Sumo Bots C

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Re: Sumo Bots C

Post by bmbw123 » December 8th, 2010, 4:03 pm

Ok thanks chalker for the confirmation. And yeah, I'm building it from scratch too. The most expensive thing was the transmitter/receiver pair (costed close to $100 but i'm sure I could have gotten it for less). Some wheels are also pretty ridiculously priced. A pair of two wheels can get into the $30's.

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Re: Sumo Bots C

Post by Primate » December 8th, 2010, 4:58 pm

chalker wrote:
Primate wrote:What would be the point of running an established event as a trial? It still ends up counting towards your score...
Trial/pilot events count towards the final team rankings, and thus don't determine who goes to nationals.
I assume you mean they don't count, which would explain it. We must do things differently here in New York; trial events count towards final score, whereas pilot events do not.
events 2012 gravity vehicle, robot arm, thermodynamics, tps

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Re: Sumo Bots C

Post by ichaelm » December 8th, 2010, 5:13 pm

JBoyd-NY wrote:Sumo Bots does not have to be an expensive event, even if your team has never participated in any of the robot events that have been run in previous years.

If you are starting from scratch, then the first thing you need is a transmitter/receiver pair that meets the rules without any expense for additional crystals. As pointed out earlier in this thread, there is a 2.4 GHz transmitter/receiver pair available from Robot Marketplace for $42.00.

Now you need something to make the frame for your robot. If you have ever seen the VEX robot kit, the material they use for their frame is simply a heavy gauge form of an erector set. While the individual pieces from an erector set may not be sturdy enough for use, there is nothing preventing you from doubling up (or even tripling up) on the pieces to increase their strength.

Now you need motors. Check with your technology department (or even some parents) to see if they have any electric screw drivers that no longer work that they are going to discard. Nine times out of ten the problem with these screw drivers is the battery has died - the motors still work fine. If you can get two discarded screw drivers where the motors still work, you have the motors for driving two different wheels, and you've saved the expense of designing and building a steering system.

Wheels - if you can't afford to purchase wheels, take a look at old skateboard wheels or inline skate wheels. Rough up the surface with sand paper and you improve their traction.

Finally, you need some sheet metal for the shell, something to make a plow-like device to push with (check out the wallpaper trim tool available at Lowes for $3.78), and batteries to power your screw driver motors. You can get a 7.2 rechargeable battery pack from batteryspace.com for $7.00. Most of the parts I've mentioned can probably be located for free, so the cost of building the robot is $42 for the transmitter/receiver, $4 for the wallpaper trim tool, and $7 for the battery, or a total of $53.00. And if your team has ever participated in any robot event in the past (robot ramble, robo cross, robo billiards, robot maze) then many of these parts are probably sitting in your storage area.
Great guide!
Also, you'll need some means of controlling the motors with the signals from the receiver. You'll probably need to buy some ESCs, unless you use continuous servos for the wheels.

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Re: Sumo Bots C

Post by maggymay » December 8th, 2010, 6:29 pm

ichaelm wrote:
JBoyd-NY wrote:Sumo Bots does not have to be an expensive event, even if your team has never participated in any of the robot events that have been run in previous years.

If you are starting from scratch, then the first thing you need is a transmitter/receiver pair that meets the rules without any expense for additional crystals. As pointed out earlier in this thread, there is a 2.4 GHz transmitter/receiver pair available from Robot Marketplace for $42.00.

Now you need something to make the frame for your robot. If you have ever seen the VEX robot kit, the material they use for their frame is simply a heavy gauge form of an erector set. While the individual pieces from an erector set may not be sturdy enough for use, there is nothing preventing you from doubling up (or even tripling up) on the pieces to increase their strength.

Now you need motors. Check with your technology department (or even some parents) to see if they have any electric screw drivers that no longer work that they are going to discard. Nine times out of ten the problem with these screw drivers is the battery has died - the motors still work fine. If you can get two discarded screw drivers where the motors still work, you have the motors for driving two different wheels, and you've saved the expense of designing and building a steering system.

