CHEAP Linear Motor/Actuator

J

Jim Thompson

Guest
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
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Wed, 20 Apr 2005 16:39:49 -0700, Jim Thompson
<thegreatone@example.com> wrote:

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.
Click to expand...
---
Voltage? Current? Slewing speed? Size? Load?

--
John Fields
Professional Circuit Designer
 
"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
Anyone know of a CHEAP Linear Motor/Actuator?

I'd like at least 4-5" of travel.
Click to expand...
The leadscrew-stepper combination on floppy drives
looks pretty cheap. Does it have to be fast? Do you
have enough volume to support really cheap? Is there
a holding force requirement?

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.
Click to expand...
Do you plan to drive this with a 10 bit DAC? Where
does such an accuracy requirement for position versus
voltage come from? (just curious)

If necessary I'm sure I could devise my own position feedback, if
necessary.
Click to expand...
LVDT's can be built cheaply. Would there be any
opportunity to calibrate each unit for accuracy, or
does it have to be accurate as first built?

Thanks!
Click to expand...
FWIW, you're welcome.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.
 
"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
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
--
I happened to see this on Ebay just yesterday:
Click to expand...
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=11726&item=5767073198&rd=1&ssPageName=WDVW
Even if this doesn't suit in itself the idea may be what you're after. Check
out satellite TV dish accessories.

Ken
 
On Wed, 20 Apr 2005 16:39:49 -0700, the renowned Jim Thompson
<thegreatone@example.com> wrote:

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
Click to expand...
How much force? There are some electrical cylinder replacements that
kinda look like a hydraulic cylinder (all enclosed). They are pricey
new, but maybe surplus or on eBay...

There were some used in satellite positioning, but the accuracy might
be a bit iffy and the ones I've seen were pretty big. Some used a reed
capsule/magnet for incremental feedback.



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
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!
Click to expand...
Have you thought about a car window motor. Maybe a bit too much travel - but
maybe adjustable.

Cheers.
 
"Jim Thompson" <thegreatone@example.com> schreef in bericht
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
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.
Click to expand...
The obvious solution is a stepping motor with a lead-screw - you can buy
these as a unit from broadline distributors. Farnell sell a Burgess unit for
66 euro (about $90) under order code 318-7603, and RS Components offer six
alternatives at similar prices.

When I've used this sort of gear, I put a neodynium-iron or a
samariun-cobalt magnet on the moving part and a Hall effect sensor nearby,
and use the output of the Hall sensor as a check (and if necessary as a
reset) for (micro-) step-counting logic. The hysterisis in the Hall sensor
means that it detects the magnet in slightly different positions if the
carriage is coming or going.

There are loads of other solutions - chart recoders used to use DC motors
driving a windlass around which you wound five or six turns of stainless
steel wire.

Cheap chart recoders relied on a potentionmeter on the windlass shaft for
position feedback, better units put a linear potentiometer on the on the pen
carriage.
I once worked on a capacitative position sensor where a grounded plate (in a
flexy) shielded a variable length of a driving plate from a receiving plate.

--------
Bill Sloman, Nijmegen
 
"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
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.
Click to expand...
Model airplane servo's are cheap. Some mechanical linkages could
be rigged to get your travel. Input is pwm, not sure if it will have <1%
accuracy, but that does'nt sound too bad.
Eric
 
"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
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.
Click to expand...
I've used the ones formerly from Airpax that are stepping motor/ acme screw
types. They come in various force ranges from an ounce to several pounds.
Airpax was part of Philips and was sold to Thomson.
http://www.thomsonmotors.com/Sections/Products/products_main.asp?PC=10600000&CL=2&L1=10000000&L2=10600000&L3=&L4=&L5=&L6=&IT=Descrip&lang=1

or
http://www.thomsonmotors.com/Sections/Products/products_main.asp?PC=8999400&CL=1&L1=8999400&lang=1&IT=descrip

Another is HSI http://www.hsimotors.com/linear-actuators/index.htm

Hope this helps. Least I could do in return for some of the material you
have supplied.
 
"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
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
Click to expand...
Oooooh Oooooooh Oooooooooh

Buy a $30 300dpi printer and kick the shit out of it.

Or, maybe not.

DNA
 
On Wed, 20 Apr 2005 16:58:16 -0700, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
Anyone know of a CHEAP Linear Motor/Actuator?

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

Do you plan to drive this with a 10 bit DAC?
Click to expand...
5"/0.01" = 500, so 8 bits ought to be plenty.

---

--
John Fields
Professional Circuit Designer
 
"John Fields" <jfields@austininstruments.com> wrote in message
news:eek:tff615oopf6ifo0s0pq4o33mveqe0aidr@4ax.com...
On Wed, 20 Apr 2005 16:58:16 -0700, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:

"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
Anyone know of a CHEAP Linear Motor/Actuator?

I'd like at least 4-5" of travel.
....
Do you plan to drive this with a 10 bit DAC?

5"/0.01" = 500, so 8 bits ought to be plenty.
Click to expand...

This is almost what I call an "arithmetic argument". <g>

On my calculator, 2 raised to the 8th power is 256.
I allowed an extra bit for the sake of precision. We
could argue about that if I was willing, but I am not.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.
 
"Larry Brasfield" <donotspam_larry_brasfield@hotmail.com> wrote in message
news:ytP9e.29$dv5.1189@news.uswest.net...
"John Fields" <jfields@austininstruments.com> wrote in message
news:eek:tff615oopf6ifo0s0pq4o33mveqe0aidr@4ax.com...
On Wed, 20 Apr 2005 16:58:16 -0700, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:

"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
Anyone know of a CHEAP Linear Motor/Actuator?

