Design of a pull out eletrical panel

[Rombus]

Well, 1278s season is over, but even though its just hours after our only regional, I'm already thinking of things i can improve on next year.

As the electrical person for our team, I'm thinking of trying and designing a "Pull out" Electrical board. This idea i had after having issues with our RC and having to replace it quickly, and to ease wiring and make for an over all cleaner look.

So heres a few questions that should start me on my design:

1. Does anyone make drawer pulls or slides that don't have backstops or locks at full extension?

2. any suggestions on what i might try and lock it in with? I'm thinking about some form of clasp kinda like whats on tool boxes.

3. if i ran the battery connector into said electrical panel, Would it be FIRST legal to use the 50amp Anderson connector or would i have to go up to the 175 amp Anderson even though the battery has the 50amp version on it?

4. I know i can remote the program and reset switches, but there is no way to remote the lights on the RC or the lights on the victors/spikes correct?

5. We have had MANY problems with the TTL chip and TTL Connection on our RC and camera, Could we use some 4 conductor cable and connectors and mount the TTL chip flat? What about the possibility of directly soldering the wires onto the TTL Chip?

6. We were having some issues with the camera acting very funny in disabled mode and programming (Jittering, tending to go to 0, 0) And i Think it may have been due to noise in the PWM signal lines. is there anyway i can shield the wires better? Twist them around the ground line?

7. Final question, Do they make such a beast as a right angle pwm cable or something less break prone than the current pwm connections? chances are next year we will be running custom pwms, so I'm looking for the best connectors to use.

Thanks for any help!

[DonRotolo]

Rick,

Complete answers to those questions would take a book. It is great that you're thinking of this stuff, though. Here are some thoughts to get you started at least:

1. Yes, you need to look for them. You can also disable or remove the stops on most rails.
2. A screw or two can hold it in place, there's a million possibilities here.
3. You must use one 50 A connector, and I think it's only legal to use one, not a second one! Ask FIRST next year, but I think you can get away with one only.
4. Correct. I doubt the judges would allow fiber optics or a similar scheme. The visibility rule is also to help you - if there's something wrong, the field techs can help diagnose it quickly with the lights.
5. Flat is OK. You can solder too, but good luck if something goes wrong. Instead, use hot-melt glue OR silicone sealer to hold everything tight - holds but removable. Also applies to PWM and other cables.
6. I don't think that was interference, I have seen it on many robots. Really, the PWM frequencies are kinda low and not likely to see much crosstalk. If you really must shield the wires, just but round shielded 3-conductor wire. Remember to ground the shield at one end only, or you'll get ground loops.
7. Yes, look at Figure 2 but that's not going to help you much. One possibility would be to make up a connector body and wire everything over to a different kind of connector, say screw terminals. (Remember, all the Red and Black pins are the same, only the White pins matter!). Or, see #5 above.

The biggest problem with what you propose is how to make and break all those connections (to the sensors, motors, etc) reliably and quickly. One expensive but good solution would be Circular MIL Connectors (look on the second page). Really high currents (check the contact rating) can use two or more pins in parallel. Clearly solvable, but you need to think about it.

Another possibility is to make a fold-out panel, so you can access it easily when you have to, but it's tucked in at competition. Eliminates a lot of problems with connecting things, too, you just need to allow for the wires to flex at the "hinge"

Good luck,
Don

[TubaMorg]

Our team has been mentally mulling this one over too. In terms of weight you don't want to get too fancy, but what do you think of a computer dock sort of strategy? You could put all of your low voltage type wiring (PWMs, sensors, etc.) through a large multipin connector to dock with additional higher voltage connectors for you motor wiring. Then design the electronics tray to slide in/out easily but still be secure. Like I said we haven't gone beyond just thinking it would be nice.

[Greg Marra]

Originally Posted by Rombus

5. We have had MANY problems with the TTL chip and TTL Connection on our RC and camera, Could we use some 4 conductor cable and connectors and mount the TTL chip flat?

That is one of the best ideas I have heard all day.

[devicenull]

Originally Posted by Greg Marra

That is one of the best ideas I have heard all day.

We have a piece of metal shaped like .. _|- holding the TTL board on. Didn't have any problems with it coming off.

[eugenebrooks]

In general, if your electrical design adds connectors these become
additional places where connections can be bad. We cut our PWM
cables to length, keeping the original male plug for the victor or
spike, replacing the female connector with a molex c-grid connector
using proper crimp tooling and careful inspection of the terminals
prior to assembly.

The cable is zip tied down to the mounting board near the victor or
spike and near the controller. The wire goes up-and-over into the
victor, spike, or RC, providing good stress relief.
We cut the female end because the original male end of the PWM
cable is required to get good retention in the spike or victor. Additionally,
one can glue the c-grid connectors together as you install them on the
RC, producing a single connector that is very difficult to have wiggle
its way off. We do this for our array of switches used to select
robot behaviors as they tend to work loose otherwise.

