Alright, same idea as my mechanical tips thread here. I’ll combine these into a one pager to hand out to rookies as well. Here are the ones I came up with so far.
Include electrical components in overall design. Many times teams just assume that they will be able to find space for electrical components at the end. Adding the placement of these components to the design early makes it easier and neater. It helps avoid precariously positioned speed controllers, relays, batteries, controllers, etc. Also remember to keep this subsystem in mind when estimating weight.
Have a test board and basic program ready early. These should be enough to at least run the drive system as soon as they are completed.
Make sure battery is easy to replace but secure. During competition, there is often very little time between matches (especially during eliminations). Easy battery change outs are therefore very important but it’s also important that the battery won’t fall out during a match so make sure it is secure.
Keep ports on robot controller clear. The tether, radio, and programming ports are all necessary throughout the competition so it’s important to make sure they are easy to access. Should also be able to see the LEDs on the controller easily to facilitate problem diagnosis.
Protect components from debris. Make sure to cover speed controllers and relays to protect them from metal shavings when working on the robot.
Use a good crimper. Good crimps on all connectors are very important to make sure the robot continues to run. Many robots have become disabled on the field because of connections coming loose.
Organize wiring. Make sure to label all wiring so that if components need to be replaced, rewiring is faster and easier. Also make sure to keep wiring neat and out of the way of moving components. Use wire ties, Velcro, etc to tie down wiring. Judges love to see a neat wiring job.
Make sure all connections are insulated. Use insulated connectors or electrical tape for all connections. Be careful of this especially on the battery connectors and the 120 amp fuse, inspectors will be checking those carefully.
Reduce wiring. Wiring adds quite a bit of weight. Make sure to use as little as needed. Long lengths of wiring also add resistance which decreases the effectiveness of the battery.
Keep several copies of your program. You can’t get the program back off the robot controller, so make sure you keep copies. Also, never save changes on top of an old program, save it as a new copy and make sure to name it appropriately (example: program_rev3).
Start work on autonomous early. Autonomous code typically takes a lot of tweaking so the earlier you start and the more testing you are able to do, the better.
just a few things that you can buy to make things a little easier are Monster Cable Power Wire it is very difficult to find, but if you find very the extremely high strand gauge wire it feels similar to a piece of liquorice in your hand and makes it extremely easy to organize you wiring. Also for major components that may need to be changed quickly (besides the battery) you may want to try Anderson Powerpoles they are quick to disconnect (think a smaller version of the battery connector, but for a single wire) and very sturdy.
Red is to red as black is to black. Do not short circuit batteries. If you must hook up a FIRST battery to something powerful, put a 1.6Mohm resistor on the circuit to avoid part damage.
Also, use the Speed Controllers very carefully. They’re $125 per part.
When machining a robot, put a paper towel or grease towel on top of your circuitry. A tiny aluminum flake can destroy hours and thousands of dollars of work.
Thou shalt not use thine aluminum frame as a grounding device.
One thing to add to the list–don’t use too little wire, either. Leave some slack, just in case something shifts. (bites tongue before he tells a rather applicable, but somewhat off-color joke)
Read the technical white paper by Al, “Robot Battery and Electrical System Guide”. A must for all who will even think about touching the batteries.
A good P-Touch labeler (and loads of extra label tape) is your friend! Just don’t leave it unattended for more than a few minutes or you’ll find that the one student with nothing to do will label items like “hammer”, “drill”, or “me”
After re-wiring our 2004 robot to prepare it for the Cal Games, we lost ~7 pounds. Scary!
A good multimeter is a must - we often use a DC Clamp meter to measure the Amps drawn by the motors to diagnose problems while the robot is running. The one we use is measures up to 400 Amps - so you can even check your total current draw during certain maneuvers.
NEVER let a curious little rookie fresh into hs touch a soldering iron until he is well educated on the uses and reasons of a soldering iron, the principle behind the bonding, the dangers of it, and that it is dangerous to use as a “fun” item that can melt plastic into many fun shapes! aand of course the proper ventilation that would be good too
When your still designing your layout. Just remeber Battery + 2 lose connectors + Metal T Square = ARC WELDING… Team 637 learned that the hard way… it was quite exciting though. Best of Luck!
Make sure that all your electrical connectors are secure; My team had a very instructional event when we discovered that our robot was losing power during competition because the connection to the battery at the main breaker was loose.
Make sure all connections are taped so that there is less opportunity for something to short.
Its a whole lot easier to use zipties than to rewire a robot due to wires being caught and ripped off.
Stay away from Victors, spikes, etc with loctite
Keep Victors cool, dont restrict the air flow to them and make sure that the fans are running before the robot is ever driven.
