Pit electrical systems

So I’m kinda taking it upon myself to help design a new pit or at least redesign of such it may be a multi-year project, however even if it doesn’t get done this summer I’d like to have it planned out by the students before the end of summer. One thing that I want to ensure is done properly to start is the electrical system. just about every team that has an established built pit such as 973’s super pit has a hard-wired custom electrical system and that’s what I’m pushing for if the funds can be arranged. But I was wondering if anyone has some critiques or possible additions to what I’m thinking.

Parts list:

  1. Probably a dual function GFCI/ AFCI breaker (haven’t figured out breaker size though because it needs to be less or equal to the incoming power so idk yet)
  1. DC fuse panel for distribution
  2. USB chargers

Incoming power would connect into a centralized breaker box mounted to 1 of two main workbenches then the power would be distributed back out to the bench it’s mounted then to the next bench and possibly the battery charger separate but that’s to be decided. Power connectors between places will be these powercon true 1 connectors that should be very suitable for the job and also safe to use. One of the workbenches will have a high amperage DC power supply with a distribution board for the lighting in the pit probably a few 10w LED’s overhead, also a large Quick charging bank for the scouting iPad’s (7) and a few extra for phones in the pit so chargers don’t take up any plugs. Also might put in a small motor testing station depending on the power supply size because I found one of the larger supplies can do 89A.

Please I’d love suggestions and critiques also im curious if anyone has done the math of pit power usage so i can better calculate things.

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I think the biggest limiting factor is your incoming power cord from the facility. I would hope they’d run at least 12AWG cords, but I can’t confirm that’s what venues provide.

I’d recommend a standard desktop ATX power supply rather than the server PSU you linked.

Hot swap server PSU’s usually use proprietary non-documented PCB-based pinouts, whereas a standard PSU has wires you can solder to as well as standard pins for on/off/etc.

Additionally, regular PSU’s aren’t nearly as noisy as 1U server PSU’s, which I’m sure everyone in and near your pit would appreciate.

There is no standard for incoming pit power supplied by the venue. Some it is several pits daisy chained to a 15 service. Others you might have more.
We have a fabricated pit cord with numerous quality receptacles. The cord is 14 gauge SWO (Industrial quality extension cord) We never pull close to 15 amps so it is sufficient.

See but they don’t offer very good amperage like at all and even the ones that due arent reliable under sustained high amperage " learned from trying to run a smart battery charger. besides they actually under full load have never gotten overpowering to me in any way.

yeah, I doubt most people get to 10 amps but that’s funny because if I read correctly and it has been a while but the standard 3 battery chargers everyone uses pull 5 amps max so idk.

If I was doing a custom set up, I would add a power meter.

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I actually thought of that but then was like nah that would be over the top… But I doubt it would be that hard to incorporate in :thinking:

You can get ones that plug in. Not even that expensive.

That’s a possible idea however I think it would be better if it was mounted because if your at an event that has like a 2 gang receptacle it’s big and bulky and can get in the way… I do know drok makes some pretty nice and cheap power monitors that are like panel mount. ill look into it :grin: thanks for the idea!

Here is a thread about 5460’s Pit Design. It is based off 973’s, with some changes to better suit our team needs. Our Electrical schematics/BOM are available there as well.


Most often, I have seen 2 or 3 pits on a single 15A (or 20A?) circuit. This may limit what you really can put into your pit, especially if someone in the next pit (or your pit) starts up a large power tool, causing a current spike, and blows the breaker for your circuit and takes down several pits.

By making the pit a charging station, you are bringing more people to the pit than you may want. It seems that you are preparing for your team to do a lot of work on your robot at competitions. Bringing your scouting crew to the pit to recharge will cause congestion.

If that one power supply goes down, you have nothing. It also requires that you have to have a DC power distribution system. You may be better served by replacing the power supply and all the USB chargers with a couple of power bars and wall-wart chargers for the devices your team is actually using.

An alternative is to purchase a bunch of USB power banks to charge cell phones and other devices in the stands as needed. These can be recharged overnight at home or in the hotel.

