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Sensors - Answer Thread

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  • #16
    Compatible Sensors

    Originally posted by FTC3525
    According to rule RE11a, "Compatible sensors from any manufacturer may be connected to the Core Device Interface Module" are allowed. What level of documentation is need for inspection to verify that a sensor is compatible? Is it not enough to show that the sensor is directly connected to the CDIM?

    Thanks in advance,
    Team 3525

    Answer: There is no documentation requirement. Sensors should be such that they work electrically (and where appropriate, logically) with the ports on the Core Device Interface Module; i.e. operate within the correct voltage ranges, operate within the current limitations, etc.


    • #17
      Legal Sensor?

      Originally posted by FTC8327

      Can we use the generic HC-SR04 sensor?

      It is this:

      Answer: As long as the sensor is electrically compatible with the Core Device Interface Module and can be connected to/controlled by the CDIM it is legal


      • #18
        Trackball Sensor

        Originally posted by FTC6832
        We saw that a standard USB mouse or trackball is not allowed under current rules even though it works. We urge this be reconsidered in the future. So many great possibilities.

        Our team is considering a trackball as an omnidirectional movement sensor to correct for drift caused by intermittent lag across motor controllers in our mecanum drive. We have discovered some trackballs that have an i2c chip that we might be able to connect to. Is it legal to connect a trackball originally made for USB to (only) the CDIM module?

        Alternately, we could make our own trackball using encoders as the rollers. We saw another post where 3rd party encoders sold by Mouser were not allowed to be connected to encoder ports on a motor controller. But what if we are using the standard motor encoders sold by Tetrix - which the motor controllers were designed to use. Can we connect those to a motor controller?

        Thank you

        Answer Modification of a trackball to use as a sensor would not be allowed per <RE15>. There is nothing in the rules that requires you to use the Tetrix encoders as they were intended.


        • #19
          Allowed Sensors

          Originally posted by FTC11737
          As long as you publish the and not mention MR others sensors like Gyro, ODS, infra red locator and etc manufacture from Modern Robotics, you only mention Color sensor in the list is this means others sensor not allowed

          Answer: Per <RE11>.a, compatible sensors from any manufacturer may be connected to the Core Device Interface Module.


          • #20
            Switches as sensors to control autonomous behavior

            Originally posted by FTC11574
            Is it allowed to have a red/blue physical switch on the robot. We would use this to switch our robot from blue alliance to red alliance for our autonomous code?

            Answer: Yes


            • #21
              Sensor Questions

              Originally posted by FTC9867

              We're wondering about the legality of the Avago ADNS3080 high-performance optical mouse sensor, available on a breakout module with level-shifting designed by 3D Robotics.

              Can be purchased at (and from many other suppliers)
              IC datasheet:

              The ADNS3080 is the kind of sensor that can be found in any optical computer mouse, whose task is to track the mouse's movement relative to the surface below it. This is done optically, using a 30x30-pixel grayscale image sensor and onboard algorithm for motion estimation. This sensor is not user-programmable. The lens provided on this particular carrier PCB is used for the focusing of the sensor on a surface. Our question is: is a 30x30-pixel grayscale image sensor a 'camera'? Is this module allowed?

              The ADNS3080 communicates over SPI. The Modern Robotics Core Device Interface does not have an SPI bus exposed, and as such we'd also like to ask about the legality of the SC18IS602 I2C/SPI bridge IC, which is available on a breakout module from Sandbox Electronics.

              Can be purchased at
              IC datasheet:

              This module's only purpose is to provide an SPI bus 'passthrough' via I2C, allowing an I2C-capable device like the Core Device Interface to communicate with an SPI device. In this case, we'd use it with the ADNS3080, but this module could also be used to connect a variety of other SPI-only sensors to the Device Interface as well. (Only one SPI bus is provided by this breakout; it is not a 'sensor hub'). This module is not user-programmable. Is it legal to simply wire it between the Device Interface and ADNS3080 (if the ADNS3080 is allowed)? 5V, GND, SDA, and SCL would be directly connected between the Device Interface and the bridge module, and 5V, GND, MISO, MOSI, SCK, and SS would be directly connected between the bridge module and the ADNS3080 (or other SPI-compatible sensor) module.

              Thank you,

              Evolution Robotics (#9867)

              Answer 1: The flow sensor referenced is not voltage compatible with the Core Device Interface (it is a 3.3v sensor and the CDIM is 5v)
              Answer 2: The SPI to I2C interface module would fall under <RE17> Additional Electronics and is not allowed.


              • #22
                Sensor Question

                Originally posted by FTC9867

                As seen here, the I2C to SPI bridge we mentioned is illegal. We have just one more question about the ADNS3080, though - the breakout mentioned does include passive components for 3.3V/5V level shifting. Would connecting its 5V-compatible MISO, MOSI, SS, and SCK pins directly to the 'digital I/O' interfaces on the Core Device Interface be allowed? We know that doing so would require 'bit-banging' SPI in software. Aside from whether or not that is feasible, is the electrical connection of the ADNS3080 breakout's 5V-compatible logic pins to the CDIM allowed?

                Thanks again,

                Evolution Robotics #9867

                Answer: Yes. As the sensor is powered by and connected solely to the Core Device Interface Module and does not violate any other rules, it is allowed.


                • #23
                  Non-legal motor as sensor

                  Originally posted by FTC4717
                  Would it be legal for us to connect a small DC motor to the CDIM as an analog sensor? We would like to use the voltage produced to measure RPMs

                  Answer: No. All motors (regardless of usage) within a robot must be part of the allowed motors list.


                  • #24
                    Limit to number of Sensors

                    Originally posted by FTC11574
                    Is there a limit to the number of color sensors you can use? We have 2 now and are thinking of trying a 3rd one to help with beacon colors.

                    Answer: There is nothing in the current rules that expressly limits the number of any type of sensor that is allowed. There are implied limits due to the number of connections available on the Core Device Interface Module (8 Analog In, 8 digital I/O, 6 I2C, etc) and the limit on the number of Core Device Interface Modules (no more than two), but it is not likely that these limits would impact your situation.