We Need Help!!!!!!!

FIRST General Forum
1

Posted by Travis Covington.

Student on team #115, MV ROBOTICS, from Monta Vista High School and Hitachi Data Systems - 3com - NASA Ames.

Posted on 4/2/2000 10:55 AM MST

Hello everyone!

Ca regional went well. Alot of teams are really good.
Look out for teams 330, 60, and 64. Oh and 115 if I
can get some help with this problem we are having.

This is the problem. During practice rounds we were
driving around picking up balls without a hitch.
Everything worked great. But when we were in our
second qualifying match the left side of our drivetrain
just would not work. It would act as though the fuse
went. After a few seconds it would work again but it
never worked the whole match, it just got worse. This
happened the rest of competition and randomly we were
still ranked 12th.

So, we replaced everything…speed controller, new
drill motor, switched the connection on the fuse panel,
realined the chains, lubed chains, and everything else
we could think of…even changing the gear ratio. None
of these things helped at all.

we found out that it was drawing about 10 to 15 more
amps than the right side. But after we switched
everything AGAIN it was the same, it drew the same
current, until of course we went out on the field where
it didnt work after about 30 seconds.

During this whole process we were taking advice from
practically every enginner from other teams as well as
a couple of crew people from FIRST. None of them had a
solution. They had ideas which we tried, but nothing
worked.

Strangest of all things…we went outside after we had
frozen up in our first final match, and it worked with
no problems. We drove it around for 5 to 10 min.
Nothing went wrong.

I am wondering if the control box could be bad. I mean
something like the competition port. I was also
wondering if a bad fuse panel could cause this.

Any ideas??

Thank you, and look out for us in Fla. (if we fix this
prob.)

Travis Covingt

2

Posted by Brian Savitt.

Student on team #56, Robbe Xtreme, from Bound Brook High School and Ethicon Inc…

Posted on 4/2/2000 11:04 AM MST

In Reply to: We Need Help!!! posted by Travis Covington on 4/2/2000 10:55 AM MST:

We had the same problem with our drive train and we opened up our drill motors and found that the wires werent sodered well so we resodered every wire and everything works wonderfully: Hello everyone!

: Ca regional went well. Alot of teams are really good.
: Look out for teams 330, 60, and 64. Oh and 115 if I
: can get some help with this problem we are having.

: This is the problem. During practice rounds we were
: driving around picking up balls without a hitch.
: Everything worked great. But when we were in our
: second qualifying match the left side of our drivetrain
: just would not work. It would act as though the fuse
: went. After a few seconds it would work again but it
: never worked the whole match, it just got worse. This
: happened the rest of competition and randomly we were
: still ranked 12th.

: So, we replaced everything…speed controller, new
: drill motor, switched the connection on the fuse panel,
: realined the chains, lubed chains, and everything else
: we could think of…even changing the gear ratio. None
: of these things helped at all.

: we found out that it was drawing about 10 to 15 more
: amps than the right side. But after we switched
: everything AGAIN it was the same, it drew the same
: current, until of course we went out on the field where
: it didnt work after about 30 seconds.

: During this whole process we were taking advice from
: practically every enginner from other teams as well as
: a couple of crew people from FIRST. None of them had a
: solution. They had ideas which we tried, but nothing
: worked.

: Strangest of all things…we went outside after we had
: frozen up in our first final match, and it worked with
: no problems. We drove it around for 5 to 10 min.
: Nothing went wrong.

: I am wondering if the control box could be bad. I mean
: something like the competition port. I was also
: wondering if a bad fuse panel could cause this.

: Any ideas??

: Thank you, and look out for us in Fla. (if we fix this
: prob.)

: Travis Covingt

3

Posted by Nate Smith.

Other on team #66, GM Powertrain/Willow Run HS, from Eastern Michigan University and GM Powertrain.

Posted on 4/2/2000 2:58 PM MST

In Reply to: Re: We Need Help!!! posted by Brian Savitt on 4/2/2000 11:04 AM MST:

: We had the same problem with our drive train and we opened up our drill motors and found that the wires werent sodered well so we resodered every wire and everything works wonderfully: Hello everyone!

