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/wti0001p?&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/FIRSTRobotics/pdfs/EDU-RC-2004_Ref_Guide_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. (http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXBCP2**&P=0)

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.

[ahecht]

Originally posted by 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.

No. DO NOT DO THAT! From page 6 of EDU-RC-2004_Ref_Guide_10-15-2003.pdf (http://www.innovationfirst.com/FIRSTRobotics/pdfs/EDU-RC-2004_Ref_Guide_10-15-2003.pdf):CAUTION: Do not connect the R/C PWM IN ports to anything other than a standard radio-control receiver. The voltage from the full-size FIRST Robot Controller PWM OUTPUTS is too high and will damage the EDU RC, voiding your warranty.

[robo-gordo]

quote:
--------------------------------------------------------------------------------
CAUTION: Do not connect the R/C PWM IN ports to anything other than a standard radio-control receiver. The voltage from the full-size FIRST Robot Controller PWM OUTPUTS is too high and will damage the EDU RC, voiding your warranty.
--------------------------------------------------------------------------------

What about using last year's EDU controller? It runs off of 7.2V like the new EDU controller. Maybe we could use that as the radio interface?

While I think it's great that they are going to the R/C controller, I wish they could have made it easier for the teams to adapt. Not everyone has people with R/C experience on their team. I would have no idea what to buy if it weren't for the CD forum. I hope InnovationFirst puts a link up for info and/or purchase on possible R/C controllers.

[sanddrag]

Hrrm. Hooking the old controller PWM out to the new controller PWM in. That would be interesting and might work. However don't try it until you can confirm it won't be harmfult to either controller.

[KenWittlief]

if you have last years edu RC controller, why would you want to connect it to this years RC controller?

when you can use last years controller and this years separately, and have two robots controlled instead of only one?

Im sure someone will start a thread very soon with inexpensive RC systems that can be purchased online for less than $100 - make/model/ website...

Remember the edu bot kit is not intended for mini competitions - its intended to use to learn the basics of programming and simple control theory.

[Damian Manda]

As the only way to remotely operate the EDU RC is now by a hobby radio, I imagine that FIRST had the EDU bot in mind as more of a platform for testing code that does not require input, ie Autonomous Mode. If they had intended the major use to be with a radio, I imagine they would have bundled one with the kit, so that we do not have to buy $100 worth of extra electronics.

Also, I found that most aircraft radios such as these:
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCZC2**&P=7
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCZC2**&P=7
also come in models for 75MHz. Does this make them acceptable for ground vehicles, of do aircraft use this frequency as well?

--Damian

[sanddrag]

I wan't everyone to read this whole thread all the way from the start before they post. We are repeating a lot of things and that's not a good way to keep the forums a well organized place.

[kmcclary]

Originally posted by Justin Stiltner 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 [tower hobbies list] For our uses we need surface channels (61-90) Here are some more explicit lists, including the appropriate freqency flag colors for the antennas:
http://www.hobbypeople.net/rcsource/faqs/freqlist.htm
http://www.rcxotic.com/frequency.shtml

Originally posted by Justin Stiltner according to IFI page 6
http://www.innovationfirst.com/FIRSTRobotics/pdfs/EDU-RC-2004_Ref_Guide_10-15-2003.pdf
The voltage from the full-size FIRST Robot Controller PWM OUTPUTS is too high and will damage the EDU RC, voiding your warranty We MAY be able to fix that with custom interface cables. I think the problem is that the IFI RC either uses 12V pwm pulses instead of 5v, and/or supplies +12v on the power lead. If so, you may only need cables set up with the appropriate current limiting resistors and zeners in the right places to ground to protect the inputs from overvoltages, and/or the positive power lead missing. (A "reversed connector" would have to be investigated and handled, too...)

Don't try it though, until we've checked with IRI about it. The new RC may be wired differently from the old one, too.

I was planning on investigating that soon, unless someone has already done it. Anyone here scope out the old RC's PWM signals yet to see their waveforms and amplitudes?

