Cheap Way to Make a Robot

Hi everyone,

Our robotics team will not be able to meet or work on robotics at our school during the beginning of this season, and we will have no access to our tools and supplies. In the mean time, we are contemplating purchasing supplies on our own to build a robot. What are some relatively cheap FRC alternatives that we could look into? We are thinking of using a raspberry pi and/or Arduino to make a small scale robot, but we don’t know how to go about doing this. Thanks.

Nicholas Carpenedo,
Team 6884 Deep-Space

Depends on if you want a “robot” or are okay with just a little “tele-bot” (what most FRC robots are outside of auto).
Arduino with a PWM hat or continous rotation servos and some sensors for a robot, el cheapo hobby TxRx set and small controllers, motor, etc for telebot.
Those can scale to pretty much anything, though your power system might have to be upgraded to accommodate.

It might be fun for your team to build an FTC robot to play the upcoming FTC game, it would encourage you to use the same design and strategy as an FRC robot but with a lot less cost and complexity. You could probably find some unofficial FTC events or invite teams from your area to small “competitions”. Building an FTC robot will also allow you to use similar design principles as an FRC robot and you can judge your work based on the performance of other FTC robots.

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You could get a couple vex kits. You don’t need any machinery. It’s not too expensive so you can divide your team into groups and do competitions among your team. You can also use those kits for future years as well.

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Studica/KauaiLabs VMX-pi + RaspberryPi offering is the closest to a drop-in replacement for the RoboRIO, if you’re looking for the ability to program using WPILib tools, sensor integrations, etc - along with extensive hardware protection built into the VMX that’s lacking on the Pi itself.

If you just want to build teleoperated machines, a hobby RC setup (AndyMark Quick & Dirty or similar from hobbyking etc) is a good option. If you just want to build gadgets, arduinos are a good option.

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+1 for Arduino. Last year I made a mini robot (about a foot cubed) using arduino and a homemade remote (also using arduino). Not sure what the exact cost was, but it was less that $200. I ended up using curtain rods I picked up for $2 as the primary superstructure material, so depending on how good you want it to look, you can get stuff really cheap.

Arduino is probably the easiest to get started with and has lots of online documentation, but doesn’t have WPILib capability or as much processing power as the other boards.

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And more to it:

  • You could buy a field set and a starter kit and not be a registered FTC team, though being an FTC team does have benefits.
  • Many regions will have remote events, where you run against the clock at home. In-person events are unquestionably better when it’s safe, but right now it’s not safe for most.
  • While it’s a little steep to start, all the materials should be easy enough to unload or hand down to a continuing FTC program. (Feeder teams make life great when you can make them stick.)

Also, here were my thoughts on a Fight Night-inspired R/C drivetrain if mechanics are worth more than programming. It uses REV UltraPlanetary gearboxes for drive and an AndyMark Cheap and Dirty for control, both of which are very recyclable in FRC builds.

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I have also heard of people using a previous year’s FTC game to go through these types of training exercises. You can probably buy the field elements for last year’s game from a nearby team for a lot less money than the buying the new game set and you would be helping out that team. Plus, you could get started before FTC kickoff. If you are not competing and you want to wrap this up before FRC kickoff, this might be a good way to go. You could compare your final designs to some of the events that were played in the 2019-2020 season to see how your designs compare with other solutions to the problem.

Same with us - and it depends as what your definition of Cheap is. Last year we finished our robot for way under 1000. We also on another project have used a pi to control some old Jaguar controllers (pwm) we had lying around. Our strategy of collaborating besides online tools and the electronics stuff is to have one adult making pickups/drop offs at whoever’s house Drop a printer and filament here - some tubing there some electronics somewhere else and each one kinda becomes a vendor. Seeing if we can keep it going we might build a practice bot of stuff we have lying around which is kinda like every season we build a competition bot out of stuff we have lying around - kinda like junkyard wars.

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Raspberry pi zero, i2c pwm board, that old pile of jaguars, victor 88?s, or OG Talons. Link that up with a 2.4Ghz wireless Xbox controller, shop batteries and a fuseblock from andymark and you have a control system.

As far as motors go… The older the team is the more CIMs are likely to be lying around.

Gearboxes and wheels can get pricey, so be careful there.

Plywood is an excellent material for the frame btw.

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Or if you want to go even cheaper, two chunks of scrap copper with a few bolt holes will work fine as busbars. Just be careful to keep them insulated and protected from wandering fingers

Depending on how much power you are putting through and how many motors, I am partial to the multi port wago wire nuts. 5$ gets you a pack 4, with space for 4 outputs per pair.

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I am also big on lever nuts; they’re safer than bus bars (in that they have a rating and shielding already) and super robust. I’ve gotten them from both AndyMark* and Amazon.

*yes while I was working there for the most part

I also am a huge fan of the XT30 Block from Rev. It’s super cute and doesn’t have that pesky exposed copper thing.

This is a pretty good way to do power distribution on the cheap, so long as you won’t be pulling more than 30 Amps per channel. They have all different size panels available. Bussmann 15600 ATC Fuse Panel - 12 Position, w/Ground Pad