Dome Pie Panel Servo Setup

Spent the last few evenings working on the dome pie panels, and after some tweaking I think I have a setup I’m happy with.

I ended up keeping the extra plate on the inside of the pie panel. It adds some detail and I like the sound the panels makes because of the extra weight. I left the hinges in the default configuration with no tweaks apart from drilling some holes to attach the servos.

I glued the hinges in place using CA glue, which sounds like it may not work so well, but I used the same glue on the hinges on the body and they’ve held up well.

Notice how the hinges are angled slightly to follow the curve of the dome.

I could have just glue the hinges directly to the dome, but I wanted to make the panels removable, so I created a small plate that glues to the dome and then then the hinges are screwed to it.

For the front Holo projector I’d purchased some push rod assemblies to attach the servos, but they were pretty expensive for something so simple, and I thought I could do better – this is what I ended up with.

It’s made up of some very cheap and readily available parts you’ll find at any hardware store. It basically some #4-40 and #6-32 screws in varying lengths, and short length of aluminum tubing that I cut up to make some linkages. I think it cost me less than $4 to make four push rod assemblies.

The long push rod is a #6-32 screw which attaches to the hinges via a piece of the aluminum tube that’s tapped at one end for the screw.

A long #4-40 screw passes through it horizontally to fix it to the hinges.

On the servo end I tap a small section of the tube on each side, and drilled a hole in the middle that allows the long screw to freely pass thru until I lock it on the side.

The servo is currently attached to the dome with some heavy-duty Velcro, which works fine right now, but I know it will eventually fail so I’ll be making a mounting brackets next.

Here’s a short video showing the setup in action

The next step is to wire all 4 servos into a PICAXE processor and tie it all together with some software to trigger sequences from the RF remote.

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Posted by Chris on July 10th, 2008 in Dome, Electronics | 1 Comment

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Holo Projector Servo Test

I’m definitely getting into the fun part of the project. I spent part of the evening trying to add a servo to the front holo projector. It was a little more tricky than I thought it was going to be. I’d seen photos and vaguely remember a setup on one of the tables at C4, but until tonight I didn’t understood the nuances of the angles and forces need to move something with a servo, so it was frustrating and fun at the same time.

Most people seem to use the same basic method to move pie panels, doors, holo projectors etc. And that’s to convert servo rotation into a linear movement using a push rod attached to the servo horn.

I’d bought some random mini servos from Tower Hobbies a while ago (Hi-Tec HS-55), and a push rod/linkage assembly from ebay. Problem was the servo was too small to fit the rod attachments. I managed to improvise and this is what I finally came up with

Please ignore the kinks in the rod, it really should be straight, but I’d tried to copy what I’d seen at C4 and got it totally wrong 😀

If I was to do this again I’d probably skip the pre-made assemble and make something in acrylic and parts from the local hardware store.

I also created a short video to summaries and demo the new setup.

As I explain in the video it’s not perfect, and I need to affix the servo more permantely to the dome rather than using velcro and I’m not entirely confident the linkage to the back of the HP will last very long.

The good news the Hi-Tec servo is definitely powerful enough to move the HP and will probably work for the pie panels as well.

I also need to decide if I’m going to add some code to my micro-controller to automate random movement.

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Posted by Chris on April 29th, 2008 in Dome, Electronics, Events, Legs | 14 Comments

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Slip ring servo board brackets

I added some support brackets to the slip ring servo boards. Nothing fancy just a small piece of extruded aluminum with a few holes in it.

I made them slightly longer than the boards to allow extra holes for mount.

Posted by Chris on April 27th, 2008 in General | 4 Comments

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Slip Ring Servo Test

I finally got a chance to fully test out my slip ring last night with some servos.

I first had to finish soldering up my little boards that would handle signal routing and power.

Rather than try and explain in words and pictures how the setup works I made this short video to try and give a good overview and show the slip ring in action.

I still need to make little brackets to secure the D sockets to the boards, and decide the best place to locate them in Artoo.

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Posted by Chris on April 25th, 2008 in Body, Dome, Electronics | 2 Comments

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Slip Ring Update

I started work on my test slip ring tonight and hope to get it installed in the next few days and report back on a new group order.

The sample slip ring has eighteen 2A circuits and I plan on grouping together 6 or 8 for the +/- 12VDC uplink to the dome, leaving ten circuits for PWM/servo signals. To save on circuits I’m not planning on routing the +/- 5VDC from each of the PWM pairs through the slip ring. As a result each RC channel will require just one wire allocated on the slip ring. I’ll just tap of the 12VDC in the dome and re-create a separate 5VDC supply for the servos.

Out of the box the slip ring wires are loose and really needed protecting.

I bought some braided expandable nylon wire wrap from a local surplus electronics store for less than a dollar.

I wrapped the ends in electrical tape to hold things in place.

Now that I have the wire wrap in place I can start soldering the wires to the connectors.

Here’s an overview video on how I plan to implement the wiring

Posted by Chris on April 14th, 2008 in Dome, Electronics | 4 Comments

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Installing some electronics

Another big step forward tonight and I’m not really sure where to start or if I can remember everything I did.

Maybe it’s easier to say where I’m at – I now have a lot of the electronics installed in the body, from fuse block and power distribution to the speed controllers and sound system. I can now control the dome and periscope from my Vex transmitter and trigger sounds with my RF remote.

There was a lot of stripping of wires, routing them, testing, and moving stuff around to make it all fit on the back panels. I also installed a second Vex in the dome to control the periscope, and eventually it’ll control some servos on the pie-panels.

Rear Panel - Earlier in the evening

From the photo it really doesn’t look like a lot but there’s a lot packed in there

Rear Panel Electronics

I’m now realizing that it may not be a good idea to run R2 around naked / skin-less at C4. I could easily see someone pulling on the wires and frying something.

Here’s a quick demo video as well.

You’ll notice in the video that the periscope doesn’t run up and down smoothly and it chatters. Some of it is due to the speed the motors run at which I can limit in the Vex, but there’s also a lot of play in the lift mech screw system itself which I need to fix somehow.

I still need to wire in the RoboteQ speed controller which will drive the feet, but you can see it at the bottom of the frame.

One problem I noticed again is that the Vex in the dome has problems receiving a signal. This maybe a big show stopper unless I can route the antenna somewhere else.

The 12 channel RF Remote also has a “problem”. The new models have a little speaker/siren on them which makes this awful bleep every time you press a button on the remote – I’m sure for most applications this is fine, but for R2 it’s got to go. You’d think it could be disabled easily, but I can’t find anything. I’m going to have to fix it before it drives me nuts.

Posted by Chris on May 8th, 2007 in Electronics | No Comments

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