R/C Control types

[Andy Brockway]

Well now that we all know we need an R/C set-up for the EduRC, some of us need help in picking a suitable system.

What might be best for frequency, AM vs FM, connectors, etc?

Thanks,

Andy

[KenWittlief]

there are two groups of RC hobbie controllers, ones specified for model aircraft, and another for RC ground/water vehicles.

so that is the first thing to check - dont use an aircraft 'band' or frequency if there is any chance someone will be flying model aircraft anywheres near your use of the EDU kit - you could cause their aircraft to crash and burn.

Other than that, AM is the least expensive form of hobbie RC - you can get 4 channel systems for less than $100 if you dont get the servos and nicad batteries. Since these transmitter are 1 Watt RF output, and you will only be operating your EDU bot several feet away from the transmitter, AM will be acceptable for every possible appication I can think of (by contrast, RC hobbiest often fly model aircraft a mile away or more - they are the ones who really NEED FM or other more secure and reliable links).

also look for used systems - I have purchased used ones in the past for $50.

It will be interesting to see how many teams pull these hobbie transmitters apart and rewire them to full sized joysticks and control boxes.

[sanddrag]

I haven't seen any "stick type" 4 channel AM systems. Any links?

As for the aircraft thing, it is technically illegal to use the 72mHz band for ground vehicles, so, you have to stick to 27, 48, or 75. 75 is the most common, 48 the least common.

[KenWittlief]

Im not certain, but I think there might be aircraft only frequencies in more that one band. The easiest way to checkis to look at the box, or right on the back of the transmitter - there will be a sticker that says 'aircraft only' or 'ground/water only'.

BTW - if your robot gets airborne going over that ramp, that does NOT make it an aircraft ! :c)

[ttedrow]

For the hams (armature radio operator), there is also 50MHz available for RC equipment.

KD4EGM

[KenWittlief]

50 hertz?! wow! the antenna must be huge! :c)

-Ken Wittlief KG2ET

[ttedrow]

Fixed

[Greg McCoy]

http://www.towerhobbies.com/listings/cat-cat-j.html



And here is a Futaba 4-Channel AM system:

http://www2.towerhobbies.com/cgi-bin...I=LXBCP2**&P=0

$110 with two servos.

[Jay Lundy]

Assuming you aren't a rookie team a crude way of doing it would be to use the old control system and use the pwm outputs from the robot controller as pwm inputs on the EDU bot. Just write a program for the old RC to map the joystick inputs straight across.

Rookies would be out of luck I guess. Either buy something or do it all autonomously.

[sanddrag]

Originally posted by Jay Lundy
Either buy something or do it all autonomously.

I had thought of this before but hadn't really looked into it. We may have uncovered something here. Perhaps this year's game will have significantly more autonomous play. C'mon, the new faster more capable, more program space controller, no edu OI system provided. Hrrm, looks suspicious to me.

Perhaps the scoring is not as dependent on driver control, that's why they didn't give any with the edu. Hey come to think of it, there are no joysticks being provided in the kit either. There must be more to this than just cutting costs.

[Justin Stiltner]

Tower hobbies listing of radios
http://www.towerhobbies.com/listings/cat-cat-j.html

most r/c vendors also refer to "channels" when you buy your radio this is what lets you select the frequency at which it will operate this link specifies the various channels
http://www.towerhobbies.com/help/frequencies.html

for our uses we need surface channels (61-90)

as for brand I recommend Futaba also the tower hobbies brand of radios seems to be constructed by futaba and from what i have seen are good quality. Ni cad batteries are included with most 4 channel systems (good thing I never seem to have enough AA batteries to operate the one radio I have that doesn't use them) or you can use normal AA batteries.

However you may need to make or buy some adapter cables to connect your receiver to the edu-rc I'm not sure of the brand of the cables used by IFI but i think they may be jr style? (its been a few years since Ive bought a radio)



EDIT:
according to IFI page 6
http://www.innovationfirst.com/FIRST...10-15-2003.pdf

The voltage fromt he full-size FIRST Robot Controller PWM OUTPUTS is too high and will damage the EDU RC, voiding your warranty

[sanddrag]

I have 9 RC cars, a plane, and a boat, so I know quite a bit about it. I just hadn't seen a 4 ch surface stick type radio before, now I have. Anyway, most of my radios are basic two channel units made by Airtronics (Sanwa) and they have never given me any problems. I also have a Hitec Lynx and it is alright, never gave any problems just don't like it as much. I have a JR XR3 computer radio that I use in my gas cars and it was defective from the factory. It took a long time for the repairs. If my memory serves me correctly, I believe I had to send it in one additional time. Also, the battery holder broke. My JR computer radio for my plane has been great with no problems. I have a couple Traxxas systems and the receivers are large by today's standards (so is the basic Hitec) and VERY sensitive to moisture. The transmitters have no indicaion of battery level. Other than that, they have been overall good though.

I haven't has any experience with Futaba but maybe that will change soon. All of the new Tower Hobbies (and Duratrax) radios are made by Futaba. HPI equipment is made by Airtronics.

[sanddrag]

Also, can we use aircraft band radios? As in 72mHz? If not, then it looks like the only option is the Futaba Attack 4ch.

Note: I know some manufacturers can convert the radio for surface use for a fee if you send it in.

[Justin Stiltner]

Well... the hardware Will work, buuuuuut the main reason for using surface channels is so you will not interfear with nearby r/c aircraft. My team will probally be using my aircraft radios however I know that noone in my flying club (only one for ~30 miles) has radios on my channel.

If you do decide to use aircraft band radios please check with your local flying clubs as to what channel you could use.

also 4 channels is quite a bit for one person to control and after you get up past 4 channels you get into a situation where switches control the servos between 2-3 or so positions or you may have a dial on 6ch or more radios.

I would go with 2 ground frequency radios of 4 channels each.

[KenWittlief]

I gotta point out that school yards are a popular place for people to fly inexpensive RC aircraft, esp electric or gliders

and if you use your edu bot at school, with an aircraft channel, there is the risk of causing someones model aircraft to crash.

It looks like they came to the conclusion that its cheaper for the teams to buy an inexpensive hobbie R/C system that it was to build them into the EDU robot controller - and its obviously less expensive to use a hobbie transmitter than to use the operator interface that we used last year.

If you are going to buy an hobbie R/C system, please make sure its for ground use, not for aircraft.