Working on the computer and power converter

I haven't posted an update since July and a question I am frequently asked is "How is the second R2-D2 coming along?".

I hope this entry answers that!

R2-D2 #1 has had a very busy summer and fall, plus a Christmas time appearance to help out Toys for Tots.  Toss in work, on-line college classes and the usual busy life, spare time for the second droid has been sparse!

But I am happy to post that with some holiday down time, I had a chance to work on R2's Intel NUC (Next Unit of Computing) PC and the Mini-Box DC converter.

First, the NUC.

Part of the attraction of this device is the Intel i3 processor, which sips at the power.  It is also an extremely small PC, popular with signage/multimedia displays, easily attached to the back of a monitor.  It measures 4 inches x 4 inches and 2 inches thick.

It comes "barebones", meaning you purchase the amount of RAM you want, the size/capacity mSATA solid state hard disk and the WiFi adapter (optional).  I put 8 gb of RAM, a 120gb SSD and went with the Centrino WiFi as well.  Once you add it all up, you've spent about the same as a modestly equipped laptop.

The NUC uses 19 volts and has the optional power input directly on the motherboard (instead of using the barrel-plug connector on the back).  My NUC sat around for several months before I realized mine was missing the connector.  The documentation stated it should be there so I contacted Intel on their support site about the discrepancy.  I was expecting to be told "too bad" since so much time had elapsed from my purchase.  However, Intel contacted me, explained I had a very early version of the device and offered to RMA a replacement right away.  I provided the model and serial number and they shipped the new one NEXT DAY AIR.  Amazing service!

With the replacement NUC here, I moved the RAM, SSD and Centrino wireless adapter to the new one.  (Notice on the left side the 2-hole power plug just above the RAM.  The previous NUC was missing this)

 After installing some updates to Windows 8, as well as numerous enhancements from Intel on the NUC, the computer is running great.  

My next goal was to make Windows 8 work more like Windows 7.  No "charm" menu, getting the "Start" menu back and so on.  Then my display turned green.  I thought it was the start menu program I was using, but upon testing the monitor and trying a different HDMI cable, it was clear the VGA converter was the culprit.  Even my BIOS screen went green-ish.

The problem with the converter failing is it also acts as the audio output.  You see, the NUC only has HDMI outputs.  Now that's great if you are only plugging into a big screen TV that will play video presentations all day.  But if you are using it in the role I have in mind, you need have audio output into R2's amplifier/speaker system.  R2 also had a small LCD sceen tucked behind one of the body panels and that uses VGA.  With the converter failing, I've put out some emails to find a reliable solution.

HDMI converter.  HDMI goes in, the jack on the right provides the audio port needed for the sound, then the blue connector is the VGA connection to the LCD display.

Since my progress seems halted on the computer for the moment, I decided to make sure the DCDC-USB-Pro is going to work alright.

The converter is a slim, well documented power converter, which will take 12 volt power and make it 19 volts for the NUC.  Jumper settings or the USB software allow you to precisely set the desired voltage, plus other options I'll cover another time.

Once thing I forgot to order when I bought it was the 4-prong to 2-prong connector, so I did that this weekend.  I can't find the cable anywhere locally and as much as I hate buying a $2 part that costs more to ship, I had to!

The enclosure is a nice touch.  I need to add a fan so things are kept cool.  The only concern I have so far is that when set to 19 volts, my tester shows 22 volts.  I don't know if my meter is a bit off or if variation is normal.  I emailed Mini-Box to get a definitive answer and until I know for sure, won't attempt to power the NUC with this yet.

So in summary, I am making progress!  I need to figure out the video/audio output concerns of the NUC, then the voltage questions of the converter.

More soon!

Center Leg Lift Development: An Overview

One of the toughest things to replicate from the STAR WARS movies is what we call "232".  

2 stands for 2-leg mode, when R2-D2 is standing upright.  Then, R2 transitions into 3-leg mode.  The body pivots, the center ankle/foot is extended out of the body and R2 is now in its driving mode.  When R2 gets where it needs to be, it returns to 2-leg mode.  Thus, "232".

Here's a video clip I pieced together that shows this effect in the original STAR WARS movie...

 

Many of us R2 builders have tried to pull off this effect in a variety of ways.  Some have specifically built their R2s out of much lighter materials, like wood or styrene, to make the movement easier to articulate.  

There are several aspects that make the 232 system.   

1)  The shoulders.  These need to pivot 17 degrees for R2 to be in 3 leg mode.  The mechanism to do this needs to rotate the entire weight of the droid precisely.  If one side doesn't move smoothly with the other, damage could occur.

