transfer table power

[Kevin L]

Nobody builds an N ga transfer table , so I am building my own. I know it needs a stepper motor and pulse control for precise control and slow realistic speed. However, surfing the net for retail help with this, and for a threaded screw feed actuator proved futile.

Does anyone have experience with, or suggestions re: sources and type of affordable stepper motors for this? Thanks.

[Xnats]

Kind of a cool idea, I never seen anyone building one of these with all my surfing. If you laid track on the lower level, used powered trucks and a dc power pack, then mount the upper rails on the trucks somehow?

[Kevin L]

Thanks Xnats. I considered that approach, but was concerned the table itself would not stay precisely parallel. I have the mechanism traveling ( manually) very smoothly, but the power challenge, and movable electrical connections still remain. It is going to automatically power whichever track it stops at and no other; also will have amber strobes while traveling, etc. Fun stuff. I don't wish to spend a ransom on the power, however.

[NIMT]

You can find what your looking for if you search for CNC milling equipment, There are a bunch on You Tube that show you about them and tell you where to get the parts to make one at.
You could also use the cable method. Stepper motor drives rod, 2 cables attached to rood push and pull transfer table back and forth. Its very accurate. Are you going to use optics for alignment of the tracks?
On the power side of things you can set up a spooling system with cables to wind a power in and out too. Your talking N so no great distance to travel. Just a power cord with a very light spring to keep tension on it would work great. don't feed power to the tracks from the table just feed the track on the table that will keep your wire size much smaller. Computer ribbon cable would work great!

[Kevin L]

Thanks Sean. I viewed the CNC site briefly and will look more in a moment. My problem hasn't been where or how to find stepper motors. It's how to find a source that will sell just one - ( most are wholesale) , sell it cheaply, and offer a modicum of tech advice as to controller match-ups, etc. I called three, and none wanted to waste their time with a hobbyist, preferring their customer be an engineer with a 200 item order.

I have not thought about optics for alignment - I have no knowlege about that. It sounds intriguing as hell. I did, however, think about optics for power transfer to each track as the table arrived, through broken-beam controllers. I had an idea that ALL the tracks could be powered initially, ( eight tracks), but their beams would all be broken by the sliding apparatus below the table, save one, whose light would pass through a lined up hole. Still cogitating on all this. I have also seen the You-Tube transfer tables, but didn't notice any offering sources, so I will look there again. Onward and upward! Tks

[NIMT]

You want a stepper motor jusk ask, I have several, do you have a certin spec you are looking for? I do not hane the threaded screw feed actuator though.

[Kevin L]

You have put your finger precisely on my dilemma. I do not know which stepper would be best for me, hence I haven't any specs to offer. I also want to solve the screw feed thingie, AND a controller if required, in the same purchase, rather than engage in a piece meal wild goose chase.

The only requirement I can arrive at is that the table must traverse about one inch in 9-10 secs, travel at least 10 inches horizontally, and be incredibly controllable, ( for accurate track alignment). Gearhead steppers seem to be the ticket for that, from what I have gleaned by osmosis, but if I buy piece meal, I am sure to get incompatible components. That's the sort of tech help I haven't been able to find, to date.

Any help would be golden. BTW-I visited your website. Cool pics. I am also up near the Canadian border, but in WA.

[tankist]

there are plenty of old printers for free on craiglist. those have at least one stepper. the really old big ones have bunch of other cool stuff as well.

i plan for transfer table as well. there are several solutions with stepper being one of them but at the moment i'm leaning more towards servo motor actually. modified for continuous rotation, very popular in robot building hobby

[Kevin L]

Steppers from an old printer might work, but they are high rpm's ( I think) and would need some serious controlling-I'm in over my head a bit with this - that's why it's fun. All of you who've answered are generous with your help. Now I'm going to go and look at your layout pics.

