Building a second robot - electronics?

When trying to do the two robot thing, do you HAVE to have two sets of electronics? Can you use that as your weight allowance and transfer that off your second robot back to your bagged robot at competition? We have a decent influx of funding this year, and I’m stewing on trying to do the second robot thing, but it would eat up a ton of it to get two sets of just the base electronics… the roboRIO, PDP, router, breaker, VRM, etc., etc. Does anyone else swap before bag?

If you’re going to do this, design around having a modular electronics panel. Make it easy to disconnect everything and label everything well. This can be a good idea but you don’t want it to take up your time at events.

You could go with one set and not use any of your withholding allowance if you keep any mounts on the bagged robot and wire everything at the competition as COTS components don’t count towards withholding allowance.

My team has never had 2 robots (comp. and practice) that look 100% alike, but they have the same manipulators on them to practice code. Because of not being the most funded team, we pretty much only had Jaguars on he practice robot and SRXs on the Comp robot. I believe we put one Talon SRX on the practice to test sensors. We are fortunate enough to have 2 roboRios (mainly to have a backup), and 2 of a couple other things, but those get removed from the practice robot to get taken to events. If you label everything, it shouldn’t be too hard to move all the electronics over, but labeling is the key or you may mis-wire the robot, or spend too much time tracing wires.

For our team, it was a multi-year process to build our way to two sets of electronics, and it has been an ongoing process as we buy more expensive stuff to replace components that are obsolete or fried.

The first thing I’d want two of is the power distribution board so I don’t have to wire all of the motors at the event. Next after that would be motor controllers, but those are pricey.

Take advantage of FIRST Choice and vouchers to build up your supply of DC motor controllers from year to year. Rob last year’s robot and reuse those. Purchase a couple extra every year. You can mix and match and choose the less expensive ones (Sparks via cash, Victors via Vex voucher and FIRST Choice).

It’s easier to move just the RoboRio and VRM than it is to install a full set of electronics. Since the RoboRio is a lightweight $400 COTS component, it makes economic sense to withhold that piece for use on your practice bot.

A practice bot with partial functionality can still be quite useful. Just having a chassis with rolling wheels on it can be enough to do some manipulator development and testing. Or a driveable bot without any manipulators can be used for some autonomous motion testing.

It’s better to have a completely identical practice bot with a complete set of spare electronics, but there are some useful intermediate setups on the way to having the full set.

My team (5842) last year Didnt have much funding at all especially after the surprise of going to worlds but that was our main priority last year was to have two working robots. It’s great for drivers and programmers to work on, and also you have all those parts for next seasons prototype/practice bot. Also when considering the electronics as the weight allowance realize that if you need to make major changes to the competition bot you may run into weight issues.

It’s awesome to have two completely identical FRC legal robots and control systems.

One alternative is to use a lower cost micro controller to get a low cost practice robot up and running for driver practice and other testing.

There are many great options these days.

Our own Arduino based Gorgon Controller is low-cost and can handle a complete robot, including pneumatics.

The CTRE Hero is also a great option, especially since it natively supports the STX.

Real roboticists interact with and experience a multitude of hardware and software platforms in the real-world. The RoboRIO is highly specialized…so building around other popular alternatives is also a great way to expand your program and it’s educational opportunities.

1058 built our two robots on a budget this year. The electronics are the toughest part to get around. Many of the design decisions we made in certain sub-systems were to keep our costs down and deliver two competition “shells” and one electronics board we could swap between the two.

Our main board was a small sheet of 3/16" or so lexan that we mounted the primary electronics to excluding things like the RSL, radio, and pneumatics items. We duplicated those on each machine so we didn’t over complicate the system and the team had a large inventory of pneumatics. The board was attached with 8 or 10 screws that went to riv-nuts on both frames so a screwdriver was all we needed to swap boards and all the connectors were easily accessible and Andersons labelled for plugging motors in.

We believe it worked out well for us even though this isn’t a normal way of making two machines. It kept our budget for two machines just around $5000 which included a lot of COTS items we used as our machining team was making more framing than a normal season plus spare parts knowing it was a tough game. Throughout our season we swapped the board between our shells which looked something like our practice robot here in late Julyjust without a climber. For Week Zero our practice robot went to a scrimmage then we held back the board (12lbs) as part of our withholding and tested our climber for Reading. During unbag the board went back on for our first event then taken off at the event before we left. We repeated this for Rhode Island and then after Boston it stayed on our robot except for a few occasions where we removed it to debug some electrical issues which was a big plus in a game where the robot was so compact. The obvious downside was as the season progressed and our to-do list boiled down to software improvements the board was sitting in the robot bag or on the way to St. Louis and the knowledge that our weight budget for improvement or spares was only 18lbs because swapping the board was a 12lb hit on the allowance.

The biggest expense will be your motor controllers. For our needs we went with Talons but the Spark controller by Rev Robotics is one of the more cost effective ways to maximize your budget. Even though teams already submitted their lists, using FIRST Choice is an easy way to get some large ticket items off of your list. Last year and going into 2017 we’ve used FC to get some of our control system needs taken care of either full or partially.

