Is Vex Receiver compatible with other RC gear ?
pogo
so cheap these days.
I had the Vex kit for one night, and then took it back when I realized the
only thing there was enough parts for was the one and only thing they showed
how to build --- too much for the money at the time. Now they're cheap as
can be.
From what I remember, though, the receiver had non-standard connectors and
was designed to only plug into the main processor. Does that sound right ? I
only want it for a cheapo RC transmitter/receiver that I will use very
infrequently.
Thanks for any help .
JCD
Curt Welch
> I'm thinking of getting a Vex Transmitter/Receiver from eBay because
> they're so cheap these days.
>
> I had the Vex kit for one night, and then took it back when I realized
> the only thing there was enough parts for was the one and only thing they
> showed how to build --- too much for the money at the time. Now they're
> cheap as can be.
>
> From what I remember, though, the receiver had non-standard connectors
> and was designed to only plug into the main processor. Does that sound
> right ?
The RF receiver unit (small yellow box) uses a yellow 4 wire cable with
standard 4 pin module phone plugs on it. (the ones you find on handsets,
not the six pin connectors used for phone lines).
I just replaced the cable that came with VEX with the handset cord from my
desk phone and it didn't work. The phone receiver had the wires crossed
(pin 1 to 4, 2 to 3, 3 to 2, and 4 to 1) where as the VEX code had them
straight through (1 to 1, 2 to 2, etc). But the connectors are the
standard 4 pin module connectors.
I haven't worked with normal R/C gear so I don't know for sure what type of
protocols and cables are standard in the R/C world but I believe this unit
is something special designed just for the VEX. I believe the signal from
the RF module is some sort of standard serial protocol but I'm not sure
about that. It might just be a fairly normal pulse width modulated R/C
signal for all I know. The R/F module doesn't have separate power so it
get's it's power from this same 4 wire cable. I assume two wires are power
going to the RF module and 2 are a serial signal of some type coming back
to the controller.
I believe the connectors for the servos are also non-standard though the
signals I believe are standard. I think the connectors might be same as
one of the two R/C servo standards but I believe they are wired backwards
on the VEX - that is, the servo is the female and the controller is the
male - I believe (but am not sure) that the standard in the RC world is the
other way around. So, without building custom cables, you can't plug the
VEX hardware (controller or servos) with normal R/C gear. But I think all
it would take is a simple custom cable.
Don't normal R/C receivers include both the function of the R/F receiver
and the decoder to send the separate signals to each servo? With the VEX
hardware, the yellow box R/F module doesn't generate servo signals for each
channel. You must use the processor module to do that for you (or something
else to do the function for you). So you can't just buy the VEX RF module
to act as a cheap R/C receiver. You would have to buy both the RF module
and the processor module before you can directly drive servos.
> I only want it for a cheapo RC transmitter/receiver that I will
> use very infrequently.
>
> Thanks for any help .
> JCD
I don't much about the RC world, but I hope that helps....
--
Curt Welch http://CurtWelch.Com/
cu...@kcwc.com http://NewsReader.Com/
BobH
> I haven't worked with normal R/C gear so I don't know for sure what type of
> protocols and cables are standard in the R/C world but I believe this unit
> is something special designed just for the VEX. I believe the signal from
> the RF module is some sort of standard serial protocol but I'm not sure
> about that.
The signals used between the receiver and the individual servos is a
simple 5 volt logic compatible PWM signal. The repeat rate of the signal
is about 50 Hz or once every 20mS. The rep rate is not critical. The
information is in the width of the positive going pulse. The center
position for servos is a 1.50 mS wide pulse. Minimum and Maximum widths
are about 1.0 - 2.0 mS, different manufacturers use slightly different
limits. I have never seen less than 0.900 mS or more than 2.10 mS on a
modern radio.
>
> I believe the connectors for the servos are also non-standard though the
> signals I believe are standard. I think the connectors might be same as
> one of the two R/C servo standards but I believe they are wired backwards
> on the VEX - that is, the servo is the female and the controller is the
> male - I believe (but am not sure) that the standard in the RC world is the
> other way around. So, without building custom cables, you can't plug the
> VEX hardware (controller or servos) with normal R/C gear. But I think all
> it would take is a simple custom cable.
