Robot Electronics and Power - Answer Thread

[Wil Wheaton]

is this part legal if connected to the hitechnic superpro board?
http://www.pololu.com/product/1403

Thanks

A: The indicated switch is legal, if and only if it is used as a sensor. No other usage is allowed. (e.g. it cannot be wired in series with a motor)

[Wil Wheaton]

Does EXI-Servo-B1226 comply with <R08>h(i)?

Thanks,
Team FTC6596

A: We are unable to find stall current specifications on this servo. If the stall current is below 800mA, this servo would be legal per <R08>.h

[Wil Wheaton]

We had a question on placing LED voltmeters on our robot. We would like to use them to measure our battery values. Rule 08 part s covers the use of LEDs. Assuming our voltage meters are viewed as LEDs, they would be allowed. Rule 08 part v covers the use of sensors. Assuming our voltmeters are sensors, they would not be allowed. The voltmeters would not be used as part of the game play but rather to monitor the voltage levels of our batteries throughout the day of competition. Are LED voltmeters considered a LED or sensors? Below is the part we are considering using.

http://www.adafruit.com/products/460

Thanks, 4592

A: The part described would not be legal as it is not a non-functional decoration and the signaling done by the LED is not controlled by the sensor prototype board.

[Wil Wheaton]

<R08>n.i. states All power used in the circuits connected to the Prototype Board must be derived from the power
connections provided within the board. No batteries or external power sources are allowed.

If we were to power the Superpro Prototype board with an external power source, would it be illegal? We know that the circuit connected cannot be powered directly by a external power source, but it doesn't say anything about the board being powered by an external power source using the connections on the board.
Thanks,
Team 4592

A: No. Sensor Prototype boards may only be powered by the connections to the NXT.

[Wil Wheaton]

We would like to know whether it would be legal to have fuses protecting our Tetrix motors. Rule <R08>q. states:

On the same topic, this Q&A post states that <20A fuses should be used on a power distribution board. Using generic fuses to protect our motors is the same thing. (Also, there are Tetrix motor power wires that have inline fuses which are legal.) Are we correct in assuming that it is the intent of the GDC to allow for this safety procedure?

A: No. Fuses inline with motors is not allowed.

[Wil Wheaton]

We would like to use an LED in conjunction with a photodiode as a custom light sensor. Would it be legal for the LED to be powered by the Tetrix 12V battery pack? The rules allow LEDs to be powered in this way when connected to a prototype board, but it is specified that those LEDs be used for visual cues.

Rule <R08>c.i. states that:


Rule <R08>s. states that:


We believe that it is the intent of the GDC to allow LEDs to be powered by the Tetrix battery pack for this purpose, but we'd like to be sure. The sensor would also include a microprocessor, resistors, and photodiodes, all connected to the HiTechnic SuperPro prototype board (as specified in rule <R08>).

A: Yes. The LEDs as described could be powered by the battery, as long as no other rules are violated. The remainder of the sensor circuitry would need to be powered by the prototype board.

[Wil Wheaton]

In post #15 in the "Electronics and Power" thread, it is answered that


We would like to use HC-SR04 ultrasonic sensors for ranging on our robot.

These require bursts of 15mA current (@5V) to operate. We would like to pause the other circuitry on our prototype board, operate the ultrasonic sensor from a charged capacitor, and then switch back to the other circuitry on our prototype board. Since the HiTechnic SuperPro prototype board can provide electricity at 5V and can provide more than 15mA of current, would such a use of a capacitor be legal? We are not attempting to generate higher than normal currents or voltages, and all the power would be provided by the prototype board. The reason we are using capacitors is to ensure that the ultrasonic sensors have a stable current during operation.

A: No. The described usage is not allowed. The capacitors are still being used to allow the system to use a total current greater than that available from the connections to the sensor prototype board.

[Wil Wheaton]

We would like to use multiplexer ICs on our prototype board to "increase" the number of I/O pins available. Would such a multiplexer qualify as parts of a sensor connected to the HiTechnic SuperPro prototype board?

Datasheet for the multiplexer we plan on using: http://www.ti.com/lit/ds/scls428h/scls428h.pdf

Would other common ICs (such as 555 timers, binary/decade counters, shift registers, latches, etc.) be allowed under the same circumstances? If using COTS ICs does not provide enough of a learning opportunity, would it be legal to "simulate" them through logic gates?

Thanks.

A: there is nothing in the current rules that prohibits the use of integrated circuits on the sensor prototype board. Be sure to pay attention to the power budget!

[Wil Wheaton]

Hello,

We had a question regarding the use of the HiTechnic Superpro board for controlling LEDs on board our robot. At our first qualifier, we had a series of purely decorative LEDs powered by the main robot battery. We're now looking to make the LEDs functional through connections to our Superpro. Our intent was to drive the LEDs with several MOSFETs that supply voltage from the main battery but which are controlled by the Superpro's outputs. However, rule R08.n.ii suggests this would be illegal, as we are powering a circuit connected to the Superpro that derives power from a source other than it (despite the fact that the LEDs may be powered by the main robot battery).

1) Is this method of powering and controlling LEDs (from the main robot battery and through connections to the Superpro, respectively) allowed?
2) Robot Electronics and Power post #28 states that (a breadboarded circuit functionally equivalent to) an Arduino could be used to control LEDs if itself was driven by the Superpro board. If the setup described in part 1 is acceptable, could an Arduino (with more PWM ports than the Superpro) be used to control the MOSFETs (which are, again, controlling power supplied by the main robot battery).
3) If said Arduino setup and described use of MOSFETs is allowed, would it also be acceptable to power the Arduino from the main robot battery given that its sole use would be to drive the LEDs with more PWM connections than the Superpro possesses.

Thank you,
Team 5421

A1: Potentially. Care needs to be taken to isolate the LED power from the prototype board power (opto-isolators, relays, etc.)
A2: Yes, if the power for the controller circuit comes from the sensor prototype board
A3: No

[Wil Wheaton]

We are using servos with servo extensions and have noticed jitteriness on the servos and when researching it, we wondered if we are allowed to use a boosted extension:
http://www.servocity.com/html/booste...xtensions.html

We are running multiple servos over 24" to the controller. We learned that as more servos are added, the signal to each servo is weakened. The boosters may help the jitteriness and/or lack of constant control.

Thanks.

A: No. Servo signal boosters are not allowed.