Need some help from the auto-rotating monitor experts...

[nitz]

OK, after sitting on the parts for a few months, I'm finally getting a start on this and I'm stoked, but also pretty lost.

I'm one of those guys who can do the software side of things no sweat, but give me something like this and I feel a bit like a monkey working on a math problem.

I have all the parts from DNA Dan's shopping list in reply 13 of this thread http://forum.arcadecontrols.com/index.php?topic=112424.0. (Well, I don't have the hinge and the casters yet, but I may not need them as I'm planning a pacman style laydown monitor setup.)

I've looked through the documentation on the Pololu site, but I'm really lost as to how to wire this baby up. Also, it sounds like I need an external power supply...I was hoping it could just run off the PC's power via usb.

So if any of you rotating monitor gurus out there (*cough* TopJimmyCooks *cough* DNA Dan *cough* DaOld Man ) could help me out with some step-by-step instructions, that would be great! And don't be afraid to dumb it down to me - I'm a total noob at this and am probably really gonna need stuff spelled out.

[paigeoliver]

There is NO WAY you are gonna rotate a monitor using teeny amount of 5 volt power you can pull from a USB slot. I have read nothing about the setup you are doing, but you are gonna need more power than a USB slot can provide.

[Nephasth]

There is NO WAY you are gonna rotate a monitor using teeny amount of 5 volt power you can pull from a USB slot. I have read nothing about the setup you are doing, but you are gonna need more power than a USB slot can provide.

Well, that was helpful.

So if any of you rotating monitor gurus out there (*cough* TopJimmyCooks *cough* DNA Dan *cough* DaOld Man ) could help me out with some step-by-step instructions, that would be great!

Definitely the guys to ask on this one!

Your motor controller will be connected to your computer via USB, but you'll also have to bring supply voltage to the controller's "VIN" terminal, most likely 12V from a molex connector from your computer's power supply (yellow wire), and hook up ground (black wire from the molex connector you took 12v from) to the "GND" terminal of the controller. "OUTA" and "OUTB" on the controller to the the motor terminals.

Software wise... you'll have to wait for the powers that be to chime in.

[nitz]

There is NO WAY you are gonna rotate a monitor using teeny amount of 5 volt power you can pull from a USB slot. I have read nothing about the setup you are doing, but you are gonna need more power than a USB slot can provide.

I kind of figured as much as I know a usb port doesn't put out much power, but I don't see anyone else using a battery so I wasn't sure how they were powering it then.

Your motor controller will be connected to your computer via USB, but you'll also have to bring supply voltage to the controller's "VIN" terminal, most likely 12V from a molex connector from your computer's power supply (yellow wire), and hook up ground (black wire from the molex connector you took 12v from) to the "GND" terminal of the controller. "OUTA" and "OUTB" on the controller to the the motor terminals.

And now I see. This is why I need so much help...I would have never thought of this, and don't know how to do it. And, unless that's fairly idiot proof, I feel I might be better off powering it with a battery. I don't want to wreck anything, and especially not my PC.

This gives me some food for thought though while I wait for the powers that be to chime in...

[darthpaul]

It looks like you are going to need a 12v power supply with about 4 or 5 amps to play it safe, I'm using an Ebay special with no problems. I'm auto-rotating my 20" CRT using a windshield wiper motor. The Pololu motor controller I'm using is now out of production but the hook-up should be similar to yours. Since I am using DaOld Man's MRotate3, I had to use the PC printers port and a parallel cable for the auto-rotating feature. 

[nitz]

OK, the molex connector idea gave me something to go on, did some reading, and had a look inside my computer. There are some unused molex connectors in there. I see one with a yellow wire, 2 black wires, and (I think) a red wire. I was surprised to see 2 black wires...can I use either one for the ground? Do I need to cut the connector off, or would just sticking some wire into the connector work?

[TopJimmyCooks]

I think I tried to interchange the two black grounds but one ground is for the 5V, one is for the 12V.  Just make sure you get 5 or 12v when you complete the circuit with a tester. 

