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Topic: Model turntable with stepper motor? (Read 2093 times) previous topic - next topic

alcazar

Hi, I was all set to buy a complete unit, but the people making it have discontinued it.

My own knowledge of electronics stops at how a transistor works, sorry.......I AM 61. :)

So...can anyone help me?

I'd like to be able to control a 7mm: 1 foot scale model railway turntable using a stepper motor to index it.

IS there a simplified system available, or am I looking at something way beyond me?

Thanks for any help.

AWOL

Would a servo do the job?
A stepper will work, but without an encoder or limit switch or some external feedback (e.g. visual), a stepper has no idea where it was parked last time the power was switched off.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

scottyjr

Welcome alcazar. Simple, cheap, readily available, complete, small, powerful, and easy to use with the many available libraries and tons of available information is the 28BYJ-48 Stepper Motor and Driver. Should be ideal for your application. - Scotty

alcazar

Hi Scotty, clicked on that, the price was right, it looks fine...but they won't ship to the UK. :smiley-roll:

How would I control that, get it to turn round, stop where I wanted it to, etc, given I could talk them into shipping to the UK, or find similar here in the UK?
Thanks again.

Robin2

I've built a large (train sized) turntable for my N Gauge trains. It uses a servo to rotate it and another servo to raise or lower a detector arm. If the arm is down the table keeps rotating until a metal tab touches the detector arm. At that point it is lined up. If it needs to move to another position the arm is lifted out of the way until the tab has passed.

The rotation servo I'm using can turn a bit more than 180deg so the table has to turn backwards as well as forwards. But that means there is no need for slip rings for any of the wiring.

The rotation servo is also the bearing for the rotation. All my stuff is visible above the table because the table will be off-scene, but I reckon it could also be hidden below.

...R

jackrae

#5
Sep 29, 2013, 07:53 pm Last Edit: Sep 29, 2013, 07:55 pm by jackrae Reason: 1
http://www.ebay.co.uk/itm/1-x-5v-Stepper-Motor-with-Driver-Board-For-Arduino-projects-UK-Stock-/190914021317?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2c735cc7c5

The above link gives the same (or similar) unit available in the UK

Or the same sort of thing from a commercial UK source

http://www.ebay.co.uk/itm/28BYJ-48-5VDC-Stepper-Motor-With-ULN-2003-Driver-Board-Use-With-Arduino-or-Sim-/221262636497?pt=UK_Computing_Other_Computing_Networking&hash=item338447e5d1

zoomkat

A Chinese supplier that say they ship world wide.

http://www.ebay.com/itm/For-Arduino-DC-5V-Stepper-Step-Motor-28BYJ-48-Driver-Test-Module-Board-ULN2003-/231048748653?pt=LH_DefaultDomain_0&hash=item35cb941e6d
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scottyjr

Quote
How would I control that, get it to turn round, stop where I wanted it to, etc


Your turntable and thus the stepper motor must have a 'home' position i.e., a starting point. Finding that point would have to be done every time the system, specifically the microcontroller, is started; easy to do in the Setup function of your sketch. From that point its simply a matter of telling the device how many steps to take and in which direction. That motor as 4096 steps per revolution. Your sketch must keep track of where the motor's shaft is currently at in order to be able to tell it how many steps and which direction you want it to go to a new position. As mentioned before, others have written libraries for this device that will make it not necessary for you to write the code to control the motor. You can simply plug in the values to attain the position you desire.

My 'home position sensor' of choice is an opto-interupter since that is a very accurate way of defining a position; think of how your desktop printer is able to position those tiny dots so accurately.

- Scotty 

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