motor advice for rotating crt setup

[Ed_McCarron]

Yeah, the heck with this simple 90 degree rotation... Lets shoot for 270.  Make it interesting.

[DaOld Man]

Yeah, that would make a game of pacman very interesting..
 

[Cornchip]

  Stay away from the 24 VDC (military voltage). Power supplies are uncommon. I used a  power supply that was affordable and most importantly safe. I bought a Pyramid 12 VDC 15 AMP PS-15KX dedicated power supply for the job. I cost me 60 dollars. It is circuit protected....so you don't even need a fuse. Wire something wrong and nothing blows or burns. I can't stress enough the safety behind having reliable proven electrics in your cab. I also use it to power my LED's and audio Amp. Oh...I should mention the AMP draw of a power window motor. Free no load running is supposed to be @ 2-3 AMPS. Full load (something binding) could cause it to peak past an amazing 20 AMP's. If you try that off a PC power supply things will happen! I ran an in line Watt's meter and saw less than the 2 amps while moving the monitor. Mind you I reduced the shaft RPM of the motor from 165 to 3 at the monitor drive shaft. Big time torque (more power is needed to move an object at it's center line than it's circumference).

 About that motor. It can be found surplus at a good price (for a new item...you can't go wrong). The make is Nippondenso (Toyota OEM) and is #30556-7030. It can be bought for  20 bucks (like I said before...it's new as well!). You won't find one at a wreckers for less. And here's why it stands out from other motors. It has a shaft 9MM in diameter versus the more common gear that all others have. It will adapt easy to a project like this. This motor is popular with the Robot Wars crowd.

 Here's an example on line surplus shop.

 http://www.skycraftsurplus.com/index.asp?PageAction=VIEWPROD&ProdID=814

 Also...resist driving a DC motor with less than it's rated voltage. Severe heating will fry the motor (as Volt's drop ... Amps increase). Touch the case of the motor as you will see. 

  I'm sure this rope system is a win. What do you do for a living Jimbo? Do you have the means to make a rope pulley? I see that stopping you unless you have some access to a machine shop. Some quality work here will pay big in the end.

 Cornchip.

[Ed_McCarron]

  Stay away from the 24 VDC (military voltage). Power supplies are uncommon.

Sorry, but I'll disagree.

24vdc may be ALSO a military voltage, but its the standard for pretty much any PLC in the industrial world.

Ebay starts around $5 for a 2.5A model.

[Cornchip]

  Yes you are correct. Just about any panel you look in will have a 24 VDC in industry (DIN Rail). I can't say why the US military went with 24 VDC at a time when the typical US car used  6VDC. The obvious would be that higher voltage is just more efficient....or that two batteries were better than one. If 24 works for you...go for it.

 Cornchip.

[bfauska]

Getting a cylinder to bind is all about the angle of travel, in the drawing shown the cylinder rotates a total of 9 degrees throughout the course of it's move.  Again I don't think that it's the best way to go in a cab, but I have NO doubt that it would work.  I've done bigger, realworld, and the problems I've had are more about the uneven power transfer of a compressible gas.  If you look at the cylinders on most heavy equipment they are almost always converting linear motion into rotary, they aren't causing things to rotate in an obvious fashion but they are are pivoting around a point.

[Ed_McCarron]

Getting a cylinder to bind is all about the angle of travel, in the drawing shown the cylinder rotates a total of 9 degrees throughout the course of it's move.

Makes sense.  My stuff is small, and the cylinder ends up swinging something like 35 degrees.

You need to stop trying to talk him out of pneumatics and talk him into using high pressure nitrogen.

We need more amusing "hold my beer and watch this" videos.

[DaOld Man]

At least my stuff aint small....

[bfauska]

Getting a cylinder to bind is all about the angle of travel, in the drawing shown the cylinder rotates a total of 9 degrees throughout the course of it's move.

Makes sense.  My stuff is small, and the cylinder ends up swinging something like 35 degrees.

You need to stop trying to talk him out of pneumatics and talk him into using high pressure nitrogen.

We need more amusing "hold my beer and watch this" videos.

Yeah, over the course of a 35 degree cylinder pivot the load changes dramaticily, I could see that being a problem.

I suppose I could try to convince him to use CO₂, if you regulate it way down it actually makes a good compact tank for a system that needs many cycles between charges.  I totally agree that one of the things this forum has too few of is "hold my beer and watch this" videos.   

At least my stuff aint small....

After Ed's comment about the videos I was already chuckling, but that put me over the edge, good stuff.

[Ed_McCarron]

At least my stuff aint small....

Har-de-har.

Small.

[DaOld Man]

Hey that looks pretty cool Ed..
What is it? A robot?
I love watching those battling robots tear each other up..
Please tell me you are into that!
I see a different forum coming up..
Got a bigger pic?

[koz319]

I did a motorized rotating monitor setup a few years ago.   I used the standard monitor 'wheel', with a vbelt (fanbelt) encircling the wheel and a sheave (pulley) on the motor shaft.   You can pickup sheaves and vbelts from grainger or emotorstore.com 

The motor is controlled by an h-bridge connected to the lpt port on the computer.  An hbridge is just is motor controller that lets the low level signal on the lpt port control a higher power circuit to the motor.  If pin one on the hbridge is high, the monitor rotates clockwise.  If pin two is high, the polarity to the motor is reversed and the monitor rotates counter clockwise.  The lpt port is also connected to the degauss circuit of the monitor, so when the rotation is complete, the monitor is degaussed.  In a previous post somewhere I put a link to the schematic for the hbridge I used if anyone is interested.