I'd like at least 4-5" of travel.
...
Do you plan to drive this with a 10 bit DAC?

5"/0.01" = 500, so 8 bits ought to be plenty.


This is almost what I call an "arithmetic argument". <g

On my calculator, 2 raised to the 8th power is 256.
I allowed an extra bit for the sake of precision. We
could argue about that if I was willing, but I am not.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.
Click to expand...
I think what Larry was trying to say was.

'You stupid dipfuck Fields.

8 bits gives you 256. I can't buy a 9 bit converter so I'll use a 10 bit
one.'

To which you might have responded

'Whoops.' :)

And 'That Folks' would have been the end of the conversation.

In the meantime,

Fuck off Barry.

DNA
 
"Genome" <ilike_spam@yahoo.co.uk> wrote in message
news:27Q9e.19$vU4.15@newsfe6-win.ntli.net...
"Larry Brasfield" <donotspam_larry_brasfield@hotmail.com> wrote in message
news:ytP9e.29$dv5.1189@news.uswest.net...
Click to expand...
[Inconsequential, unheated "arithmetic argument" cut.]

I think what Larry was trying to say was.

'You stupid dipfuck Fields.
Click to expand...
No, I was not trying to say that. We all flub sometimes
and it should not be an occasion for name calling among
adults. You can speak for yourself, but not for me.

8 bits gives you 256. I can't buy a 9 bit converter so I'll use a 10 bit
one.'

To which you might have responded

'Whoops.' :)
Click to expand...
He still might, but acknowledging an obvious error
is hardly worth the bandwidth.

And 'That Folks' would have been the end of the conversation.
Click to expand...
One could hope.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.
 
On Thu, 21 Apr 2005 08:16:46 -0700, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

"John Fields" <jfields@austininstruments.com> wrote in message
news:eek:tff615oopf6ifo0s0pq4o33mveqe0aidr@4ax.com...
On Wed, 20 Apr 2005 16:58:16 -0700, "Larry Brasfield"
donotspam_larry_brasfield@hotmail.com> wrote:

"Jim Thompson" <thegreatone@example.com> wrote in message
news:9opd61p1bm2695bg8989kv3pdkvqur7geo@4ax.com...
Anyone know of a CHEAP Linear Motor/Actuator?

I'd like at least 4-5" of travel.
...
Do you plan to drive this with a 10 bit DAC?

5"/0.01" = 500, so 8 bits ought to be plenty.


This is almost what I call an "arithmetic argument". <g

On my calculator, 2 raised to the 8th power is 256.
I allowed an extra bit for the sake of precision.
Click to expand...
---
Yup. brain fart on this end...

We could argue about that if I was willing, but I am not.

Suits me.

--
John Fields
Professional Circuit Designer
 
Really old hard drives (PC-XT vintage) used a taut band driven by a
200-step/rev stepper motor to position the head. They come apart
easily, too. Taut band drives give zero backlash.

For 10-mil accuracy, you can probably use a good-quality ball bearing
drawer slide as a stage. At power-up, drive the motor to one end and
let it stall, so you know where you are, then step to your desired position.

Cheers,

Phil Hobbs
 
On Thu, 21 Apr 2005 12:54:50 -0400, Phil Hobbs
<pcdh@SpamMeSenseless.us.ibm.com> wrote:

Really old hard drives (PC-XT vintage) used a taut band driven by a
200-step/rev stepper motor to position the head. They come apart
easily, too. Taut band drives give zero backlash.

For 10-mil accuracy, you can probably use a good-quality ball bearing
drawer slide as a stage. At power-up, drive the motor to one end and
let it stall, so you know where you are, then step to your desired position.

Cheers,

Phil Hobbs
Click to expand...
Good idea!

I also thought of going to Pep Boys and buying a power radio antenna
;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
On Wed, 20 Apr 2005 20:27:01 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On Wed, 20 Apr 2005 16:39:49 -0700, the renowned Jim Thompson
thegreatone@example.com> wrote:

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

How much force? There are some electrical cylinder replacements that
kinda look like a hydraulic cylinder (all enclosed). They are pricey
new, but maybe surplus or on eBay...

There were some used in satellite positioning, but the accuracy might
be a bit iffy and the ones I've seen were pretty big. Some used a reed
capsule/magnet for incremental feedback.



Best regards,
Spehro Pefhany
Click to expand...
"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?

(Like all new things I get involved in, I don't know rat-shit, but I'm
a quick learner... like the Bosch EC motor controller design... I just
breadboarded a circuit in parallel with their discrete design,
observed where it was struggling, immensely improved it, then swapped
in my breadboard... tweaked it, then integrated it ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson wrote:

On Wed, 20 Apr 2005 20:27:01 -0400, Spehro Pefhany
speffSNIP@interlogDOTyou.knowwhat> wrote:


On Wed, 20 Apr 2005 16:39:49 -0700, the renowned Jim Thompson
thegreatone@example.com> wrote:


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

How much force? There are some electrical cylinder replacements that
kinda look like a hydraulic cylinder (all enclosed). They are pricey
new, but maybe surplus or on eBay...

There were some used in satellite positioning, but the accuracy might
be a bit iffy and the ones I've seen were pretty big. Some used a reed
capsule/magnet for incremental feedback.



Best regards,
Spehro Pefhany


"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?
Click to expand...
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.
--
Tim Hubberstey, P.Eng. . . . . . Hardware/Software Consulting Engineer
Marmot Engineering . . . . . . . VHDL, ASICs, FPGAs, embedded systems
Vancouver, BC, Canada . . . . . . . . . . . http://www.marmot-eng.com
 
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