Because i had a small FF case with a wierd power supply on the pc, I used a separate ATX power supply for the motor, cab fan and marquee lights.  However, if I had an ATX power supply for the pc, a spare molex off of that would be plenty to pick up the motor as well.

The 131:1 pololu gearmotor needs between 12v and 18v, 12v works fine.  Nephasth explained how everything is fed through the pololu board, but if you need anything else, post.

[Le Chuck]

If one was using one of the LED screens with a Lazy Susan mount I don't see why a center mounted 5v servo wouldn't have the torque to muscle a 90 degree rotation.  You just need to isolate the support of the monitor from the force to move the monitor.  If you have a light monitor I think it is definetly worth a shot.  I'd be more worried about getting it to rotate slowly enough, you don't want the screen picking up momentum and stressing the servo. 

[TopJimmyCooks]

This is a wheel on wheel system.  The gear ratio given by the small wheel/tire on the monitor disc allows a tiny motor to be used, hence 12v 1/2A power supply to it.  Direct drive takes more like a windshield wiper motor with associated car amperage (3-4 amps or so?) or an Ond-style costly stepper motor.  Even then, there's still a geartrain.  It keeps the cost way down to use the robotics type motors, controllers, and their well developed software. The speed control can be set from 0 to max in increments ranging from 0 to 1000, so speed control may be finer than with a servo.  The servo with the horsepower and chassis to direct drive an lcd would be big bucks. 

I could see a servo that could do 900 degree rotation and accept a decent sized gear on the output shaft, interfaced with a larger gear on the monitor rotation axis (basically what Ond did) but the gear parts get so costly so quick its hard to be cost effective.  That's why the DNA Dan/Weisshaupt solution is so great, no expensive gears. 

[Le Chuck]

I am also a huge fan of the DNA Dan/Weisshaupt way but I definetly am going to explore the world of mid sized servos to direct drive a monitor, worst case scenario is I burn out a $20-$30 servo.  As for mounting if you're using a 3 or 4 inch lazy susan bearing it should be pretty staight forward to center mount the servo securely in the existing bearing support.  I know that Pololu has a beast that can move around 430 ozs at 12v but I don't know what the torque stall is at something like 5v.  

Edit:  Just found this servo that rocks 800 oz at 6vs for only a measely $300  

A bit better:  GWS S04 BBM can move 10kg at the post for the low low energy price of 4.8v.  The cost, under $20.  Totally trying this. 

[Nephasth]

Direct drive takes more like a windshield wiper motor with associated car amperage (3-4 amps or so?) or an Ond-style costly stepper motor.

Or a smaller monitor.

[TopJimmyCooks]

Edit:  Just found this servo that rocks 800 oz at 6vs for only a measely $300 

Dang, its on backorder.   

The issue with the lazy susan bearing is they're lightly loaded, but they're still being used at an angle they were never intended to do.  There's more resistance to rotation than you would think, especially when starting rotation from stopped.  The reason to use them is they cost $4.   

Had forgotten about the minibeast! 

[Le Chuck]

I thought there were some verticle force tested 4" bearings out there in the $10 to $12 range.  I'll see if I can dig one up.  Has anybody vertically stress tested the horizontal bearings?  They are rated in the 200 to 300lb range for horizontal.  At 5  to 10lbs for an LED monitor I'd think it'd be okay but would prefer to see some numbers behind that.  

Edit:  Found it. This bearing isn't actually a lazy susan bearing but a turntable bearing.  They do the same thing but are machined very differently.  I haven't been able to turn up the data sheet for it yet but most all turntable bearings have great verticle ratings as they are just small slewing bearings (think wind turbine or helicopter).  I'll be picking up one of these and putting it through some tests.   

[nitz]

Thanks Guys, some interesting discussion.

So I'm gonna go with wiring the 12V wire off a molex connector. Hoping to get a chance to play around with it on the weekend. If I get anything done worth sharing I'm gonna start a project thread.

EDIT: Could someone elaborate a little more on how I should do this? I was planning on using the same wire I'm gonna use for my CP which is 22 guage I think, or possibly 20. Should I try sticking this inside the molex connector, or is that a bad idea? Could it be dangerous? Should I just cut the connector off and wire that directly to my motor controller? Or would that be dangerous? Pretty clueless about this stuff, and definitely don't want to start a fire or damage anything.