The standard RC servo cable is 3 wires, +Batt, ground and signal. Some
of the
monster servos are coming with separate power leads so that you don't
have to
pull all of the motor current through the receiver power distribution,
but they are the exception.
> Don't normal R/C receivers include both the function of the R/F receiver
> and the decoder to send the separate signals to each servo?
Yes.
> With the VEX hardware, the yellow box R/F module doesn't generate servo
> signals for each channel. You must use the processor module to do
> that for you (or something else to do the function for you).
If the data stream looks like a standard RC transmitter data stream,
this is easy to do in a microcontroller with a couple of timers. There
is probably no reason to assume that it does though.
Good Luck,
Bob
pogo
news:20070803185746.603$t...@newsreader.com...
Hello Curt and thanks for the info. Also, thanks to Bob H. who responded to
this.
I just took a quick look-see thru eBay and along with your comments managed
to refresh my memory about RC gear enough to know that the Vex kit is not
what I need. The RC receivers that I am used to allow the servos to plugged
directly into them --- which is what I am looking for. I don't want the
extra trouble of *requiring* a processor in addition to the receiver - I
want to be able to substitute the R/C receiver *in place of* a processor, so
the Vex setup is not what I need.
Anyway, thanks a ton for your help! It made my decision easier and faster.
Thanks !
JCD
Buddy Smith
> The RF receiver unit (small yellow box) uses a yellow 4 wire cable with
> standard 4 pin module phone plugs on it. (the ones you find on handsets,
> not the six pin connectors used for phone lines).
Correct. There is a GND, +5V, and signal. The other wire is "tether"
which is used to tell it it's operating from a tether.
The signal is a "standard" servo signal, it's just 6 of them in a row.
ttyl,
--buddy
Curt Welch
Ok, cool. I had forgotten about the fact you could tether the transmitter
dirrectly to to the controller.
How does it know which channel is which? Is there some type of
start marker in the signal or is it just the signal spacing where there's a
longer delay between groups than between pulses in the group?
I've got the VEX hardware but I've never worked with standard R/C equipment
and I don't know a lot about what is available in that market, so I too
have some questions maybe someone can help me with...
Is this VEX format the standard for R/C gear as it's transmitted over the
air? Is it FM or AM or something else?
Does the VEX transmitter use the same standard as all other R/C gear so you
could use it to control normal R/C devices or use other standard R/C
transmitters to control a VEX device?
And is there one standard in the R/C word for hobby stuff for what is
transmitted over the air or are there multiple standards?
Anyone ever create a digital system for the hobby market instead of using
these analog pulse width system or is all the R/C world just using the old
pulse width system?
BobH
> Buddy Smith <nullset....@dookie.net> wrote:
>> Curt Welch <cu...@kcwc.com> wrote:
>>
>>> The RF receiver unit (small yellow box) uses a yellow 4 wire cable with
>>> standard 4 pin module phone plugs on it. (the ones you find on
>>> handsets, not the six pin connectors used for phone lines).
>> Correct. There is a GND, +5V, and signal. The other wire is "tether"
>> which is used to tell it it's operating from a tether.
>>
>> The signal is a "standard" servo signal, it's just 6 of them in a row.
>
> Ok, cool. I had forgotten about the fact you could tether the transmitter
> dirrectly to to the controller.
>
> How does it know which channel is which? Is there some type of
> start marker in the signal or is it just the signal spacing where there's a
> longer delay between groups than between pulses in the group?
In standard hobby radios, it is just a long "sync period" between
pulses. Each channel follows the sync period in sequence. The sequence
is not standardized between manufacturers.
If you look at the composite signal on a scope it will look something
like this:
|<------------ 1 Frame ------------------------------------->|
_ _ _ _ _ _ _
_________| |___| |_____| |_____| |____| |____| |_____| |_______________|
| T1 | T2 | T3 | T4 | T5 | Tn | Tsync
T1..Tn are the periods of each pulse that will route to the individual
servos. N may be as small as 1 or as high as 10. The frame period is
about 20mS. The difference between the sum of all of the channel times
and the frame time is the sync time. On "computer" radios I have looked
at, the frame time is constant with the differences going into the sync
period, The analog radios used a constant period sync time and the frame
time varied as the sum of all the channel periods + the sync time. The
decoders are made with parallel in/out shift registers or Johnson
counters (see CD4017). The pulse train shown clocks the shift register
or counter, while an RC time constant watches for a long pulse to reset
the counter or parallel load a 1000000 pattern into the shift register.