The TTL card is very problematic. You can solder it onto the pins
of the RC using a high quality soldering iron with a very fine tip,
or you can make a bracket to retain it. We made a bracket to retain
ours and had no problems with it working its way off at PNW. The PWM
cable on the TTL card stays on quite well, but it is again very important
to zip tie the cable down with a little stress relief so it can't pull the
connector loose from the TTL card.

The two pwm cables that plug into the camera are very problematic.
We removed the sockets from the board and soldered cables directly
to the board. We also glued the camera to the board using epoxy
and some small wood blocks. The de-soldering job is very tricky as
the board has plated through holes, but it is worth doing in order to
remove the possibility of these connectors coming out during a match.
You could also epoxy a piece of a popsicle stick to the male and female
connectors, to hold the plug in place. Again, double zip tie the cables
to the bracketing mounting the camera near the camera, so the cables
do not get pulled loose from the camera.

We use the AMP mil-spec terminals, and the AMP crimper, available
from digikey. We have been using the commercial grade crimper, but
I have noticed some of the terminals slipping a bit during crimping
and am considering stepping up the mil-spec crimper to remove this
problem. The mil-spec crimper has a feature that prevents the terminal
from sliding as you squeeze the crimper, preventing a bad crimp.
We have never had a pull out on the amp mil-spec terminals,
and we test a few of these to desctruction prior to wiring the robot to
make sure everything is crimping properly. The wire always breaks
before it pulls out...

Before I worried too much about using shielded cables to remove
noise problems, I would use the analog inputs to make some
noise measurements. Your problems might be getting caused
by issues other than electrical noise on the wires.

With appropriate wiring methods, it takes no time at all to change an
RC, or spike, or victor.

Eugene

Originally Posted by Rombus

As the electrical person for our team, I'm thinking of trying and designing a "Pull out" Electrical board. This idea i had after having issues with our RC and having to replace it quickly, and to ease wiring and make for an over all cleaner look.

So heres a few questions that should start me on my design:

1. Does anyone make drawer pulls or slides that don't have backstops or locks at full extension?

2. any suggestions on what i might try and lock it in with? I'm thinking about some form of clasp kinda like whats on tool boxes.

3. if i ran the battery connector into said electrical panel, Would it be FIRST legal to use the 50amp Anderson connector or would i have to go up to the 175 amp Anderson even though the battery has the 50amp version on it?

4. I know i can remote the program and reset switches, but there is no way to remote the lights on the RC or the lights on the victors/spikes correct?

5. We have had MANY problems with the TTL chip and TTL Connection on our RC and camera, Could we use some 4 conductor cable and connectors and mount the TTL chip flat? What about the possibility of directly soldering the wires onto the TTL Chip?

6. We were having some issues with the camera acting very funny in disabled mode and programming (Jittering, tending to go to 0, 0) And i Think it may have been due to noise in the PWM signal lines. is there anyway i can shield the wires better? Twist them around the ground line?

7. Final question, Do they make such a beast as a right angle pwm cable or something less break prone than the current pwm connections? chances are next year we will be running custom pwms, so I'm looking for the best connectors to use.

Thanks for any help!

[Rombus]

Wow, thanks for the help so far! This is one of those whatifs I'm taking to the next step. I'm hoping that if we can do this for next years bot ill be able to do a white paper on how we did it.

To explain my idea a bit better: This idea sprang up from having to replace the RC mid day on Thursday and the cuts on my hands that ensued. Plus we had an issue on Friday where a single chip of metal was causing a 5v short that was giving us some headaches. The idea with a removable pull out panel is that we can set it aside if we are working on the robot and not worry too much about metal shavings, and if i need to change a wire or something i can do so without getting in the way of the build team.

The panel would have 3 banks of connections:
1 main battery connector: The battery and 120 amp switch would be mounted on the robot, and the main battery power would be delivered to the panel via what i hoped would be another 50A Anderson connector.

X Motor connections: these would be provided by Anderson power pole connections. We used these in 2005 and really liked them overall, but some supply issues and could not get them this year. I think the would work well for this application since they can be combined and mounted.

X TTL/Data/Servo connection. This is the sticking point. The DB25 we used this year worked well, but i don't know if it would really work as well on a pullout design. an edge connector (Think PCI card) would be cool, but might not stand up to the wear.


Our camera problems this year were not so much the fact the TTL was falling out but that it was not making connection somewhere, Either a pin or female mate was bent weird or out of shape somewhere, since code wise it was fine, and wiring wise we were also fine. I couldn't nail down the problem, one time it would work, then we would loose it again, quite frustrating when everything is right >.<.

again thanks for everyones help! now to start fleshing this idea out some more

[ECarlson]

We've had a self-contained, pull-out, electrical/electronics system box for the past 2 years. We've used straps to hold them in place. This year's was more compact than last years. We were planning on making it plug in this year, but that turned out to be difficult to accomplish, so we just had sets of connectors that plugged into the box by hand. The motor cables connect with groupings of smaller Anderson connectors. The signal cables for the sensors and stuff connect with DB-25 connectors.

We have lots of photos of them in the photo galleries on my web site (link below).