Wheels - if you can't afford to purchase wheels, take a look at old skateboard wheels or inline skate wheels. Rough up the surface with sand paper and you improve their traction.

Finally, you need some sheet metal for the shell, something to make a plow-like device to push with (check out the wallpaper trim tool available at Lowes for $3.78), and batteries to power your screw driver motors. You can get a 7.2 rechargeable battery pack from batteryspace.com for $7.00. Most of the parts I've mentioned can probably be located for free, so the cost of building the robot is $42 for the transmitter/receiver, $4 for the wallpaper trim tool, and $7 for the battery, or a total of $53.00. And if your team has ever participated in any robot event in the past (robot ramble, robo cross, robo billiards, robot maze) then many of these parts are probably sitting in your storage area.
Great guide!
Also, you'll need some means of controlling the motors with the signals from the receiver. You'll probably need to buy some ESCs, unless you use continuous servos for the wheels.
JBoyd-NY - Thanks for the easy-to-understand list (you made it sound so easy). One thing...I'm pretty sure that SO-SumoBot'ers HAVE to come to competition with at least 2 extra crystal sets for a total of three frequencies.

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Re: Sumo Bots C

Post by JBoyd-NY » December 8th, 2010, 6:37 pm

You need two extra sets of crystals if you are using 27 MHz, 49 MHz, or an older 75 MHz transmitter. The newer 75 MHz transmitters are digital, and allow you to select the specific frequency by setting it on the transmitter and then setting a dial on the receiver. 2.4 GHz transmitters automatically switch to an unused frequency, so they don't need any crystals at all.

One word of caution regarding 2.4 GHz - it is used for many things besides remote control vehicles. Some WiFi networks operate on 2.4 GHz, and bluetooth devices also operate on that frequency. When you turn on a 2.4 GHz transmitter, it looks for any other transmitters using a 2.4 GHz frequency. It does not look for Bluetooth or WiFi usage, and they may cause interference. Its better to use a 2.4 GHz transmitter/receiver pair that bind together - when you first turn them on, you need to input a code that pairs the two devices. Once that is done, the receiver will only listen to signals that are sent from the transmitter it is bound to. Any other 2.4 GHz signals using the same frequency channel are ignored, reducing the chances of interference.

The $42 transmitter/receiver sold by Robot Marketplace is one that binds the transmitter to the receiver.

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Re: Sumo Bots C

Post by maggymay » December 8th, 2010, 6:50 pm

Ok, so the crystals aren't absolutely needed if you have the digital transmitter/receiver but don't we need to be able to verify or prove that our Bots use (at least) three separate frequencies. I'm a little familiar with the crystal sets at this point but digital?...)

I think my head is going to explode.

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Re: Sumo Bots C

Post by JBoyd-NY » December 8th, 2010, 7:12 pm

At impound you will be asked what three frequencies your bot can operate on and which frequency your bot is currently set for (actually, at Nationals you will be asked to email those frequencies before the tournament). If you have a digital transmitter/receiver, then it is capable of operating on any of the 30 frequencies in the 75 MHz range, so you just pick three of those.

I write the three frequencies for every bot on the competition sheet for that team. When we match up bots for competition, I check the frequencies they are set to operate on. If there is a conflict, then I select one of the alternate frequencies for a team and they are told to switch to that frequency.

Basically, when I ask for the frequencies, I take the competitors at their word - however, if you claim three separate frequencies and when asked to use an alternate one you can't (because you never really had three frequencies to begin with), then you would forfeit all of your previous wins and be DQd from the event. You may also hurt your team severely: remember that part of the Code of Conduct you agreed to states "Failure to show honesty and/or courtesy by a participant, coach, or guest of the team may result in the disqualification of the team from that event, the entire tournament or future tournaments.".

