24v Power Conector to from the PDB to the cRIO

[mcf747]

Hi everyone,

I have attempted to post on the official first forums but it says that an administrator must approve me so I am going to post her for some one to help me or re-post for me on the FIRST forums.

I know the power adapter linking the cRIO and the Power Distribution Board has 4 "terminals" (please correct me if I am using the wrong terminology) but according to 3.2.6 in the Control System Documentation you only need to use 2 out of the possible 4 connections between the PDB and the cRIO

How do I build a cable for passing 24V power to the cRIO?
1. Take a color coded pair of 22-14AWG wire and cut to length
2. Optionally twist the pair now for better cable management.
3. Strip 5-6mm off of both ends of both wires.
4. Use a small flat head screwdriver to actuate the Sauro CTF04BV8-CN connectors
5. Insert the positive wire in the port labeled “V”
6. Insert the negative wire into the port labeled “C” next to the “V” port.
7. Insert into the Sauro CTM040V8. Tighten screws to ~¼Nm.
8. Give a smart tug to verify the connection is secure.

I was wondering if anyone knows what the other two are for?

Thnanks for any help you can provide,
Matthew Forman
MorTorq 1515

[ATannahill]

Nothing, leave them empty.

[mcf747]

Thanks for the quick reply.

I understnad that for our contex at least at this time they may not be important but I have to think they do something because they are there. So if anyone else may acually know what they are used for I am quite interested to find out.

Thanks again for the quick reply though with the important info.

Matthew Forman
MorTourq 1515

[EricVanWyk]

As rtfgnow said, "Nothing, leave them empty."

Unfortunately, you won't find an answer beyond RTFG's. They really don't have a purpose. Consider them to be bonus terminals (that you can not use).




BTW - I prefer "PD" over "PDB". I pronounce it "Petey".

[mcf747]

Ok thanks for both of your help.

Matthew Forman
MorTorq 1515

[Phalanx]

Actually the poles are in pairs. + - and + - for the 24V plug on the power distribution board.

If you look here on page 11 you will see it marked.
http://www.usfirst.org/uploadedFiles...s-Rev-0-4f.pdf

[mcf747]

Thanks Phalanx,

I did read that documentation and did see that, but my question was more to the effect of why there are 2 pairs of positive and negative?

Matthew Forman
MorTorq 115

[Mike AA]

Originally Posted by mcf747

Thanks Phalanx,

I did read that documentation and did see that, but my question was more to the effect of why there are 2 pairs of positive and negative?

Matthew Forman
MorTorq 115

Probably for powering 2 CRIO?

-Mike AA

[Russ Beavis]

Why does the PD have 4 terminals (a pair of + and a pair of -)?

Short answer - Because the cRIO has the same 4 terminals and we wanted the PD to use the same pinout.


Then you might ask "well, why does the cRIO have a + pair and - pair?" According to the datasheets for the cRIO, its internal power supply is designed to be driven by redundant power supplies for extra ruggedness.

Many high-availability/critical applications require multiple power sources for safety/reliability. So... if you need that level of performance, you can include an extra power supply and use both to power the cRIO. The module will use whichever power supply is outputting a higher voltage. If one supply breaks, the other supply will continue to power the cRIO.

Russ

[dlavery]

Originally Posted by Russ Beavis

Why does the PD have 4 terminals (a pair of + and a pair of -)?

Short answer - Because the cRIO has the same 4 terminals and we wanted the PD to use the same pinout.


Then you might ask "well, why does the cRIO have a + pair and - pair?" According to the datasheets for the cRIO, its internal power supply is designed to be driven by redundant power supplies for extra ruggedness.

Many high-availability/critical applications require multiple power sources for safety/reliability. So... if you need that level of performance, you can include an extra power supply and use both to power the cRIO. The module will use whichever power supply is outputting a higher voltage. If one supply breaks, the other supply will continue to power the cRIO.

Russ

Russ-

Thank you for a succinct and informative answer. It is always helpful when answers are provided with a philosophy of "you may not use this in FRC, but we recognize that the world is larger than just FIRST, so here is some information that may be useful beyond the boundaries of the competition." While sometimes that information may never get used, more often that extra knowledge can spark a thought that leads to a new application or the creation of a new development that might never have happened otherwise.

It is a much better approach than "you don't need to know, and we are not going to tell you."

-dave



.

[crake]

Originally Posted by Russ Beavis

Why does the PD have 4 terminals (a pair of + and a pair of -)?

