Sumo Bots C

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Re: Sumo Bots C

Post by JBoyd-NY » December 9th, 2010, 6:31 am

As GH reported back in June, Robot Marketplace has a 2.4 GHz transmitter/Receiver that they are selling for $42 for the pair ($32 for the transmitter, $10 for the receiver). Look at http://www.robotmarketplace.com/products/0-GWS24TR.html

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Re: Sumo Bots C

Post by maggymay » December 9th, 2010, 6:42 am

JBoyd-NY wrote:
As GH reported back in June, Robot Marketplace has a 2.4 GHz transmitter/Receiver that they are selling for $42 for the pair ($32 for the transmitter, $10 for the receiver). Look at http://www.robotmarketplace.com/products/0-GWS24TR.html
Duh. Thanks JBoyd.

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Re: Sumo Bots C

Post by jander14indoor » December 10th, 2010, 12:01 pm

illusionist wrote:I have also heard that it might be a trial event in Michigan too... Can anyone confirm that?
I can confirm that in Michigan Sumo Bots will be run as a trial event and NOT count towards the team score. Michigan regionals are making their own decision on Sumo Bots, your coach should contact your regional director to see how they are handling it.

I think someone else already pointed out that while New York (and possibly other statesional) counts trial events towards team scores, Michigan (and the National tournament) does not.

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Re: Sumo Bots C

Post by illusionist » December 10th, 2010, 1:15 pm

Hey, Jeff I know you had experience in Region 8, so do you have any clue as to how they will run it?
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Re: Sumo Bots C

Post by old » December 10th, 2010, 2:54 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.
I don't think you fully understand how spread spectrum radio (or radio in general) actually works. There is no way for a transmitter receiver pair to simply ignore signals on the same frequency, or to respond to only the signal to which it is bound. Spread spectrum (if implemented correctly and fully) can go a long long way towards eliminating unwanted interference by transmitting and receiving on a range of frequencies rather than on only one (as is done on classic radio systems). There are also ways in which data can be encoded and error checked so that the receiving device does not accept that data as legitimate unless it passes some error checking algorithm. In the end any radio transmission can be jammed with sufficiently powerful signal spread over a sufficiently large band. It is possible that if there are enough 2.4ghz devices in the room where sumo is run that a 2.4ghz sumo bot won't run reliably. It makes little difference what the sources of 2.4 ghz are, though it does matter how powerful they are. A 2.4 GHZ microwave oven can put out over 1000 watts of energy while a bluetooth transmitter is on the order or 0.001 watt, and 2.4 ghz WiFi can be somewhat higher. Some 2.4 ghz R/C system are much more resistant interference due to their ability to use both spread spectrum and frequency hopping, while some just take an initial look on power up at the available frequencies and pick one that is presently not being used (and pairing on that frequency). If we keep the crowd and their phones away from the bots then there should be relatively little possibility for jamming (accidental or intentional) but if 50 people with bluetooth activated on their phones are huddled around the Sumo bot field then there is at least a reasonable possibility that there will be interference.

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Re: Sumo Bots C

Post by JBoyd-NY » December 10th, 2010, 4:08 pm

I obtained my information from the Ashurst Model Flyers web site on the Spectrum 2.4 GHz systems (http://www.activemax.co.nz/index.php?op ... &Itemid=84), which states the following:

"HOW DSM WORKS
Collision avoidance eliminates the possibility of more than one Direct Sequencing Spread Spectrum system from transmitting on the same frequency. Here's how it works: When the transmitter is turned on, the system scans the 2.4GHz band looking for an open channel. 79 channels are available. When an open channel is found, the system locks in and transmits on that channel as seen below.

This process takes about 2 seconds. In the unlikely event an open channel is unavailable, the transmitter continues to scan without emitting a signal until an open channel becomes available. The transmitter will remain on that selected channel until it's turned off. Each individual module is factory programmed with its own unique serial code called GUID (Globally Unique Identification code). Once a receiver is programmed to a specific module (called binding) the receiver will only recognize that module ignoring signals from any other sources. And with over 4 billion possible GUID codes, it's virtually impossible for a receiver to listen to anything other than its bound transmitter."

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Re: Sumo Bots C

Post by harryk » December 11th, 2010, 6:20 am

So has anyone heard of it being run on carpet? They're trying to do that at the invitational today
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Re: Sumo Bots C

Post by maggymay » December 11th, 2010, 6:42 am

On carpet? I have seen a bot match (not Science Olympiad or official 'SumoBot") on video that they used a carpet square for the ring. Running the event on carpet would make a difference to me, I'd want to know ahead of time and maybe adjust my wheels' surface or something...if the team has only practiced on a smooth surface (like maybe on a wooden gym floor or in a linoleum hallway at school) that would put you at a disadvantage if you got to competition and found out the surface was carpet instead.

Just looked in the Rules Manual and it says nothing about the surface of the ring, just that it needs to be 'five foot by five foot square'.

The surface issue needs to be addressed in the official Rules Clarification at soinc.

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Re: Sumo Bots C

Post by harryk » December 11th, 2010, 7:00 am

maggymay wrote:On carpet? I have seen a bot match (not Science Olympiad or official 'SumoBot") on video that they used a carpet square for the ring. Running the event on carpet would make a difference to me, I'd want to know ahead of time and maybe adjust my wheels' surface or something...if the team has only practiced on a smooth surface (like maybe on a wooden gym floor or in a linoleum hallway at school) that would put you at a disadvantage if you got to competition and found out the surface was carpet instead.

Just looked in the Rules Manual and it says nothing about the surface of the ring, just that it needs to be 'five foot by five foot square'.

The surface issue needs to be addressed in the official Rules Clarification at soinc.
Yeah I totally agree, they need to make a clarification, which is weird becaus they specified that in the trial rules last year
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Re: Sumo Bots C

Post by harryk » December 11th, 2010, 7:12 am

Question submitted :)
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