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Re: Sumo Bots C

Post by maggymay » December 8th, 2010, 9:47 pm

JBoyd-NY wrote:You need two extra sets of crystals if you are using 27 MHz, 49 MHz, or an older 75 MHz transmitter. The newer 75 MHz transmitters are digital, and allow you to select the specific frequency by setting it on the transmitter and then setting a dial on the receiver. 2.4 GHz transmitters automatically switch to an unused frequency, so they don't need any crystals at all.

One word of caution regarding 2.4 GHz - it is used for many things besides remote control vehicles. Some WiFi networks operate on 2.4 GHz, and bluetooth devices also operate on that frequency. When you turn on a 2.4 GHz transmitter, it looks for any other transmitters using a 2.4 GHz frequency. It does not look for Bluetooth or WiFi usage, and they may cause interference. Its better to use a 2.4 GHz transmitter/receiver pair that bind together - when you first turn them on, you need to input a code that pairs the two devices. Once that is done, the receiver will only listen to signals that are sent from the transmitter it is bound to. Any other 2.4 GHz signals using the same frequency channel are ignored, reducing the chances of interference.

The $42 transmitter/receiver sold by Robot Marketplace is one that binds the transmitter to the receiver.
Re: a 'binding' digital transmitter....does VEX make one? And how can you tell if a transmitter/rec. is a new one or not? I guess maybe that's why there are so many for sale on eBay...are people dumping their older equipment(with crystals) for newer digital gear?
Also...what exactly *is* a VEX V.5, is it any different from a 'Vex Starter Bundle'?

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Re: Sumo Bots C

Post by ichaelm » December 9th, 2010, 5:22 am

maggymay wrote:
JBoyd-NY wrote:You need two extra sets of crystals if you are using 27 MHz, 49 MHz, or an older 75 MHz transmitter. The newer 75 MHz transmitters are digital, and allow you to select the specific frequency by setting it on the transmitter and then setting a dial on the receiver. 2.4 GHz transmitters automatically switch to an unused frequency, so they don't need any crystals at all.

One word of caution regarding 2.4 GHz - it is used for many things besides remote control vehicles. Some WiFi networks operate on 2.4 GHz, and bluetooth devices also operate on that frequency. When you turn on a 2.4 GHz transmitter, it looks for any other transmitters using a 2.4 GHz frequency. It does not look for Bluetooth or WiFi usage, and they may cause interference. Its better to use a 2.4 GHz transmitter/receiver pair that bind together - when you first turn them on, you need to input a code that pairs the two devices. Once that is done, the receiver will only listen to signals that are sent from the transmitter it is bound to. Any other 2.4 GHz signals using the same frequency channel are ignored, reducing the chances of interference.

The $42 transmitter/receiver sold by Robot Marketplace is one that binds the transmitter to the receiver.
Re: a 'binding' digital transmitter....does VEX make one? And how can you tell if a transmitter/rec. is a new one or not? I guess maybe that's why there are so many for sale on eBay...are people dumping their older equipment(with crystals) for newer digital gear?
Also...what exactly *is* a VEX V.5, is it any different from a 'Vex Starter Bundle'?
A Vex V.5 is a type of vex microcontroller. It is one of many possible "brains" for a vex system. You do not need a microcontroller if your robot is radio controlled.

There are many different vex starter bundles. One has the V.5 microcontroller, another has a cortex microcontroller, and another has no microcontroller.

Vex makes a radio system that connects via WiFi protocol. That is not really the same thing as binding, so I don't know how interference-resistant it would be next to other 2.4GHz systems. You need the cortex microcontroller to be able to use it, though, and that's pretty expensive.

If I were you, and I were on a budget of less than $500, I would ditch the vex idea and take JBoyd's advice. The $42 transmitter and receiver pair is a great deal. I wonder how many people at states will be using the exact same transmitter! :P

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Re: Sumo Bots C

Post by maggymay » December 9th, 2010, 6:07 am

Ok, JBoyd-NY is looking like a friggin' genius at this point. Now IF we can just get all these parts. I've been looking on the Robot Marketplace website and don't see the $42 binding transmitter/receiver?

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