: : Ca regional went well. Alot of teams are really good.
: : Look out for teams 330, 60, and 64. Oh and 115 if I
: : can get some help with this problem we are having.

: : This is the problem. During practice rounds we were
: : driving around picking up balls without a hitch.
: : Everything worked great. But when we were in our
: : second qualifying match the left side of our drivetrain
: : just would not work. It would act as though the fuse
: : went. After a few seconds it would work again but it
: : never worked the whole match, it just got worse. This
: : happened the rest of competition and randomly we were
: : still ranked 12th.

: : So, we replaced everything…speed controller, new
: : drill motor, switched the connection on the fuse panel,
: : realined the chains, lubed chains, and everything else
: : we could think of…even changing the gear ratio. None
: : of these things helped at all.

: : we found out that it was drawing about 10 to 15 more
: : amps than the right side. But after we switched
: : everything AGAIN it was the same, it drew the same
: : current, until of course we went out on the field where
: : it didnt work after about 30 seconds.

: : During this whole process we were taking advice from
: : practically every enginner from other teams as well as
: : a couple of crew people from FIRST. None of them had a
: : solution. They had ideas which we tried, but nothing
: : worked.

: : Strangest of all things…we went outside after we had
: : frozen up in our first final match, and it worked with
: : no problems. We drove it around for 5 to 10 min.
: : Nothing went wrong.

: : I am wondering if the control box could be bad. I mean
: : something like the competition port. I was also
: : wondering if a bad fuse panel could cause this.

: : Any ideas??

: : Thank you, and look out for us in Fla. (if we fix this
: : prob.)

: : Travis Covingt
If you’re losing just one motor, I doubt it would be the competition port or Arena Controller. Is the light still staying on when the motor goes out? If so, the communication between the OI & robot, as well as the internal processors on the RC, are ok. One other question(which gave us problems at Great Lakes): is the dynamic braking on the speed controller controlling your drive motor turned on(jumper removed or on pins B & C)? If so, the high switching currents generated when quickly changing direction or stopping could be causing the breaker to trip. With just a few seconds before it comes back on, it points to a breaker problem of some type, it’s just a matter of figuring out what is causing the problem.

Nate

4

Posted by Travis Covington.

Student on team #115, MV ROBOTICS, from Monta Vista High School and Hitachi Data Systems - 3com - NASA Ames.

Posted on 4/2/2000 3:23 PM MST

In Reply to: Eliminating a few other things… posted by Nate Smith on 4/2/2000 2:58 PM MST:

Okay so the robot controller and operator interface
seems to be okay.

Also we do not have the speed controllers on the brake
mode. We noticed that was giving us problems before.
We are going to try to redo the wiring on the bot and
change some other things as soon as we get to
nationals. I hope that will fix it.

Thanks for the help

Travis

5

Posted by Jerry Eckert.

Engineer from Looking for a team in Raleigh, NC sponsored by .

Posted on 4/2/2000 3:32 PM MST

In Reply to: Re: Eliminating a few other things… posted by Travis Covington on 4/2/2000 3:23 PM MST:

Is the motor on the bad side running significantly hotter than the opposite side?

6

Posted by Travis Covington.

Student on team #115, MV ROBOTICS, from Monta Vista High School and Hitachi Data Systems - 3com - NASA Ames.

Posted on 4/2/2000 3:59 PM MST

In Reply to: Re: Eliminating a few other things… posted by Jerry Eckert on 4/2/2000 3:32 PM MST:

: Is the motor on the bad side running significantly
hotter than the opposite side?

Not really. As soon as we install a new one it seems
to be fine. The are equally warm (not hot). But after
we have it out on the floor under some load the current
draw just sky rockets, and the motor is shot. We are
pretty sure that it is not a problem w/ side loads or
too much friction.

7

Posted by Jerry Eckert.

Engineer from Looking for a team in Raleigh, NC sponsored by .

