Chief Delphi - Electrical team training

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Electrical team training

I have been working on a short series of powerpoints for training new electrical team members. Please post any recommendations for revisions or new powerpoints!

NOTE: These aren't comprehensive, sit-down training lessons.Sitting and watching someone babble in front of a projector is boring both for the teacher and the student. These are more intended to be used as a preface to a hands-on activity.

Powerpoints 1-3:
Introduction and terminology
Power system
Signal system
Attachment 15159

Powerpoints 4-5:
Motors and motor controllers
Cable management
Attachment 15160

Re: Electrical team training

Quote:

Originally Posted by evanperryg (Post 1288050)

Sitting and watching someone babble in front of a projector is boring both for the teacher and the student.

That depends on the teacher, and the student.

Re: Electrical team training

Be sure to get them into good wire organization habits. Also how to properly use the wago tool.

Re: Electrical team training

Here are some suggestions:

Presentation 1:

Tell the students that Ground is what all voltages are measured relative to. It'll help standardize readings later on, and if anyone goes into EE, they won't be surprised.
Servo can be velocity controlled (continuous rotation servo). Be careful, because those are commercially available.
Encoders don't tell you how fast something is spinning so much as how much they've spun (and maybe which direction, depending on the particular encoder)

Presentation 2:

Page 2: Clarify "continuous". I understand it to mean continuous voltage, but that's not necessarily the entire picture. Power systems (especially on the robot) are effectively DC, but past the motor controllers, they can kind of look like AC. Also, the current for motors is generally very much non-constant (but continuous).
Your power diagram isn't *necessarily* complete. You also have 12V going to your analog header and digital out. But that may or may not be important. It may also be prudent to delve into a discussion about the different current capabilities of different ports.

Presentation 3:

I wasn't aware that we had 24V level signals on the robot. Or 12V level for that matter.
As a matter of principle, not everything is PWM. You have CAN capability and I2C capability, neither of which actually use PWM. I'm also fairly certain that the cRIO does not communicate to the breakouts using PWM, though that would be an interesting design.
Just so that you don't confuse people, a solenoid is not the pneumatic piston. The solenoid is the valve you use to control the pneumatic piston.
Should you include some discussion of analog sensors? I don't know about your team, but my old team used to use quite a few of them. They're generally more abuse-proof than encoders.

Presentation 4:

Instead of characterizing current as low, medium or high, why not characterize it in amps?
It may be advisable to give more information about the motors, but then again, this is an electrical perspective, not an electromechanics perspective. Oh well.

Presentation 5:

Careful you don't shoot yourself in the foot by saying the example on slide 2 is necessarily easy to trace. Also, cable management does not necessarily mean shorter wires (the shortest wire is a direct line, which generally results in mechanical interferences and the rat's nest).
Upside down parts aren't necessarily bad. If I want to really save space, you'd barely be able to access anything without having to take the thing apart. A lot of things would be upside down. Especially the things that need airflow.
I would like to debate the notion that zip ties are bad for cable management. Sure, they're not necessarily the most ideal for every situation, but once you've gotten permanent cable bundles, nothing holds them together better than zip ties. They're lower profile, and if done nicely, it looks professional. But, if your team has decided not to, then don't. Better to have a stable standard than a debated and ignored standard.
An interesting byproduct of cable management is that you will incur service loops, and possibly higher resistance/impedance over your cables. This *could* affect the performance of your robot, as well as running signal lines next to high current noncontinuous DC lines. Cable management is not only about keeping things neat, but also keeping systems modular and maximizing the performance of signals. Many teams attack the CM side by using breakouts to DE-9/DA-15/DB-25 connectors in order to combine signals into a shielded cable assembly for each system, as well as using interchangeable connectors (Molex, XT90, Andersons) for power systems.

Overall, it's a good introduction to electronics for FRC. I would say that anyone who learned everything in the powerpoints would understand what the electronics divisions work with and possibly what the purpose is, but definitely not how the electronics divisions work, and probably not enough to look at any team's robot and understand the electronics components. You've done a great job covering most of the components, and some of the system level stuff, but there probably could be a lot more done with the systems level view (i.e. showing how everything fits together with both signals and power, showing the entire data flow from environment to actuator, showing where the DS falls into all of this). It's a great start, and I hope that you will continue working on this presentation. It has the potential to really be a role model for teaching FRC electronics.

P.S.: One suggestion for making the presentation itself better: A prof once told me that in order to be a really good lecturer, you have to explain each point three different ways. But you can't put everyone to sleep either. Take that as you will.

