Dual Receiver Board

I posted this photo a few days ago for people to try and guess what I was working on. Alas, nobody got it right.

Short answer: It’s a Dual Receiver Board.

Dual Receiver Board

We’ve had issues at some events where our 2.4GHz Spread Spectrum radios cause problems like interfering with WiFi setups, and we’ve been asked to limit where who go. Luckily, on my Futaba 10C I can quickly switch out it’s transmitter module to either be 2.4GHz FASST or old school 72MHz FM. So I devised this little board to allow me to have two receivers (FM and FASST) connect to Artoo at once, and flip between them with a flick of a switch.

I’ve had this idea for a while, but only now getting around to implementing it because Maker Faire is in a few weeks, and I know we’re going to have interference problems and I didn’t want to limit myself to either FM or 2.4GHz – or have to make a fiddly change in the field.

Receivers connect on the left and the real servos and speed controllers connect on the right along with receiver power. Ignore the black/red/white wire color on the cables coming out of the receivers. I’m only connecting to the signal out on pin 1 for each channel, and the only nice wire I had handy was standard servo cable. The last pair in the row adds power/ground and are tied to the select switch.

I’m also tinkering with some other droid controllers and this will allow me to have them connect without disrupting too many things, but more on that later.

Posted by Chris on May 10th, 2010 in Electronics | 1 Comment

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Maker Faire Upgrades

Maker Faire is just a day away, and I’ve had a busy time getting ready. This is probably my favorite event of the year, and we will have a good showing, with 4 droids and 6 builders in attendance. Bonnie Burton from SW.com will also be there running a kids workshop on Star Wars Puppet Craft.

Over the long Memorial Day weekend I stripped Artoo down for some long needed repairs and upgrades I’d been putting off.

I’ve replaced the center foot with the a new one from JAG with the taller skirt. Here’s a comparison shot with the new foot on the right

Sadly, with extra tapper of the foot skirt, the “Special” 3 inch Ace casters are too big and had to be re-worked. To be honest, they were a bit of a squeeze in the old foot, so I was on the hunt for some nice 2.5″ casters! I searched and searched locally, but couldn’t find anything suitable, I had three options, order something online, hack what I had, or just install one caster.

Long story short, I tried the last option, and even went as far as creating a new mounting bracket for one 3″ caster, but when I was done I then had to redo my ankle locks as there was now a backward tipping as well as the forward tipping. Hard to explain, but bottom inline I needed to redo my locks, which meant drilling more holes in the ankle that I wasn’t prepared to do….. back to the drawing board.

Because of time, and on Gerard’s suggestion, I resorted to trimming down the 3″ casters I already had. I mounted them in my drill press and filled them down.  It took forever, there was rubber dust everywhere, and it’s not something I want to do again.

What I’ve also realized is that never trust a label, the original casters were labeled 3 inches, but they were closer to 2 7/8th. Here’s a before and after comparison

After some finegaling, and making a new mounting plate,  I got them installed in the new foot – nice and level, unlike when I had the 3″ wheels.

Getting the right caster for the center foot can be tricky, it’s a balancing acts. You want the biggest wheel you can get fit, but because space is tight, the deeper you recess them to get things level the less space you have for a bigger wheel.

oh! and just as I was done with trimming the wheels, I went back and looked at one of the online stores I’d found earlier in the weekend, and what do I find – they’re LOCAL, or almost. They’re called California Caster and based in San Francisco, and had 100’s if not 1000’s of caster products in stock. I just had to make a trip up there. This was just a small selection of casters they had on display

Even though my new center foot was running again, I picked up these replacement 2.5″ wheel for the next round of maintenance.

I also replaced the radar eye with one I picked up from Dave Shaw many moons ago, luckily the old hole placement didn’t screw anything up. It doesn’t look too much different, and the wife thinks I’m crazy for swapping it out. I had the hardest time matching the Kryder blue, and it’s way to clean, but none of my panels match anyway 🙂

I can’t remember exactly what else I worked on, this was my droid on Sunday morning, all stripped down.

There’s been a long list of things I wanted to re-work, like shortening and re-routing some wires that were bugging me, to tweaking the front vents. I almost added servos to the utility arms, but that would require me filling them down and repaint – which I didn’t have time for.

But I did hinge manage to hing some doors in the body. I made some little aluminum brackets to help mount the servos to the frame

I know I worked on more stuff for Makers, but I can’t remember exactly what 🙂

oh! I remember, I’ve also been working on a small wireless controller based on a iPAQ Mobile phone, but more on that later.


Posted by Chris on May 28th, 2009 in Dome, Electronics, Feet | No Comments

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Dome Servo Power Upgrade

At the recent Clone Wars events it became clear that the little Power Distribution Board that was supplying power to the dome servos wasn’t going to cut it. It would work for a while, but the onboard 7806 regulator would soon overheated and shut down to protect itself.

