Distro block, maxi fuse box, and ground stem

3 Questions:

1 We misplaced our 40 amp maxi fuse box, so we purchased the stinger 3 sided one, is this ok?

2 Right now, we dont have either the weight, nor the ability to use the ground stem, so we are using the ground block on the mini fuse box (for 20-30 amp fuses). is this also suficcent?(and legal?)

3 We lack both weight space and product to use the Distrobution block included in the kit. So we have the breaker split wire to the Maxi and mini fuse box seperately. i could find nowhere where it posted the distro block as a requirement, does anyone know betteR?

thank you all.

** Start drilling your holes…**

The ground stud is a must use in your robots circuit this year. Also if you are using the 40 amp breaker from the KOP you need to use the power distrobution block, using other 40amp breakers i would think the same thing is neccessary due to it not only splitting ground connections it also splits your live voltage which you would rather not be splitting from a fuse panel.

Team update 9 gives an acceptable source for the MAXI fuse blocks, As far as your ground question the Rules <19> to <23> don’t mention having to use the ground stem, I would double check to make sure you are using the min wire sizes, the same current goes out as comes back, A too small wire in the ground system is as much a problem as on the supply side. You might want to post to the first web Q&A section about the ground stem. The Distrobution block is as far as I can tell from rule 19 is an optional item. The driving issue is current safety, That’s why they gave us the wiring chart with min wire sizes on it. Good luck

Hello All,
The wiring diagram (schematic) shows the wiring for this year. If you use 40 amp circuit breakers you must use the distro block and the 4 way maxi block or allowed equivalent. One of the Q&A responses allow you to remove the unused section of both the distro block and the maxi fuse block. All teams must use the ground stud. If you use the maxi fuse block, the grounds for those motors must come back to the distro block just as shown in the diagram and return to the stud via #6

Al thanks for the update.

I dont believe we will have a problem with the wire size, since we are using 6 awg wire for all main power. The Stinger Fuse Box (recommended on the Q&A) does do a little bit of distrobution, so if possible, i think im going to use it as a distributor: (ASCII ART)

These 3 are power ins(interconnected), we use 1 as an in from the breaker, and 1 as an out to the other fuse box
|+|+| These 3 are outs, 2 to the motors, other is unused.

We did ground everything back to the mini fuse box, but as you guys say, we may use the stud.

I really dont want to waste a pound on something useless like that distro box unless it is absolutely needed, especially because our Stinger MAXI fuse box is rated for up to 4 awg wire.

Please reread Al’s post, the distribution block and ground stud are required for this years robots circuit. If they werent going to help in the long run they wouldnt be required.

Ok, thank you all for your help.

I know you don’t want to hear this but the suggested replacement is a SFB1MAXPT which is a single maxi block. (See Team update #9 page 3) The one you describe which has a common input and three or four outputs is not allowed. Sorry, I questioned FIRST on this last week. The original four independent fuse holders on a single block or four single blocks are the only allowable parts. The SFB1MAXPT snaps together to form larger blocks.
BTW see my post about terminating #6 & #10 wires into these blocks here in the electrical forum. They are designed for #4 - #8 wire but only grab about half of a #6 and about a 1/4 of #10 strands. If you use super flexible wire, then even less of the strands are captured.


I have read the rules back and forth. R42 references the wiring diagram, no requirement stated. R44 states 6 AWG to all fuse panels. I could not find the requirement to use the grounding stud in the Q&A either.

Is this required and where is this stated? I have run between the fuse panels with #6 ground wire and to the distro block.

Your absolutely right, but reread the rule again.

<R42> Electrical devices “MAY ONLY” be wired as indicated in this section. For your convenience, reference the 2004 Robot Power Distribution Diagram.