Posted on 4/2/2000 9:51 PM MST

In Reply to: Re: Eliminating a few other things… posted by Travis Covington on 4/2/2000 3:59 PM MST:

: : Is the motor on the bad side running significantly
: hotter than the opposite side?

:
: Not really. As soon as we install a new one it seems
: to be fine. The are equally warm (not hot). But after
: we have it out on the floor under some load the current
: draw just sky rockets, and the motor is shot. We are
: pretty sure that it is not a problem w/ side loads or
: too much friction.

Current in a circuit is a function of voltage and resistance. The higher the voltage
and/or the lower the resistance the higher the current flow. The voltage isn’t a factor,
so the only way for the current to increase is for the load resistance to decrease.

Assuming your robot is wired according to the rules, there should be only three
components in the load side of the circuit: the circuit breaker, the wiring, and the
motor. The normal resistance of the breaker and wiring is negligible, leaving the
motor as the primary suspect.

Joe or one of the others can probably give you a much better idea of the factors which
might cause the motor resistance to suddenly decrease. If you really believe there are
no mechanical problems (abnormal loading, etc.), is it possible metal shaving are getting
inside the motor casing?

Another possibility is an electrical short. If the power connections at the motor are
properly insulated, check all the wiring from the speed controller for damaged
insulation. If you use staples to fasten the wiring to the chassis make sure none of
them have nicked the insulation.

Jerry

8

Posted by Justin Stiltner.

Student on team #388, Epsilon, from Grundy High School and NASA, American Electric Power, Town of Grundy.

Posted on 4/2/2000 10:23 PM MST

In Reply to: Re: Eliminating a few other things… posted by Jerry Eckert on 4/2/2000 9:51 PM MST:

We had the exact same problem only with our arm we would start the match fine, the arm would come down and we would get our load of balls then as I back up to dump the arm would just go crazy!! it would start extending and retracting and bouncing up and down like you had picked up the joystick and were shaking the stick side to side and it was trying to lower itself which was raising the front of our bot off the ground which it shouldent have been able to do but it was ignoring the contact switch and woulent respond to ANY joystick command. I could still drive fine but the arm would not respond. this happend 2 times at the same station on the same side (the area controller was on channel 9 if your interested) and if we hit the reset button about 3 times it would work for about 5 seconds then start doing it agin, and it was drawing soo much current that the low battery light was comming on with a fresh battery. we never resolved this problem and it dident happen on the other side of that alliance station. It is a mistry to me, the crew and everyone else we asked. Does anybody have any suggestions? the arm has 2 van door motors on it and they are running on 2 victor blue speed controllers. we also switched the joystick that controlled the arm but we were never on that side agin so we couldent tell if that was the problem or not.

Justin Stiltner
Team 388
Grundy Va,

9

Posted by Jerry Eckert.

Engineer from Looking for a team in Raleigh, NC sponsored by .

Posted on 4/2/2000 10:14 PM MST

In Reply to: Re: Eliminating a few other things… posted by Travis Covington on 4/2/2000 3:59 PM MST:

One more suggestion… Once you identify and fix the problem you might want to
replace the breaker on the bad side with a new one. Assuming the current load
has been causing it to trip frequently, it may be stressed and not as reliable as
an unused one. I’m not familiar enough with these specific devices to know how
likely this is, but swapping it can’t hurt.

Jerry

10

Posted by Nate Smith.

Other on team #66, GM Powertrain/Willow Run HS, from Eastern Michigan University and GM Powertrain.

Posted on 4/2/2000 11:15 AM MST

In Reply to: We Need Help!!! posted by Travis Covington on 4/2/2000 10:55 AM MST:

Travis,

We saw a problem very similar to what you’re describing during our first few qualifying matches in Chicago. What was happening is that the 30A circuit breakers were tripping when placed under a load. We also had problems diagnosing the exact cause and solution for this problem, even after 2 other teams helped us out, but it appears to be related to an excessive side load on the drill transmission due to our beveled gears in our gearbox. When we shifted the drill transmissions into Low, the problem disappeared. So, we have some new gearboxes ready to put in at nationals, that will give us back the speed that we had originally. Hope this helps…

Nate
: Hello everyone!

