Re: [FTC]: Samantha? Like it or hate it?
 

Thanks for the info aklego. I wonder what it'd take for FTC affiliate partners to have a battery tester (load tester) at the FTC events for teams to use. Perhaps it could be at the field table under FTA supervision ... sure they're cheap and individual teams could attain them.

However, it's the 'I didn't know I needed to know that' which is the most irritating aspect of the Samantha module, and such a battery load tester would incontrovertibly point to the correct problem if employed by the FTA.

Re: [FTC]: Samantha? Like it or hate it?
 

Not sure that that would be practical, or even neccessary.

FTC robots place hugely different loads on the batteries (just stall 4 motors to see what happens to a bettery). What would be an appropriate load to test at?

During practice and Auto testing, we've learned that if the *NXT* is reading the robot's 12V battery at less than 13.0V (when at idle) then it's time to change the battery. (Calling them 12V batteries is missleading). In fact, at competiton, we don't let them get below 13.5V before changing.

Strange things start to happen to the Motor/Servo Controller interfaces when the idle voltage drops under load, so if you want reliable control (regardless of the Sammantha Module) you really need to watch your batteries.

At least with the Samamtha you can see the instant loss of link if it occurs (the white light starts blinking).

Some other tips....

Make sure the Samantha power is the FIRST thing in the power chain (not at the end of the chain after two motor controllers.)

Consider splitting the power from the switch and running dedicated wires to the Samantha Module and the first motor controller. It's legal if you use the correct gauge wires. We splice and then heat shrink the splice.

Charge at the low rate. Overheated batteries don't last as long as cool ones.

Re: [FTC]: Samantha? Like it or hate it?
 

Have to ask the question here (because I honestly don't know the answer)

Why?

Electrically it is all the same wire. Internally in the controllers the two power connections are jumpered together...

The only reason I can come up with is that the Samantha is less tolerant of intermittent connections. And if your module is at the end of the chain, there's more chance of an intermittent connection affecting it. If, however, you make sure there are no intermittent connections in the first place, it doesn't seem necessary.

OK, you could potentially have a voltage drop over the wire, but at 13v, even with 8 motors all at stall (about 56 Amps -- maximum current) after 2 continuous feet of 16AWG wire (absolutely the worst case I could come up with) you would have a drop of only about 1 volt. Under "normal" 8 motor heavy operating situations (average 1 foot, 28 amps), your maximum drop is about 0.3v). That's not enough to cause a problem if your batteries are reasonably charged enough in the first place!

Re: [FTC]: Samantha? Like it or hate it?
 

I guess this is where theory vs reality comes into play.

If you assume that those tiny screw terminals provide perfect electrical contact, and that the students wiring said terminals do a perfect job of stripping and inserting the wires, then you are correct.

However, IMHO the reality of the situation is very different. Many kids will nick a few wires when stripping (there goes a few % in cross section). Maybe not all the strands get crimped tightly under the screw (there goes a few % in cross section). Maybe the wires get compressed and as a result it releases the tension from the screw (there goes a few % in cross section and adds a few ohms of resistance). Before you know it, 12 screw terminals (up and back) make the wire look pretty imperfect.

Every mechanical connection is also a potential failure point (complete or partial) and a less than perfect connection provides less than perfect resistance, inductance and capacitance.

Finally, I personally don't know what's between the power in and power out terminals on the servo and motor controllers (since I haven't pulled a controller apart) so who's to say there isn't an inductance that your meter isn't seeing (but a 40A spike will see).

Since these robots get severly beaten around, the more mechanical connections in a chan, the more it increases the likelyhood of an intermittant connection getting noticed.

Since I can eliminate any chance of the Samantha seeing a power glitch from any one of those (14) connections just by splicing off the main switch cable, seems like no-brainer insurance to me.

Phil.

Re: [FTC]: Samantha? Like it or hate it?
 

Samantha was easier to use than Bluetooth. We had very few problems with Samantha and the problems that we did have were easy to fix. It took us a while to figure out how to set up and configure the Samantha but that was because Samantha was new and none of us knew how to use it. We followed the directions that were on the FIRST website and played around with it and we got it to work. Most of the problems we had involved the computer not connecting to the router or not using the correct templates for autonomous and teleop. The only other problem we had more than once was when the Samostat said that the IP address of the Samantha was 169.254.___. __. That problem was easy to fix all we had to do was turn the robot and the brick off and then turn them back on. If that didn’t work we unplugged and then plugged back in the router or reconfigured the Samantha. Our Samantha died at the Maryland competition for unknown reasons but my guess would be that it had something to do with being in a cold car for too long or something like that. We had problems with FCS not connecting to Samantha when the computer did. Trying to rescan for the Samantha didn’t work so we had to exit out of the FCS. We had to turn on the Samantha before we looked for it using FCS or it wouldn’t find it even if we rescanned. Better instructions for setting up the Samantha would have been helpful. The only complaints I have about Samantha are that we could only get one which meant that if it broke we were screwed and that some of the tech people at the Maryland state and Pennsylvania York qualifier competitions knew less than I did about Samantha and FCS.

Re: [FTC]: Samantha? Like it or hate it?
 

I'm FTA'ing at our state tournament and just encountered an odd issue that is extremely successful at preventing Samantha connections. A team.gif of the wrong size on the NXT will totally foul up the works. It makes the FCS post a variety of errors.

Credit where credit is due. The kids figured it out.

Re: [FTC]: Samantha? Like it or hate it?
 