Use as short of wires as possible Voltage drop & useless added weight=bad
Make sure to use appropriate gauge wire necessary and I recommend having someone print the FIRST diagram of the electrical system on a plotter. That way it is visible while working and everyone can see it. Plus the poster is great for teaching rookies with.
It is absolutely important that you follow the robot manual electrical section when building your robot. This section is not “suggested building” it is required building practice. At competition your robot will be inspected by trained individuals and your robot must conform to the book. As you have seen above, the battery is capable of welding metals together and the danger of far worse also exists. (All persons working in the same room as a robot must have safety glasses on.) All battery terminals should be insulated with tape or heatshrink and all connections should be well insulated either using correctly terminated crimp on connectors or adequate heatshrink. If you want help at a competition, your controller must be visible while the robot is moving and easily changed if it is defective.
Above all else, when you don’t know how to do something or you just have a question, please ask here. You will receive correct info from knowledgable people most of the time.
Thanks for all of your input. I’ve posted the updated list in the white paper section. If anyone has any other suggestions, let me know and I’ll update the document. Feel free to use it as a handout for your team and for new rookie teams. Hope it helps .
Also: (I had a math teacher do this!)
In math, black is for numbers greater than zero, or positive, and red is for numbers less than zero, or negative. DON’T CONFUSE MATH AND ELECTRONICS!!! LOTS OF SMOKE AND BAD SMELLS!!
Red is ALWAYS positive in electical systems, and you should color-code your wiring correspondingly. Black,or sometimes green, but mostly black, is Negative (actually ground, but it’s easier to think of it as negative sometimes)
White is signal, and, unless you use other sensors, that’s it.
I had a math teacher try to jump a car. Melted his battery, he did.
As Sparks mentioned, in a FIRST robot, red is alway positive and black is always ground. In the past there have been rules governing this, and there probably will be again this year.
Anybody who has worked on a robot will tell you that the wiring can quickly become a mess and make things difficult to tell what’s what. Something that we do (and I know other teams have done) is color code everything with colored tape. For example, if we choose green for a certain motor, we’ll put green tape on everything that connects the RC to the motor. You will see tape in the following places
RC pwm output
PWM cable on both ends and in the middle
Fan on top of speed controller
Both wires coming out of speed controller to motor
Motor itself
You will also see the same tape on all power paths to the speed controller
Breaker panel
Breaker
Red/Black wires at both ends
This allows us to quickly determine which wires go where in the case that we have to get in there and work on things. Its a lot easier to ask somebody to trace the green wire than try and describe a certain red wire. We use part STD-C-ND available from Digikey. It’s a little pricey, but well worth it. I’ve also seen some teams use labels from a labelmaker and stickers (I seem to remember Scooby Doo stickers )
O yes wiring can become in our electrical team’s words a “rats nest”… I work on electrical last year and I wasnt sure that it was going to be hard to find a way to organize the wires… WOW I was wrong… It became a mess very fast… So we did find a way to organize like Scheck said… Our color coding is very helpful to me too… As long as we remember what colors go are what…
Sparks,
I don’t want to make a big deal here but so people don’t get confused I need to say these few things.
For First robots, the rules state the use of red for wires connected to battery positive and black for wires connected to battery negative. This is a convention for most electronic wiring but other colors are used all the time by designers. Measure first to be sure.
The term “ground” is sometimes used for “signal common” or power supply common but the term implies that somewhere the signal common is actually attached to ground. In AC power distribution this wire is green or green with a yellow stripe and it must connect to a rod or pipe in the ground. Ground may or may not be the power negative terminal. No connection between battery and robot frame are allowed even though many electronic systems will “ground” the common point to the frame.
Although Red and Black wires are used for power wiring and motors on First robots, the red and black wires between the speed controllers and motors can actually be tied opposite the convention depending on the direction of the speed controller or Spike. Again always measure, you may find 12 volts when measuring between a motor black lead and the battery black lead.
Other colors are used all the time and the only way to be sure is to check with the manufacturer, wire vendor or by measuring.
Oh, By the way, black is the wire color for the “hot” in 120 volt AC house wiring. In three phase power systems, black wire is used very often for all phases with some kind of indicator as to which phase the wire represents. Black is also commonly the wire color of both sides of 220 volt house input wiring.
Red in house wiring is commonly used for “switched” power wiring or for anything the electrician chooses. When pulling in multiple circuits in a single conduit or raceway, different circuit “hots” will use a combination of colors (i.e.black, blue, red, yellow, etc.) with white as the neutral and green as ground.
Color codes vary across the country and municipalities so even the above colors may not apply in all locations.
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