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Comments by Brandon

  • New products: Discrete addressable through-hole RGB LEDs

    New products: Discrete addressable through-hole RGB LEDs

    - 22 May 2020

    Hello, Paul.

    Thank you for sharing your solution to the problem you encountered!

    Brandon

  • Brandon's line following robot: The Chariot

    Brandon's line following robot: The Chariot

    - 18 November 2019

    Hello, Chester.

    Unfortunately, my code ended up fairly messy by the time of the competition, and I have not cleaned it up since then, so I do not think it would be very useful in its current state. If you have never programmed a line following robot before, you might find the line following example for our 3pi robot helpful as starting point for understanding how the PID algorithm works.

    I do not currently have a wiring diagram to share, but the connections are fairly simple. The power from the battery runs through the rocker switch and to the input of the voltage regulator. If I were building this robot again, I would probably use a pushbutton power switch instead of the rocker switch. The output of the regulator goes to the VIN of the A-Star and VMOT on the Qik motor controller. The A-Star's 5V output (from its onboard regulator) supplies the VCC power to the Qik as well as the power to the reflectance sensor array. I used digital pins 2-7 on the A-Star for the 6 reflectance sensors and pins 10 and 11 for communicating with the Qik via software serial. There is also a common ground connection for all of the boards.

    Brandon

  • Brandon's line following robot: The Chariot

    Brandon's line following robot: The Chariot

    - 17 September 2018

    I do not have a schematic diagram for this robot, but the connections are fairly straight forward. The rocker switch is wired between the battery and the input of the regulator. The output of the regulator is powering the Qik motor controller and A-Star 32U4 Mini. The QTR sensor array is powered from the 5V pin on the A-Star 32U4 Mini. The rest of the connections depend on what pins you are using to read the sensors and send serial signals to the motor controller. If you have more specific questions when you start your line follower, you can post a request for help on our forum, and we would be glad to help there.

    You should be able to swap an Arduino Uno in for the A-Star 32U4 in this system, but it is much larger, so you would probably need to find a different way to mount it.

    Brandon

  • Brandon's line following robot: The Chariot

    Brandon's line following robot: The Chariot

    - 27 August 2018

    I noticed you posted similar questions on our forum; I have responded to it there. We can continue the conversation in the forum thread you created since it is probably a more appropriate place for a detailed discussion.

    Brandon

  • Brandon's line following robot: The Chariot

    Brandon's line following robot: The Chariot

    - 24 August 2018

    It sounds like you have it correct, except I powered the whole system (including my microcontroller) from the 7.5V D24V25F7 step-down regulator. I used a connector to attach the battery to my robot so it could be removed and charged separately. The positive wire from the connector runs through the rocker switch and to the voltage regulator, and the ground wire goes straight to the regulator. The output of the regulator providing power to both the Qik 2s9v1 Dual Serial Motor Controller and the A-Star 32U4 Mini LV.

    I did not use any low-voltage cutoff circuitry. I was careful to not run the robot for too long between charges, and in general it only runs for a couple minutes at a time, so it was easy to check the battery regularly. I considered adding a simple voltage divider from the battery to one of the free pins on the A-Star 32U4 Mini to alert me (with an LED) when the battery voltage dropped too low, but it did not seem necessary for the short run time.

    Brandon

  • Brandon's line following robot: The Chariot

    Brandon's line following robot: The Chariot

    - 28 February 2018

    Hello, cpod.

    The Chariot and Mostly Red Racer (the winner of the competition) both used PD control (no integral). The integral term is useful for counter-acting some external force consistently working against the robot. When following a line, you do not typically have that kind of constant force working against your robot's goal, so in most cases you can simplify by leaving out the Integral term.

    I find it easiest to start tuning at a somewhat slow speed and gradually increase your speed once your P and D coefficients are working fairly well. At slow enough speeds, you probably don't need a D term at all, especially for a relatively straight line. If you want to be able to drive quickly around sharper turns, you will need your P term to be large, which will likely cause an overshoot. This is where the D term comes in to compensate. Essentially, the D term takes a history of the error and reacts to the change accordingly. If the error is getting smaller, it acts to weaken your robot's response to avoid overshoot. Similarly, if the error is getting bigger, the D term should act to increase your robot's response. There are a lot of good tips for tuning in Ben's posts in this thread. You might consider creating your own thread on our forum if you run into more specific questions when tuning your robot.

    Brandon

  • Video: Setting the Current Limit on Pololu Stepper Motor Driver Carriers

    Video: Setting the Current Limit on Pololu Stepper Motor Driver Carriers

    - 29 January 2018

    Hello, servane.

    When setting the VREF voltage, you can connect the driver as shown in the minimal wiring diagram found on the product page for each stepper motor driver carrier, excluding the motor connections. Once the current limit is configured appropriately, you can momentarily remove power and then connect your motor as well.

    If you have additional questions about using one of our stepper motor driver carriers, I recommend posting a request for help on our forum.

    Brandon

  • New product: Sharp 15cm GP2Y0D815Z0F digital distance sensor

    New product: Sharp 15cm GP2Y0D815Z0F digital distance sensor

    - 25 January 2018

    Hello, Peter.

    Theses GP2Y0D815Z0F sensors output a simple digital signal (low when detecting an object, high otherwise), so you can use Arduino's digitalRead() function to read them. For controlling motors, your Arduino code would depend on what kind of driver/controller you are using and what you wanted the motors to do based on the sensor reading. If you have specific questions or concerns, you might consider posting on our forum , which is a more appropriate place for discussing details like code.

    -Brandon

  • Video: Setting the Current Limit on Pololu Stepper Motor Driver Carriers

    Video: Setting the Current Limit on Pololu Stepper Motor Driver Carriers

    - 22 December 2017

    Hello, Aatif.

    I am glad you liked the video! Sorry you are having problems with your DRV8825 carrier. There are several things that could be causing a problem like that, including stepping too fast for your motor or having too heavy of a load. If you would like help troubleshooting the problem in more detail, you can post on our forum with more information about your system as well as pictures of your setup and we would be happy to help.

    Brandon

  • New product: Pololu Dual MC33926 Motor Driver for Raspberry Pi

    New product: Pololu Dual MC33926 Motor Driver for Raspberry Pi

    - 18 October 2017

    Hello.

    The regulator is optional and allows the Raspberry Pi to be powered from your motor power supply. If you are powering the Raspberry Pi separately (e.g. through its USB power connector), you do not need the regulator.

    You can find more information about adding the regulator in the "Powering the Raspberry Pi from the motor driver board" section of the Dual MC33926 Motor Driver for Raspberry Pi product page.

    Brandon

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