: Ca regional went well. Alot of teams are really good.
: Look out for teams 330, 60, and 64. Oh and 115 if I
: can get some help with this problem we are having.

: This is the problem. During practice rounds we were
: driving around picking up balls without a hitch.
: Everything worked great. But when we were in our
: second qualifying match the left side of our drivetrain
: just would not work. It would act as though the fuse
: went. After a few seconds it would work again but it
: never worked the whole match, it just got worse. This
: happened the rest of competition and randomly we were
: still ranked 12th.

: So, we replaced everything…speed controller, new
: drill motor, switched the connection on the fuse panel,
: realined the chains, lubed chains, and everything else
: we could think of…even changing the gear ratio. None
: of these things helped at all.

: we found out that it was drawing about 10 to 15 more
: amps than the right side. But after we switched
: everything AGAIN it was the same, it drew the same
: current, until of course we went out on the field where
: it didnt work after about 30 seconds.

: During this whole process we were taking advice from
: practically every enginner from other teams as well as
: a couple of crew people from FIRST. None of them had a
: solution. They had ideas which we tried, but nothing
: worked.

: Strangest of all things…we went outside after we had
: frozen up in our first final match, and it worked with
: no problems. We drove it around for 5 to 10 min.
: Nothing went wrong.

: I am wondering if the control box could be bad. I mean
: something like the competition port. I was also
: wondering if a bad fuse panel could cause this.

: Any ideas??

: Thank you, and look out for us in Fla. (if we fix this
: prob.)

: Travis Covingt

11

Posted by Travis Covington.

Student on team #115, MV ROBOTICS, from Monta Vista High School and Hitachi Data Systems - 3com - NASA Ames.

Posted on 4/2/2000 11:32 AM MST

In Reply to: EXACT Same problem seen on the mystery machine posted by Nate Smith on 4/2/2000 11:15 AM MST:

Hi

Our drivetrain consists 4-8in wheels with 48 tooth
sprockets powered by 2 drill motors w/ 18 tooth
sprockets. In low gear. The thing is we were driving
this thing around for 4 weeks before competition w/ no
side load problems or any thing. Weve had this
drivetrain for 3 years and nothing has gone wrong
since. Also…we did replace the wiring on the motors,
in fact we replaced the actual motors 3 times. So im
not posotive either of these solutions would work, but
we can try again. We are desperate

Any other ideas

Thank

12

Posted by Joe Johnson.   [PICTURE: SAME | NEW | HELP]

Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.

Posted on 4/2/2000 7:51 PM MST

In Reply to: Re: EXACT Same problem seen on the mystery machine posted by Travis Covington on 4/2/2000 11:32 AM MST:

Have you actually backdriven the wheels on the two sides to get a feel for whether or not something is causing a hang up on the bad side?

Backdrive effort is a pretty good method to judge efficiency of gear trains.

Also, have you tried switching the left and right side wiring so that you can judge if this is an electrical or a mechanical problem?

This is not a fool proof method. As it turned out on the Mystery Machine they had multiple problems that caused us to be confused by this technique — actually, this is probably worth going over –

Like you, they had one wheel (the left side) that would not go under load. We found that it was tripping the breaker. When we switched the wires from side to side, the right side would not go under load.

As it turns out, ,they had binds in BOTH sides of their drivetrain (bad bevel gear bearing design, I hate bevel gears ;-).

Anyway, we were prevented from finding it because

  1. they had not removed the no-backdrive pins from the transmissions and
  2. they had a bad electrical connection on the motor that did NOT trip the fuse.

The bad connect caused high resistance that kept the RIGHT side from tripping the fuse. We kept looking for trouble in the wiring on the LEFT side (replacing the whole side piece by piece and then entirely). It really took a lot to discover that there were several problems causing the strange behavior.

I’ll try to stop by the pits in FL to see if you have fixed the problem. I am sure that you will have more help than you can really use, but I will stop by just in case.

Good luck.

Joe J.

13

Posted by Travis Covington.

Student on team #115, MV ROBOTICS, from Monta Vista High School and Hitachi Data Systems - 3com - NASA Ames.