Re: Electrical team training

1-5)

"Source is the amount of power available for a circuit"

"Sink is drop in voltage across a circuit"

Read literally, you are saying "source" is measured in watts and "sink" in volts. I don't think that's what you intended.

1-6)
Voltage is the "Difference between amount of electrons at 2 ends of the source"

Not really. It's the difference in electrical potential.

1-7)
current is "The amount of electrons flowing in a circuit (kind of)"

It's the number of electrons flowing past a given point in the circuit per second, divided by
6.24×10¹⁸

1-12) encoder "Detects how fast something is turning"

...and/or how far it has turned.

4-3) Maximum efficiency is "Most torque and RPM per Amp"

Efficiency is output shaft mechanical power expressed as a percent of input electrical power.

Re: Electrical team training

Also get into the stuff they need to do:

Wire stripping theory (don't nick the strands, strip length is important, twist stranded wire ends to avoid stray strands)

Wire colors that are legal. (In fact, have them read some parts of last year's electrical rules, making sure they understand that these are LAST YEAR's and not valid for 2014)

Wire gauge and current capacity

Crimping tools, techniques, and terminals (and what the colors on the terminals mean...)

Screw torque (and where to find the specification!)

Wire dress (keeping wires neat - how and why)

Zip ties and the right way to cut the ends off (no sharp ends)

Insulation and chafing (e.g., against a metal edge)

The danger of electricity and batteries (high current generates heat, wires and batteries can explode, etc.) (warm connections and wires are damaged connections and wires)

Safely carrying a battery.

(the above are some of the more importat of my peeves)

Re: Electrical team training

Quote:

Originally Posted by Ether (Post 1288070)

6.24×10¹⁸

I'm forgetting, is that a coulomb of electrons, or another constant? For a second there, it looked like 10^-5 moles.

Re: Electrical team training

Someone really needs to make some funny 'video game' style assembly shorts for a FIRST control system. When you plug things in wrong....boom. Would be a lot cheaper than letting the real smoke out.

Re: Electrical team training

I like it. Remember to give credit and source where your pictures and information comes from.

Re: Electrical team training

Quote:

Originally Posted by DampRobot (Post 1288084)

I'm forgetting, is that a coulomb of electrons, or another constant? For a second there, it looked like 10^-5 moles.

It is the number of electrons in one coulomb of charge.

The elementary charge (electron or proton) is 1.60217×10⁻¹⁹ coulomb.

There is a proposal to re-define the ampere SI unit as coulombs per second.

Re: Electrical team training

Wow, thanks guys!!!

Quote:

Originally Posted by nathan_hui (Post 1288067)

Here are some suggestions:

Presentation 1:

Servo can be velocity controlled (continuous rotation servo). Be careful, because those are commercially available.
Encoders don't tell you how fast something is spinning so much as how much they've spun (and maybe which direction, depending on the particular encoder)
Page 2: Clarify "continuous".
Your power diagram isn't *necessarily* complete. You also have 12V going to your analog header and digital out. But that may or may not be important. It may also be prudent to delve into a discussion about the different current capabilities of different ports.
I wasn't aware that we had 24V level signals on the robot. Or 12V level for that matter.
As a matter of principle, not everything is PWM. You have CAN capability and I2C capability, neither of which actually use PWM. I'm also fairly certain that the cRIO does not communicate to the breakouts using PWM, though that would be an interesting design.
Just so that you don't confuse people, a solenoid is not the pneumatic piston. The solenoid is the valve you use to control the pneumatic piston.
Should you include some discussion of analog sensors? I don't know about your team, but my old team used to use quite a few of them. They're generally more abuse-proof than encoders.
Instead of characterizing current as low, medium or high, why not characterize it in amps?
It may be advisable to give more information about the motors, but then again, this is an electrical perspective, not an electromechanics perspective. Oh well.
Upside down parts aren't necessarily bad. If I want to really save space, you'd barely be able to access anything without having to take the thing apart. A lot of things would be upside down. Especially the things that need airflow.
I would like to debate the notion that zip ties are bad for cable management.
An interesting byproduct of cable management is that you will incur service loops, and possibly higher resistance/impedance over your cables. This *could* affect the performance of your robot, as well as running signal lines next to high current noncontinuous DC lines.