I’m not surprised, I currently have 8 servos in the dome, 4 for the pie panels, one for the front Holoprojector, one for a side panel, and two for the periscope – with more to be added. Idle, each requires around 8-10mA, but when active they can easily require an Amp or more under heavy load, which can add up fast when you have a few things going at once.

Space is tight on the power board so it’s hard to add decent heat sinks, and even if I could I wasn’t convinced that the single 7805/ 7806 (which can deliver a maximum of 1Amp) was up to powering all the servos from one IC.

One of the problems with servos is that they can sometimes stick and not return to neutral fully, and will continue to draw more power than necessary. Anyone who’s played with servos will know that if they’re even slightly misaligned or put under stress in the neutral position will cause them to hum (which means they’re drawing more than the normal 8-10mA). I’m pretty sure that’s what happens on some of my dome servos, but not all the time. It’s virtually impossible to adjust them all to be perfect, especially as things can move or shake in a fast spinning dome.

The dome is fed by a 12VDC supply coming up thru the slip ring, and servo/signals are connected to a custom board at each end of the slip ring. The 12VDC routes to the power distribution board in the dome that then re-creates the various voltages I need, from 5VDC all the way to 24VDC.

The solution to the servo power/overheating problem is to use a better DC regulator to replace the 7806, but I had a bunch of events coming up fast, was short on time and resource, and basically needed to fix the problem overnight.

So I create a simple power board with parts I had on hand, including three 7805 regulators which would power only 4 servos each, plus I added a big heat sinks on each one and a fan to help keep them cool.

Here’s the board coupled with the original servo board. It’s somewhat clunky and I will replace it at some point with a more streamlined solution and a single better regulator, but for now it worked fine to get me thru the events.

If you’re interested in makng your own servo power supply or even a fully blown Power Distrubution Board, it can be done for not much money. 7805 regulators are easy to find, most surplus stores carry them for around 50c, or at a pinch you can pick them up at RadioShack for under $2. Versions that can deliver higher loads are also available, but can be harder to find or sometimes a lot more expensive.

Google on “7805 circuit” or “7805 power supply” you will find dozens of examples of simple circuits to make your own boards. Here’s a good example.

The regulators also come in 6, 8, 9 and 12V varieties. So as I said you could make a distribution board for not much money if you’re up to the challenge.

I also have to stress again that I’m not an electronics expert. Please double check anything before trying to copy me. In this case there are definitely better was to ‘fix’ this problem.


Posted by Chris on August 26th, 2008 in Dome, Electronics | 4 Comments

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Periscope Installed

I’ve been tardy posting updates this last week – been busy trying to get stuff back together for the new Clone Wars movie.

I finally got my periscope installed and functioning. Here’s a short video of it in action

There’s still some small quirks I need to iron out, but I’m pretty close to being done with it (for now). One of the big issues is that everything has to be align perfectly, and taking the dome on and off isn’t as simple as it used to be. What I’ve quickly realized is that with every gadget I add maintenance goes up exponentially.

I repainted the periscope housing after tweaking the curve at the top to match my dome. While I was at it I clean up some spot that I wasn’t happy with

Right now the dome pie panel velcro’s on top of the periscope, but it’s hard to get it to sit flush with so much spring in the velcro. It also very hard to align things perfectly and to get it to stay put. I’m probably going to use magnets instead or even use the small side screws I added. Right now they’re just for show to mimic the ROTJ periscope.

I’m not convinced that the clear lenses look correct either, it’s hard to tell but I suspect the original had a slight frosting to it.

I really need to document the wiring and micro-controller setup for this, but here’s a few overview shots of the periscope installed and there are more in the gallery.

Right now, up/down is manually controlled by the Futaba transmitter, at some point I’ll probably automate this. I also have a small 08M Picaxe micro-controller dedicated to automatically rotating the periscope when it’s fully extended. In addition I have to route 12VDC from the main dome power board back down to the periscope light circuit. The Picaxe and the small mini-servo that rotates everything runs on 5VDC and just taps off of the power for the lift servo.

There are two small micro switches, the first trigger the micro-controller to start randomly turning the periscope when it reaches the top

The second turns on/off the lights when the periscope is raised/lowered


Posted by Chris on August 12th, 2008 in Dome, Electronics | 2 Comments

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More Periscope Work

I’m still fiddling with the periscope, I added some LEDs, a servo to make it turn and something to mount it to the lift mechanism.

But first I had to adjust the dome pie panel cut out to give more clearance. I marked off the area I wanted to cut and Dremeled in a few slots to start things off and finished it with a small hacksaw blade.

The main periscope assemble is mounted atop PVC tube to add more height.

I wanted to easily remove it for maintenance and also allow some height adjustment at the same time. This little tube is fixed to the lift mech

And the main PVC riser tube slips over and locks into place with a couple of screws

I installed a small HiTec HS-55 servo into the top of the PVC tube to turn the periscope side to side when it’s extended. Attached is a round plate the aluminum based of the periscope will screw into.