Posted on 4/2/2000 8:26 PM MST

In Reply to: Have you backdriven the wheels by hand? posted by Joe Johnson on 4/2/2000 7:51 PM MST:

WOW Thanks

Yeah we havent tried that because like mystery machine
we DID NOT remove the backdrive pins, but we would
greatly appreciate you stopping by and helping us out a
little.

Your probably right about the multiple problems because
drivetrain isnt the greatest and it could use some
advice from Dr. Joe.

Thank you so much.

Travis

14

Posted by Dodd Stacy.

Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.

Posted on 4/2/2000 4:13 PM MST

In Reply to: We Need Help!!! posted by Travis Covington on 4/2/2000 10:55 AM MST:

Have you tried to localize where the problem lies? Being a hopeless dummy about all things electrical, here’s what I’d try:

  1. With the gearboxes in your normal driving alignment, block up the chassis and turn over the wheels by hand (backdriving the motors), left side, right side, forward, backward. If they don’t feel substantially different, you are probably free of driveline problems.

  2. Swap the PWM inputs to the two speed controllers, left for right, and operate the bot under the conditions that cause you problems. It will steer backwards, but you can adjust to that. If the problem swaps sides, its cause is probably in the control code or in the communication link. Using the tether could assess the latter.

  3. Swap the PWM inputs back where they belong, and then swap the speed controller outputs, left for right. Try again (still steering backwards). If the problem swaps sides, its cause lies between the battery +12V terminal strip and the speed controller (including connecting wiring).

  4. If the problem DOESN’T swap sides in 3), then I’d suspect a wiring fault between the speed controller output and the motor on the bad side, maybe an intermittant short to ground through some chafed insulation, maybe aggravated during match interactions? You can check this by disconnecting the suspect wiring and temporarily jumpering from speed control output to motor on the bad side.

I apologize for suggesting the obvious, but I always screw up when I don’t ask and answer the dumb question before looking for detailed explanations.

Good luck,
Dodd

15

Posted by Daniel.

Coach on team #483, BORG, from Berkeley High School and NASA Ames & UC Berkeley.

Posted on 4/2/2000 5:34 PM MST

In Reply to: Suck and See posted by Dodd Stacy on 4/2/2000 4:13 PM MST:

Good points, all of them. In the event that your motors still have their locking pins cuz maybe you like staying on the ramp at the end of the matches :wink: , you can run the wheels up on blocks and make a mark on one of the ribs. Watch and count and see if there’s a dramatic speed difference. If the problem side goes slower you may be able to attribute the problem to friction. My guess is it’s something more electrical. Wherever possible, make sure you fill gaps with solder. The crimp side of quick connects can and should be soldered.

It sounds to me like it is very likely a breaker problem. Your robot is working during practice backstage but it doesn’t work on the field. What are the differences? I know many factors change but most shouldn’t effect anything. What things might?

  1. Perhaps your driver is working too much against the clock in the matches and is working too much to keep the robot alive during practice. Sudden changes in direction whether the moter is on dynamic breaking or not cause problems. Quick acceleration is also a cause of heating up. You need to be nice to these motors. Watch the driver and see how he moves the joysticks. He cant use the robot like he’s playing a computer game. Motion needs to be gradual. It’s a delicate machine.

  2. Are you playing for heavy contact? Do you do a lot of pushing? This also could cause problems.

The puzzle is that the problem is isolated to one side. All the things I mentioned could be problems and then the smallest wireing bug or friction difference between the two sides may be popping one of the breakers before the other. At which point you stop moving and both sides cool down before you manage to cause the other motor to pop it’s breaker. So perhaps it’s not so much a sided problem as it seems.

I, like Dodd, don’t know anything about anything electrical. Hope I’m making SOME sense.

Good luck!
-Daniel

16

Posted by Travis Covington.

Student on team #115, MV ROBOTICS, from Monta Vista High School and Hitachi Data Systems - 3com - NASA Ames.

