CHEAP Linear Motor/Actuator

[Tim Hubberstey]

"Pricey" is right!

I'm gravitating toward

stepper-motor/belt-drive/ball-bearing-drawer-slide/some-kind-of-sensor

approach.

Looks like I need about a ft-lb or so of torque, 3.6° would do.

Sources, suggestions?

How about a stepper motor with a direct-drive connection to a piece of
Redi-rod (that's what it's known as in Canada - threaded steel rod up to
36" long). Use a nut welded/soldered to a pushrod as an actuator or
drill and tap your actuator directly. 0.25" rod has 20 threads/inch ->
0.05"/revolution. Your 0.010" resolution only requires 60-degree steps.
Measured backlash on a random sample of 0.25" bolts and nuts from my
junk drawer appears to be around 0.004".

This is a very standard way of converting rotary motion to linear
(lathes, old floppy drives, etc.). You might even be able to salvage the
head positioner out of an old 8" floppy drive. Newer floppy drives use
taut-baud positioners which wouldn't be as easy to hack.

 

[Tony Williams]

I'm gravitating toward
stepper-motor/belt-drive/ball-bearing-drawer-slide/
some-kind-of-sensor approach.

A chain and two sprockets. Nut and bolt through
one link of the chain to get the linear output.
Drive one sprocket with a dc motor+gearbox. Put
a potentiometer on the other sprocket to sense
the position. 0.030" in 6" is 0.5% linearity
required off the pot.

 

[Tony Williams]

A chain and two sprockets. Nut and bolt through
one link of the chain to get the linear output.
Drive one sprocket with a dc motor+gearbox. Put
a potentiometer on the other sprocket to sense
the position. 0.030" in 6" is 0.5% linearity
required off the pot.

Followup.

American Standard 25-1 chain has a 0.25" pitch.
A standard 9-tooth sprocket would be 2.25" per
turn. A Spectrol 533-series 3-turn potentiometer
would have measuring range of 6.75", with 0.25%
linearity.

 

[Jim Thompson]

How about a stepper motor with a direct-drive connection to a piece of
Redi-rod (that's what it's known as in Canada - threaded steel rod up to
36" long). Use a nut welded/soldered to a pushrod as an actuator or
drill and tap your actuator directly. 0.25" rod has 20 threads/inch ->
0.05"/revolution. Your 0.010" resolution only requires 60-degree steps.
Measured backlash on a random sample of 0.25" bolts and nuts from my
junk drawer appears to be around 0.004".

This is a very standard way of converting rotary motion to linear
(lathes, old floppy drives, etc.). You might even be able to salvage the
head positioner out of an old 8" floppy drive. Newer floppy drives use
taut-baud positioners which wouldn't be as easy to hack.

Hi Tim, I thought about that, too. Doesn't that get a bit noisy?
Although I thought of nylon-nut-steel-screw (or vice versa) as a
possible solution.

...Jim Thompson

 

[Roger Hamlett]

Hi Tim, I thought about that, too. Doesn't that get a bit noisy?
Although I thought of nylon-nut-steel-screw (or vice versa) as a
possible solution.

Noise, is dependant on slop in the gear, and how you drive the stepper. If
you micro-step (even to a 'simple' level like 8 steps), and the gear has
some form of spring bias, the result can be smooth and quiet. Some 'Type
N' stepper motors are sold with an internal nut, and a hole right through,
to drive exactly this configuration.

Best Wishes

 

[John Woodgate]

I read in alt.binaries.schematics.electronic that Jim Thompson

Hi Tim, I thought about that, too. Doesn't that get a bit noisy?

Put some thick grease on it.

Although I thought of nylon-nut-steel-screw (or vice versa) as a
possible solution.

Screw needs to be rigid, so make that the steel bit.

 

[Lasse Langwadt Christensen]

Anyone know of a CHEAP Linear Motor/Actuator?

I'd like at least 4-5" of travel.

Ideally I would simply feed this device a voltage and it would go to a
position accurate to 0.010", although realistically I could probably
live with 0.030" position accuracy.

If necessary I'm sure I could devise my own position feedback, if
necessary.

Thanks!

...Jim Thompson

something like this?

http://www.bullnet.co.uk/shops/test/channel_master_linear_actuator_m.htm


-Lasse

 

[alireza121]

Hello,

Is anybody to help me?I am a newcomer to this forum and have a question and need guidance :

I need a driver to run an on/off actuator as proportional actuator.I made some experiments and found that core of both
actuators(consisting of thermal wax and spring)is the same and the difference in them is electronic driver(the on/off
actuator doen't have electronic driver,but proportional actuator has it),I need this electronic driver-its circuit
or description about its performance-

Looking forward to hearing you,

Many thanks in advance,

Alireza121