R/C Control types

[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:

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...I=LXCZC2**&P=7
http://www2.towerhobbies.com/cgi-bin...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/FIRST...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??? 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!

- 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??? 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.