Individual servos are connected to the output bits on the counter or
shift register. This arrangement lest you drive an 8 channel
receiever/decoder with a 4 channel transmitter and not have stuff get
confused.
What I have shown here is an approximation. The polarity of the signals
varies with the manufacturers implementation, and it has been a couple
of years since I looked at one and I may have swapped it. The basic
content and format is right though.
> And is there one standard in the R/C word for hobby stuff for what is
> transmitted over the air or are there multiple standards?
Mostly one standard with the PWM/PPM gear. For FM gear, some vendors
deviate + during a pulse and others deviate -, but the timing is pretty
standard. The signal format is generally referred to as PPM, but it
looks like PWM to me.
> Anyone ever create a digital system for the hobby market instead of using
> these analog pulse width system or is all the R/C world just using the old
> pulse width system?
Yes, all off the major vendors have what is called PCM which is actually
a digital code transmission. As far as I know, all of the PCM formats
are manufacturer proprietary and not released. I have seen web sites
where people have been reverse engineering the formats, but all are
works in progress as I remember.
Good Luck,
Bob
BobH
> Curt Welch wrote:
>> Anyone ever create a digital system for the hobby market instead of using
>> these analog pulse width system or is all the R/C world just using the
>> old
>> pulse width system?
>
> Yes, all off the major vendors have what is called PCM which is actually
> a digital code transmission. As far as I know, all of the PCM formats
> are manufacturer proprietary and not released. I have seen web sites
> where people have been reverse engineering the formats, but all are
> works in progress as I remember.
I forgot to add that the new spread spectrum 2.4GHz radios are probably
sending a digital code transmission. I would bet a beer that they are
using the numerous 802.15.4 chips, but would enjoy sharing a beer with
somebody who has been inside one and could tell me.
Bob
Curt Welch
Thanks Bob for all the info!
Andrew Schwartz
Futaba receiver and it works fine. very inexpensive way to get a
transmitter and crystals.
Andy
"pogo" <po...@nopogo.com> wrote in message
news:zSRsi.493$O_6...@newsfe06.lga...
Too_Many_Tools
Good discussion guys.
When I was looking at Vex, it was apparent that significant
engineering had gone into the product to make it non standard and
specific only to the Vex product line....meaning that you would have
to buy anything more you might need from Vex...at very high prices.
I suspect that the transmitter is stock (Futaba?) and the receiver has
been modified to make it Vex specfic.
Personally I would go with a standard transmitter and receiver
set...life is too short to reverse engineer every product
interface....especially one which is dependent on a surplus source
that is rapidly drying up and from a manufacturer who is going out of
their way to make your life difficult.
TMT
Curt Welch
I wonder how much of that approach was the VEX/FIRST guys and how much was
Radio Shack? I suspect it was mostly Radio Shack (or the intent to try and
sell it through a retail store like Radio Shack) but don't know any of the
inside scope on the history.
Too_Many_Tools
>
> - Show quoted text -
I too have thought about who was responsible.
I know it did not come free...someone spent significant engineering
time to make sure that almost everything in the system was unique to
their criteria..to lock the user into the sole source pricing...and
that cost money and time.
I do know that because of that shortsightedness I do not use Vex
related items unless absolutely necessary...again life is too short to
waste time dealing with hardware and interfaces designed to waste my
time..and to nickel and dime my budget.
TMT
Too_Many_Tools
* the clothing or worn in bracelets.
*
* In Europe, this system has already been used at track and field events
* where the competitors wear the device attached to their jersey. This
* provides their coordinates during each event and can be used for the
* timing of races.
*
* Widespread use among sports figures could go a long
* way toward popularizing the chip among the young.
*
* According to microchip researcher Terry Cook, U.S. military recruits are
* also being introduced to the bracelet, just as Marine recruits at Parris
* Island helped test the military's Smartcard prototype.
*
* Eagle Eye Technologies of Herndon, Virginia is marketing a microchip
* embedded in a sportswatch to be worn by Alzheimer patients who have a
* tendency to wander. When the patient strays from home, Eagle Eye calls up
* an orbiting satellite, which "interrogates" the patient's microchip to
* determine the patient's position to within the length of a football field.