Whew. I just finished FTA'ing our state championship. I'm sold on the concept of samantha but not the current hardware. I FTA'ed at a regional several weeks ago and there were huge differences. At the regional, NONE of the teams had used samantha before. (All were from rural Alaska and their schools were 100% Mac based, hence no FCS.) As a result, all of their modules were brand new. We plugged them in and, excepting the low battery issues, they worked perfectly.

Yesterday was quite different. (We had some interference from an existing network that was jumping channels but that was quickly resolved and the affected match was replayed. And, contrary to rumors, there was not a jammer in the building.) The biggest issue was the samantha robustness. Or, more correctly, its lack thereof. Known powerhouses that had been using their modules for months were the ones having problems. Their modules had intermittent faults. Most frustrating, unless the module was really toasted, the problems would only occur during a match. The culprit, confirmed by the onsite FIRST rep, is weak solder joints. The "Samantha Best Practices Guide" is only a bandaid, and does nothing for teams that may have inadvertently damaged their module before it was published. We also had lots of locked up NXT's and the previously mentioned guide would indicate that samantha hardware faults were again the cause. Burned out LED's were also not rare. Bluntly, samantha was beta tested on 1,645 unsuspecting teams this year. The test results are in and the samantha hardware did not pass.

FIRST would do well to publicly admit the issues sans candy coating and explain how it is going to be rectified next year. It is safe to say that teams are tired of control issues.

As an aside, one thing that would be helpful would be to provide significant realtime information to teams. The small battery icons next to team numbers on the timer display are a great start but they are hard to see, especially in the heat of battle. I would not have been adverse to having a rep from each team looking over my shoulder at the FCS screen--It would have made my job easier for teams to see the disconnects as they happen.

Having said all that, from the reports of some events, our tournament was an unqualified success. We had 40 teams, each had 5 matches and we finished qualifiers a mere 15 minutes behind schedule.

Re: [FTC]: Samantha? Like it or hate it?
 

I diagnosed a related issue last night.

An intermittant Network connection issues was traced back to an intermittant power connection at the Sami module.

Turned out NOT to be the module, but the plug-in cable/connector combo.

On closer inspection the red wire seemed stressed at the entry point to the white plastic connector, and slight wire jiggling could cause the Sami to reset.

The Sami module was tested on a spare power cable (where the heck did that come from ??????) and was proven to be robust. So we replaced the cable. All was good.

We disected the "stressed" part of the suspect wire, and found NO broken conductors. We can only assume that a prior incident had caused the actual metal barrel of the power plug to become deformed (spread) enough that wire movement caused intermittant connections with the mating part inside the Sami module. VERY hard to diagnose, but causes problems whenver the robot took a hard bump.

Once again, this is a VERY rough and tumble environment and teams MUST be educated on how to tie down cables and protect connectors. I'm still amazed to see how many NXT's and Batteries fall out during a match.

As an aside... I can't imagine LEGO ever assumed that the NXT USB cable connector would see the wear and tear that FTC is now forcing it to endure. Multiple plug/unplug cycles during code testing, then it becomes a CRITICAL link for the actual competition. This is probably a $0.50 part.

Seriously !!!

Phil.

Re: [FTC]: Samantha? Like it or hate it?
 

Loose power connectors was definitely an issue. About 20/74 teams here in Oregon were affected bad connectors causing power loss to Samantha. Bad connectors was definitely one of the top causes of field problems.

As far as I could tell in the field, the female half of the plug was getting enlarged, perhaps due to side to side wiggling of the connector when being connected/disconnected. I instructed teams to squeeze it smaller (with either needle nose pliers or a small screwdriver), and that seemed to make things better.

Re: [FTC]: Samantha? Like it or hate it?
 

Our programmer thinks the problem is deeper than that. To show us, he held the power and USB cables and shook the samantha module around without it losing connection. He then put it on a robot and ran the robot the field wall, and it lost connection. He says it might be the hardware inside the samantha, not simply the cables. We may look for what's wrong - it'd be great for us teams know what the main problem is before worlds.
But still, it's working better than the bluetooth FCS.

Re: [FTC]: Samantha? Like it or hate it?
 

Normalmutant, your programmer is correct. Try putting the module on your robot and establishing a connection with the FCS. Without starting a match, shake your robot and see if you can get it to drop its connection. Now try the same thing but with tele-op running. The FIRST rep at our event indicated motion induced drops are much more likely while the NXT and samantha are actively communicating, and my experimenting has shown that to be true.

From the info in this thread, it seems like there is not a single problem but, rather, problems that manifest themselves in nearly the same way:

Network interference--dropped connection
Poor power connection/wiring problems--dropped connection
Manufacturing defects in power cord (rare?)--dropped connection
Low battery (FCS initially reporting green)--dropped connection
Loose USB cord--dropped connection and/or locked up NXT
Bad solder joints--dropped connection and/or locked up NXT
Programming/firmware bugs--dropped connection and locked up NXT
Others?

Re: [FTC]: Samantha? Like it or hate it?
 

Has anyone here seen the following occur:

Establish connection from FCS to Samantha
Run TeleOp and hit wall or go over corrugate or get hit by robot
NXT "freezes", but FCS and Samantha still communication (LED light is still white). A freeze is when you press buttons on the NXT and it doesn't respond.
Have to remove battery from NXT to reset it.

If you have seen it, can you repeat it happening in the same way. If so, please IM me. I'd love to get some more information from you about this.

Re: [FTC]: Samantha? Like it or hate it?
 

Oh, okay. We guessed that there was a spike in the power level when the robot rams into a wall. We're planning to do some testing, too. We'll keep you posted.

That's happened to us and our sister team a couple of times. I don't know how to duplicate it.