[tankist]

you probably will want to read up on steppers, they have no RPM so to speak. speed is only dependant on controller operation mode at that instance of time. and actually controller is 50% of the deal if not more, by itself stepper is useless. thats why i'm leaning toward servos - easier control

[Stillakid]

Perhaps you might find something in this article that would help:)
http://carendt.com/articles/FAQs/traversers.html

And here too...............
http://model-railroad-hobbyist.com/node/4293

[jeffjgale]

Thought you might like to see my Transfer Table, It's made from a DVD head unit. Regards Jeff.

http://i206.photobucket.com/albums/bb320/jeffjgale_2007/100_1336.jpg

[maverick405]

What an excellent idea, I'll be looking a bit more closely at some of the "no longer required" things around my house.

[gunrunnerjohn]

I'd have never thought of a DVD tray, but it's perfect for N-scale I would imagine. :D

[jeffjgale]

These are some closer pics of the DVD reader head unit.
Regards Jeff.
http://i206.photobucket.com/albums/bb320/jeffjgale_2007/100_1334.jpg

http://i206.photobucket.com/albums/bb320/jeffjgale_2007/100_1331.jpg

http://i206.photobucket.com/albums/bb320/jeffjgale_2007/100_1329.jpg

http://i206.photobucket.com/albums/bb320/jeffjgale_2007/100_1333.jpg

[gunrunnerjohn]

Clever, and you could probably do three or four N-scale tracks with the movement. :D How are you driving the stepper?

[Kevin L]

I'm likewise keenly interested in your stepper control. My stepper arrived today, so this is timely.

[jeffjgale]

The DVD head unit has a Standard DC motor and as I am only having 2 tracks, one at each end I will use a DPDT on/off/on switch for direction and a momentary switch to control power.
Regards Jeff.

[Xnats]

That was a pretty cleaver Jeff. Thanks for taking the time to share :thumbsup:

[gunrunnerjohn]

That's not a stepper? I'm pretty surprised it has a DC motor.

[jeffjgale]

That's not a stepper? I'm pretty surprised it has a DC motor.

G'day gunrunnerjohn, the motor is as below,
RF-300CA-11400-6.0
Mabuchi RF-300CA-11400. ... RF-300CA-11400-6.0. SKU: 1112002. 3V/2400RPM,4.3g-cm,6 mm shaft DC Motor Voltage Range (VDC): 1-3. Current (Amps): 0.07. RPM (MAX):2400. Torque (g-cm): 4.3
https://www.rapidonline.com/netalogue/specs/37-0440.pdf

Regards Jeff.

[gunrunnerjohn]

I was actually thinking of the head positioner, of course the tray is simply in or out, so a DC motor works fine for that.

[Kevin L]

I bought a motor - not yet installed-thinking it was a stepper. I blew it, as it s a DC motor only, although it may work fine, once installed. But I was surprised that you have a motor with 2,400 rpm's. Mine is 120 rpm, which when used with a 16 thread-per-inch threaded rod, ought to move the transfer table at a realistically slow speed of 8-9 secs per inch. However, I am concerned about precise positioning at each track juncture. I'll be a lot smarter in a week or so. I'll probably wind up getting a stepper. Onward and upward.

[gunrunnerjohn]

The stepper is the way if you want to automatically position the table precisely.

[jeffjgale]

I was actually thinking of the head positioner, of course the tray is simply in or out, so a DC motor works fine for that.

As you can see this is the head position unit that I have used and it had a DC motor, Regards Jeff.

http://i206.photobucket.com/albums/bb320/jeffjgale_2007/100_1331.jpg

[gunrunnerjohn]

I'm surprised that they use a DC motor there, the CD drive I disassembled used a stepper.

[Kevin L]

I'm still fighting the good fight regarding locating a stepper. I even have a local electronics supplier researching it, with no response to date.

My q to him was: can a stepper be controlled simply by using a momentary DT switch, or will it need controller circuitry, and pulse power, etc. No one seems to answer this question. I assume the apparently mandatory circuitry is only necessary if one is going to control the stepper with a computer, which I'm not planning. Yet, a unipolar stepper has either 5, 6, or 8 wires - where does one find out how to hook those to a simple, reversible DT momentary switch. Any thoughts?

[gunrunnerjohn]

I can answer that, you'll need control circuitry to control a stepper. If you have a computer to do the task, you can generate the stepping profile there.