*
* Sounds protective? Relevance recognizes the bonafide use of this
* technology but we continue to harbor reservations about its potent
Curt Welch
IF THEY NEVER APPLIED FOR A JOB WITH THE COMPANY.
Several of the 451 people who filed claims had been IN PRISON at the time
of the company's alleged discrimination, but the commission FORCED the
company to give them WINDFALL PAYOUTS anyhow.
Under the Americans with Disabilities Act, a strip club was shut down
because its stage area was "not accessible to a stripper in a wheelchair."
]
* to extend universal healthcare benefits, to guarantee welfare reform, to
* improve public education...the list of crises and problems to be fixed
* seems to be never-ending.
*
* Implement National ID Cards, they promise, and a bright, secure future
* can be ours. [snip]
*
* Recently, treasonous federal courts have ripped to shreds over 200 years
* of American constitutional law, ruling that, "A person's property has no
* constitutional rights." So-called "anti-terrorist" legislation makes
* possible the immediate arrest and imprisonment of any and all persons
* *suspected* of being a "terrorist." These persons shall be deemed a risk
* "to internal security."
*
* A persons' home, auto, bank account, and other property shall be seized.
* This will be accomplished using _forfeiture laws_, originally designed
* to stop drug dealers and kingpins, but now used across America by Gestapo
* pol
Curt Welch
countries where the allies may want to gain some advantage (especially
access to cheap resources) and administrations (like Nicaragua's Sandinista
government) which do not fit an American-dominated world order.
The third observation is that telecommunications organizations - including
the telephone companies - are not blameless in all of this.
These companies, to which people pay their monthly bills believing that
the phone calls they make and the faxes they send are secure, should well
be aware of the wholesale interception of 'private' communications that
has been occurring for decades.
Yet they neither invest in encryption technology nor insist that organizations
such as the Washington-based Intelsat Corporation provide encryption.
They do not let their customers know that their international communications
are open to continuous interception. Wittingly or unwittingly, this lack of
action assists large-scale spying against the individuals, businesses and
government and private organizations that innocently entrust their
communications to these companies.
ECHELON is a staggeringly comprehensive and highly secret global spying
system. Around the world there are networks of spy stations and spy
satellites which can intercept communications anywhere on the planet.
P18
Over the last 10 years a lot has been heard in New Zealand about the dangers
of 'bureaucratic capture', about senior officials controlling their min
BobH
in the world, just as they do for written messages.
It has nothing to do with whether someone is deliberately tapping your phone,
simply whether you say a keyword or combination of keywords that is of
interest to one of the UKUSA agencies.
P47
The keywords include such things as names of people, ships, organizations,
countries and subjects. They also include the known telex and phone numbers
and Internet addresses of the individuals, businesses, organizations and
government offices they may want to target.
The agencies also specify combinations of these keywords to help sift out
communications of interest.
For example, they might search for diplomatic cables containing both the
words 'Suva' and 'aid', or cables containing the word 'Suva' but NOT the
word 'consul' (to avoid the masses of routine consular communications).
It is these sets of words and numbers (and combinations of them), under a
particular category, that are placed in the Dictionary computers.
The whole system was developed by the NSA.
P51-
The only known public reference to the ECHELON system was made in relation to
the Menwith Hill station. In July 1988, a United States newspaper, the
Cleveland Plain Dealer, published a story about electronic monitoring of
phone calls of a Republican senator, Strom Thurmond. The alleged monitoring
occurred
Curt Welch
*
* And based on this assumption, the French Police conducted their own
* interviews, but my friends happily knew me well enough. When they
* found out they had been misled, the French Police called everybody
* back and apologized.
*
* Nevertheless, an enormous amount of effort was put out in France to
* go and talk to all these people and a similar thing was done in
* Germany. This was not all free. It was hideously expensive. And the
* repercussions --- I don't know what they are yet. I haven't talked
* to all the families.
*
* In the end, everything I received back was essentially destroyed.
*
* My computer was broken.
*
* All my prints were badly damaged.
*
* Some of them had been wadded up and thrown away and then taken out
* of the waste basket and flattened out again.
