2011 Minibot electronics

[Al Skierkiewicz]

Since R92 is a list of the permitted parts and the NXT requires the AA battery pack, I would expect that those batteries would be legal. Since the only motors allowed are Tetrix motors that cannot be driven directly by the NXT, the NXT battery will not provide power to drive motors. (See above post of R92)

[Jon236]

Maybe it's time to teach the students how to make a speed controller (1/2 H-bridge....since all we want is a one-way trip (powered, at least!))

[ATannahill]

Originally Posted by Jon236

Maybe it's time to teach the students how to make a speed controller (1/2 H-bridge....since all we want is a one-way trip (powered, at least!))

You can have your one way trip, I don't want the field reset team to pull out a shotgun to get our minibot down.

[EricVanWyk]

Is it legal to have a tether wire between the robot and the minibot? Wires are allowed in R92X, but I'm not clear whether or not the sizing box in R91 precludes them.

My apologies if this has been discussed elsewhere, it is impossible to follow all these threads!

[JohnHorton]

Originally Posted by Jon236

Maybe it's time to teach the students how to make a speed controller (1/2 H-bridge....since all we want is a one-way trip (powered, at least!))

That begs the question, can we fab our own parts? I'd love to skip the NXT controller and just build an H bridge run by a flip-flop. State 0 on it would be triggered by the "launch" command from the hostbot, sending the motor forward and State 1 would be triggered by a switch on top, when the minibot hits the target, reversing the motor so that Dean Kamen won't go after my bot with a pole saw.

However, they don't list discrete components on the list. I guess that's something for the Q&A.

[Tom Line]

Originally Posted by JohnHorton

Well, a 9v regulator would work, but that isn't listed on the components allowed.I find it kind of odd they don't allow basic electronics (resistors, caps, etc.) for the minibot. Correct me if I'm wrong.

I think a simple DC loop of Battery - Lightswitch - motor(s) - back again might be the best, as far as electronics go.

I believe their assumption was that if you are using the NXT, it drives a PWM signal out (at least, I believe that's how it drives the servo motors used in FLL). You would use that to send the duty cycle to a motor controller which in turn would actually use the 12V battery to power the motors.

[ptan]

Originally Posted by Tom Line

I believe their assumption was that if you are using the NXT, it drives a PWM signal out (at least, I believe that's how it drives the servo motors used in FLL). You would use that to send the duty cycle to a motor controller which in turn would actually use the 12V battery to power the motors.

The allowed Tetrix motors are ordinary DC motors. You can power them directly from the 12V battery through a light switch if you wanted.

In FTC, the NXT connects to the HiTechnic motor controller which converts the I2C from the NXT brick to control an HBridge powering the DC Tetrix motors.

[Just a Mom]

Does anyone else find it frustrating that we must use the FTC kit to build the mini robot? There are no FTC teams near us that I know of so the only way we can do this is to buy a kit and they are already on back order.

[JohnHorton]

Originally Posted by Just a Mom

Does anyone else find it frustrating that we must use the FTC kit to build the mini robot? There are no FTC teams near us that I know of so the only way we can do this is to buy a kit and they are already on back order.

As per my understanding, you don't have to use the FTC kit, it just helps. Making the whole thing out of polycarb. or aluminium, using the 12v NiCd, and the lightswitches is possible, and a lot simpler than using the NXT and co.

[Travis Hoffman]

Originally Posted by Just a Mom

Does anyone else find it frustrating that we must use the FTC kit to build the mini robot? There are no FTC teams near us that I know of so the only way we can do this is to buy a kit and they are already on back order.

You can obtain a free FTC kit as part of the FIRST Choice program (ala carte kit of parts items that were not handed out to all teams) on www.andymark.com.

There are 1265 sets left as of 11:45 AM this morning, 1/10/11.

Be proactive - order now.

Please see http://www.andymark.com/SearchResults.asp?Cat=245 for instructions on how to login to FIRST Choice.

[Al Skierkiewicz]

It has also been pointed out (offline) that a tether would not fit in the 12" cube. Food for thought.

[Nishant]

For those of you interested in using NXT equipment:

FIRST now allows:
BB. NXT compatible sensors and related connectors/cables.
(Team Update 1)