Interesting little tidbit for an otherwise bland slide, added.
They can be used for both purposes, added.
fixed.
Can't believe I forgot those! fixed. We gutted our practice bot and are going to rewire it as training, so I will explain the current limitations then.
welp... I'm not going to even try to explain how that typo occurred.
odd. I had a list of signal types there, and suddenly just PWM. fixed. Also, coming soon, the pwmRio!!!
The picture of a piston is to show them what a piston looks like. (it's not like I can't walk 10 feet and grab a few from our box of pistons, you know?) I will clarify the difference in speech.
The new members are fresh out of middle school. Most or all will have no concept as to the scale of current, so I figured 'low, medium, high' was better. Added numbers with those, though.
Again, this is more of a basic primer, so the basics are enough. They will learn more of that sort of thing wiring 2 or 3 robots before the season. (They will wire the 2013 practice bot, a kitbot possibly, and a vex robot for 1625's vex challenge)
We had an 8-solenoid block strapped upside down in our bot. Not happening again. That stupid thing fell off almost every match until a mentor gave up and strapped it on with 5 feet of velcro.
I accept your challenge. We should make a new thread for this. They work for everything, but aren't the best option, in many cases.
I have heard similar things, I will make that understood in speech.

Quote:

Originally Posted by DonRotolo (Post 1288073)

Also get into the stuff they need to do:
Wire stripping theory (don't nick the strands, strip length is important, twist stranded wire ends to avoid stray strands)
Wire colors that are legal. (In fact, have them read some parts of last year's electrical rules, making sure they understand that these are LAST YEAR's and not valid for 2014)
Wire gauge and current capacity
Crimping tools, techniques, and terminals (and what the colors on the terminals mean...)
Screw torque (and where to find the specification!)
Wire dress (keeping wires neat - how and why)
Zip ties and the right way to cut the ends off (no sharp ends)
Insulation and chafing (e.g., against a metal edge)
The danger of electricity and batteries (high current generates heat, wires and batteries can explode, etc.) (warm connections and wires are damaged connections and wires)
Safely carrying a battery.

This will be taught when we rewire our 2013 practice bot.
My team has quite a fun little story from '11 about wire colors. Sure to stick with the new members, too.
Good plan. will add.
This is another thing that we will teach when wiring the '13 practice bot.
Tighten it so that the terminal doesn't move, but not any tighter. See bullets 1 and 4.
Got a whole powerpoint for it!!
We don't use many zipties for a few reasons. I am going to increase their use, but not by much.
see bullets 1 and 4.
Will explain when talking about the power system.
see 1 and 4.

Quote:

Originally Posted by techhelpbb (Post 1288093)

Someone really needs to make some funny 'video game' style assembly shorts for a FIRST control system. When you plug things in wrong....boom. Would be a lot cheaper than letting the real smoke out.

We should make it like surgeon simulator!!!

Re: Electrical team training

Updated Powerpoints, including the 6th powerpoint I didn't include earlier. Thanks so much to all of you who helped!!

Powerpoints 1 and 2
Attachment 15171
-Introduction to FRC electrical
-The power system and power safety

Attachment 15172
-The signal system
-Motors and motor controllers

Attachment 15173
-Cable management
-The electrical pit*

*powerpoint 6 is specific to my team's electrical toolboxes. I suggest modifying ppt 6 in order to explain your team's electrical pit.

Re: Electrical team training

That's pretty cool!

You are missing some motors in the motor section. Also, the window motor isn't the only thing that can be controlled by a spike. You can control banebots rs390, rs395, rs545, rs555, the twelve volt rs775, as well as the andymark pg motors, the denso motors, the snow blower motor, and the vex 393 with a spike relay.

Re: Electrical team training

Quote:

Presentation1 Page5

Voltage
Difference between amount of electrons at 2 ends of the source

More accurate (but still not strictly correct): Difference between concentration of electrons at 2 ends of the source

Quote:

Presentation4 Page3

Maximum efficiency
Most torque and RPM per Amp

Most output mechanical power per input electrical power.

Quote:

Presentation4 Pages8&9

Jaguar
Very High Current

Talon
High Current

How much higher is the Jaguar current than the Talon current?

Re: Electrical team training

Quote:

Originally Posted by magnets (Post 1288675)

Thanks, will fix!

Quote:

Originally Posted by Ether (Post 1288680)

Page 5 "Voltage": "Difference between amount of electrons at 2 ends of the source".

The above is not correct.

Edited: I was sort of surprised when you said this. I was beginning to arm myself with sources saying I'm right when you edited :/

Thanks, Ether. I forgot to fix the motor controller current data. The IFI controllers can handle more current than Jags, and Talons fall right in the middle.