It cost Sturges $100,000 in legal fees, loss of major clients, much income,
seizure of his life's work, the tools of his trade, and made him feel
depressed about his life's work.
Our government uses Orwellian terror tactics
to control the politically incorrect:
Jock Sturges:
At my lowest point in this affair, I almost decided to jump
from the San Francisco bridge. I had stopped my car.
----
# FBI
# 450 Golden Gate Avenue
# San Francisco, CA 94102
#
# Dear Sirs, 7/6/90
#
# I am responding to a report on CNN last night.
#
# They showed a photographer, Jock Sturges, and some of his unpublished
# photos, and said the FBI confiscated them. According to the report, no
# sex was involved in the photos, he's a reputable ph
Buddy Smith
----
: "Lock 'em Up", The Washington Post, 5/19/96
:
: Harvard economist Richard Freeman thinks it's ironic that proportionally
: more people are in jail in the Land of the Free than in any other nation
: on Earth. The U.S.A. has FIVE TIMES the incarceration rate as the United
: Kingdom, Germany or France.
:
: Freeman says that prison is emerging as America's answer to the "reduced
: demand for less-skilled male workers." European countries deal with unem-
: ployable guys by putting them on the dole, he says.
:
: In this country, we throw them in jail after they commit a crime to survive.
----
Factoid: poor black households' telephone usage is dramatically different
from other groups and can be picked out statistically using just the time,
length, and number of calls per telephone.
[ page 61, "The Rise of the Computer State", David Burnham, 1984 ]
The Los Angelos Police said they kept beating Rodney King while he
was rolling around in pain on the ground was because he wasn't
following orders AND they thought he was on PCP. [What???]
"The only thing Rodney King was guilty of was resisting slaughter"
---Jimmy Breslin
----
July 1st, 1997, News 4 NBC TV NYC: Police Commissioner Bratton says an officer
who shot a black youth dead---in the bac
pogo
--- including phone calls --- gets its own daily summary file regardless
of content.
That's what I did (for company Internet traffic) when activities made it
prudent to put someone on the individual 'watch list'.
(For example, "Bob Brain".)
----
Then there was a manager under heavy stress, who was pissed at top management,
knew his department had a good chance of getting cut in the next several
months, then the talk turned to guns...
This was a very long diatribe; only a little is shown here because I got
tired re-writing the words so it's not literally their traffic anymore.
In email he sounded like a major flake. In person he sounded normal.
***************** BEGIN OF JOBTALK EXCERPT *******************************
An oddity: a Xxxxx Yyyyyyy is getting stressed out by his area's upcoming
personnel cuts; he's made a presentation to Mr. Cheese for project ideas
that might avoid him being cut. This stress is normal, but suddenly talk
about him being a gun-nut came up. It doesn't appear to be a problem, but
I thought I'd let y'all decide for yourselves. ---guy
> First, I am having a real bad day. I am dealing with it well though.
> In fact I admire myself for it. In the past several weeks I've begun
> to respect myself highly for putting up with all the obstacles and
> bullshit I run into EVERY*FUCKING*DAY. 99% of all other people don't
> have my strength and will. Which is why people fear me or find me
> threatening.
>
> I've got an employee w
BobH
* enter and leave the United States each day, lawyers familiar with the
* intelligence agency consider the decision to mark a significant increase in
* the legal authority of the government to keep track of its citizens.
*
* The mission of the NSA is to eavesdrop on electronic messages of foreign
* governments and protect the electronic communications of the United States.
* To accomplish these goals, the agency has SEVERAL THOUSAND listening posts
* around the world and a HUGE bank of computers in its heavily guarded head-
* quarters at Fort George Meade, MD, near Washington.
*
* A Special Senate Intelligence Committee report in 1975 found that the
* computer system functioned like a "GIANT VACUUM CLEANER" capable of
* sweeping in ALL ELECTRONIC MESSAGES to and from the United States.
* [snip]
*
* Mr. Jabara is a lawyer who for many years has represented Arab-American
* citizens and alien residents in court. Some of his clients had been
* investigated by the FBI.
* [snip]
*
* The FBI's investigation of Mr. Jabara, who has not been formally accused
* or indicted for any crimes, began in August 1967. In November 1971, the
* Government acknowledged, the FBI asked the NSA "to supply any available
* information" about the lawyer that "might come into its possession during
* the course of its foreign intelligence activities".
