 Newtons - over what length of travel - uni-directional or bi-directional - how rapidly does it need to change - any other requirements
or, what do you actually want to achieve?
thanks for the reply Sulaiman, The travel distance is 1.2cm max unidirectional
i want to give a feel of "weight" to a push button that is made out of plastic.
I want to make a piece of plastic feel like a piano key when u press it down. I was probably wrong on 1-12 Newtons, probably does not have to be that much. So this is how it is
plastic surface --------------- || || actuator || ---------------- Base
so the actuator is controlled by a microcontroller applying a changing force giving the effect of a piano key to the person who is pressing it.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
You stil have not given any clue what the point of this is. The simplest and cheapest way to get the feel of a piano key is to use a real piano key. Anything else would cost 100 times as much and be almost impossible to design. Your actuator and sensor must be extremely fast and the math involved is quite complex too if you want a good approximation.
To get the feel of real mass the force will be very high for a short time. The simplest way by far to get that is to use a real mass.
You stil have not given any clue what the point of this is. The simplest and cheapest way to get the feel of a piano key is to use a real piano key. Anything else would cost 100 times as much and be almost impossible to design. Your actuator and sensor must be extremely fast and the math involved is quite complex too if you want a good approximation.
To get the feel of real mass the force will be very high for a short time. The simplest way by far to get that is to use a real mass.
Well I have seen digital pianos/midi controllers that are fully weighted(i.e feels like a real piano when you play them) are pretty expensive and very heavy because of all the weights and stuff.
So I was pondering the possibility of eliminating the mechanical bits using an actuator. I came across this when i was thinking about topics for my thesis
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
The device you're looking for could be a solenoid
I like Steve's idea of eddy current braking get a strong (neodymium / NdFeB) magnet and slide it across a thick piece of copper or aluminum to feel the effect. The effect of eddy current braking will be force proportional to velocity whereas you want force proportional to acceleration (I guess)
Afterthought; you could use a relay like this
- remove the plastic cover - glue your key to the top moving metal part - use a spring or magnet to bias the relay to close the contact points - turn the relay upside down
When you press on the lever the contacts will open to signal the controller of a keypress. Some 'tweaking' of the contacts may help. Apply your tailored voltage or current waveform to vary the back-force
This has the benefit of a built-in switch - saving space/cost/complexity.
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I need some help looking for a device
