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Author Topic: Need some advice on a large scale turn table project.  (Read 1675 times)
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Hi Guys, I'm new here & a total noob to the Arduino & electronics in general. I'm currently going through the Getting Started with Arduino 2nd Edition book.
When I'm done with the book, I've got a project I need to build. I'll try my best to describe it without pics.
Think of it as a 3' diameter turn table/lazy susan made from plywood.
On the perimeter of it I'd like to put a motor/drive wheel perpendicular to the plywood surface, so spin it.
It needs to spin in both directions/back & forth, but only about 90 degrees & very slowly.
The turn table needs to hold about 100 or so pounds, so I'm thinking I'll need a motor with a lot of torque.
I need it to run on batteries for a few days, but it wont be turning constantly.
I'd like to put a motion detector in the Arduino and when it sees motion, rotate a few times, then wait for the next time.
So I have my Arduino, but don't know what motor & batteries I'll need. Do I need a motor shield or an ESC?
I've looked at these (do I need one):
http://www.pololu.com/catalog/product/2503
http://www.pololu.com/catalog/product/2502

Or what type of gearing I'd need & if I need brushes or not.
http://www.pololu.com/catalog/product/1102

And also read this:
http://arduino.cc/playground/Learning/LeadAcidBatteryAdapter
Maybe I could use 1 or 2 12v batteries....

I'm also wondering if you can ave a shield on top of a shield?
If possible, I'd also like to have sound with the wave shield & maybe blink a few LEDS...
Can I do all this with one Arduino?

Any help/suggestions/ideas, would be greatly appreciated.
thx,
Barry
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Quote
It needs to spin in both directions/back & forth, but only about 90 degrees & very slowly.
How slowly? One revolution per second? One per minute? One per day? One per week?

When it stops, how critical is the position?

Quote
The turn table needs to hold about 100 or so pounds, so I'm thinking I'll need a motor with a lot of torque.
Not necessarily. Good bearings under the platform would reduce the amount of torque required, as does the 18" radius there the load is applied.

Quote
I'd like to put a motion detector in the Arduino and when it sees motion, rotate a few times, then wait for the next time.
When the degree of rotation is limited to 90 degrees, how can it "rotate a few times"?

Quote
but don't know what motor & batteries I'll need.
You haven't given us enough information to help.

Quote
Do I need a motor shield or an ESC?
Depends on the kind of motor you end up with. For a servo, no for either. For a stepper motor, yes for the shield, no for the ESC. For other motors, yes for the shield, maybe for the ESC.

Quote
Or what type of gearing I'd need & if I need brushes or not.
Can't answer about the gearing without knowing the speed and the motor type. If you are painting, brushes are a good idea.

Quote
Maybe I could use 1 or 2 12v batteries....
Pick the motor, first. Then, get batteries suitable (voltage- and current-wise) for the motor (and Arduino).

Quote
I'm also wondering if you can ave a shield on top of a shield?
Depends on the two (or more) shields.

Quote
If possible, I'd also like to have sound with the wave shield & maybe blink a few LEDS...
Can I do all this with one Arduino?
Is "a few" 10 or less or 1000 or more? The devil is in the details, as they say.

Most likely, a single Arduino will be plenty.
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Hi, You're going to be doing power things here.  Some info: http://arduino-info.wikispaces.com/ArduinoPower
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Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
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Hi Paul,
Thanks for the reply. Sorry if I didn't give enough info. Since I'm such a noob, sometimes I don't even know what info. I need to give.

Quote
It needs to spin in both directions/back & forth, but only about 90 degrees & very slowly.
How slowly? One revolution per second? One per minute? One per day? One per week?

When it stops, how critical is the position?

I'm thinking around 10 sec. to rotate 90 deg. or 40 sec. per revolution (if it where allowed to rotate 360 deg.) It could be 1-2 sec. longer or shorter, but I won't know exactly until I see it.
The position isn't that critical, but it needs to be consistent. e.g. If it rotates 90 deg. to the left, then 91 deg. to the right, eventually it'll go 360 deg., but I need it to keep facing in the same direction.

Quote
Quote
The turn table needs to hold about 100 or so pounds, so I'm thinking I'll need a motor with a lot of torque.
Not necessarily. Good bearings under the platform would reduce the amount of torque required, as does the 18" radius there the load is applied.

Good to know thanks.

Quote
Quote
I'd like to put a motion detector in the Arduino and when it sees motion, rotate a few times, then wait for the next time.
When the degree of rotation is limited to 90 degrees, how can it "rotate a few times"?

I didn't say a full rotation. I mean rotate to the left 90 deg., back to the right 90 deg., back to the left 90 deg. , back to the right 90 deg. stop and wait. Like rotating\turning your head back & fourth.

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Quote
but don't know what motor & batteries I'll need.
You haven't given us enough information to help.

I'm trying. :-)

Quote
Quote
Do I need a motor shield or an ESC?
Depends on the kind of motor you end up with. For a servo, no for either. For a stepper motor, yes for the shield, no for the ESC. For other motors, yes for the shield, maybe for the ESC.