Then you might ask "well, why does the cRIO have a + pair and - pair?" According to the datasheets for the cRIO, its internal power supply is designed to be driven by redundant power supplies for extra ruggedness.

Many high-availability/critical applications require multiple power sources for safety/reliability. So... if you need that level of performance, you can include an extra power supply and use both to power the cRIO. The module will use whichever power supply is outputting a higher voltage. If one supply breaks, the other supply will continue to power the cRIO.

To add to Russ' reply... The 4 position plug on the cRIO-FRC is the same that is used on other cRIO's. The FRC has a single-input supply whereas other cRIO's have dual-input supplies. So why have 4? Because its a standard connector. Do you use all 4? Not with the FRC hardware.

[mcf747]

WOW...

Thanks for the detailed answer from Dave, Russ, and Crake. I understand that the cRIO is capable of taking 2 power supplies. What do you guys think about running 2 12 volt rc batteries in series (to get 24 volts) to act as a backup battery for the cRIO. I think I remember reading somewhere that the PDB has a backup battery built in but that could just be to many hours on the forums. Another reasion would be because you could never have to much redundancy. I hope this would be cleared up in the rules but Dave if you want to cherp in, please be my gust.

Originally Posted by Russ Beavis

According to the datasheets for the cRIO, its internal power supply is designed to be driven by redundant power supplies for extra ruggedness.

Russ I was also wondering what datasheets were you referencing? I do not recall seeing anything in the materials provided by FIRST and if it was something you found I would love to have the link. I love to read theses types of things and educate myself as well as humanly possible on the components I work with and anything I may come across.

Thanks again,
Matthew Forman
MorTorq 1515

[Russ Beavis]

I forgot about the difference that Chris Rake mentioned - the cRIO setup for FRC (and, I believe, all of the new "integrated" cRIO setups) does NOT include provisions for a second (redundant) power supply. We learned about that diff during development but decided to use the "complete" pinout that all of the "non-integrated" cRIOs utilize (which is, for our purposes, also compatible with the FRC cRIO).

Unfortunately, this means that we can't exploit redundant power supplies in FRC. Don't be too sad, though - designing fault tolerant systems is what I do for a living and they're generally not cheap (and they need to be completely and fully architected from the ground up to be truly fault tolerant). You really have to NEED such performance to justify the development effort and cost (eg military, medical and aerospace apps).

Datasheet for the cRIO-FRC http://decibel.ni.com/content/servle...structions.pdf

Note the "NC" (Not Connected) pin in the middle of the 4-pin power connector on page 1. That "NC" pin is used as the redundant power supply input on all "non-integrated" cRIO systems (ie the versions that include separate controller and backplane modules).

It's because of that "middle" NC pin that the FIRST Power Diagram stipulates that the outer two pins be used to power your cRIO. Since we wanted to use the same connector on the PD and copper traces on PCBs don't really cost anything, we connected the "NC" pin on the PD to the same 24V output from the PD (hence the "+ - + -" arrangement on the PD instead of "+ - NC -").

Regarding that backup battery - eliminating the need for a backup battery was a highly desirable feature for the PD. The use of switching power supplies with wide input voltage range and solid transient response obviates the need for that extra storage device. I don't think that anyone's going to miss that battery...

Sorry for the long-winded response. I do like to "talk".

Russ

[EricVanWyk]

Originally Posted by Russ Beavis

Since we wanted to use the same connector on the PD and copper traces on PCBs don't really cost anything, we connected the "NC" pin on the PD to the same 24V output from the PD (hence the "+ - + -" arrangement on the PD instead of "+ - NC -").

mcf747 -

My apologies if my earlier answer seemed curt. I was answering the question of "Why does the PD have the extra pole on the 24V connector?". The more interesting answer given by Russ & Chris answer the question "Why does the cRIO have an extra pole on the 24V connector?"

Unfortunately, the extra pole doesn't have a purpose in FRC2009.

[mcf747]

Russ, thanks for the data sheet.....I always love new reading material.

As far as the power connector I now understand what the NC on the power connector meant.

I also cannot say the joy it brings me not to have a backup battery, but what can I say, I think redundancy runs through my veins.

Also if some one could make a quick post on the official FIRST forums in the Electrical section summing up what we said here or even just a link, I think it would be very beneficial to other electrical people out there who come across this same question. Also since that is where FIRST really wants us to be working with each other with the new control system....i think. (Not to put CD down) I would do it but I have a "frozen account" because I created after the forums came back online after the incident.

Matthew Forman
MorTorq 1515