How Can I Avoid Student Mistakes

[pnitin]

Here is one post on How to prevent electrical reverse polarity or connection mistakes on your FRC robot. It address specifically for power electrical.

http://www.mindsensors.com/blog/how-...our-frc-robot-

[GreyingJay]

I actually have a story about mentor mistakes, electrical polarity, and "trust but verify".

My very first day as an FRC mentor, I was introduced to the head controls mentor and, looking for a job to give me, he handed me a package of addressable LED rope light he had just purchased from Adafruit, an Arduino board, a power supply, and said "here, take those two students and make this work".

I guided the students through a series of "what do you think we should do next?" exercises while learning the answers myself at the same time. OK, let's download the Arduino IDE software to a laptop. Let's Google for the spec sheets and sample wiring for these lights. Let's find some sample code. Let's get some jumper wires and a breadboard and wire something together. Let's double check everything before we turn it on. It looks good, let's turn it on...

Nothing. It just wasn't working. We checked it over again. Everything was wired just as it should be. Dead power supply maybe? Off to get a multimeter...

Lo and behold, the output voltage from the power supply was the reverse polarity from what was marked on the casing. The box said tip-positive but it was definitely sleeve-positive. A lot of "NO WAY!" and grumbling from myself and the head controls mentor.

So we reversed the power leads and AHA! Colourful flashing lights! Thankfully, the lights were reverse-polarity protected.

As I left that night, one of the parents came over and said "Hey, not bad for your first day!"

[techhelpbb]

Originally Posted by GreyingJay

Thankfully, the lights were reverse-polarity protected.

Usually if you put any diode backwards on a power supply insufficient to destroy it, it will simply not conduct any meaningful current. Even a light emitting diode (LED). Of all the things where you can do that - there's a great one you can usually not destroy something.

Now if those LEDs have some crazy microcontroller - then you'd have a problem.
Watched someone do that with LED modules for a large sign once.
At $500 a module I think blowing out the module controllers wasn't very fun.

On things I used to make that were low power I used to put a bridge rectifier in the DC power input. This insured that no matter the applied polarity the circuit always got the right polarity. Sure I lost some voltage doing that but when I found them hooked up backwards I would just say 'there's some part money well spent'.

[rich2202]

The Dlink's are especially vulnerable. We have burned out more than our share of routers. Most of FIRST's equipment has reverse wiring fault protection. But, the Dlinks do not.

So, ANYTIME the wiring of the Dlink power cord is changed (even if it is just disconnected and reconnected), I make the students verify polarity and voltage with a volt meter before they can plug in a Dlink. The power cord is not color coded, so it is easy for the students to wire incorrectly.

[Aur0r4]

One big one is gaining and maintaining the student's respect. This is a mixture of enforcing rules/behavior policies but also building rapport. Too much enforcing leads to students who behave in front of you but develop a common connection of not really liking you. Very unlikely to behave when you aren't around. Obviously being too soft and "fun" causes them to disobey rules right in front of you.

Don't be afraid to joke around with students.

The other big thing is letting them know that if they DO break something that they should feel comfortable telling you so the problem can be fixed. This goes back to my initial comment. If they are terrified of breaking something, they will only hide it when they do. We have all broken lots of things....usually professionals have epic stories of screwing up.

As long as something really, really dumb didn't cause it, I don't get worked up. They don't need a long lecture to know not to do that thing again. Especially if they have your respect, they'll feel the worst about letting you down.

And, then again, I've done plenty of really, really dumb things myself in my day...

[geezloueez]

Thanks to everyone for all the great tips. I will be using lots of these suggestions. I'm especially thankful to know that sometimes the equipment has reverse wiring and I will make sure the students and I check the polarity of each piece.

Originally Posted by pnitin

Here is one post on How to prevent electrical reverse polarity or connection mistakes on your FRC robot. It address specifically for power electrical.

http://www.mindsensors.com/blog/how-...our-frc-robot-

Great blog pnitin. I'm sure this practice will save us some money and probably a few headaches.

[mindsensors.com]

Originally Posted by pnitin

Here is one post on How to prevent electrical reverse polarity or connection mistakes on your FRC robot. It address specifically for power electrical.

http://www.mindsensors.com/blog/how-...our-frc-robot-

There is a follow up to pnitin's post on our website. Detailed instructions on how to solder the XT60 connector can be found here.

[2544HCRC]

I like many of the suggestions on here. As a mentor might I just add a couple of other things not mentioned.

I tell kids that nobody plans mistakes, but they happen. Especially when people get tired. Which pretty much defines FRC. Double check, and watch where you are if something goes wrong. Drilling on your lap is not acceptable practice. Neither is drilling on someone elses lap. (both seen).

Sometimes you just need to walk away. To say our budget is tight is an understatement. Everything we buy is a choice between things we need. A couple of years ago I had a student wire a brand new camera backwards. Brand new... Just out of the box. We had saved for the camera and it was destroyed instantaneously. I just walked away. There just wasn't words. It has become legend.

Nothing is worth getting hurt. It's easy to start taking short cuts when time is tight. Don't. Disable and dissipate. Watch for stored energy. I had a kid reach through a drivetrain (chain) on a live robot. One of the few times I screamed at a kid, legend. It was truly fear and addreneline on my end.

Teach kids to measure. Close enough is not good enough. A marker is NOT a layout tool.

Good luck!