Posted on 4/2/2000 5:50 PM MST

In Reply to: systematic is the way to go. posted by Daniel on 4/2/2000 5:34 PM MST:

: 1) Perhaps your driver is working too much against
the clock in the matches and is working too much to
keep the robot alive during practice. Sudden changes
in direction whether the moter is on dynamic breaking
or not cause problems. Quick acceleration is also a
cause of heating up. You need to be nice to these
motors. Watch the driver and see how he moves the
joysticks. He cant use the robot like he’s playing a
computer game. Motion needs to be gradual. It’s a
delicate machine.

-on that note…I am the driver and honestly I was a
lot harder on the robot during practice than I was
during qualifying…AND the left side dies as soon as
the bot gets to the other side of the field or shortly
after we get a couple of balls.

: 2) Are you playing for heavy contact? Do you do a
lot of pushing? This also could cause problems.

Again no, we really have no contact when these problems
occur. We were not very aggresive. It seemed to
happen even with no contact with other robots.

: All the things I mentioned could be problems and
then the smallest wiring bug could be the real
problem…

This is really what I think we need to concentrate on,
we didnt rerally think our wiring was bad but I bet it
is. That was one of the only things we did not check.
Im pretty sure (like you said) that we need to solder
all crimps and connections. I hope that is the
problem.

Thank you so much for the help…everyone

17

Posted by Travis Covington.

Student on team #115, MV ROBOTICS, from Monta Vista High School and Hitachi Data Systems - 3com - NASA Ames.

Posted on 4/2/2000 5:34 PM MST

In Reply to: Suck and See posted by Dodd Stacy on 4/2/2000 4:13 PM MST:

Okay

Sounds good. Weve done some of these things but not
all. Thanks for the suggestions. I am almost positive
it is a wiring problem somewhere, a loose wire or
short… possibly on our giant conductor (our base is
3/16 aluminum plate) whoops!

Travis

18

Posted by Daniel.

Coach on team #483, BORG, from Berkeley High School and NASA Ames & UC Berkeley.

Posted on 4/2/2000 5:38 PM MST

In Reply to: Re: Suck and See posted by Travis Covington on 4/2/2000 5:34 PM MST:

You can make quick conects fit tighter with a pair of pliars. You don’t want those to be a loose connection.

However I don’t think it’s a short. It works during practice, yah? Think about the differences between practice and competition. Nothing says your wires should only short during competition rounds. Seems pretty unprobable.

Do check though.

Watch those joystics. Make sure your driver isn’t going crazy, cuz if he/she is…just wait til florida heat makes that problem about 10x worse.

Good luck again!
-Daniel

19

Posted by Matt Rock.

Student on team #115, MVRT, from Monta Vista High School.

Posted on 4/2/2000 6:25 PM MST

In Reply to: also… posted by Daniel on 4/2/2000 5:38 PM MST:

I can assure you its not the driver. He practiced all summer with last years robot and got quite good at it. When the robot works he can do everything and a little more smoothly and without a hitch. And when it comes to florida, if we get the robot working, you’ll get to see just how good he is. Good Luck to all, and thanks for all of the suggestions.

: You can make quick conects fit tighter with a pair of pliars. You don’t want those to be a loose connection.

: However I don’t think it’s a short. It works during practice, yah? Think about the differences between practice and competition. Nothing says your wires should only short during competition rounds. Seems pretty unprobable.

: Do check though.

: Watch those joystics. Make sure your driver isn’t going crazy, cuz if he/she is…just wait til florida heat makes that problem about 10x worse.

: Good luck again!
: -Daniel

20

Posted by Daniel.

Coach on team #483, BORG, from Berkeley High School and NASA Ames & UC Berkeley.

Posted on 4/2/2000 8:51 PM MST

In Reply to: Re: also… posted by Matt Rock on 4/2/2000 6:25 PM MST:

I’m not questioning that he’s good. I’m questioning that he’s hard on the robot. It could be that your last years robot could take a little more of a beating than this years robot can. All it takes is a LITTLE too much heat and those breakers trip. It’s not a gradual thing where it gets worse and worse. One second it’s working and the next it’s not.

It’s worth checking.

-Daniel