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We have a small inverter that we have an Anderson connector on and swap a couple batteries to the stand for the scouting computer. But beware that I showed up in the stands one of the times and found that Chairman’s team was using it to power a curling iron for hair prep. :open_mouth:

That’s totally understandable. How can one do good work unless one is looking one’s best :wink:

Oh wait! Maybe your team members mistook the purpose of scouting and identified some team (members) they wanted to pick…

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I’m just suggesting for overnight and storage. But I do see your point about points of failure and maybe redundancy would help or spare parts because they are hot swappable.

At the District and Regional events held in the Houston area, the event organizers used a generator to provide power for the pits when they are located in a gym. We are asked to unplug everything from the power feed before leaving at the end of each day so it is not possible to charge anything in the pit overnight. There are volunteers who go through the pits after everyone leaves and unplugs anything left plugged in. This is to avoid a big inrush when the generator is first turned on that may blow breakers. Understandably, this may not be the case where you compete.

Totally. If the lead students had their pick, they’d take Maya from 3284. It’s a good pick, and would immediately elevate our Safety into award contention. I think my first pick would have to go to a programmer, if I was selecting.

To stay somewhat on topic, we have a power strip built into our custom tool cart. A single 12awg heavy cord feeds ~8 outlets strip (spaced out), the 2 led light bars, the battery chargers (4 outlets), and charges up to carts built-in batteries for the motors that drive it. We have a plastic 2 level shelf that has another multi-outlet strip 10-12, that I now mostly use for phone chargers. We also have another 4 outlet extension cord that we use for laptops. The outlets on the cart are used mostly for drill battery chargers, for heat/solder/glue guns, or dremels. We don’t bring bigger stuff. We also have some lights and a TV that hang up in the pit, and we usually have another small extension cord to run those, maybe back to the outlets on the cart, or whichever is convenient (since the location of the TV is dependent on pit location). It would be interesting to log our power usage, and I may do that since we have a logger still from back when we were selling LED lights.

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I think it would be really cool and interesting to see multiple teams power usage data… I mean how much does an event use :astonished:

I have to remind everyone that wiring your own electrical distribution for your pit may violate venue fire and electrical codes. These codes vary widely by location and may require wiring to be performed by a licensed electircian. Codes in rural areas are vastly different (and less stringent) than those in larger cities. Codes for buildings where large groups of people are expected (stdiums, theaters, etc.) or wiring for schools are even more strict.

1293 also adopted a system of using old robot batteries as means to power the scouting laptop (used for data entry from paper forms). One battery almost got us through the day, though our cable setup (SB50 on one end, automotive 12V on the other to power a basic auto parts store inverter) didn’t have a voltage meter so we didn’t know when it hit the bottom until it did. (That was confirmed with a Battery Beak, but that’s in the pits and meant a long walk with the battery.)

For charging up a lot of USB-chargeable devices, I swear by the Anker PowerPort 10 in my business (which involves sending people with a fleet of ten tablets for classes). I tried the AmazonBasics version, and some kind of charge built up on the cables that shocked my leg (and I’m not sure if it’s related to a tablet that refuses to charge now, but I can’t rule it out). Sent it back immediately, bought another Anker one. They are rock solid, and they only take up one AC outlet. Charge them overnight at the hotel, or top them up during lunch in the pits.

To blend the two and charge iPads with robot batteries, there is their 5-port car charger which would give you about 2A per port if something is connected to each one. But neither that nor the fast-charging options using USB-C PD are going to top up a fleet of seven for the night, so I’d probably still have a PowerPort 10 for that anyway.

(Also, no I’m not an Anker shill. Just an Anker stan.)

For several years, 3946 has used a single surge-suppressed and usually fused/circuit broken 6 outlet power strip. Two of those feed 3-bank battery chargers, two usually feed cordless tool battery chargers, leaving two for whatever, commonly a laptop charger, phone charger(s), or pit lights. Once we ditched the canopy and since cell phone lights and pocket flashlights have taken off, pit lights have been less of a thing.