A couple of years ago I started to work on alternate control methods for my droid. I’m happy with my Futaba controller, but it’s pretty bulky and heavy, and it would be nice to be able to hide in a crowd without stuffing it in a restrictive bag.

The secondary goal was also to allow more easier scripting of complex routine that I’d started to build into my droid. You can only do so much with the channels provided on an RC controller.

For a while I thought phone control was the answer and I developed a Windows Mobile application that could interface with my droid and allow simple function.

But I wasn’t happy with driving with a touchscreen. Nothing beats a real analog joystick for fine control. Also, at the time multi-touch input wasn’t available on phones, so as soon as I stopped to click on an action like sound, everything else stopped, e.g. driving.

Communication was via wi-fi on the phone to a small computer onboard Artoo. It worked pretty good until I turned on my regular Futaba radio controller. It also runs on the 2.4GHz spectrum and it crippled my new wi-fi controller. So I shelved the project because most of the events I go to there are lots of other radios.

Then about a year ago I started to dabble with XBEE and using it to control my droid. I went thru a few prototype setups and came up with a very workable solution that I demonstrated at R2LA in October 2010.

At it’s heart are two Arduino micro-controllers that talk via XBEE. The smaller Arduino is tethered to a Playstation controller, with an added LCD screen to help with function selection and setup. It sits on a custom board to tie it all together, which looks bigger in the photo than it really is, but I wanted to show the setup.

The second Arduino is the brains in the droid and interfaces to the speed controllers, servos, and a VMusic2 for sound. I chose an Arduino Mega because it has 4 hardware serial connections and plenty of IO for future expansion. Initially configured to control 11 servos but the board can handle dozens and dozens.

The beauty of using XBee is that there are several different version that run on differnt frequencies (e.g. 2.4GHz, 900Mhz), but are also plug compatible – so switching from one to another is very easy. For my tests I focused on 900MHz as I really wanted to avoid the crowded 2.4GHz spectrum.

Even though the Playstation controller is relatively small compared to my Futaba setup. I still wanted to reduce the size further or allow me to hide it all together. I decided to add additional joysticks which are tethered to the main controller. I can hold them in the palm of my hand, and if I hide the wires in the arms of my jacket or shirt, then nobody is the wiser. In this mode control is limited to dome, drive and triggering sound but that’s good enough for me right now.

Back to R2LA, I couldn’t take down my full droid, so I built up a demo bot using all the same functions and components as a basic droid, like motor controllers, sound, dome rotation etc. I even had a little Artoo mounted on a servo to simulate dome rotation 🙂

Okay, the NPCs and AX3500 was total overkill but it was all I had on hand.

I drove it in from the car with the controller hidden and the extension joystick in my hand. People thought it was an autonomous robot and didn’t quite understand what or why it was there. They soon realize it was with me, but very few people spotted the controllers and they continued to talk to me thinking it was autonomous (while I drove it around the room.) When I finally told people they were very surprised.

I’ve not touched the project since last October, but this week I finally got it out and worked on testing it in my droid.

I’m going to use my dual receiver board I built a few years ago, it will allow me to switch back and forth between my Futaba and XBEE controller without rewiring. 🙂

Early tests on a full size droid are looking good, the little analog sticks aren’t as precise as those on the Futaba but I can live with it for now, especially if I can switch back and forth. And being able to totally hide the controller is awesome!

Stay tuned for more details soon.

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.

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.

See Also:

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

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

For those of you following along from the start you’ll know that I’m using the Vex System to control my droid.

Vex was originally a joint venture between IFI Robotics and RadioShack, but they parted ways back in 2006 and IFI took full control of the Vex Labs company.

Recently Vex Labs introduced the second generation Vex system called Vexplorer. On the surface it’s a simpler (and cheaper) design, but does have some cool things in the starter kit like a 2.4 GHz remote camera. The remote transmitter is a lot smaller too, more like a game controller.

It maybe worth checking out if you’re shopping around for a programmable micro-controller to run your droid.

Looks like the micro-controller is NOT programmable. So I can’t see this being much use beyond using it as a standard RC setup.  VexLabs has dubbed the new controller Vex-Blue vs Vex-Red for the original system I use.