I read that (and FIRST intreprets that) as the Power Distro Diagram is your bible. You may only wire your robot as indicated. As I stated before, if you have no need for the maxi fuse block then you can leave the distro and the fuse block out. I can’t imagine any team would give up the drills or the Chalupas but it is possible. This is a safety issue as much as anything. I can tell you from experience, there was a lot of scary wiring jobs last year.

yeah…during one of the practice rounds at the chesapeake regionals, a bot caught on fire, cause being bad wiring :wink:

Section 5.6.1
“Except as noted herein, each Ground (GND or Common (-) wire from a speed controller, relay, or Robot Controller must go directly from that item to one of the 12 Common (-) terminal tabs on the circuit breaker/fuse blocks.”

I hope this helps. This will be what the inspectors will be looking for.

Tim Tedrow


Who did you talk to at FIRST that said the wiring diagram is the the rule, rather then a suggestion?

I read <R42> as saying that the robot MUST be wired as the rules say. Then it refers to the power distribution diagram. It says that the power distribution diagram is a conveniance, which is far from saying that it is the bible.

As ttedrow points out, section 5.6.1 says that you may wire the speed controllers ground to the circuit breaker panel, with no mention of the ground stud for speed controllers connected to a 40 amp circuit.

I was under the impression that all of the SFB*MAX’s were allowed. I know i have seen many teams using the 4 fuse one (most like the one in the kit), and we just purchased the 3 fuse because of availability.

I now do see on update 9 the problem, but why must they keep doing this to us? I just spent 40 bucks on this one (before the update), and we dont have the monitary resources for anything else. I wonder if this will clear because it was like this before the update (like with the soldering of the blue wires on the drill motor).

If anyone can post on the Q&A about this discrepancy, and whether any of the SFB*MAX’s will be applicable (seeing as the SFB3MAX is the same one as 3 SFB1MAX’s), i would be very thankful.

Today we did wire in the distro block, as well as the ground stud, although it really sucked to have to do all that crap when it was wired more efficently the other way.

ETA: The wording on the fuse box says : “Maxi-Fuse Panel Option” , which implies that you can use any fuse holder, but this is just one they recommend. Right now we dont have the option of purchasing another one, due both to money limits (1200 bucks goes mighty fast!), and time issues, so we are kind of stuck with the 3.

the distribution block and ground stud are required for this years robots circuit

Where do you guys see in the rules where it says the ground stud is REQUIRED?

Instead of using the ground lug, we have used the center “phase 2” of the Allen Bradley Distribution block which is more than enough to hold the current in not better than crimp on ring connectors to a ground stud.

However if someone could let me know if I missed something in the rules about the ground stud “required” I’d like to read it again.

PS: Attached is a very quick sketch I did of what I mean. I hope you guys can make heads or tails of it…




“All electrical devices must be isolated from the robot frame; the robot strucure may not be used to carry electrical current. The negative (return) wiring must be electrically isolated (floating) from the robots frame. (The isolated ground arrangement is neccessary due to polarity reversals that occur under certain operating conditions such as motor direction reversals.)”

Thats one main purpose for the ground stud!

Dez, all that says is that electricity must be isolated from the rest of the system. This could be done with say… the ground wires on the BUSS fuse connector, like my team had up until this thread, or other such things. I dont see how forcing the teams to use lower guage wires (ie, using the distro block ) adds safety.

Up until this, we had straight 6 awg wires running from battery (both terminals) to our fuse boxes, which is easily the safest it can get. Instead, now we need to go to each fuse box with a lonely 10 awg wire, which is going to get a heck of a lot hotter than the 6.

Thats one main purpose for the ground stud!

My diagram mets the requirments of “isolated from the robot frame”. It doesn’t say ground stud required does it? The distribution block is a form of isolation is it not?

It is and it is not a form of isolation. The way its a form of isolation is it is “isolated” from the frame but then its also not a form of isolation due to the constant flow of electricity right next to it. The point of the distrib. block is to have the center empty with common on one side and hot on the other. The ground stud is to place a common central ground area on the bot which comes directly from the batteries common terminal post.