Some research is in order, you can start here.

http://www.eham.net/articles/7231

http://www.aaroncake.net/circuits/stepper.asp

I've used steppers in aerospace applications, and in order to get maximum reliability, a lot of time was spent on the stepping profile. If you have a mechanical platform with some mass, it won't stop on a dime, you have to slow it down or it'll overshoot.

For your purposes, you probably won't have any feedback, and maybe you could simply step it slow enough that you don't need a ramped profile to start and stop it.

[Kevin L]

Thanks for the URL's. My NAVY electronics experience is 50 yrs old, so I'm a bit over my head if I must build a controller. The whole stepper thing is finally sinking in to me that I will probably not be able to simply move a momentary toggle switch either right or left to move & reverse the transfer table. Duh.

Buying a controller is always doable, of course, but I can't afford those that I have seen to date. The project doesn't warrant that kind of expense in any event. One of your suggested sites claims it can be built for under $10, by a capable tech. Moreover, steppers do not "advertise" rpm's, since they are so variable, but surely they must have a " top speed" which may or may not hve to be reduced for realism and precision.

As a lifelong home builder, I can do anything in wood, but am out of my element here. I feel sure I will finally land on some sort of answer - thanks for the input, gunrunner. Food for thought, as I return to your suggested URL's.

[gunrunnerjohn]

By the time you geared it sufficiently to actually move the table, you'd wear out the toggle switch to change tracks! :D

Steppers really simply have a torque specification, since you can step them at any rate. They do have a maximum step speed, which translates into a maximum RPM. There's some really complicated equations to explain the torque curves, normally not an issue for a hobby project. For a simple project, as long as you don't approach the limits, you really don't have to consider any of that. I'm pretty sure you can come up with a stepper controller for not much money, it's been years since I've thought about them. I did all the control with a uP and just had drivers for the motors.

[Kevin L]

Hi again, gunrunnnerjohn-

Forgive the density I am exhibiting here, but what you seem to be saying is that I will never be able control the movement of the transfer table by simply operating ANY switch manually, but rather MUST control the movement via computer direction. If so, steppers are not my answer.

Also - your mention of having to gear the stepper motor is new to me. I note that gearhead DC motors are a separate animal, and that steppers themselves do not need or come with gearing. My plan was to simply couple the 1/4" shaft to a 1/4" ACME threaded rod, which I now have, and move the table with the aforementioned DT momentary switch.

Looks like I may have hit a wall on this. Thank you for your time and thoughts, tho.

[gunrunnerjohn]

You don't necessarily need a computer, but you do need electronics. I don't see toggle switches doing the job here. Truthfully, I never even considered running steppers with toggle switches, that thought never entered my head. :)

As far as gearing, that's going to depend on the load and the stepper motor's capability. Note that most steppers you'll find will rotate 90 degrees for each step. I'm not sure where the idea that steppers don't ever need gearing comes from, I've never used one that didn't have some gearing for the application. You could provide the mechanical advantage with a belt, small pulley on the motor, large one on the driven load.

[alhoop]

I would not recommend a stepper motor for the Transfer Table drive. It would involve a microcontroller to control with a lot of code to drive it. I Had a turntable driven by a stepper motor with 0.9 degree steps and it still was jerky. You can use a DC motor drive chip like the Microchip TC4424 or IXY systems IXDN404PI. I have built a controller using the 404PI to drive the Walthers HO 923-3131, the Marklin Z scale 8994, the Herkat 1203 N-Scale and a homemade string driven N-Scale turntable built around the 120' Walthers turntable bridge and Bachmann tender trucks.(search youtube for sdtt1 alhoop1 to see it in operation). The 404PI chip was controlled by a Picaxe-18M2 multi-tasking microcontroller.
Track location was done using an IR emitterr on the bridge and phototransistors at each track location. Reed switches and a magnet mounted under the bridge table was used on the Walthers and the others were modified as they will stop at each track location.
Using the controller you just select a track number and push a button, the table drives to the selected track number with no further intervention from the operator, much like I did with the Walthers 130' turntable in N-Scale magazine Nov-Dec 2010.
Al

[gunrunnerjohn]

You've just said a mouthful! First, you say that using a stepper is too complicated. Then you introduce all sorts of feedback with photo-transistors and IR emitters! Both will take some doing, that description doesn't convince me that a DC motor is the way to go.

