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.

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.

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.