DC Motor Selection - Where to begin?

[Gadi]

Greetings,
I am stepping into my first self designed, open ended project beyond
the ivory walls of school and the grey walls the cubicle, and I have
realized I don't know where to begin! If I have found the wrong forum
any redirection would be much appreciated.

I am looking to create, for all intents and purposes a low power
haptic device. I want to use a PWM controlled DC motor powered from a
rechargeable battery to create a wide range of vibrations to indicate
information to the user. From this I think I need a motor that has
the following features:

1) Relatively small profile
2) Powerful enough to create a wide range of vibrations, even very
intense ones
3) High quality, long life, no cheap motors!
4) DC, Single direction is fine
5) As low a power consumption as possible

My issue is I don't know how to go from my list of specifications to a
concerted motor search. Any help would be appreciated, from specific
recommendations to (perhaps the more helpful over time) help with
resources to learn how to conduct this kind of search on my own.

Thanks for much for your help!

-Gadi

 

[Gadi]

Item 3 points you to Maxon, Faulhauber or Pittmon -- unfortunately the
'not cheap' applies to the cost as well.

If you find those prices too high, Johnson and Mabuchi are the big
Japanese motor suppliers, and may have something good enough yet
affordable.

For experimenting check the surplus houses -- they all seem to have lots
of motors, and many have pager motors with weights already attached.

--
Tim Wescott
Control systems and communications consultinghttp://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes,http://www.wescottdesign.com/actfes/actfes.html

Hi,
First off thank you so much for your help!

I have a few quick follow up questions:

1) What are some good resources for purchasing motors?
2) What specifications for motors define these qualities:
a) Can it be controlled via a PWM signal? (I suspect this is any
brushed DC motor or a brushless DC with added circuitry, but I am not
sure)
b) How much weight can it rotate, and at what speed, at the motors
peak efficiency? (Alas my memory of dynamics is a bit rusty, how do I
go from torque/power to an idea of how much weight the motor can spin
at peak efficiency)
c) What specifications should I look for to indicate higher
efficiency, lower power usage to accomplish the same amount of work as
another motor?

Thanks again for your help,

-Gadi

 

[[email protected]]

Greetings,
I am stepping into my first self designed, open ended project beyond
the ivory walls of school and the grey walls the cubicle, and I have
realized I don't know where to begin! �If I have found the wrong forum
any redirection would be much appreciated.

I am looking to create, for all intents and purposes a low power
haptic device. �I want to use a PWM controlled DC motor powered from a
rechargeable battery to create a wide range of vibrations to indicate
information to the user. � From this I think I need a motor that has
the following features:

1) Relatively small profile
2) Powerful enough to create a wide range of vibrations, even very
intense ones
3) High quality, long life, no cheap motors!
4) DC, Single direction is fine
5) As low a power consumption as possible

My issue is I don't know how to go from my list of specifications to a
concerted motor search. �Any help would be appreciated, from specific
recommendations to (perhaps the more helpful over time) help with
resources to learn how to conduct this kind of search on my own.

Thanks for much for your help!

-Gadi

First you need to put some numbers into your spec. Mass, speed,
acceleration and losses of the load.

 

[Gadi]

First you need to put some numbers into your spec. Mass, speed,
acceleration and losses of the load.

Hi,
Thanks for your reply, those are some good questions, I hope my
answers make enough sense to help better answer my original questions.

Since I am trying to create varying levels of vibration intensity I
suspect I will be adding an uneven weight to the end of the motor.

Mass - I intend to experiment with various weights at the end of the
motor to see how different masses vary the vibration. Only after more
experimentation can I truly settle on an exact mass. Considering that
space is an issue, even using more exotic weights, I cant imagine my
weight will exceed 100g, around 50g being a more realistic estimate.

Speed - Once again, I dont know what rotational speed is best just
yet, though I suspect that to create more intense vibrations I will
need rather high speeds. For my purposes now I suspect I will need
something that can do a few hundred rpm to 10,000+ rpm to give me a
proper range to experiment.

Acceleration - I am not sure how to best describe what I need in this
area since I don't really know how to give a specific number or number
range for acceleration and my memory of dynamics is rusty at best. A
responsive motor is desirable in order to create a more complete range
of possible vibration sequences. I don't know how to get acceleration
from these numbers but I suspect they are enough for someone who knows
more than I do. Lets say, worst case/high end numbers: I want to
accelerate a 100g weight from a 0rpm to 10,000rpm in under 0.5
seconds. Is that even reasonable to ask for? How about a 100g weight
from 0 to 5,000rpm in under 0.5 seconds and to 10,000rpm in under 1.5
seconds? How can I go from here to a number to look for in a motor
spec.

The final thing you asked for is "losses" which, I must apologize, I
have been unable to figure out just exactly what that is, and how to
take a guess as to what my "losses" will be for my specific
application. If you could offer me an explanation or point me to a
resource I would very much appreciate it.

I hope that is enough information to offer a better idea at what my
requirements are.

Thanks for your time,

-Gadi

 

[JosephKK]

For retail, try MPJA associates, All Electronics, Herbach & Rademan, and
other surplus outfits.

For the precision motors plan on going to the manufacturer.

Johnson & Mabuchi web sites list distributors -- I have never tried
buying these motors, so I couldn't say who to call.


Correct. Just about any DC motor will run off of PWM drive

I do not believe that brushless DC motors can be PWM for speed
control. Plus they have their own style of variable speed controls.

 

[neon]

low power and the torque required to move your work. it is finaly a matter of efficiency that you require.