Things that new members need to know about electronics

[Karma]

I'm heading up our electronics team this year, and I've got enough experience to handle the electronics, but I would like to get the newcomers on our team up to speed BEFORE the season starts. There are a couple things I've found such as a basic electronics textbook. But I'm wondering what you all recommend for the new members to be reading up on. Also if you could recommend any small projects that would be helpful for training the new guys that would be appreciated.

[Billfred]

My advice: Get them studying the 2005 and 2006 wiring diagrams to get the basic flow of things. (I include the 2005 diagram on the hopes that FIRST will bring back the IFI breaker panel, which I missed dearly last year.)

If you've got the spare parts, let them go ahead and wire up some basic things, like a Victor, a small motor on a Spike, and a pneumatics solenoid. (Naturally, you want to check all that before you apply power.)

Also teach them some good practices, like wire management, soldering, and how to make a good crimp. (When 1618 did it this week, I had to recall how to do it myself. The off-season takes you out of practice, y'know.) Some instruction on battery management probably wouldn't hurt, either.

[jts]

We recently had our new members completely disassemble the 2005 robot, including all the wiring, and then had them put it back together again. Those involved with the electronics benefited the most from this and I think in the future we will do more of this "hands-on" type of learning.

[sanddrag]

Originally Posted by jts

We recently had our new members completely disassemble the 2005 robot, including all the wiring, and then had them put it back together again. Those involved with the electronics benefited the most from this and I think in the future we will do more of this "hands-on" type of learning.

We tried that once. The robot never did get fully functioning again. All I'm saying is be careful before you go taking stuff apart. Make sure someone is committed to putting it back together.

[jts]

Originally Posted by sanddrag

We tried that once. The robot never did get fully functioning again. All I'm saying is be careful before you go taking stuff apart. Make sure someone is committed to putting it back together.

It works better if senior members of the team or even mentors supervise and explain what all the parts are and why each is important as they are being removed. We broke it up into two meetings, one for disassembly and the next for reassembly. It certainly is not something that can be left for the new members to complete by themselves, but it is a very effective way for students to see where each piece fits into the puzzle.

[Stephen Kowski]

What you want to look for are any technical posts from Al Skierkiewicz on chief delphi and possibly, if you can find it, his white paper on batteries....even though it is meant for the batteries it has a lot of good electrical info in there.

[Jeremytice]

I am one of the student co-leads this year for the electrical team. One good thing to do during pre-season is to show them the proper practices with all the tools. Another thing we did was go over the schematics from previous years and then showed them the robots. That helps them understand the electrical system a little better. We also gave a run through of all the parts we use and also let them make a couple of harnesses. Another thing I would suggest is to make them read through last years electrcial rules. That way they get an understanding of what they can do and what they cant. Good luck!

Our team has a small, in house competition. We divide the team into 4 small teams, and spread the veterans out onto those teams. Then, our mentors give us a game, ususally involving bots only 18x18x12. this teached the new members how to wire, build, and make mistakes. All in all, it's out most educational couple of weeks pre season.

[sanddrag]

I would emphasize good wire routing. The wiring system should somewhat resemble a system of streets and/or freeways (aerial view). Do not make every wire a straight shot between two points, but on the other hand, you usually don't need a 22 inch long wire to connect to a point 5 inches away. You get what I'm saying. Channel your wires neatly. Put them into thoroughfares.

[DonRotolo]

I agree with the Crimping lessons, these are easy to do poorly and that will cause problems.

I also agree with Al about wiring neatness, a rats nest is impossible to troubleshoot, tight wires fail, and sloppy work is inexcusable. Make it look like a work of art.

I would also emphasize battery safety and the need to keep them charged. There are some threads on this from earlier this year that you can search for.

Don

[Al Skierkiewicz]

OK,
I have a list. First and foremost, teach which end is the hot one on a soldering iron. A burn from a hot iron is the gift that keeps on giving and the smell of burning flesh is something you will never forget. Next work on safety using all tools, small hand tools especially. An errant student with a pair of wire strippers can easily take out an eye or other damage when out of control. Learn to gauge the safe distance by extending your arm and seeing if it bumps into anyone or thing. Get used to moving until there is free space around you and you have some experience in using the tools.
Next on the safety list is battery. Most people think that the battery is safe because it is only 12 volts, but the power density is high enough to cause burns and other injuries if misused. No loose chains or dangly bracelets around the robot because of the chance of electrical contact. Batteries are heavy, always use two hands and never, and I mean never lift by the battery cables.
Next on the list is practice, practice, practice. You can't be good at crimping, soldering, wire runs, or layout the first time. Know that a good solid crimp is one that has just enough insulation removed to allow the wire to penetrate into the contact (about 1/4", the width of your little finger nail), and has the right amount of force applied to the tool. Test the connection by pulling and pushing. If the contact moves, crimp it again. A bad crimp will heat up and deliver less power to your motors.
Know the electrical portion of the robot manual by heart. I will test you on it later. The manual, FIRST_Guidelines,_Tips,_&_Good_Practices_Rev_D http://www2.usfirst.org/2006comp/oth...ices_Rev_D.pdf on the First website also has an excellent section on electrical. I didn't write it, but it is an excellent reference.
Just as in most everything, the shortest distance between two points is a straight (or nearly straight line) Centrally locate the battery and the fuse panel. Then move out to the speed controllers and spikes and then finally to the motors. As a rule of thumb, at stall, each foot of a single #10 wire will drop 1/10 of a volt, #12 will drop almost 2/10 and I won't even talk about #14. I like to use the "wire foot" analogy. 1 WF(wire foot)=1 foot of # 10=1/10 volt@100amps. So #6 is .4WF/ft, #12 1.6WF/ft, #14 is 2.5WF/ft. All you have to do then is measure the wire length (don't forget both wires) and calculate for your wire size, then add 2WF for the speed controller and you will know how much voltage you can deliver to a motor. (remember the battery at full charge has an internal resistance of 11WF) Good crimps should have negligible drop but bad crimps can have easily 2WF per crimp or more.
On the fuse panel use the first position for the RC power (on the IFI panel either #1 or #2) to keep the voltage at the highest for this critical component. If the RC is not happy, you don't drive.
Before applying power or even before hooking up the battery, make sure each member of the electrical team has looked over every connection. Make sure hardware is tight and all wires are the correct polarity. Speed controllers get really unhappy when connected backwards or with the wrong polarity and again the RC is the heart of robot, make sure it is correct.
Finally, when you are ready to power the robot, make sure no one turns it on until they are sure no one has a hand inside and the robot will not run off and hurt someone or something. We have the person who is turning the robot ON, shout "clear" to make sure everyone is away from the robot and moving appendages. Keep the wheels off the floor for the first test and during controller calibration.
We use 3M color wire coding tape to mark everything. The breaker, breaker position, wire going to the controller, PWM output on the RC, PWM cable, fan on the controller, the wire going to the motor and the motor with the same color tape. This way if the "red" motor isn't turning and the fan on the "red" controller is turning then we go to the "red" circuit breaker position on the panel and see if the "red" breaker in in place. If the "red" controller is showing no PWM connection, then we follow the "red" PWM cable back to the "red" position on the RC to see if it is connected. Mark wires at both ends. No need for schematics to troubleshoot on the field.
Above all, remember you can ask me anything at anytime. I check here almost everyday, sometimes more often.
Keep safe and have fun.