Miscellaneous Robot Electrical Parts and Materials - Answer Thread

[Pierluigi Collina]

LED Legal

Hi, team 7750 Mechanical Maniacs
is wondering if these LED's would be legal?

https://www.amazon.com/Magic-BEAM-Lighting-10-Meter-Controller/dp/B01K8GK532/ref=sr_1_2?ie=UTF8&qid=1481050162&sr=8-2&keywords=Magic+beam+lights

There is an IR receiver to change the colors and we could maybe have that disconnect if needed, but we don't have them yet so don't know for sure.

Answer: the LED's by themselves are legal if they can be powered and controlled via legal methods. The IR receiver block is not legal (per <RE17>)

[Pierluigi Collina]

Modern Robotics Color Beacon

Can you clarify if the new MR Color Beacon is a legal FTC part. It seems to be both I2C RGB LED (which can't be powered from DIM) and I2C Sensor (which must be powered from DIM)

http://modernroboticsinc.com/color-beacon

Thanks!

Answer: The device appears to be an I2C controlled LED module and does not meet the LED limits as listed in <RE12> and as such would fall under <RE17> and not be allowed.

[Pierluigi Collina]

Mechanical Switch

One of the kid on our team is wondering if we could use a mechanical switch to turn something on or off without it passing through the Core device interface module. It would be like touch sensor to turn LED lights on or off. Would this be allowed?

Answer: the described use of a mechanical switch would fall under <RE17> and not be allowed. A switch can be used as a sensor, via the Core Device Interface Module

[Pierluigi Collina]

New Label on Matrix Battery (now Modern Robotics)

Game manual part 1 rule RE03 states battery Matrix part # 14-0014 is a legal battery. We have nine FTC teams and purchased new batteries from Modern Robotics. Below is the URL to the product. The part number is 14-0014 but the batteries we received have a label that says "Modern Robotics" not "Matrix". Exact same battery with a different label. In two separate competitions we were told the batteries are not legal because they are labeled "Modern Robotics". The judges said that Modern Robotics parts are not allowed. We showed the judges the website and manual. We were allowed to compete in that specific regional but were told we needed to verify with FIRST before moving on to future competitions. Please clarify for us. We assumed the part number was correct since it it listed in the manual.

http://www.modernroboticsinc.com/12v...h-nimh-battery

Answer: Yes. The battery is legal for competition use. Apparently Modern Robotics is re-branding the battery to be in line with the remainder of their products.

[Pierluigi Collina]

D-Sub Breakcout Connector

Would the following wire connector be legal, or would it fall under addtional electronics?

https://www.amazon.com/So-myshtech-Connector-15-pin-Terminal-Breakout/dp/B014H47NLI/ref=sr_1_5?ie=UTF8&qid=1481666882&sr=8-5&keywords=so-myshtech

Thanks,
Circuit Breakers - 6566

Answer: The connector is legal as long as the use does not violate any other rules. In particular, care should be taken to make sure that all connections made via this type of connector fit within the current limits for the connector. (i.e. the per pin current limits could prohibit running motor connections through the connector). Appropriate wire gauges should also be used for all connections and the connections should be well insulated for safety.

[Pierluigi Collina]

Matrix Power Switch Concerns

Hello,

As recommended by:

<RE01> Main Power Switch - The Robot Main Power Switch must control all power provided by the Robot main battery pack and it must be used in one (1) of the following configurations:
a. FIRST strongly recommends that Teams purchase a separate Main Power Switch, either TETRIX (part #W39129) or MATRIX (part# 50-0030). This is the safest method for Teams and Field personnel to shut down a Robot.

We purchased a MATRIX (part# 50-0030) switch. However, the MATRIX switch comes with 18 gauge wire (FTC rules say power wire should be at least 16 gauge) and is only rated for 6 amps (whereas the battery and core controller are both fused to 20 amps).

So, it appears that the MATRIX (part# 50-0030) that we are required to buy does not meet the FTC rules (for power wire gauge) and is substantially under-rated (6 amps vs. 20 amps) for the entire system.

Given this, can we use a 3rd party switch that is rated for 20amps?

If not, what are we suppose to do (we cannot use the core controller switch, as cannot make it accessible):
- Install the MATRIX (part # 50-0030) switch - It seems it will probably melt (has anyone used this switch? Does it melt?)
- What are we suppose to do with the illegal wire that came on switch? (has anyone competed with this switch/wiring?)

Thanks,
FTC BlueSmoke Team

Answer: The switch you have purchased is selected by Modern Robotics for use with the Matrix system and is safe to use. The current ratings you are reading from the switch are AC ratings (6A@125V) not DC ratings.

The only two legal external power switches are the two explicitly listed in <RE01>

The wire gauge rules in <RE14> are for use by teams in modifying, extending, custom making, etc., wiring within the robot (i.e. anything your team makes or modifies should follow the guidance in <RE14>).