[TopJimmyCooks]

5V or 12V 1/2A - no danger of "letting the magic smoke out" or messing anything up really so go for it.  paper clips, tinfoil, hot glue, do what'cha gotta do!

[Le Chuck]

There is no issue setting it up as a molex connection.  It would be a nice clean solution, but if you wanna start snipping ends and hard wiring there is not issue with that either.  I wouldn't just shove some 20g into the molex connector though, drop by radio shack and pick up some ends so you can do the fitting properly, you'll be happy with the result. 

[Nephasth]

I would recommend using bullet connectors for those inexperienced with wiring and wanting a connection that can be seperated at will. They only require standard crush type wire crimpers, no special crimping. Using male and female quick disconnects would work too, but I would recommend fully insulated connectors in this case.

ETA: When wiring a two wire connection like this, it is a good idea to alternate connector sexes on each end of the harness to help prevent connecting it backwards (i.e. a male and female connector on each side of the harness, so wire #1's male connector will only mate with its corresponding female connector, and wire #2 on the same side has a female connector installed so it will only mate with with its corresponding male connector on the other side).

Bullet connectors:


Fully insulated quick disconnects:

[TopJimmyCooks]

Nep, you're going to get into contract trouble if you're found recommending a non-Molex product.  It's not worth losing your endorsement deal over. 

  -the legal  department. 

[Nephasth]

 

Molex is always my recommended connector manufacturer to those who have the tools to properly use them.

[kahlid74]

Day late to this thread but you're on the right track.  Topjimmy knows his stuff so you should be all good with the above recommendations.  The only thing I'll warn you about is using a lazy suzy in this fashion can produce unknown results.  Those who have used it should know it's reliability but you are using it on a place it's not meant for, which Topjimmy stated before.

I plan to rotate a 42 inch LED TV in my showcase cab.  I plan to use Stepper motors with controls by Arduino's programmable interface and gears.  Topjimmy and Ond got me going in the right direction so If you're looking for another way to go Ond's build has a whole bunch of documentation.

Also, don't let Ond's method scare you.  The small Lbs*in torque required for a small LCD monitor can be accomplished with a small stepper motor/control.  So it's pretty cheap too.

[Le Chuck]

The only thing I'll warn you about is using a lazy suzy in this fashion can produce unknown results.  Those who have used it should know it's reliability but you are using it on a place it's not meant for, which Topjimmy stated before.

If you use a table top lazy susan you're right but there are thousands of bearings out there that are designed for rotational movement along a vertical plane.  The issue is that some lazy susans are thrust bearings (horizontal loads) and some lazy susans are radial bearings (axial loads).  Turntable bearings and slewing bearings do the same thing but are meant for industrial rather than household applications and are poured steel or iron rather than stamped aluminum yet are still commonly refered to as Lazy Susan bearings as well.  I did mention looking for vertical stress test data on table top lazy susans (thrust bearings) in an earlier post but further analysis leads me to conclude that this isn't necessary given the amount of affordable bearing solutions on the market, I have a good sized radial bearing lazy susan in the mail for $11 shipped.  What makes the "lazy susan"nice is that you don't need an axle as you have two fixed planes, but you sacrifice a lot of strenth doing that.  You can get flanged radial bearings in a 3/16 in diameter that have a dynamic capacity of over 300lbs.  They only go up from there, the trick at that size is finding an axle you can support the tv from.  Jump that up to 3/4 inch and you've solved the support problem for the axle and the bearing can support a midsized pachyderm. 

This was not meant as a rant but merely to clear the air about bearing application in rotation since I notice a lot of folks have written bearing solutions off and I think that they have a lot to offer. 

<significant edits for clarity>   

[nitz]

Thanks for all the help guys, I'm feeling a lot more confident about putting this together now.

[kahlid74]

The only thing I'll warn you about is using a lazy suzy in this fashion can produce unknown results.  Those who have used it should know it's reliability but you are using it on a place it's not meant for, which Topjimmy stated before.