- Keith

[Justin Stiltner]

Just to give everyone an idea if you really really want to use your joysticks with the r/c gear open up the transmitter.. it uses pots to read the sticks, simply take those out transplant them into your joystick.. or measure the resistance on em and get some extras and extend the wires and your all set. You can buy extra transmitters only for around $45-50 or so. Personally I have been wanting to drive the robot with my r/c transmitter for a long time.

[kmcclary]

Originally posted by Justin Stiltner Just to give everyone an idea if you really really want to use your joysticks with the r/c gear open up the transmitter.. it uses pots to read the sticks, simply take those out transplant them into your joystick.. or measure the resistance on em and get some extras and extend the wires and your all set. You can buy extra transmitters only for around $45-50 or so. Personally I have been wanting to drive the robot with my r/c transmitter for a long time. An EXCELLENT idea Justin, but it depends on the circuitry in the transmitter.

First off, PC Joysticks are set up as roughly 100K RHEOSTATS (actually, I've measured 90K +/-5% on the Flightstick). IOW, you don't get all three wires to the pot out to the connector, only one end, and the wiper. In addition, the WIPERS are common, and there's no extra wires in the cable to bring out the other end of the pots.
In a PC application (as in the robot controller), this variable resistance is used with a capacitor in the interface, to create a R-C timing circuit. (That's "Resistor-Capacitor", not "Robot Controller" or "Radio Control"... Too many RC acronyms around here!!! ;) )

Now if your transmitter is also using an R-C timing circuit (older R/C transmitters used 555 timers too, just like the early PC interfaces), then all you have to worry about is matching the RC constant. If your pot in the transmitter is a different value, simply change its associated capacitor value so that the value R*C is the same as before with the Flightstick's pot, and you should be all set.

However, if your transmitter is a newer, microprocessor controlled one that uses the pots as a Voltage Divider like the robot controller Analog Inputs (one end to +xx volts, one end to ground, and the middle wiper is some fraction of that voltage depending on position), then the pot's value is NOT critical, but you'd need to REWIRE your Flightstick. Not a problem if you have the cash to buy another set of Flightsticks, but remember we will no longer be getting new Flightsticks each year. Veteran teams have to reuse their old Flightsticks from now on, so don't trash them up without replacements!

My recommendation in that case is to either:
A) Buy a cheap set of joysticks for the r/c, or
B) Leave the cords on as-is and add a NEW set of connectors to the sides of the joystick cases and bring out all of the pot wires to them. However, since the joysticks have common wipers, you may also need a switch to separate them.

Unfortunately, current robot build rules FORBID OI joystick modifications of ANY kind, so if you can't use them as is, your best bet is to buy extra Flightsticks or a cheap set of PC joysticks for the transmitter that you CAN rewire.

FYI, I have made a schematic of the Flightstick, and have included the full PC Joystick Standard Connector Wiring as a legend (all four buttons and pots), so when we get that far, I can provide it to everyone to help with their modifications.

A quick question for someone to check that has a working robot and a Dashboard Monitor rig all set up: Which way is it? Is the variable's value in the robot program equal to zero, or 255 when the Flightstick is held at the upper left hand corner and the thumbwheel rolled forward? (That's the minimum resistance value positions.) I'm guessing zero, but I don't remember...

EDIT:
BTW, I also wish to know the directional relationship between program variable's 0-255 value and the 1ms-2ms PWM signal... THAT will help us here, too. Thanks!
/EDIT

Please check all three channels (X,Y,Thumbwheel), so I can also verify my directions. I wish to finish up the legends in my Flightstick schematic before I release it to the public, and still need that data.

Thanks!

- Keith

[Dave...]

Originally posted by kmcclary

EDIT:
BTW, I also wish to know the directional relationship between program variable's 0-255 value and the 1ms-2ms PWM signal... THAT will help us here, too. Thanks!
/EDIT


Keith,

We hooked up the 2004 Edubot controller up to an oscilliscope and found the following:

Frequency of signal: 58.8 Hz (17ms)
Amplitude: 5 V (positive going pulse)
PWM__Pulse width__"fwd/rev"__LED color
1_______.875ms________full rev____RED
127______1.5ms________neutral_____ORANGE
254_____2.07ms________full fwd____GREEN

I hope this helps.