Shoulder linkage and linear actuator

2)  The center leg lift.  (This is what I am working on.)  As you see in the video clip above, the center ankle and foot need to fit inside the body.  Then, it needs to smoothly extend out and be prepared to handle the load placed on it.  It needs to deploy quickly, as seen in the movie.  This is a challenge since most modern linear actuators that can handle 150 pounds or more have travel speeds of 1/2 an inch per second.  With the ankle and foot size taken into consideration, my setup travels 8.5 inches.  However, when you take into account gravity and the weight of the ankle/foot and wheels inside it, that could be a bit quicker.

Center leg lift setup I'm working on

3)  Locking the ankles.  R2's ankles, where they attach into the foot, are triangular and bolt into a channel in the foot.  Many lighter droids can stay in 2-leg mode simply because they do not put nearly as much force on the joint.  A 200-pound aluminum robot is a different story!

Note how the ankles are triangular in shape with a single hole mount point to pivot

Ankle freely travels in the foot.  This needs to be secured for proper movement in a 232 setup.

Locking the ankles is challenging.  There isn't much room inside the ankle, or the foot, to put much in there.  The foot is already largely off limits since the foot motor/drive system is in there.  And this is probably the toughest piece of the puzzle, since R2 can't go back upright until those ankles rotate.

So you now have the basics of what 232 is all about.  In my next post, I'll show you how the center leg lift is coming along!
 
 

Modifying the frame for the COM-8 Rear Door

Today I received the Rear Door Assembly from COM-8 down in Texas.  COM-8 (James) makes frames and accessories for them.  The frames are very similar to the ones offered by Jerry Greene (JAG) a couple years ago.  JAG passed the frame building torch to him and COM-8 offers R2 builders some nice, bolt together packages for those who prefer aluminum frames for their droid builds.

While the frames are similar in lineage, my JAG version 5 frame needed some minor tweaks to install the Rear Door Assembly (RDA)

The RDA will give me a swing out door, essentially.  Also, the space that is currently left open for a flip down electronics tray, I can utilize to mount things into this new structure.

The parts come anodized blue and COM-8 includes a detailed instruction manual.

The best tip in the manual is keeping track where the engraved "H" is!

Assembly goes along pretty quick from there

For the JAG frame, the vertical rods in the back will need to be removed since the included ones will replace them.

The JAG frames use the Inner holes in the frame ring....

The threaded rod needs to be removed from the JAG frame.  The hole below it is what the COM-8 frames use and we will use to install the RDA

Once the threaded rods are out, I countersunk the hole so that in its place, a 1/4-20 flat head screw could be installed.  It has to be extremely flush as the hinge of the RDA will go over it.

Thankfully the holes were already there on my frame, with the exception of one, which took my friend a few moments to drill out, then countersink

Now it was time to install the RDA assembly...

The larger spacer goes up top while the lower part sits flush on the frame ring.

....and here it is, aligned and works fine!

Mounting the shoulder actuators

Over the past few weeks, I've been working with my machinist friend on some ideas on installing the linear actuators into R2's frame.  Originally the shoulders were designed to work with an actuator with a 3 inch stroke but the shoulders actually have a bit more movement than that...about 3.4 inches.  The way the shoulders work, the four bolts rotate thru the grooves.  They all for the shoulders to rotate back, when in 3-leg position and upright, in 2 leg.  They also also for a few degrees to tip forward, allowing us builders to articulate and create "body rocking/body movement".

 

I decided to go with 4 inch stroke actuators equipped with potentiometers.  In the closed position, they will put R2-D2 in it's 3-leg position.  Since the stroke is larger that the movement allowed (3.4 inches), I will use the data from the potentiometers to stop them before they exceed the travel allowed.  

Attaching the actuators to the shoulder levers went fine, although we decided to use a 1/4-20 sized bolt.

Since the potentiometer equipped actuators are longer than the original design, we had to come up with a way to fit them into the frame.  Before we could snub them into the lever, we had to do something about the bottom attach point.  We want the actuator to be straight for its vertical lifting and retracting.

To overcome this, we did two things:  We made mountings to bolt under the frame ring and small cut outs for the actuators to mount straight.

With that side done, it was on to the next....and now, the actuators are both installed!

Dome gear, dome drive and more

Over the past week or two, I have been working on making more progress on R2-D2 #2.
With the dome plate made, it was time to make a dome gear out of aluminum, as I had done for the first droid.

I cleaned up the dome gear some and my friend, Fred, insisted it should be shinier, so he hit it with some steel wool.

For better clearance for the dome drive sprocket to spin under the dome gear, I added a washer to each spot the mounting screws came thru.

I'm using the Pololu 37D 67:1 motor which turns at 150 rpm.