The motor is a 24v dc motor that I drive at 12v with an old PC power supply.  If you want to use an old supply, just check its power rating on the 12v rail.  It should list either watts or amps for the 12v supply.  The one I used was rated for about 170w @ 12v.  170w/12v = just over 14 amps for the motor.  I measured current draw during rotation, and this was plenty.  The motor is only running for about 4 seconds at a time, so there is not really enough time to generate any heat.  The power supply/motor/hbridge have been working fine for about 3 years now.

There are two limit switches in the cab to signal orientation - I just used basic happs buttons I had left over.  I cut two small lengths of coathanger and screwed them to the back of the monitor 'wheel', these activate the limit switches.  The limits serve two functions, they interrupt the low level signal to the hbridge when hit, stopping the rotation (the normally closed side of the switch is opened when pressed), and a signal is sent to the lpt port when limit is reached (the normally open side of the switch is closed when pressed, and is connected to the lpt port).

I wrote a command line util that will rotate the monitor based on whatever paramaters you send, rotation direction, whether to degauss, and a timeout in seconds.  The timeout just shuts the motor off after 'x' seconds, so the monitor wont spin forever if the limit switch fails for some reason.    This utility can be added called from a front end, but is pretty clunky in its current form.  I'm about halfway through a much better version that should work with most frontends, but it seems like I  just haven't  had the time to finish it.   I actually use a slightly modified version of mame,  just added a few lines to the source code and recompiled so mame rotates the monitor automatically based on the orientation of the game.

Here is a link to a video of the monitor rotating & degaussing when a game is selected:





Here are a few pics of the cab, plexi, bezel, motor & belt, and hbridge.  I couldn't easily get to the back of the cab to take pics of the limits or better pics of the belt, sorry.  Maybe this weekend.


Koz

[DaOld Man]

Thanks Coz.. This is what ive been envisioning.
To have the monitor automatically turn by the game that was being started.
I was just thinking of using relays driven off the lpt port, instead of the H bridge.
I was thinking of simplicity and ease of repair. If a relay fails, just unplug it and plug in a new one.
But an H bridge would be more efficient.
Can you send me your program that you wrote for this? Id like to experiment with GLaunch.

[danny_galaga]

I never wrote explicitly that you only need 90 degrees or so of chain on the circumference, but its obvious to all.

Seems this solution is gaining popularity... now we just need a tester...

The only problem I see with this solution over others, is that the bike chain adds to the circumference of the circular plate, which means your cab is even wider than it was with just a circular plate. the friction-based caster-roller solution, for example, avoids this.

Thinking out loud though, you could do a two-layer solution like Jimbo, with the second layer slightly smaller than the first, and the chain connected there, thus not adding extra to the circumference... that would mean one part of the plate would not have casters holding the plate up.... would that introduce instability to the plate mechanism?

you could also just route a channel for the chain to sit in. i was thinking about that last night. route or a sandwich of three disks to create the same effect...

[telengard]

I'm watching this thread closely...

This is the last thing I'd like to do to my cab.  I don't mind manually rotating (only takes a sec or two) but it'd be nice to have it auto rotate and degauss w/ the push of a button or even when starting a game.

~telengard

[Jimbo]

Hi all, thanks again for the replies.  I managed to get a car mechanic friend of mine to donate a 12V power window motor to my cause!   It's quite a beast (bigger than I had originally envisaged) but it looks like it might do the trick: -



Its a bit too big to mount on the front side of my monitor's seat, but there's enough room behind the seat frame to mount it there, so the drive shaft would slot through a drilled hole in the frame and I could stick the aforementioned "drum" or sprocket level with the rotating monitor wheel: -



The red line in the above photo is where I thought I could put some sort of barrier to prevent the magnetism knackering the monitor, since the motor is sitting quite close to it.  Does anyone have any thoughts/advice on whats best to use here, or if you could see a better way of protecting the monitor?

koz319, I like your setup, it seems nice and simple, and I'm thinking either the rope pulley system or maybe something similar to yours would be perfect.  I could possibly (through my mechanic friend) get hold of a car cam-belt and sprocket. As the monitor is only rotating 90 degrees in either direction, I figure the toothed sprocket on the motor shaft would be needed, but I could glue or pin the cam-belt to the monitor wheel, negating the need for any toothed-system to be attached to that.

I'll be trying to sort out a power supply for the motor over the next few days, and I want to start thinking about wiring up a circuit to limit the rotations to 90 degrees. Ideally I'd like a single microswitched pushbutton on my cab that starts the rotation in the appropriate direction, I don't want two buttons (one for each direction). Eventually it would be nice to wire it to the parallel port of my PC so I can rotate through software, depending on the game.

[DaOld Man]

It cab be done pretty easy with two 3PDT relays, rated at the current the motor draws.
You will need two limit switches.
I had a drawing of what I was going to attempt to do, but I cant find it now. I will post it when I come across it.
Also koz mentioned a H bridge which would do the trick too.

[kelemvor]

I think it'd be cool to put a big crank on the side of the cab and you could just go crank it around.  Would be more of a neat retro mechanical look.  heh.

[DaOld Man]

Yeah, crank out some games, man!
 

[Anubis_au]

Jimbo

A good starting point for the electronics design is this page:

http://lillypad.4mg.com/lillypad/extraspad.html

Though I've seen other designs. If I stumble across more I'll post a link.

I'm still wondering how I am going to couple the motor to the circular plate in my future cab. Good luck with your implementation.