Chief Delphi - VEX motor w/o robot controller?

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VEX motor w/o robot controller?

Can a VEX motor (PWM-3wire) be modified to work directly connected to a battery so that we do not have to use the robot controller and radio to turn the motor on/off?

Re: VEX motor w/o robot controller?

Yes it can.

Just don't use it to compete in any FIRST or VEX events.

Re: VEX motor w/o robot controller?

We don't plan on using the VEX motor in competition. We are using VEX materials to prototype. We don't have any Tetrix stuff yet.

Re: VEX motor w/o robot controller?

I've thought very vaguely about how minibots can be designed - simply put, our team is holding off on that for now in order to ensure the Robot has a solid design and will be finished on time.

However, reading this made me go look at the rules, and they raise an interesting question..

There's nothing in the MINIBOT section specifically that would prevent this. However, it would appear that <R48> applies:

Quote:

<R48> All electrical loads (motors, actuators, compressors) must be supplied by an approved power regulating device (speed controller, relay module, or Digital Sidecar PWM port) that is controlled by the cRIO-FRC on the ROBOT.

ROBOT – the composite electromechanical assembly designed and built by a FRC team to perform specific tasks when competing in the 2011 competition LogoMotion. The ROBOT must include all the basic systems required to be an active participant in the game – power, communications, control, mobility, and actuation. The ROBOT implementation must obviously follow a design approach intended to play the 2011 FRC game (e.g. a box of unassembled parts placed on the FIELD, or a ROBOT designed to play a different game, would not satisfy this definition). The ROBOT includes both the HOSTBOT and the MINIBOT (ROBOT = HOSTBOT + MINIBOT).

So... from this combination of rules and definition, it would appear that the minibot has to be controlled from the cRio? But that goes directly against:

Quote:

<G19> After DEPLOYMENT, MINIBOTS must remain completely autonomous. Violation: The TOWER on which the MINIBOT is DEPLOYED is diabled. If the MINIBOT is not deployed on a TOWER, then the ALLIANCE’s TOWER upon which the highest RACE SCORE was earned will be discounted.

I think this might be a good question for the GDC to clarify...

Re: VEX motor w/o robot controller?

Quote:

Originally Posted by grosh (Post 999223)

We don't plan on using the VEX motor in competition. We are using VEX materials to prototype. We don't have any Tetrix stuff yet.

So.. are you asking how to do it, then?

Re: VEX motor w/o robot controller?

Quote:

Originally Posted by CrazyCarl461 (Post 999230)

So.. are you asking how to do it, then?

Yes..how?

Maybe I should have been more clear. We are using VEX motors for prototyping MINIbots designs. We will NOT use them in competition we are only testing ideas.

We have tried stripping the wires from the VEX motor (PWM connection) and tried directly connecting them to the battery. BUT the motor does not spin. We have tried ever combination of wire colors possible.

Re: VEX motor w/o robot controller?

Quote:

Originally Posted by grosh (Post 999232)

We have tried stripping the wires from the VEX motor (PWM connection) and tried directly connecting them to the battery. BUT the motor does not spin. We have tried ever combination of wire colors possible.

Those wires go to a circuit board inside. One is power, one is ground, and one is PWM signal. If the circuit receives no PWM signal, it will not command the motor to move. If you want to just straight up power the motor, you need to open it, disregard the circuit board, and solder wires directly to the motor inside.

Also, your "hey let's just try hooking up these wires" approach to problem solving frightens me. I don't know what battery you're using, but please be aware of the safety considerations involved in doing such a thing. Your approach could lead to a deadly situation given different circumstances, say, 120VAC instead of low voltage DC. Have the patience to learn what you are doing from someone who already has.

Re: VEX motor w/o robot controller?

Eagle,
The robot rules have been slightly modified by Team Update #1 and only the two sections at the end of the manual apply to the minibot. R48 does not apply to the minibot for instance.

Grosh, I hope you haven't killed the VEX motor. You are lucky you haven't burned yourself or damaged the battery. Do some research first, then make an informed decision on how to hook something up.

Re: VEX motor w/o robot controller?

Quote:

Originally Posted by sanddrag (Post 999286)

Also, your "hey let's just try hooking up these wires" approach to problem solving frightens me. I don't know what battery you're using, but please be aware of the safety considerations involved in doing such a thing. Your approach could lead to a deadly situation given different circumstances, say, 120VAC instead of low voltage DC. Have the patience to learn what you are doing from someone who already has.

Thanks for the advice. We are well aware of the dangers of plugging in wires to a wall socket. The standard VEX battery is 9V when fully charged. Don't know the exact amperage but we have tested it by putting our tongue between the pos/neg leads.

Re: VEX motor w/o robot controller?

Quote:

Originally Posted by Al Skierkiewicz (Post 999311)

Eagle,
The robot rules have been slightly modified by Team Update #1 and only the two sections at the end of the manual apply to the minibot. R48 does not apply to the minibot for instance.

That's definitely good news... but reading the update I don't come away with that impression. The definition of ROBOT was updated, but it still says "ROBOT = HOSTBOT + MINIBOT", and rules like R48 still say they apply to the ROBOT, not just the hostbot...

Granted, I think the intent for the game is clear, made even more so by the demonstrations at kickoff... but the wording of the rules still doesn't seem to make that distinction clear.

Re: VEX motor w/o robot controller?

Eagle,
I will check and get back to you.

Grosh,
The 9.6 volt battery is 1000maHr and 7.2 volt battery is 3000 maHr. Either can produce fire if misused and under certain conditions can produce burns, and explosive release of gases generated within the battery. Either of these batteries when fully charged is capable of several tens of amps into a short. A standard nine volt battery is about 500 maHr but can't source nearly the current that NiCd or NiMH technologies can.

Re: VEX motor w/o robot controller?

Do you have the new 2 wire motor 269s or 393s? They are both already wired for 2 wire use and come with their mini gear boxes. - The 2 wire motors were designed so future VEX teams could possibly make their own custom circuits.