Dave...

[Adam Y.]

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.
Meh. It really does not matter what radio you get. Most people in the battlebots community use aircraft radio by having them retuned.
A stupid question but I am guessing that the use of programable r/c radios is bad.

[kmcclary]

Originally posted by Dave...
Keith,
We hooked up the 2004 Edubot controller up to an oscilliscope and found the following:

Frequency of signal: 58.8 Hz (17ms)
Amplitude: 5 V (positive going pulse)
PWM__Pulse width__"fwd/rev"__LED color
1_______.875ms________full rev____RED
127______1.5ms________neutral_____ORANGE
254_____2.07ms________full fwd____GREEN

I hope this helps.

Dave... Definitely! Thanks! OOC, While you're set up - Does "0" also yield .875ms, or something lower?

Gee, are you up for an experiment??? :D If it's not too much trouble, would you like work together to plot either a chunk, or even the entire transfer function of an 884?

FYI, I wish to EVENTUALLY collect this table at high resolution:
edubot pwm in / data value / edubot pwm out / led color / 884 motor direction & pwm width across a resistor.

Given that and the motor spec sheets, I can then plot all of the transfer functions, motor power curves, etc., so we all know EXACTLY how they behave, how the deadband REALLY works, etc.. If you're game, I can set up an experiment for you and send you the procedure. You then send me the raw data back. I'll plot, analyze, and post the results for everyone.

If not, that's OK. Can you at least take about three equally spaced Value to PWM data points on each side of center, and find out where the 884 LED color change points REALLY are? I just want a clue as to the linearity, and where the 884's REALLY kick in "from neutral". I'll have the students do the rest later once we get a Win2K system at the school so we can try out the EduBot CPU.

FYI, we're just crippled right now or I'd do it myself. It's driving me nuts. We're finally moved into the school this year, but the entire school DISTRICT is one big *MAC* house. NO Windows boxes at ALL. We can't do a thing with programming yet at the school (or even fire up and download the EduBot defaut programs) until we run the politics AND finances to get at least ONE Windows system in and set up to run the MPLAB environment! We have C++ compilers, so we THOUGHT we'd be OK, but because of FIRST's system reqs, we now find we can't crunch and download into the Edubot. That shocked us. No one on our team even has a spare laptop or system capable of the environment to loan us either, so we're scrambling. (And no, I'm not trying to beg here for one.)

Let me know if you're game for this experiment.

Thanks, Dave! And BTW, I LOVE your tagline! :D

- Keith

[Dave...]

Originally posted by kmcclary
Definitely! Thanks! OOC, While you're set up - Does "0" also yield .875ms, or something lower?...

...Gee, are you up for an experiment??? :D If it's not too much trouble, would you like work together to plot either a chunk, or even the entire transfer function of an 884?

FYI, I wish to EVENTUALLY collect this table at high resolution:
edubot pwm in / data value / edubot pwm out / led color / 884 motor direction & pwm width across a resistor. ...

- Keith

Sounds like an experiment for our team. I'll look into bringing the oscilliscope to the school (or maybe they already have one), or bring a few people back to work and perform the task set before us.

The Victors were changed last year (883 to 884) with a decreased deadband. This was to "allow finer motor control", so we would need two different transfer functions/curves.

I'll keep you posted through boring email...

[Justin Stiltner]

Just so you know the way that the rules were worded last year it is only forbidden to modify the joystick that first gave you... IE you were allowed to buy your own flightstick and modify it which we did and were allowed to use(fyi we added an switch to the side of the flight stick so it was pretty noticeable and we never had any problems at regional or nats)

*EDIT*
im going to open up my futaba conquest transmitter tonight and take some pics so we know what kinda setup they use
*/edit*

[caffel]

They want to add the combat robotiers to their target market.
Its that simple.
Notice that the new controller doesn't have the word 'Edubot' on it.