I’ve also add the LEDs to the main periscope housing. On the front is an array of 6 rectangular LEDs. These are very close to one’s used on the original ROTJ periscope

They’re glowing orange in the photo but they’re deep red in person. Power is 12V and no resistors needed as they’re in series

Here’s the block of LEDs soldered together before I installed them

I’ve wired in some bright white LEDs inside and some colored one’s on the back of the housing, I also re-appropriated one of my old PSI boards to blink a couple of LEDs to add a bit of variety.

Getting closer 🙂


Posted by Chris on August 1st, 2008 in Body, Dome, Electronics, Feet | 3 Comments

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Lift Mech Support Bracket

I replaced the original drawer slider bracket with something a little bigger. It’s cut from a piece of alu angle and makes the whole setup a lot more solid. You can see the original bracket in the background.

The slots make it easy to align on the dome ring

I still need to work on the riser below the periscope assembly and fix it to the lifter.

Posted by Chris on July 24th, 2008 in Dome | 1 Comment

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New Periscope Lift Mech Prototype

I’ve been busy prototyping a new periscope lift mechanism for Artoo.

Some of you may remember my earlier posts and videos demonstrating a mechanism I’d purchased from Daniel, unfortunately I gave up on it a very long time ago. In my opinion the design was flawed from the start and I never did get it to work well, but not for the lack of trying on my part.

Now that I’ve finished adding servos to the dome I was anxious to get the periscope working. I remembered seeing photos of Wayne Orr’s lift mech and thought I’d try and do something similar. Rather than fabricate something new he uses a drawer slide as the basis for the design and a small motor to hoist the periscope up on a platform.

The only catch with Wayne’s implementation is that the periscope and life form scanner mechanisms extend deep into the droids body. I don’t have this luxury as I’ve left the top ring cross bar in place to support the slip ring. So anything I come up with would have to fit within the approximate 10″ height restriction of the dome. The periscope assembly itself is around 6″ tall, so that would be the minimum requirement but if I could get more height that would be a plus as I could add an additional riser or have room for a servo to rotate the periscope once extended.

I’d shopped around and bought a selection of drawer slides, but couldn’t find anything shorter than 16 inches locally. Once I had them on the workbench I realized that it really didn’t matter because whatever extended out would need to be hacked off anyway. In the end I picked a 20 inch slider made by KV because it’s two sliding components worked in lock step, which was important to my design.

I removed the stops and hacked it down to just over 10 inches and cut a small section of the inner slider that would run up and down on the sliding bearing, which itself ran inside main track.

This is the start point with the slider on the right

And it extended all the way to the left. Notice the two part slider has moved and not just one piece.


Unfortunately I have to jump a few steps as I didn’t take many photos of my late night tinkering with the lift platform and various iterations of how I tried to move it.

I’d originally added a roller to the top (similar to Wayne’s) which would guide the rope, but in the final design it wasn’t really needed – and currently acts as the end stop.

Right now I have a fixed motor on the lift platform that pulls itself up with a piece of string attached to the top of the slider. It uses gravity to lower itself back down as the motor unwinds the string.

I’m using a small Vex motor, but basically it’s a servo that can continuously rotate, so I can plug it directly into my receiver without the need for a speed controller.

It looks like the platform is sloping in this photo, but I’m hoping it’s just the angle of the shot 🙂

Here’s a short video of it in action

I have a lot more work to do on this and not sure how well it will work inside Artoo, especially at an angle. My short list of things to work are:

  • Add support to help stop the drawer slide shaking.
  • Extra weight to the platform to help it lower.
  • Make sure it’s all level
  • Limit switches to stop the motor
  • Possibly automate with the PICAXE micro-controller, rather than control it manually via the Futaba transmitter.

In closing I also wanted to mention that I’d experimenting with having a spring loaded wheel on the motor (same position as it is now) that would run along the side of the drawer slide to pull the platform along. I still like the idea and may give it another try later. It definitely had a smoother action and having a wheel on the motor made the lift a little faster – Unfortunately I couldn’t get the spring mechanism to work right.

Posted by Chris on July 22nd, 2008 in Dome, Electronics | 10 Comments

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Dome Pie Panel Control

I’ve almost finished the electronics and programming to control the new hinged pie panels. I’m using a small 18X PICAXE micro-controller coupled with a few buttons on the RF remote.

Check out the video of the panels in action.

I’m also in the process of replacing the veclro that attaches the servos to the dome with something a bit more permanent. The brackets are made from aluminum angle (1.5″x1.5″ and 1/16″ thick).


They’re attached to the top of the hinge and the bolts from the mounting plate that already fix to the dome.

As a side note, if I was doing this again I’d adjust the hinge position a tad. The pies open to the vertical position, but it would have been nice if they’d open a little further, and I figured out (too late) that the lower the hinge is on the pie panel the further it will open – but too far and the hinge will not clear the dome properly.

See Also:

Posted by Chris on July 17th, 2008 in Dome, Electronics | 2 Comments

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