If you use a table top lazy susan you're right but there are thousands of bearings out there that are designed for rotational movement along a vertical plane.  The issue is that some lazy susans are thrust bearings (horizontal loads) and some lazy susans are radial bearings (axial loads).  Turntable bearings and slewing bearings do the same thing but are meant for industrial rather than household applications and are poured steel or iron rather than stamped aluminum yet are still commonly refered to as Lazy Susan bearings as well.  I did mention looking for vertical stress test data on table top lazy susans (thrust bearings) in an earlier post but further analysis leads me to conclude that this isn't necessary given the amount of affordable bearing solutions on the market, I have a good sized radial bearing lazy susan in the mail for $11 shipped.  What makes the "lazy susan"nice is that you don't need an axle as you have two fixed planes, but you sacrifice a lot of strenth doing that.  You can get flanged radial bearings in a 3/16 in diameter that have a dynamic capacity of over 300lbs.  They only go up from there, the trick at that size is finding an axle you can support the tv from.  Jump that up to 3/4 inch and you've solved the support problem for the axle and the bearing can support a midsized pachyderm. 

This was not meant as a rant but merely to clear the air about bearing application in rotation since I notice a lot of folks have written bearing solutions off and I think that they have a lot to offer. 

<significant edits for clarity>   

Le Chuck, can you give me some examples/links to Axis/Bearings able to hold 30Lbs?  I've been doing some rough looking in my area and haven't found what I'm looking for yet.  Then again I'm new to this stuff so I'm not 100% sure what I'm looking for.  I would PM for this but I thought it would be good for others searching on this to find it.

[Le Chuck]

Le Chuck, can you give me some examples/links to Axis/Bearings able to hold 30Lbs?  I've been doing some rough looking in my area and haven't found what I'm looking for yet.  Then again I'm new to this stuff so I'm not 100% sure what I'm looking for.  I would PM for this but I thought it would be good for others searching on this to find it.

Sure thing.  Depends on what you're wanting to do and how you're wanting to hook up so I'll put a few solutions:

Axle based solution:  Both of these and pretty much any like them have a tolerance of several hundred pounds.

Flangette Collar Bearings - These are great because they have set screws in the collar so your axle doesn't just pull out.  Available in two bolt and four bold models. (tolerance of over 7 KNs on this model!)   

Pillow Block Bearings - similar to the above but they mount differently.  Many of these are not self lubricating so come with a grease zerk.  For arcade use you'd likely never have to lubricate.

There are also regular collar bearings and rod end bearings and all kinds of others that come in a variety of sizes a good price.  Just watch for key words like ceramic and surgical because prices will climb exponentially. 

Turntable based solution: Much lower weight tolerance but still around a 100 lbs or so, a data sheet should be coming with the sample I ordered and I'll update.

Aluminum Turntable Bearing - Right now this is the only axle free solution that is remotely affordable (various sizes available).  When I was in Germany slewing rings in the 100mm to 200mm range were commonly available at Einhaeupl's but they are harder to come across in the states it seems.  I've heard that you can get them at tractor supply stores so hit that up if you have one near by.  Other than that I'll keep searching for a steel supplier as you lose a lot with aluminum. 

[TopJimmyCooks]

. . . a data sheet should be coming with the sample I ordered  . . .

Got a rotating monitor project coming up?


I would have used that VXB turntable bearing if I had known of it before going with the LSB.  That is awesome and a great price. 

[Le Chuck]

Got a rotating monitor project coming up?

I would have used that VXB turntable bearing if I had known of it before going with the LSB.  That is awesome and a great price. 

I'm percolating for the kid's cabinet I'll be doing for their Christmas.  I'm getting the stuff now though because I really want to do a proof of concept on a 4.8v rotation using a robotics servo and that turntable bearing.  Once I get the pot issue sorted (or fail miserably) on my caanoo hack I'll be using the first linked flange bearing to support the scaled yoke. 

[kahlid74]

Thanks for the bearings examples.  I also saw that first site had shafts as well.  I got my motor and primary voltage controller today so I'll be rigging it up here in the next few days especially when I get my Power supply.