WARNING: do not take the 12v PWM output from any FIRST robot cotrollers and attach it to the new Edubot controller's PWM in.
According to the manual, the PWM in will not handle such a high voltage.

[ChrisH]

Originally posted by caffel
They want to add the combat robotiers to their target market.
Its that simple.
Notice that the new controller doesn't have the word 'Edubot' on it.


Actually I think the combat robotiers are a small market compared to the existing RC market. Do you have any idea how much simpler the new edubot controler could make it to sequence landing gear doors to open at the right speed and in the right order? The Scale guys will go ape once they figure it out.

I haven't actually seen one yet, but I assume it's still a little big and bulky for sailplanes yet. Otherwise you will see auto thermalling planes before too long.

[caffel]

Its less than 3" x 5" and about 5/8" thick.
It weighs nothing.

[kmcclary]

Originally posted by caffel
They want to add the combat robotiers to their target market. Its that simple.
Notice that the new controller doesn't have the word 'Edubot' on it. Oooooh, EXCELLENT point, Charlie! I think you're right!

BTW, slightly off topic, but note that IFI has a "parallel" website to InnovationFirst.com:
- http://www.ifirobotics.com/

It's VERY instructive to explore. I was hoping to catch a glimpse of the new controller there, but they're a few years behind us in CPU tech. (Darn...) IMO, IFI is probably using FIRST to finance the development of their products, and then selling them to the BattleBot et al crowd via IFIRobotics storefront to help extend the product lifetimes, and float the company off season. (IMO a smart business move.) I don't see the EduBot's CPU there yet. The Issac32 is our controller from at least two years back (see the battery screws).

Can any old timers here tell us: Is the "Issac16" from even EARLIER FIRST contests? If so, what year(s)?

Now what *I* want is for us to have access to the IFIRobotics 120A *885* Victors (or *150A* "Thor"!) and some SERIOUS drive motors, and/or the "SC" ("Spin Controller") versions of the smaller Victors, which would be great for things like soccer ball shooters! <drool> :D

Back to topic...

I see on the IFIRobotics website a "PWM Signal Driver". See:
http://www.ifirobotics.com/victor-SC-spin-controller-robots.htm

I'll bet that's the WRONG way though (standard 5V PWM R/C signals up to 12V PWM signals...)

Gee... If the only problem is the peak PWM voltage out of the Robot Controller PWM outputs, that can EASILY be handled with simple resistor-zener voltage clamps on each PWM input of the EduBot. Would only cost a couple of bucks to whip THAT up. LOTS less than even a CHEAP R/C rig!

- Keith

[Joe Ross]

The Isaac 16 is a cut down version of the Isaac 32. However, it was never used for FIRST. It was designed specifically since many battlebot teams don't need so much I/O.

[kmcclary]

I'd avoid AM radios with FIRST robots, and go *only* with FM. FM is much more noise immune, and between the microprocessors, and all the electrical noise from the motors et al, IMHO you're just asking for trouble with an AM rig.

Compare during a lightning storm how static filled an AM radio gets, to the quietness and clarity of an FM broadcast, and think about what the robot is "listening to" for its instructions.

- Keith

[sanddrag]

Innovation FIRST now has links on thier site to this
http://www.robotcombat.com/marketplace_rc-quattro.html
and this:
http://www.robotcombat.com/marketplace_rc-4yf.html

[earthchild]

Meh. It really does not matter what radio you get. Most people in the battlebots community use aircraft radio by having them retuned.
A stupid question but I am guessing that the use of programable r/c radios is bad.

Well, I do Science Olympiad and they had a new rule that said that aircraft bands(72mhz) cannot be used for ground vehicles because of FCC Regulations beginning in May 02. As far as I know, Robot Battles and Battle Bots have also disallowed it too. I doubt FIRST will be any different. :(

:yikes: My first post

[Justin Stiltner]

If you notice, it was said that they have them retuned, it has been illegeal to use aircraft band radios on ground models for years. First and IFI would prefer that we use whatever is approprate for our uses, IE if the edu R/c was in an aircraft, use aircraft band, however they wont make a rule aginst use of it.. because the edu r/c isnt used in competition, and we wont be using the hobbie r/c ssytem in actual compeition or with the real robots.