We cut a sprocket out of Delrin (plastic) and used the hole pattern for the motor hub that Pololu sells.

To mount the motor, I used the Pololu motor bracket.  I just flattened it out and drilled some holes to attach it to the metal frame ring.

And here it is in operation...

Making a [very cool looking] Dome Plate

As I get the second R2-D2's build back on track, one piece I did not have was the dome plate.  This is the part where all of the gadgets will mount to inside R2's dome.  For example, the periscope, the life form scanner and other things.

The one I have in the first R2 is a 1/8" inch thick dome plate.  While it works fine, I wanted something thicker the next time around. 

The great thing about being part of an R2 Building Club is the way people share their ideas with one another.  Another builder shared with me a drawing of a dome plate that was really well laid out and looked great.  Using the 1/4" inch aluminum, it has numerous grooves, holes and cut outs that reduce the weight of the finished piece.

Once I had a chance to review the drawing with my machinist friend, it was pretty clear we had a good amount of work ahead of us.  We had to tell the software what to cut thru, what parts to cut down an 1/8" of an inch, where to place tabs and so on.  This took about two hours to do.  Once we were happy with the calculations and previews of the end result, we created the g-code for the Mach 3 software.  The Mach 3 software takes that code and controls the X, Y and Z axis of the CNC machine.

Software loaded, everything is calibrated....

I purchased a 17 inch by 17 inch piece of aluminum plate from my local metal supplier.  Once the piece was clamped in and the CNC machine was calibrated, it was time to sit back and watch it work.

And watch, we did.  Since our CNC machine can only use one tool at a time, it did the entire piece with its 12mm cutting bit.  More advanced machines could change tools to remove move material with larger bits, getting the job done much quicker.  However, for us hobbyists, this works just fine despite taking a lot longer.

Specifically, this took 8 hours and 41 minutes to cut!  Then, another hour or so to remove all the tabs that hold many pieces in place until completed.

8 hours and 41 minutes later!

Once all the pieces that were no longer needed were removed, you can see how neat this part looks!

The original metal plate weighed just over 6 pounds.  After all the excess material was removed, the dome plate weighs 1.87 pounds.

To remove all the metal scratches and lines left from the cutting bit, I had a friend bead-blast it.

To protect the finish, we clear coat the dome plate...

Granted, the only time people will see this part is if R2's dome is off.  But, it was a great challenge to see if the CNC machine could make this piece!

What's new so far in 2013

Over the past few months, I have been making R2-D2 parts for myself and other builders.  Side Vents and the Data Panels took up a lot of time but it was a lot of fun.  Working with my machinist friend, Fred, I've learned a great deal about working with aluminum, using a CNC machine and more.  After years of building with hacksaws, Dremels and so on, its fantastic to learn how to use bigger and better tools!

CNC machine cutting a Side Vent from 5052 aluminum

Making Data Panels

With my first R2-D2 functioning fine, I wanted to get back into getting the second one built.  Recall that the second one is going to be my "uber" or "ultimate" R2-D2.  Basically taking everything I learned building the first and making this one.   Once completed, the first R2-D2 will have its blue parts painted pink, giving me a "girl" R2 for patient visitors.

Over the past few days, with the assistance of my friend, we've installed the Data Port into the frame and made a surround piece that wraps behind the CPU Arm.  Back in December we also got the CPU Arm mounted and actuated.

Data Panel installed into the frame.

Bottom part of the CPU Arm enclosure

Gently peeling the protective plastic layer from the aluminum to glue a rubber stopper.

Surround enclosure installed

Looks great with the skin on. 

Rubber stopper prevent damage to the CPU Arm tip

Back view of the surround

The CPU Arm assembly we made required some trimming of the metal shaft to fit the door opening.  Then my friend came up with an ingenious way to mounting it all into the frame.

We had to take apart the metal CPU Arm and internal linkages to properly size them to fit the door opening.  We then fabricated an adapter to thread from the L16 Firgelli Actuator and the threading of the CPU Arm tip

The inside of the metal CPU Arm was filed to fit actuator inside, then we came up with a way to secure it inside.

Servo on the left doesn't have enough torque but the one on the left will.  The CPM Arm bracket  is ready to be installed

The CPU Arm hangs directly over the frame ring, so it won't be in the way of the skins nor the mechanisms behind it.  You can see the two levers, one of which the large servo will attach to.

Close up

Arm pivoted out

Drilling and tapping two holes into the frame rod to attach the large servo to.

Servo installed, linkage from CPU Arm lever attached.  Now to attack to the servo

Testing it out, plenty of power to lift the CPU arm...and the actuator pushes the probe out