Robot Electronics and Power - Answer Thread

[Wil Wheaton]

I have a few HiTec HS-322HD Servos from older FRC KOPs. I have found older FTC forum posts that said these are ok on FTC robot. I am assuming that they are. Just asking to be sure.

A: Yes, as long as the mentioned servo is not modified from it's original manufactured state, it would be an example of a legal
standard sized hobby servo.

[Wil Wheaton]

Can we use the continuous rotation version of this servo

http://www.servocity.com/html/hs-425..._sport_bb.html

or do we have to use the HS-485HB?

A: No, the servo listed is modified by Servo City from it's original manufactured state and as such is not
legal for FTC. Legal continuous rotation servos are produced as continuous rotation servos, without
modification.

[Wil Wheaton]

Can we use any brand of continuous rotation servo or do we need to purchase the modified HiTec HB-485 servos from a vendor like ServoCity?

A: There is no requirement to use a particular brand of continuous rotation servos. All legal continuous rotation servos are manufactured as such by the original manufacturer. Servos modified from original state by anyone (retailers or teams) are not legal.

[Wil Wheaton]

Could either of these sensors be used as long as they are connected to a protoboard?
a) A LV-MaxSonar-EZ0 sensor for distance detection.
b) V7-2B17D8-048 Switches for touch detection.

A: This type of question has been previously answered. Please see Post #16 in the Robot Electronics and Power portion of the Forum

[Wil Wheaton]

Q: In last year's competition, we had some issues with our power connections, and have considered the possibly of the battery to power switch connection as a possible cause. We use a lot of Anderson power poles, and were wondering if we can replace the connections on the batter with power poles, i.e. cut off the old connection (keeping the fuse) and using crimp on power poles. Thanks.

A: Yes. This is explicitly allowed by <R08>.x

[Wil Wheaton]

Is it possible to have two DC motors connected into the same ports? The rules say:

"f. A robot is constructed with either TETRIX or MATRIX motor and servo controllers, not both. Any quantity of
TETRIX (HiTechnic) or MATRIX Motor and Servo Controllers are permitted provided that the quantity doesn’t
exceed the technical specifications for these devices, the NXT, and the software. Motor controller outputs may
only be used to directly control DC motors. Servo controller outputs may only be used to directly control servos.

g. A maximum total of eight (8) TETRIX or eight (8) MATRIX DC motors are allowed and must be controlled by a
compatible TETRIX or MATRIX controller. A robot is constructed with either TETRIX or MATRIX DC motors, not
both"

Any number of controllers is allowed. Does that make using a single port for two DC motors illegal?

A: It is legal to connect up to 2 motors to a single motor controller output port. Attempting to connect more than 2 risks damaging the motor controller and creating a risk to field and field personnel and is not allowed. Note that due to the way the motors connect to the Matrix Controller, it is not possible to connect more than 1 motor per port

[Sheldon]

We have a problem with our motor controllers where the screw holes will break off, therefore making us unable to screw them to our robot. To fix this problem, we 3-D printed our own motor controller cases which we reinforced. However, we are unsure of whether this is considered modifying the electronics, since we only modified the casing and not the actual circuitboard.

A: Opening the motor controller case and replacing it with a custom printed case would constitute modifying electronics ans is not allowed.

[Wil Wheaton]

Can you interface an Atmel mC similar to the ATmega168 on a breadboard and use that to control an RGB led strip in a game-functional manner?

I'd like to consider adding RGB led light strips to both sides of the robot's undercarriage.

The light strips would be functional in the following manner.

- Prior to starting of the match, they would pulse a light teal color.

- When the match started the front half would display green, the back half red, indicating which direction is the front of the robot as relates to the controller. If the driver reverses the front then the leds also reverse. e.g. Either end of the robot can be driven "forward", the leds tell the driver which way is forward at any given point in time.

- During the 30 second endgame, the leds pulse purple, so our driver immediately knows it's the end game.

- I noticed that it's possible that the rack and pinion positions may get slightly out of whack and if that happens it's really bad as the whole robot gets torqued. Having a control mode where the motors on either side may be operated independently could be useful to correct this during a match. This is dangerous though and the leds would flash red if the controller was in this mode.

- When the match is over, revert to pulsing teal, but slightly faster than at the beginning to indicate the robot is tired.

A: The controller would be legal to add to the robot, if and only if it is controlled and powered by connections to a sensor prototyping board. Additionally, the robot may not perform any functional actions prior to match start or after match end. The pulsing lights as described pre/post match would be a violation of pre/post match functioning.

[Sheldon]

IS this a legal part to use for holding our wires? http://goo.gl/HTuJ0d
Igus E045-16-028-0 Energy Chain Cable Carrier, Polymer, EZ-Split Crossbar

Product Features
Very easy cable/hose installation
lightweight
small pitch for low noise and smooth operation
Links can be easily added or removed to adjust length

Thanks

A: Yes, this product is a legal COTS per rule <R08.t>

[Wil Wheaton]

I know that NHT (6-pin cable) extension are not permitted by rule and that HiTechnic is an approved source for those cables. Those cables come in a maximum length of 90 cm (~36 inches). The cable run our team needs exceeds that length. How do I work around this? May I use an extension jack (mindsensors.com sells 'extenders' which allow (1) approved cable to join with another approved cable)? HiTechnic indicated to me that this approach would serve my needs. Please advise.

A: There is no legal way to extend an NXT cable. The mindsensors extension jack is not a legal part. The 90cm maximum length is based on electrical limits within the NXT system.