Well I’m almost done with the mechanics of my dome periscope, and I’m turning my attention to the life form scanner, in particular the antenna to raise and lower it.

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

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.

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:

• Dome Pie Panel Servo Setup
• Dome Pie Panel Hinge Experiments
• Discussion of my Pie Panel setup on Astromech.net – some really cool suggestions.

I’ve finished re-installing the pie panels using hinges and servos, so now I’m starting to think again about the gadgets that pop out, like the Life Form Scanner as seen in ESB.

Yesterday at Ace, I found some perforated brass sheet that’s close to the screen material used in the movie. It was $25 and probably big enough to make at least 6 screens. According to the label the product is distributed by K&S Engineering, Stock No. 6412, UPC 6 76116 06412 2.

I’ll have to paint it silver, and the perforated design is not totally accurate but it’s close enough for me.

I’ve also been researching mini/compact power antennas for the Life Form Scanner lift mechanism.

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.

See Also:

• Dome Pie Panel Control
• Dome Pie Panel Hinge Experiments
• Discussion of my Pie Panel setup on Astromech.net – some really cool suggestions.

I had to find a better way to mount the RF remotes to my new Futaba transmitter. I’d originally had them mounted to the sides of Vex transmitter, but really didn’t want to go this route this time around.

I’m still toying with the idea of taking the electronics from the two RF remotes and installing it all in a custom box that would look similar to the Vantec HitchHiker /keycoder, but it’s been almost a year since I blogged something similar, and I’ve yet to do it 🙂

After some experimentation, I went with a very simple acrylic bracket to fix the main RF remote on the front of the Futaba, making it very easy to control with either hand. It does cover the screen, but to be honest it’s rarely used and the bracket is easily removed or lifted.

The bracket is only secured in one spot, the bottom of the Futaba with Velcro for easy removal.

I mounted the second RF remote sideways on the battery compartment on the back of the Futaba. Right now it only has functions that aren’t used often, so I don’t think it’ll be to inconvenient having it there.

The only real catch with this setup is the antennas, occasionally I’ve found it necessary to extend them if I get to far away from Artoo.

Spent the last few days playing with the new Futaba 10C transmitter.

I had to re-calibrate the joysticks with the RoboteQ AX3500, and took the opportunity to review my speed controller setup, and tweak some of the parameters. After I was done looked like something like this –

Control Input: RC
Motor Control Mode: A and B Mixed
Input Adjustment: Logarithmic Strong
Amps Limit: 60
Acceleration: 682 (milliseconds)

I changed the Input Adjustment to Logarithmic (from Exponential) and decreased the Acceleration Delay to 682 ms. This controls how fast Artoo reaches his maximum speed and time to stop. I found that anything lower made him too jerky as he tries to stop on a dime. Both these parameters will make Artoo a little bit more responsive.

On the Futaba I increased the end points on each of the servo channels to 140%, but I suspect I could have left them at 100% due to the joystick calibration on the RoboteQ.

I also had had to reverse the direction on some of the channels.

I’ve managed to get the signal Fail Safe to work on the Futaba. Many of the older Futaba can’t do this, or at least not on all channels. For example, I know the 7 ch 2.4Ghz receiver can only do it on channel 3/Throttle. Which makes sense for airplanes, but not very good for robotic applications.

The default setting on the 10C is “Nor” which will set the receiver to continue to send the last good signal received out to the servo, or in my case the speed controller. This would cause the droid not to stop if I ever lost power on the transmitter or it’s link to the receiver in the droid.

Hoping that I’ll never need to use it, but at least it’s setup now.

As a side note, I’d almost went with an RC setup from Spektrum which offer a separate receiver (BR6000) specifically design for robotics, but it’s only 6 channels and I’m not crazy about the Spektrum transmitter setup, and really liked the extra knobs and sliders on the Futaba 10C.

I’ve also discovered that the extra FM antenna on the 10C is easily removed, and has zero effect in the transmitters operation. I was suprised to even see it installed when I got the unit. I’ll need to make a plug to fill the hole.

My Futaba 10C arrived yesterday. It’s a 10 channel 2.4Ghz FASST spread spectrum capable receiver and a big step up from the Vex transmitter I’ve been using.

It’s the newest receiver from Futaba and positioned right in the middle of their higher-end line up and very competitively priced. I’ve had it on back order at Tower Hobbies since late February and the price was around $580 after a coupon and shipping and handling. Compare this to almost $1,300 for the 12 channel Futaba or $2,200 for the 14 Channel, I think they have a winner on their hands – plus both of which are 72Mhz out of the box and will costs several hundred dollars to go to 2.4Ghz.

A couple of reasons for my upgrade

• I’m tired of having channel conflicts at events and the 2.4Ghz system will fix this problem. For most builders it’s probably not an issue as you’re probably the only bot at an event, but I seem to be at a lot of events where there maybe dozens of RC devices being used, and often run into trouble.
• The Vex transmitter was pretty bulky and hard to hold – it’s done me well and I’ll need to couple the Futaba with a micro-controller for some functionality I had planned for the Vex micro-controller.
• The 2.4Ghz antenna is much shorter and the range is supposed to be better, especially indoors.
• I’ve experience a slight delay/lag when routing the control signals thru the Vex microprocessor – there was no real way around this with the old setup.

The 10C is comparable to the older Futaba 9C that many builders use, but it’s 2.4Ghz spread spectrum out of the box rather than 72Mhz, and it has the extra channel. However the case is all plastic and I’ve already managed to ding it. I suspect the 9CAP will be discontinued at some point as it has issues with upgrading to a full 9-ch 2.4Ghz system. I almost bought the cheaper Futaba 7C ($280 at Tower Hobbies), but the 10C had some extra featured I really liked, in particular there’s a lot more switches, knobs, sliders and dials to use on opening doors and lifting things.

It more of a pro unit and can also switch between 2.4Ghz spread spectrum and regular 72/75Mhz bands using standard Futaba modules, whereas the 7C can only be 2.4Ghz.

The 10C weights in at 2lb 4oz, about the same as my Vex transmitter, which surprised me. The 10C feels much lighter in my hand, but it’s probably because it’s less bulky.

It came with a tiny R6014FS 14-ch receiver, but only 10 of the channels can be used with the 10C. It’s also compatible with with some of the 7-ch Futaba FASST receivers.

A word of warning on the new Futaba receivers. Whereas many previous receivers offered a signal output of 3.0 Volts, the latest generation of ICs has been designed to operate at the lower voltage of 2.7 Volts in order to increase their operational speeds.

My initial tests with the RoboteQ and Dimension Engineering speed controllers was successful, but your mileage may vary and worth checking with the manufacturer before making a purchase.

The plan right now is to replace the entire Vex microprocessor sub-system with either PIC, PICAXE or Arduino micro-controller. I’ll probably directly connect the Futaba receiver to RoboteQ drive system speed controller, and eventually route all the other channels thru the micro-controller to help automate some of the functions.