[kahlid74]

The question then becomes what type of shaft to use and gear vs pulley.  Anyone have any thoughts on one versus the other and what to look for specifically with shafts?  I see a lot of shafts rated for linear motion but what about rotational motion or are they the same?

[Le Chuck]

Most shafts you get that have a sufficient linear rating will have a sufficient radial rating.  This has to do with the basic shaft design (round and all) but there is variance if you're working at high rotations... which we aren't... so it doesn't matter.  If the shaft can hold the load and fits the bearing you'll be fine. 

As for gear and pulley that is more determined by what sort of drive you want to use.  There is no reason to even have gearing if you have a strong enough motor or servo to connect directly to the axle.  If you need to offset though I am still a huge fan of the wheel and roller from the DNA Dan builds.  (Same type that Darthpaul just used on his automation opus... and I think that Switchcade used it as well)

[DNA Dan]

Go for it Nitz! You can do it! I've been around, but just now saw your thread.

What I did for the pololu motor controller is I bought an actual molex pigtail so you can plug directly into the power supply of the computer. This way you have a plug and play design that is fool-proof. You want to use the 12V rail for this. The USB connection is strictly for communication to the software. I purchased the board already assembled because they have a nice terminal block on it for the power. You can extend the pigtail to reach the controller, but I would use similar wire, not some cheapo thin stuff. For the limit switches, I actually bought connectors from pololu for this so I could plug into the board easily. Check out --> http://www.pololu.com/catalog/product/1901 they even make the wires precrimped if you don't want to spend the extra time making your own http://www.pololu.com/catalog/category/72  If you have to solder any joints, just make sure they are well taped, shrink wrapped, etc. You can also install a connector in there, but I typically prefer to have a solid wire with only connections on the ends. The design of your cab will mostly dictate this and only you will know for sure where it might help to be able to break the wire and pull the motor controller out. For mine, I made a complete run with no other connections and put them in a harness. I also ran coin door, marquee light, top fan, etc, all in the same harness so the interior guts are nice and tidy.

The connections to the board will be 2 wires for power (Screw down terminals) and 4 connections (2 each) for the limit switches. That's it. The rest is all USB mini plug for the communication. Almost forgot, there are also two wires for the motor leads.

For the rotation, I actually prefer the axle design. I think that offers the least amount of drag and deflection. The issue with all these approaches is getting that axle mounted in the center of the monitor setup so it doesn't rotate lopsided. Remember, any lopsidedness with become evident when you try to make the bezel. One orientation or the other will not be perfectly centered top to bottom or left to right.

[DNA Dan]

For the molex computer stuff I used www.frozenCPU.com Be careful though, you could spend and entire paycheck here!

If you're concerned about ventilation, I used this for my fans up top http://www.frozencpu.com/products/9389/bus-202/Manual_12V_Variable_Speed_Controller_-_4-Pin_Molex_Connector_to_Dual_3-Pin_Fan_Connector.html?tl=g47c17s285

That website has a lot of good parts for using PC molex power supply connection to do whatever you really need.

[nitz]

Awesome, thanks DNA Dan, this makes things pretty clear.

This is what I love about this forum...ask for some help with something and get it in spades. Since coming here I've learned/done stuff I probably never would have attempted otherwise.

[DNA Dan]

Same for me dude. I am just paying it forward to keep the community alive.

[Ond]

I have been following along with this discussion, just some thoughts....  Stepper motors although more expensive than other motor types mentioned allow for simplicity of design.  With precise control of rotation you can focus on keeping the overall solution simple.  Someone mentioned that gears can be expensive.  I put a lot of thought into this and came up with a highly affordable but very robust solution in the form of toy helicopter Gears.  I looked up the biggest baddest model helicopter on the market and then sourced the spare parts from that.  The gear set uses a 'fishbone' profile that is very strong (think of the forces at work in a big ass helicopter model taking off) and also means zero slippage.  I've seen slippage issues with friction based rotating solutions.  From memory there was change out of about $35 for the gear set I bought so I bought a back up pair just in case.  The large ratio of these gears allows for high torque to play with.  I've yet to push the turning speed to see what I can get out of it, but that's next on my list.  Maybe rotate through 90 degrees with consistant precision stopping in under 1.5 seconds? (or shred the gears trying  ).

