The 2022 control system has been announced with new support boards being developed by Rev Robotics. It may be too late to influence a change, but I’m interested in what people think about the PDP.
This year, there have been numerous posts trying to find ways to connect more then 16 things to the PDP. We’ve also seen an explosion in brushless motors that can draw more power, and an increase in brownouts because team’s don’t manage their power draw, indicating that perhaps less ports is prudent.
Assuming that the battery doesn’t change, how many ports should the new PDP have?
I think as long as there’s 2 more slots more than there are motors allowed on the robot, that should be fine. So let’s say you could have 16 motors and then two extra slots for custom circuits or something else.
12, but allow for multiple boards. Teams then have to weigh the costs/benefits of running one board and fewer outputs vs two boards with more outputs but greater space/weight needs.
Perhaps two models; one smart PDP that supplies the mandatory regulated and lower voltage rails, and another that is simply breaker slots and maybe current monitoring.
I quite like this idea, but I’d do it a bit differently. Have however many ports that can be used for motors, plus one or two with a 10A limit that can be used only for CUSTOM CIRCUITS. Don’t impose a strict limit on the number of motors, that way teams can still use two BAG and other small motors on one branch circuit.
I’d also like to see the rule changed to allowing two motor controllers each with a BAG motor on the same branch circuit instead of needing one motor controller for the two motors (so they always have to get the same voltage). But that’s a different issue than we’re talking about in this thread.
The problem with that is the last few years there’s been no quantity limits on motors (e.g. the limit on number of motors has been set by the number of PDP ports)… so clearly the PDP should have infinite ports!
As teams increase the number of items that require ports, like secondary processors and limelight, there is no reason not to future proof the pdp. I say 21+. This also allows for higher power serves and solenoids.
I would like to see another low current unregulated 12V bus like the current PDP’s VRM/PCM/RIO slots if more 40/30A slots isn’t on the table. I’m thinking one 20A non-resetting fuse protecting 2-3 pairs of Weidmuellers set aside for custom circuits.
The big problem here is the current limitations of the battery (which are enforced by the main breaker). I think it would be cool to see an option to use a second battery in parallel with the first. That would double the capacity and current capabilities while leaving the voltage the same.
For an added design trade-off, have teams running a second battery comply with a lower weight limit. You could just have the batteries count towards a (higher) weight limit, but I think that would create an incentive to try to lighten the battery/cables which isn’t good.
You could enforce your dual battery weight system with a modifier on the robot weight of -15 lbs if you run dual battery. 15 lbs is a close enough approximation.
Why in series? That would make it a 24v system. Are you thinking of having a voltage regulator step it down to 12v to help prevent brownouts?
And yeah, -15lbs is what I was thinking as well. That being said, you could adjust it higher or lower than that to “tune” the trade-off. If 2 batteries give a HUGE advantage, make it -20lbs instead. If the weight penalty is too high, make it -10lbs.
I don’t know that that’s a huge tradeoff. Keep in mind that the best teams have saving weight down to an art form, to the point where the first question asked of any new product in the FRC market isn’t how strong or powerful it is, but how much it weighs. It’ll also ensure that teams that can afford to use 2 batteries per match and 8 Falcon drivetrains massively overpower rookie teams stuck with the kitbot. We’ve done a good job of raising the floor, now let’s not raise the ceiling with it.
In my opinion, it should be left as a design constraint just like the max weight, height, frame perimeter, or BOM cost.
And that would put it right in the range of a 6s lipo. 3s is too low and 4s is too high for most of the current control system. Not saying we should swap battery tech, but the opportunity would be nice.
I voted 16, though I am open to more fused low-amperage connections for custom circuits or external battery packs for some things.
I’m not wild about additional motor-capable ports for a few reasons:
Brownout concerns
Mild safety concerns (in that gearing may get too aggressive when you can throw gobs of power at something)
Preservation of the design challenge (our design choices had us sweating each circuit this year)
A tiny bit of equity and inclusion, in that each motor circuit is easily another $75-200 between the controller, motor, and probably a gearbox. ($74 would be a base SPARK with an AndyMark Snow Blower Motor. Base SPARK with a RedLine and 20:1 57 Sport would be $144.50 plus shipping. Talon SRX with a 775pro and a 20:1 Versaplanetary would be $199.93 plus shipping.)
Be kinda cool to offer a place to physically mount the Main breaker. There’d still need to be the option to “remotely” mount it since the PDP tends to get buried.
Came here to say this. Maybe even offer a few in different sizes - make it modular. Some years we need a ton of 40A giant breakers, other years it’s just a few of those and a bunch of tiny custom circuits. Provide a reasonable no-thought default, allow for mix & match.
I think allowing more motors would raise the floor rather than the ceiling. Top tear teams already know how to work around motor limitations. PTO’s like the ones used by 3310 and 195s 2019 bots, or the use of pneumatics like the integrated elevator climber on 254s 2019 bot .
Mid-level teams could have more mechanisms done and thrown on the bot, without putting time into integrating.
Yep, spacecraft run on 28 V busses (nowadays 32 V, due to lithium batteries) for the same reason. It’s so nice being able to run heaters through 26 AWG wire and micro-D connectors.
I’m not referring to adding more motor slots, I’m in full support of that. My comment is referring to specifically the potential ramifications of allowing 2 batteries in parallel.
