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.

Related:

• Proctor Glove Wheel Casters
• New Larger Casters and Angles
• Caster Fix and Test
• New Wheel Casters
• Fitting Casters for R2’s Center Foot

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.

Related:

• Electrical System Update
• Slip Ring Spin Test
• Slip Ring – Cutting the Frame
• Slip Ring Update
• Slip Rings
• Variable 12-24V Converter

Check it out. Looks very straightforward and is probably very similar to what Scott is doing on the Jedi system to decode the signal.

But for those on a budget and want to try their own hand at connecting the VexTX/RX to a microcontroller without having to hope thru an intermediate RX this could be a good solution.

From the post:

The nice this about this, is that all of the channels are on a single line. This makes it very easy to interface with a microprocessor. A quick review of the PPM format:

• 20 ms total before repeat.
• Each channel is sent as a high signal followed by a 1 ms low. The width of the high signal determines the value sent. A zeroed channel has a width of 1ms. A full positive channel is 1.5ms and a full negative channel is 0.5 ms.
• On the Vex there are six channel (The six peaks that you see) for a total of about 12ms buffered by approximately 8 ms.

To interface with a microprocessor, simply plug the output of the receiver into your microprocessor. Send 5V to Vdd and Ground to Vss. Tie the output of the receiver to 5V over about a 10K resistor. Start measuring pulses on that channel. If you measure at least a 6ms low(The buffer) start recording pulses. (These are your data pulses.) Record all six channels and then decode the length of each pulse.

Update: I just got a message from fellow builder Jamie who has also worked on something similar. Here’s a thread over on the Arduino forum.

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

Related:

• More Periscope Work
• Lift Mech Support Bracket
• New Periscope Lift Mech Prototype
• Periscope Port Detail
• Periscope LEDs and RoboteQ

I’d posted earlier this week that I’d started with a box I made out of aluminum angle, and added a bunch of momentary toggle switches, I then took the guts out of two RF remotes and wired them up inside. Sounds easy but it didn’t feel like it at the time.

The switches are mini (on)-off-(on) momentary, I really wanted to try and get sub-mini’s that just did (on)-off, but I couldn’t find any at a price I was willing to pay. I think the switches I ended up with worked out to be around a $1 each after shipping.

Space is very tight and I really didn’t want to make the box any bigger than absolutely necessary, so I ended up trimming the RF boards down and consolidating the antennas as well as removing the two batteries.

The switches center solder tabs are common and wired together

This is the spaghetti I’d created once I was “done” wiring the switches in

With being generous with the wire I’d forgotten it all had to fit in the box somehow! So I ended up shortening everything down. I also wrapped the backs of the switches and any critical parts of the boards in electrical tape.

I’d tried really hard to fit rechargeable batteries inside too, but ended up with a better solution I think. I ran a cable out and up into the battery compartment of the Futaba to share it’s battery. The cable has a Y split in it for easy removal. The RF remotes come with a 12V battery, but I’ve tested and found that they work very happily on the 10VDC coming from the Futaba. When I double checked my older remotes their batteries had dropped to 6V and were still working fine.

So, that’s my new CTEC keycoder almost done.

Lessons:

• Having the antenna internally limits range so I’ll be moving it outside.
• Total cost was roughly $94 (incl. two RF setups $60, aluminum $10, switches $24), and about 2 or 3 days of work. On the other hand the Vantec Hitchiker product is around $450 – and only works with their special Futaba 75Mhz FM 9CAP, but does have some great features that I will need a cheap micro-controller to replicate.
• My keycoder weights in at 10oz, adding to the already heavy Futaba setup at almost 2.5lb. So I may look into making a plastic box – but the weight of the switches definitely adds up.

One last tricked I learned is that you can have multiple remotes control a single RF receiver. Yep, you heard that right. I’ve been controlling multiple RF receivers with one remote for a while, but had no idea it would work the other way around – each remote doesn’t not need to have the same code even. I accidentally found this out while trying to mate the new keycoders remotes to my droid and found that my older remotes still worked.

Related:

• Mystery Box
• Mounting RF Remotes to the Futaba
• Sound System Demo Video
• Sound System Work
• 12 Channel RF Remote Notes
• What the Beep!

This photo should give it away

More photos in a few days

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

Related:

• Lift Mech Support Bracket
• New Periscope Lift Mech Prototype
• Periscope Port Detail
• Periscope LEDs and RoboteQ

Just like with the periscope the limitation will be the height of the dome. I can’t extend the antenna into the body because of the slip ring cross bar on the top of the body – so anything I come up with has to remain within the 9-10 inches of the dome.

Everyone has a different approach to things. I plan on making my own radar screen and body/cap assembly. My rough sizing calculations have it coming out around 6″, maybe a little shorter, from the top of the radar screen to the bottom of the body.

From studying photos of what other people have done, most seem extend the antenna into the body, but as I said – I don’t have that luxury. But what they also do is un-attach the antenna from the spool/motor housing. This allows you to rotate the antenna 90 degrees saving some space, rather than having the motor adding to the height.

A couple of weeks ago I bought the shortest antenna I could find on eBay hoping it could get it to work, the jury is still out but I suspect I’ll need to find something even shorter.

It’s a Harada MX-1 and once I removed some housing and un-attached the mast from the body this is what I was left with

Unfortunately, the mast was still too long, collapsed it’s close to 7″, and once I stick the LFS assembly on top that’s still too tall.

This is a rough drawing on what the plan is

So I’m still looking for a short (and cheap) antenna. I did find this one (a Metra 44-PW32) which is meant for old school Minis, but the cheapest I’ve found it is $73 – which is more than I want to pay at this point.

The mast is approx. 5 1/2 inches when collapsed which should work if I extend the body of the LFS assembly over it

So if anyone has a lead on something please let me know.

See Also:

• Discussion on Astromech.net
• Life Form Scanner Screen Material