Building on a budget isn’t easy, but as a Business major its a fun aspect of FRC by learning ways to stretch your budget and maximize what you are getting out of your machine(s). Our system wasn’t a perfect solution however it worked really well for our needs. Something we considered was that we didn’t have access to more than our hallway for consistent practice so a full functioning machine wasn’t our most cost effective solution. We haven’t fully discussed what we’ll do this year but we might try to squeeze more drive practice in between events.

Our second robot did end up with its own board by the Fall using smorgasbord of motor controllers taken off older machines.

Sorry to change the topics but has anyone not used the D Link or Openmesh routers for their practice robots?

We’re looking to go 2 bots this year, and we’re on the fence about ordering a radio… I know FRC announced the 2016 radio would be “legal” but IIRC they didn’t clarify if the 2017 Radio would be in the KoP. Would be nice to know.

[As always, assuming the rules for this year are consistent with recent years] - Bottom line - yes, you can make do with one set of electronics, and transfer it from your “practice” robot to your “competition” robot on the first day of a three-day event, or during your last “unbag window” if you’re doing two-day events.
However, doing so would greatly reduce the value of the “withholding allowance”. Any item (whether control system, manipulator, sensor, or otherwise) transferred onto the competition robot after stop build day must either be broken down to individual COTS components, or counted against an event’s withholding allowance. Even before we built a “second robot”, we found it highly useful to have a “second control system” so we could bag one wired into the competition robot and work with the other between stop build and competition.

Edit: having two robots and one control system will support drive practice, but will probably not support much improvement of your drive system or manipulators after stop build, unless you’re uncommonly fast at pit builds.

FWIW, we have always (yes, back to rookie year) used our withholding allowance for a manipulator (or two). The only time we withheld our control system was rookie year, when we did transfer it part-by-part to the competition robot. I am still amazed that we managed to pass inspection before the first round of competition.

Assuming it’s not a functional change, it’ll probably only be included in Rookie kits.

That’s what we figured… however given the out of stock status at AM, and unknown return date, knowing definitively one way or the other would be nice. :slight_smile:

Their was a discussion about a similar topic in 2015. Someone talked about bringing their whole second robot in their trailer so that they could take a part off their backup to put on their competition robot if they needed it. All in all, the discussion on the thread concluded that this was illegal since their whole second robot would be in the withholding allowance and that was way over weight. So my best guess is, if you plan to bring a backup electronic panel to each competition from your second robot, you need to disconnect it from the second robot and only bring the electronics panel to the competition to be legal.

It depends on your reason for having a second robot, and on when you begin training the drive team.

For us in 2016, the second robot was built to enable drive team practice simultaneously with robot improvements – hardware and software. We built two (almost) identical robots, so that whichever one was closest to our target competition set-up could be used for practice as soon as it reached that point. Then, the other robot was brought up-to-date. Then we started adding the next feature on the priority list. After that was installed and shop-tested, build would swap robots with the drive team, and the cycle would repeat. The same cycle continued whenever we had out-of-bag time (equivalent to Thursday at a Regional).

Here is a shot of the two robots, during a brief interval when both were in the shop.

We got the climber added just before MSC and used it there a couple of times. It was working much better at CMP and IRI.

As long as I can remember the second robots we’ve had on my current and previous teams have used DLink/competition routers. We always take it with us to events so we have a spare just in case.

It’s worth it to have separate electronics for both machines, even with the expense. With FIRST Choice, it’s easier to get a second copy of most components, and you can use PWM-based speed controllers across both robots to keep the costs down. If you switch anything between robots, maybe just switch the roboRIO if you can’t round up the funds for a second copy.

It’s far too valuable for most teams to withhold 30 lbs of whatever contacts the game piece – this is an easy way to make sure both robots behave as close as possible and allows easier updates between competitions. We’ve taken this approach for the last 2 years.

Historically, all teams have recieved a router every year. I’d also check to see if you can borrow a D-Link from another nearby team if you don’t get one in the KOP.

For the purposes of driving a second robot in your home lab, it does not have to be any particular D-Link or OpenMesh router - any WiFi router that you can power from on-board the robot and that can provide IP addresses for your RoboRio and your driver station laptop will work.

Keeping with the thread topic, 2706 made it a priority early on that we were going to build two copies of our robot for drive practice (and also wiring practice, fab practice, etc.). We received one complete RoboRio control set in the rookie kit last year and one of our mentors was generous enough to buy a second whole control system to donate to the team.

Our two robots were virtually identical except one used Victor SP’s and the other used Victor 888’s - most sourced from vouchers and/or FIRST Choice.

Edit: here’s a better photo of the twins

Certainly infinitely better than not having two fully-functioning independent robots, but I have it on good faith that there is a noticeable difference in the response curves of the Victor 888 and Victor SP. Looking at data helpfully provided by 1718 here, the 888 does not have a linear response curve (look at Victor 888 cool, not Victor 888). I don’t have good data for the Victor SP, but I would assume it has a linear response curve like the rest of the more recent motor controllers. This could likely make a difference in driver practice and autonomous programming for small movements at low voltages.