[Pierluigi Collina]

Additional Battery for LEDs

Is it legal to attach an additional 12-volt battery to the robot to provide power to the undirected LED lights on the robot?

Answer: No, unless the battery is an internal battery (as supplied by the LED manufacturer) as listed in <RE12>

[Pierluigi Collina]

Grounding Robot Frame

<RE03> states "Robot main power is provided by exactly one (1) battery pack that connects
directly to a single Core Power Distribution Module or through a switch that connects to a single Core Power
Distribution Module. Voltage and/or current sensors are allowed to connect between the battery pack and the
Core Power Distribution Module."
Our robot still has the battery connected to the PDM but we have an additional wire with a ring at the end (to attach to the chassis) branching off the negative PDM wire.

Question: Is it legal to ground the negative PDM wire to the chassis of the robot?

Answer: No.

[Pierluigi Collina]

LED questions

We have some question about LED lighting.

1. It is our understanding that you can not power low voltage (~2v) LED's from the 5v outputs on the CDIM (these outputs are current limited and work great). Could this be considered next year?

2. If we use the core power distribution module and a motor controller to power them, we would need a current limiting resistor in the circuit. Is this allowed?

3. Would the following lights be allowed?

https://www.amazon.com/dp/B00IR23JGA/ref=twister_B00IXD7GKI?_encoding=UTF8&th=1

4.Can you use common cathode RGB LED's

https://www.amazon.com/uxcell-Common-Cathode-Emitting-Diodes/dp/B005VMDROS/ref=sr_1_1?ie=UTF8&qid=1483836615&sr=8-1&keywords=rgb+led

and wire the common to the core power distribution module and pick up the positives from separate outputs on a motor controller?

Answer 1: We cannot comment on what will or won't be considered for next year's rules. In general we are always trying to find ways to allow teams to express their creativity in a safe and manageable manner.

Answer 2: Yes. A current limiting resistor would be allowed.

Answer 3: We are not able to comment on the legality of each individual possible LED. Be aware that very bright LEDs are likely to raise concerns at the playing field.

Answer 4: It is not safe to cross wire between a motor controller and the CPDM. If an LED is being controlled by a motor controller, all connections to the LED should come from the motor controller. Furthermore, it is not safe to cross wire multiple motor controller outputs to a single device of any sort.

[Pierluigi Collina]

More LED Questions

We'd still like some clarification of the use of decorative or signal common cathode LED light strips as questioned in part 4 of post 24. http://ftcforum.usfirst.org/showthre...ll=1#post33859


Certainly we could plug in one cathode/anode pair into the CDM or a motor controller port, and physically change the colors between matches, this seems perfectly legal, but not very interesting.

We had tried cross wiring between the CDM and Motor controller, but see in the above post that this not legal.

1 - Another option is to use transistors or relays to control the power via a port on the DIM, but wonder if that would be considered a circuit rather than 'passive' electronics, and thus not allowed? (Or if passive electronics even apply since the LED's are not sensors?)

2- If we used diodes (passive) to prevent back feed and wired two motor outputs to the common cathode, would this be legal, or is this considered cross-wiring?

3- If both of the above answers are no, Is there any legal way to control the colors of a common cathode LED strip other than physically changing the inputs?

Answer 1: This does not fit the passive electronics that are allowed by <RE11> and is therefore a custom circuit and not allowed per <RE17>

Answer 2: This does not fit the passive electronics that are allowed by <RE11> and is therefore a custom circuit and not allowed per <RE17>

Answer 3: Answers to robot design questions are outside the scope of what we can provide.

[Pierluigi Collina]

LEDs Controlled with Transistors

Are LEDs that are fully powered by the 12 battery on our robot controlled by the PWM ports on our core device interface module using transistors allowed?

Answer: No.. Transistors fall under <RE17> "Additional Electronics" and are not allowed.

[Pierluigi Collina]

Non-Powered Electronics

We were wondering if we are allowed to mount an unpowered beacon circuit board on our robot for aesthetic purposes, or if it would fall under additional electronics.

Thanks,
6566 - Circuit Breakers

Answer: No. All electronics within the robot must comply with the robot electronics rules. The unpowered beacon board would indeed fall under <RE17> "additional electronics"

[Pierluigi Collina]

Grounding Chassis Frame w/ Current Limiting Resistor

If we used a current limiting resistor of 47 ohms @ 0.25 watt between the negative terminal on the Core Power Distribution Module and the chassis, we can limit the grounding of static charges to the chassis to be 0.02 amp max. Please find attached circuit diagram.

Since the robot frame is not used as a connector in this circuit, please advise if this allowed?

Answer: No. Any electrical connection to the chassis or other non-electrical parts of the robot is not allowed.