[Joe Johnson]

From my discussions with my local hobby shop folks, it is my understanding that

#1 Any of the aircraft radios/controllers can be purchased in ground frequencies (typically local shops will not stock them but you can get them in 2-4 weeks)

#2 Most manufacturers have programs where (for a fee) you can get aircraft radios retuned to ground frequencies.

I have not verified this but it has the ring of true truth to it.

Joe J.

[kmcclary]

Originally posted by Justin Stiltner First and IFI would prefer that we use whatever is appropriate for our uses, IE if the edu R/c was in an aircraft, use aircraft band, however they wont make a rule against use of it.. because the edu r/c isnt used in competition, and we wont be using the hobby r/c system in actual competition or with the real robots. Yes, using the aircraft band IS illegal, period. Regardless of a FIRST ruling, DON'T use the aircraft band for your robot under ANY circumstances.

From a practical point of view, remember that in some areas schools often have the only clear field, so many R/C airplane enthusiasts use local school yards after school and on weekends for their flying. If you fire up your edubot on an aircraft band while someone is flying in your school's field nearby, you'll probably crash their plane. Believe me, they'll be pissed off, and your team could even be liable for the damages to a multi-hundred dollar R/C airplane because you were illegally on their frequency.

Considering the exponential growth in the number of schools involved in FIRST these days, the constant elimination of other clear fields in communities from population growth housing/building construction, and the fact that our "hot" time includes almost two months of contiguous weekends, conflict is a non-trivial possibility that will only increase with time.

Therefore, use ONLY ground frequencies. If you crash someone's car, you were both on the band legally (and R/C car are expected to take crashes! :D )...

BTW, regardless of ground frequency, R/C car controls are often only two channel. Given a four or more channel radio if you skip the first two servo channels for your drivetrain you'll protect yourself from most R/C Cars that happen to be on the same frequency (though your grippers may be "jumpy", so watch out). Even if they have more channels, R/C cars normally use the first two servo channels for speed and steering and the rest for switches, which simply turns your motors on to a set value instead of making them behave wildly as they run their car.


BTW, Another advantage of FM radios is that they tend to "lock" onto the strongest nearby transmitter. Since all are roughly equal in power (with full batteries), that means a given receiver normally listens to the closest transmitter of that frequency, which should be yours.


Originally posted by Joe JohnsonFrom my discussions with my local hobby shop folks, it is my understanding that
#1 Any of the aircraft radios/controllers can be purchased in ground frequencies (typically local shops will not stock them but you can get them in 2-4 weeks)
#2 Most manufacturers have programs where (for a fee) you can get aircraft radios retuned to ground frequencies.#1: True. The problem is that most ground freq radio sales are for cars, which are typically only 2-4 channel and use the "knob/trigger" controls, so that's what they stock. Most joystick >=4 chan radios stocked locally are for planes and choppers, all on the wrong band(s). Therefore, you'll probably have to order it. Online ordering is normally the fastest and cheapest, but if you work through your hobby store, you get local sales/service assistance (and maybe a new team sponsor!!!).

#2: Depends highly on the brand, and the model. High end models/brands are often worth the changeover, as they normally have modular transmitter "bricks" which can be swapped out easily in minutes. OTOH, Cheapie rigs normally aren't worth the effort and expense for the entire guts are on one PCB. You'll either basically have to replace the entire board inside to change the transmitter's band, or incur a tech's bench time to change components and realign the radio. Either of these tasks can easily cause the retrofit to exceed the price of a new transmitter.