It really doesn't take that much code to drive the stepper motor, and I'm the guy that has put as many as five of them in a 4" panel mounted aircraft cockpit instrument! As far as jerky, that will depend on the gearing and step size of the motor.

[Kevin L]

These comments are timely for me, as I am dealing with this situation just now. I was helped by one of Gunrunner Johns posts, as one of the suggested sites he supplied had a comment by another user. That user suggested using a DC motor, and simply controlling it with an old MRC "PulsePower" train controller. I hooked my table up to an MRC ControlMaster 20 controller, and it powers and controls the table beautifully. It is realistically slow, and extremely positionable with just manually using the potentiometer control. I am very pleased with this answer, as all that electronic circuitry is undecipherable to me.

When my electronics dealer returns to business next week, I plan to buy the components to build a control box that copies the temporary MRC box. I believe that will be only a pot , a pulse controlling widget or some sort, and a 12v xformer. I could be all wet on that, but we'll see.

I also plan to ask him about the phototransistors for track alignment spoken about in alhoops comments.

I appreciate these helpful comments by Gunrunner John, alhoops and others. This forum is a wonderful source of expertise.

[sstlaure]

Not a cheap alternative but you could always get one of the HO scale transfer tables and steal the guts. They're on sale right now at Walthers.

[alhoop]

..... First, you say that using a stepper is too complicated. Then you introduce all sorts of feedback with photo-transistors and IR emitters! Both will take some doing, that description doesn't convince me that a DC motor is the way to go.


Hello Gunrunner:

Speaking from experience, I think it is disconcerting to see a locomotive being jerked around, whether on a turntable or a transfer table. The Ir emitters etal was for a fully indexed table where the operator selects a track number and pushes a button and the table drives to that selected track.
No manufacturer that I know of has used a stepper in their turntable or transfer table design.

PS:Maybe here is why
http://www.piclist.com/techref/io/stepper/linistep/smoother.htm

Kevin:

Here is a simple motor controller that cost about $10 not counting the motor. It gives very precise control and if you decide to go with a micro-controller just sub the micro for the switches. It automatically brakes the motor when a switch is released. If you want to check that feature out, use a current limited power supply that you can short the output without damage and hook it up to a motor. Short the motor leads together and see if the motor doesn't stop immediately.

Al

[gunrunnerjohn]

Hello Gunrunner:

Speaking from experience, I think it is disconcerting to see a locomotive being jerked around, whether on a turntable or a transfer table. I guess I'm wondering where the "jerked around" comes from. If you really want to run the TT at a scale speed, the steps would be so small that there would be no "jerking".

In any case, I've said my piece, I don't need a transfer table at this time.

[flyin-high]

Hi, I manufacture turntables and transfer tables, "S" and "O" gauge.
My turntables are powered with either a DC gear motor or a stepper motor with a touch pad control. The TT stepper system is very precise and can be programed to alien either the head or tail end of the bridge to the desired track. Very SMOOTH!!! EXCELLENT system but is much more expensive. Customers who have purchased the more reasonable TT drive system like them very good with one customer from Texas wishing to upgrade to the stepper motor.
As for the transfer table, I presently use a DC gear motor powered by a "HO" transformer. It is operates very good but is manually aliened/eyeballed to the on/off track by the operator. I am now working on using the stepper system for the transfer table. As I understand, the stepper motor is designed to "count parts of a degree" as it is rotating. My transfer tables are operated using timing belts at each end of the bridge. Very precise and low HP requirements. I tried the "threaded rod" and it is noisy, requires more power and the bridge speeds up and slows down with no change in the power.
Because I use timing belts to power the bridge back and forth, they can only travel "LESS than 1/2" of the belt circumference. Any questions, feel free to email.
Thanks, Dave