*
* As a result, the NSA provided the FBI summaries
* of six overseas conversations of Mr. Jabara.
*
* In earlier court proceedings, the FBI acknowledged that it then
* disseminated the information to 17 other law-enforcement or intelligence
* agencies and three foreign governments.
* [snip]
*
* John Shattuck, Washington director of the ACLU, who represented Mr. Jabara
* said "It is difficult to imagine a more sweeping judicial approval of
* government action in violation of constitut
Curt Welch
a car in LA at night. This was somewhere around the time of the Rodney
King beating. I was watching C-SPAN. Some sort of police officers
association meeting...
It was amazing how often he was pulled over, and the cheesy reasons the
officers gave.
"Your tail light was broken"
He got out with the camera still on, showed the tail light was fine, and
asked the officer what he was talking about.
"Oh, you're right. Sorry."
He was pulled over again and again and again.
----
The New Jersey State Police admitted they were targeting black drivers.
Pulling them over, and searching their vehicles inch-by-inch.
----
* The New York Times, December 14, 1995, Philadelphia, Pennsylvania
*
* Six officers - five whites and one Asian-American - have plead guilty
* to corruption charges, including illegal searches, lying under oath
* and planting false evidence.
*
* The guilty pleas have led to a review of more than 1,600 arrests of
* mostly black and Hispanic suspects that were made by the officers
* from 1987 to 1994.
*
* Fifty-six convictions have already been overturned.
----
* The New York Times, November 26, 1995
* "Several Blacks Sue Beverly Hills, Asserting Bias by the Police"
* by Kenneth B. Noble
*
* Saying they had been victims of a callous police force, six blacks
* filed suit this week against the City of Beverly Hills, including
* the Police Chief and the Mayor.
*
* The plaintiffs include a handyman at a local church and the mother
* of two young boys, all of whom say they or their families were
* singled out because of their race.
*
* The handyman who works at an Episcopal church here, said that o
pogo
*
* [The instrument is implemented and pictured] The ARS instrument was
* selected to receive one of R&D Magazine's 1995 R&D 100 Awards; the
* awards are given annually for the one hundred most significant
* technical innovations.
*
* The technique is suitable for any noninvasive identification of fill
* materials in sealed containers.
But no, massive monitoring of people suspected of no crime is the
appropriate response.
They were just warming us up for the CALEA telephone monitoring bill.
----
Here is part of the story on why we let trucks full of cocaine and
heroin just roll right into the United States.
* "Diminished U.S. Role Below Border Plays Into Traffickers' Hands"
*
* By Molly Moore and John Ward Anderson
* Washington Post Foreign Service
* Sunday, September 8 1996; Page A01
* The Washington Post
*
* Due to their new 'Mexicanization policy':
* Mexico became the main gateway into the United States for illegal
* narcotics, with the amount of cocaine making the journey climbing to
* an estimated 210 tons last year.
*
* Mexico's drug arrests plunged nearly 65 percent, from 27,369 the year
* before the policy changes to 9,728 last year, according to data that
* the Mexican government supplied to the State Department.
*
* Cocaine seizures in Mexico were cut in half, dropping from more than
* 50 tons in 1993 to slightly more than 24 tons in each of the last two
* years -- the smallest amounts since 1988, Mexican government figures
* show.
*
* The GAO report charges that Mexico's greatest problem is, in
* fact, the "widespread, endemic corruption" throughout its law
* enforcement agencies. Earlier
bubbajoe
http://www.roboticscommunity.com/robotics/Re-Is-Vex-Receiver-compatible-with-other-RC-gear-18475-.htm
:
the vex radio is basicly a futaba 6EXA from my examination of the radio
all the internal boards the carry the same part numbers as a futaba 6EXA
so I tested it with futaba 127 on 72mhz as well as 75mhz recievers and it
works flawless and can also be converted to 2.4 ghz
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bubbajoe
http://www.roboticscommunity.com/robotics/Re-Is-Vex-Receiver-compatible-with-other-RC-gear-18475-.htm
:
carry futaba part numbers and I have tested them with futsaba 127
recievers and they work fine
-------------------------------------