If you want bearing strength I recommend automotive bearings and bearing cages with a steel shaft to mount the monitor onto.

[DNA Dan]

For me the real appeal of a stepper motor is you could mount it AS the bearing itself. You'd need a beefy stepper, but the shaft could act directly as the rotation point with the monitor attached directly. You would save time and money on not having to screw around with the rotation parts so much, (lazy susan bearing, axle or whatnot) but the savings alone will not account for the cost of these industrial stepper motors. If mounting directly you'd probably want something 20mm shaft diameter or so and those can run hundreds of dollars. The other issue is the software interface. You'd have to use labview or some other software, something I lack experience with.

I like Ond's idea about a stepper with a gear ratio in there. This way you could have the cost savings of a smaller stepper. The issue again though is you need to create the rotation mech, unless the gearbox can handle this directly.

[kahlid74]

For me the real appeal of a stepper motor is you could mount it AS the bearing itself. You'd need a beefy stepper, but the shaft could act directly as the rotation point with the monitor attached directly. You would save time and money on not having to screw around with the rotation parts so much, (lazy susan bearing, axle or whatnot) but the savings alone will not account for the cost of these industrial stepper motors. If mounting directly you'd probably want something 20mm shaft diameter or so and those can run hundreds of dollars. The other issue is the software interface. You'd have to use labview or some other software, something I lack experience with.

I like Ond's idea about a stepper with a gear ratio in there. This way you could have the cost savings of a smaller stepper. The issue again though is you need to create the rotation mech, unless the gearbox can handle this directly.

The answer in short to your software interface is Arduino.  Arduino is easily coded and can control stepper motors who talk in "pulses"  It's been done with Arduino and "EasyDriver" which is a sort of small version of power/control for Stepper motors.

For my rotation, I'll be using a 428 oz*in torque motor that uses a 50 volt 5 amp controller with Pulse controls being powered by a 40v 5 amp power supply.  The 50 volt 5 amp controller then connects directly into Arduino.  Arduino tells the controller to execute X pulses and a direction.  Since my "box" will be 42" wide and 30 lbs, I'll have to use a gear ratio, but because gears are such a pain I'll be using a V-Belt to accomplish the same thing.  The V-Belt pulley's are super cheap along with a moderate V-Belt that is adjustable in size.

Ond's project originally was identical in design except where I'll be using the Arduino he used the KTA-190.  The KTA-190 is super simple to control but it's expensive compared to an Arduino and the Arduino can do a heck of a lot more to boot.

I should have all of my parts within the next week where I then will be building a test podium, mounting all of my parts and playing with the rotation.  Based on my success I'll create a new project thread for the machine.

[DNA Dan]

Which Arduino board are you using? I thought they were limited to 12-18v? Or is the motor powered separately?

[kahlid74]

Which Arduino board are you using? I thought they were limited to 12-18v? Or is the motor powered separately?

Motor powered separately by a 40v 5 amp Power Supply specifically rated for Stepper motors involved in CNC operations.  So it will work perfectly.

[darthpaul]

I know I'm still relatively new to this forum and no one loves gears and servos more than I do but isn't this all a little overkill, we are talking about an LCD monitor? I have done a rotating 21" CRT monitor using the friction method powered by a windshield wiper motor; simple, cheap and it works flawlessly. To control the speed, I am using PWM that is built into DaOld Man's MRotate plugin, no need for gearing.

[Le Chuck]

I know I'm still relatively new to this forum and no one loves gears and servos more than I do but isn't this all a little overkill, we are talking about an LCD monitor? I have done a rotating 21" CRT monitor using the friction method powered by a windshield wiper motor; simple, cheap and it works flawlessly. To control the speed, I am using PWM that is built into DaOld Man's MRotate plugin, no need for gearing.

Right but if you wanted to spin the monitor at 500 RPMs you probably couldn't... but they could.  That's the difference.