Should we invest in a second roboRIO?

Knowing that FIRST is going to introduce several new control system components, including an upgrade to the robioRIO, would it be wise for our second year rookie team to invest into a second roboRIO?

Related question… What does your team use as a control system for for programming, prototyping or a second robot? Are there more economical solutions that don’t require a brand new code base or new skills for programming team?

Thanks in Advance for your help!

Karl Fleischmann
Lead Mentor
Team 7491 - Cyber Soldiers

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I wouldn’t invest in one now for the reason you stated. You’ll be out $400 and you’ll be missing out on the features of the newest model in the 2022 season unless you put down the money for a new one again. However, if original models get a significant price drop in the near future and/or are available on FIRST Choice for cheap in 2021, I don’t see a reason to hold out until the new one comes out to get a second control system.

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In any other season I would say absolutely you should get a second control system. It will allow you to build a second robot for driver practice and give you a full set of spares in case something breaks.

But this year is a pretty unusual case with competitions all but canceled for 2021 and a new control system announced for 2022. If you plan on continuing to meet as a team over the next year and you think having a second roboRIO will help you get more kids involved, it might be worth it to buy it now. If you can get by with just the one for now though, it probably makes sense to wait and get a new roboRIO when it comes out sometime next year. The announcement said that the current roboRIO should continue to be legal for 2022, but I have a feeling at some point that will stop being true (like the 8-slot cRIOs were legal for a few years after the 4-slot was introduced but at some point the 4-slot became required). Better to get the newer hardware with better specs that will likely be legal for longer if you can afford to wait.

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Incorrect. R54 in 2014 (the last year of the cRIO) declared both to be legal. You were not wise to run the 8-slot cRIO by then as the 4-slot one was superior in nearly every way (smaller, lighter, more solenoid power, greater operating voltage range), but you could.

Outside of large-scale migrations (cRIO to roboRIO, or new radios, or stuff like that), the only significant chop I’ve seen in the last decade was removing the Jaguars from the CAN bus. But by the time it happened, they were truly obsolete and not seeing much action.

That said, I agree with the thrust of your statement: I’d wait, unless there was a very real student engagement angle this year.

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Hmm, must have misremembered that. Thanks for the fact check

We have two, but I would not buy your second one now unless you can pick up a used one cheap from (I hate saying this) a team that is dissolving or something like that.

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For prototyping, you may want to look into using a really simple setup to run motors, etc. For PWM, this could be just a signal generator (e.g. Thrifty Throttle 3 - AndyMark Inc – there are many). You’d also need something for power – would not have to be a full PDP. This way, you could use the real motors to prototype mechanisms (instead of a drill or whatever else). For CAN, there are options also – could be a PC running the CAN utility, or cheaper alternative offerings from some of the FRC CAN vendors. This could get you several bench setups for prototyping for a lot less than a single roboRIO.

For programming, you might want to start out with simulation (Introduction to Robot Simulation — FIRST Robotics Competition documentation) – no roboRIO required, can easily be done from home, etc.

I’d encourage teams to do these two things, which could keep you from needing a second roboRIO until the point you build a second robot.

If you already have raspberry pis in the lab or were thinking of investigating them, picking up a Kauai Labs VMX-pi might be a good way to get a second control system for closer to $200-250. Scott and his team have been great about ironing out the couple of problems I had getting started with improved VSCode and documentation, and I think it’s a “mechanical-mentor proofed” product at this point.

I’m planning to use the platform for five “take home robotics” kits while we’re still in distance learning, rather than send home full roboRIOs.

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That’s a good idea. I’d tried the simulation components a while back, but couldn’t get it to work well in the time I had available to test it. I might revisit it and get some of our programming team to check it out.

Through time, we have invested in additional RoboRios. We have a “protocase” that we use for SW development Protocase – UPDATE – RoboRavens. We used to have little servos for our PMW testing, currently have a GlowWorm we are experimenting with. Open the case, connect to the AC and work. Since then, we have build a second case that contains the motor controllers and have motors we can control. But we need to use a battery in that case as our power supply can’t provide enough current…

If you are using brushed DC motors, you can use some small 12V hobby motors instead of the FRC legal motors. They will draw much less current than even the lowest power FRC legal motor allowing you to use a 12 laptop charger to power your test system. Put a piece of tape on the shaft like a flag and you can see it turning and the direction it is turning.

My last employer built large 3-phase motor controllers in the range of 100 to 1200 hp. One of the last tests on the production line was to hook them up to a small motor (1-2hp) to make sure that they could control it correctly.

One team I worked with in the past experimented with using inexpensive DC panel meters purchased from AliExpress. The ones they purchased was able to average the PWM output so they got different voltages indicated as the motor controller was set to higher output levels. The polarity of the meter corresponded to the direction of motor rotation. Their software test system was powered from a 12V laptop charger rated for around 3A.

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Has there been a price increase on the VMX-pi? I looked into it recently as an option for a small off season FRC bot following all the recommendations on CD, and the only place I can find it for sale is from Studica for $400. It comes with the nice bundled NavX functionality but otherwise the VMX-pi plus a Raspberry Pi is about the same cost as the $435 RoboRio from AndyMark.

If you email them, there is a $100 discount for FRC teams.

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I bought the “board only” VMX-pi from Studica for $199 about six weeks ago, but the link on their site for that option disappeared by the time I received it. Also, the Kauai Labs site now shows the VMX-pi enclosed in the Studica Case, where before it was showing the board without any case. They may have decided to no longer sell just the boards for now.

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This makes more sense now, I had not looked into the VMX-pi perviously which is why I was curious about the pricing difference compared to comments here on CD.

Thanks for the tip! Our school announced no in person classes until 2021 so I’ve put any ideas with this aside until we can get back into our build space, but it’s something I’ll remember for next year.