- Keith

[Justin Stiltner]

I posted this in another thread but its good info...

the folks over at r/c heli base have an white paper on the operation of a normal r/c controller... from this paper i found out that nearly all 3-7 channel non computer radios use the same encoder chip... so that means that your 4 channel ground radio can actually transmit 7 channels of data, all you have to do is free the extra input pins on the encoder (they are grounded) and attach your pot and voltage reference and you now have an 7 channel radio!!
here is the link
http://www.rchelibase.com/radio/index.html

btw ive looked in my radios and it seems that to retune one you would only need to replace the crystal, maby a few coils and adjust a few trimmers if i can get my hands on an frequency counter i may try it myself

[kmcclary]

Originally posted by Justin Stiltner I posted this in another thread but its good info...

http://www.rchelibase.com/radio/index.html

[...] from this paper i found out that nearly all 3-7 channel non computer radios use the same encoder chip... so that means that your 4 channel ground radio can actually transmit 7 channels of data, all you have to do is free the extra input pins on the encoder (they are grounded) and attach your pot and voltage reference and you now have an 7 channel radio!! Be careful... If you're planning on jacking in our standard PC Joystick, watch your pot values. PC Joysticks run from 90K-100K (Flightsticks are about 93K), whereas many R/C pots are closer to 5K. That may be able to be compensated for via a capacitor change in the R/C.

It depends on how they're doing the encoding. Many radios are using a small CPU for multichannel encoding, cause they're CHEAP. But you're right. You should always peek under the hood to see if they give you more channels than are brought out to the case controls. :D

Originally posted by Justin Stiltner I posted this in another thread but its good info...
http://www.rchelibase.com/radio/index.htmlbtw ive looked in my radios and it seems that to retune one you would only need to replace the crystal, maby a few coils and adjust a few trimmers if i can get my hands on an frequency counter i may try it myself Maybe, maybe not. You can't change a 27MHz rig to a 75MHz one. You may be able to shift from 72MHz to 75MHz though. However, be warned that FCC rules state that to legally modify a transmitter in the US you have to either be a Ham (be a licensed Amateur Radio Operator), or hold a First Class FCC License.

There are exceptions under Part 15 of the FCC rules for building VERY low power transmitters, but I was told at the hobby store this week that people who modify R/C transmitters are definitely regulated, even if you're only attempting to switch channels on one to another allocated frequency. That was news to me, and I haven't had time to verify it yet. (It may be an attempt to encourage business...) You USED to be able to at least switch your own crystals within a single band, but now my local shop is claiming that's true only if the radio is designed for user plug-in crystals, and to insure compliance the FCC is now taking a harder stand WRT people who take the soldering iron to transmitter circuitry.

Now home brew encoders are fair game. You can always build your own 8-channel encoder, and pipe it into the already established transmitter brick! If it's worth it to you to save a few bucks, you may be able to take a standard 2-channel car r/c transmitter and some 555 timers, and build your own 8-channel transmitter. You'll still need the receiver though, so I'm not sure it's worth the time. Great learning experience though. Back in college I built my own 8-channel R/C encoder and decoder with an Ace R/C kit. VERY simple circuits.

Hmmm... I wonder... Anyone have a source for cheap prebuilt R/C transmitter and receiver "upgrade bricks" (transmitter/receiver only modules that fit into some modular radio line) to which we can tie our own encoders and decoders? THAT may be a cheap way to go!

- Keith

[Justin Stiltner]

the low end transmitters we are probably working with (non computer radios) that i have seen don't have the transmitter brick you talk about, from what i have seen they are all single board models, no modules of any type, of course different brands may be different. Yes the pot values are different.. however in my link there is also an data sheet telling you the values and even a basic circuit diagram.

To my knowledge changing crystals is still completely legal, and as most radios have a small "shuttle" that the crystal sits in that guides it into the radio it makes it very easy to do so. Rember that some (not saying all are like this but I know some are) model shops, the employees are still amazed that the radio can do what it does, and dont have a working knowlage of the laws and regulations reguarding their modification. Not saying that your hobbie shop is like that but unless you hear it from a very very reputable source i would take most things with a grain of salt.

/edit
The encoder used in my radios(futaba conquest) is an NE5044 this is a specialized enocoder expressly made for r/c use.

[Adam Y.]

They want to add the combat robotiers to their target market.
There will be absolutely no demand for this controller by the robot combat people considering the fact that the only thing the controller had going for it was a secure radio signal. Im not sure about the other controller though. The demand for the older controller will most likely stay high though.