OK

Quote
Quote
Or what type of gearing I'd need & if I need brushes or not.
Can't answer about the gearing without knowing the speed and the motor type. If you are painting, brushes are a good idea.

OK

Quote
Quote
Maybe I could use 1 or 2 12v batteries....
Pick the motor, first. Then, get batteries suitable (voltage- and current-wise) for the motor (and Arduino).

OK

Quote
Quote
I'm also wondering if you can ave a shield on top of a shield?
Depends on the two (or more) shields.

OK

Quote
Quote
If possible, I'd also like to have sound with the wave shield & maybe blink a few LEDS...
Can I do all this with one Arduino?
Is "a few" 10 or less or 1000 or more? The devil is in the details, as they say.

5-10 LEDs

Quote
Most likely, a single Arduino will be plenty.

Great thanks for the info.
I hope I've given you enough details now.
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Hi, You're going to be doing power things here.  Some info: http://arduino-info.wikispaces.com/ArduinoPower

Thanks Terry, I'll give it a read. Hopefully I'll be able to make since out of it. :-)
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Hi, You're going to be doing power things here.  Some info: http://arduino-info.wikispaces.com/ArduinoPower

Thanks again for the link Terry, I've found your site very informative.

I'm thinking I'd need to use a 12v motor & battery setup per (1. The motor voltage is 6 ~ 12V) on your site:
http://arduino-info.wikispaces.com/ArduinoShieldL298N
 
I'm still not sure what size or gearing I'd need for the motor?

Would either of these shields work for me?
They're a little different from the example above.
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=292 (Could I but the WaveShield on top of this one?)
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=288 (I don't need the XBee)
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Or should I just use this: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=127
and not worry about stacking shields?
I can power both the Arduino & the motor with this guy, with a 12v battery, right?
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Or should I just use this: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=127
and not worry about stacking shields?
I can power both the Arduino & the motor with this guy, with a 12v battery, right?

Yes, but remember that the nominal 12 VDC means an appreciable amount of energy will have to be turned into heat by the voltage regulator.  Depending upon how you mount and house the project (e.g. if you enclose both the Arduino and motor in a small space) that excess heat can cause issues.   If your project is going to be in a temperature controlled space kept at comfortable room temperatures that probably won't be a problem.  However, if it's intended to be outside in +100°F weather it may not function correctly for long peroids without adequate ventilation (and possibly a small fan).
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Or should I just use this: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=127
and not worry about stacking shields?
I can power both the Arduino & the motor with this guy, with a 12v battery, right?

Yes, but remember that the nominal 12 VDC means an appreciable amount of energy will have to be turned into heat by the voltage regulator.  Depending upon how you mount and house the project (e.g. if you enclose both the Arduino and motor in a small space) that excess heat can cause issues.   If your project is going to be in a temperature controlled space kept at comfortable room temperatures that probably won't be a problem.  However, if it's intended to be outside in +100°F weather it may not function correctly for long peroids without adequate ventilation (and possibly a small fan).

Thanks, If I went to 6V would heat still be an issue?
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Thanks, If I went to 6V would heat still be an issue?

Technically you can use a 6 VDC supply or battery with the built-in Arduino regulator, but the voltage regulator works best with more than 1 VDC  between the supplied voltage and the 5 VDC  it's trying to output.  However, yes the lower the difference between the supplied voltage and 5 VDC the less energy will be wasted as heat.

Keep in mind though, a 12 VDC battery might not cause you any problems, especially if the ambient temperatures aren't going to be high.  I just wanted to bring the possibility to your attention so you give some thought to thermal management before you run into any problems.
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OK, how do these look for my parts list so far:
Will I get forward & reverse with speed control, with this setup?

http://arduino-direct.com/sunshop/index.php?l=product_detail&p=127
http://www.pololu.com/catalog/product/1107
http://www.gruberpower.com/12-volt-12-amp-hour-ah-battery
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Strictly speaking that gives you adjustable power control. If the load on the platform varies as its turning then the speed will as well. If you purchased one of Pololu's motors that have an attached encoder then you would have a way to get feedback as to how quickly the motor is actually turning and you could control it precisely.

...but again that's mostly academic. Assuming your platform won't have outside influences putting more load on it then it should turn at a pretty stable speed. Your component selection is fine.
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For a simple setup, a pot can be placed under the center of the lazy susan for position determination and the table turned by a motor on the edge via a friction drive. A large servo might be disassembled and used for this function.
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Strictly speaking that gives you adjustable power control. If the load on the platform varies as its turning then the speed will as well. If you purchased one of Pololu's motors that have an attached encoder then you would have a way to get feedback as to how quickly the motor is actually turning and you could control it precisely.

...but again that's mostly academic. Assuming your platform won't have outside influences putting more load on it then it should turn at a pretty stable speed. Your component selection is fine.

Thx very much for the info. I was wondering if I'd need the encoder or not, but no, the load on the platform wont change, so I think I'm good without it.
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For a simple setup, a pot can be placed under the center of the lazy susan for position determination and the table turned by a motor on the edge via a friction drive. A large servo might be disassembled and used for this function.

Thanks for the info. Could you send me a link to this pot you speak of? I'm assuming it's not the type you put plants in. :-)
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