Posts by Jon

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Leviathan: an autonomous Raspberry Pi-controlled electric boat

Posted by Jon on 11 September 2014
Leviathan: an autonomous Raspberry Pi-controlled electric boat

Heikki Leivo and Matti Koljonen are currently working together to develop a miniature autonomous electric boat, which they are calling Leviathan. The boat is made of polystyrene foam, uses brushed DC motors and servos for movement, and is controlled by a Raspberry Pi, which reads data from GPS and a MinIMU-9 inertial measurement unit for navigation. Leviathan is equipped with a camera and also features a D24V6ALV step-down regulator for powering servos and other electronics. The boat is also controllable over WiFi.

The electronics inside Leviathan.

Matti and Heikki plan for their vehicle to be able to run pre-defined routes, capture photos, and record video, among other things. You can learn more about Leviathan on its website.

New product: DRV8838 motor driver carrier

Posted by Jon on 5 September 2014
Tags: new products
New product: DRV8838 motor driver carrier

If you’ve checked out my company profile, you might have noticed that my focus at Pololu is on developing mechanical parts. So, I am particularly excited to reveal this basic board I designed! (Don’t worry, like Jan mentioned in this blog post, we have support structures for checking all of the work we do, so other experienced electrical engineers here assessed and contributed to my work.)

The DRV8838 motor driver carrier is the smallest motor driver we’ve made yet. With a motor supply range from 0 V to 11 V and the ability to deliver a continuous 1.7 A (1.8 A peak) to a single brushed DC motor, the DRV8838 is an exciting option for controlling any one of our plastic or micro metal gearmotors. (That includes the high power versions.)

For more information about this carrier, see its product page.

But Jon, why are mechanical engineers designing PCBs?

As our products get more sophisticated, we find ourselves wanting to integrate mechanical and electrical aspects of our design process. To give the mechanical engineers better perspective on what goes into designing electronics, we were each assigned a simple board to develop. We expect this to improve our all-around engineering abilities and also to lead to additional benefits for our customers, like better documentation and support.

Modding the Zumo: encoders, WiFi, GPS, USB, 120 MHz, and joystick control

Posted by Jon on 1 August 2014
Modding the Zumo: encoders, WiFi, GPS, USB, 120 MHz, and joystick control

Forum user Erich uses our Zumo chassis as a platform for teaching robotics, but instead of using the Zumo shield, he has been making his own custom electronics that let it do many more things. One of his most recent projects, which he describes in this forum post, involves a control board he designed that uses a Freescale ARM Cortex-M4F running at 120 MHz. He says it is capable of running WiFi, USB, GPS, and processing encoder signals in real-time.

His robot also uses a mini-sumo blade, Zumo reflectance sensor array, and a pair of 75:1 micro metal gearmotors with extended shafts connected to a pair of optical encoder boards.

Erich also used the ElecFreaks’ joystick shield to run his modified Zumo, which sounds like a lot of fun! For more information on this project, including some of the problems he had to overcome to get it all working, see this forum post or visit Erich’s website.

Erich has posted to our forum about his projects before; you can find a list of the forum posts he made that we blogged about below:

March 2013: Zumo Robot with FRDM-KL25Z Board

September 2013: Zumo Robot with Pololu Plug-in Modules

October 2013: Zumo Robot with Pololu Plug-in Modules, assembled

December 2013: Zumo Tournament Videos

May 2014: Optical Motor Shaft Encoder in Zumo with Signal Processing

Firetail UAV System

Posted by Jon on 25 July 2014
Firetail UAV System

We mentioned it in passing in an earlier post, but we think that the Firetail UAV System deserves its own post. Since then, Firetail’s creator, Samuel Cowen, has continued to develop this open-source UAV autopilot system, posting regular updates on his blog and sharing his project on the Pololu forum.

Firetail is designed to be installed in any fixed-wing RC airframe and autonomously fly up to 512 waypoints. The system includes software for a ground control station, which allows users to see the location, speed, altitude, and orientation of the aircraft. Users at the station can also upload and download autopilot settings and plan flights using Google Maps.

To test Firetail, he built his own RC aircraft, which uses an Arduino Due to process signals from an RC receiver, and reads data from an AltIMU-10. Depending on how the user sets up the autopilot mode, the Firetail system either flies the craft, or simply allows the user to fly the craft while streaming telemetry data to the ground control station.

You can learn more about the Firetail system on its website.

New products: Scooter wheel adapters

Posted by Jon on 11 July 2014
Tags: new products
6 mm scooter wheel adapter pieces assembled with the included hardware.
6 mm scooter wheel adapter with included hardware.

You have probably seen wheels on things like scooters, skateboards, baby-strollers, and inline skates, and noticed just how similar these common wheels are in size and shape. In fact, they are so similar that the industries built up around them have converged upon using a few standard bearings. We found that one of the most popular bearings used with wheels like those is the metric 608 ball bearing. The 608 bearing has well defined tolerances, measures 22 mm wide by 7 mm tall, and features an 8 mm bore.

We recently used these measurements to create a series of adapters that enables you to use these widely-available wheels as drive wheels, which opens up a much larger variety of wheels to use with our motors!

Exploded view of the scooter wheel adapter assembly with a gearmotor and scooter wheel.

These adapters mount via set screw(s) to your motor’s output shaft (works best with D-shaped output shafts) and clamp tightly to the wheel.

We have versions of these adapters that support our gearmotors with 4 mm, 5 mm, and 6 mm shafts.

Ibex: a wall-climbing robot by Operative RC

Posted by Jon on 20 June 2014

Forum user Lukeness made a detailed post about the design of his wall-climbing robot, Ibex, which is now available for purchase on his website, Operative RC.

The lightweight and compact RC-controlled wall-climbing robot uses a brushless DC motor for suction, and features a drive solution that uses four of our micro metal gearmotors, each driving a 32mm Pololu wheel and mounted with our micro metal gearmotor brackets.

The post includes pictures and videos of various iterations of Ibex and includes Luke’s reflection on the disheartening results of one of Ibex’s iterations. We’re glad to hear that Luke “stuck” with it, and now has a robot he is happy enough to market! We look forward to hearing more about Operative RC when more products become available.

Zumo tennis ball collector

Posted by Jon on 2 June 2014

Forum user patman715 posted to the forum about his modified Zumo Robot. The video above shows a Zumo with a two-servo gripper and arm capable of lifting tennis balls into an on-board storage bin. It is all controlled by an Arduino Leonardo, and two of our 100:1 micro metal gearmotors (we suspect they are HP versions) seem to give it plenty of oomph for carrying around the extra load.

New products: sub-micro plastic planetary gearmotors & compatible wheels

Posted by Jon on 22 May 2014
Tags: new products

Need a “little” help with your next electronics project? Get it up and running with our sub-micro plastic planetary gearmotors! Measuring a minuscule 6 mm in diameter and weighing just over a gram, these gearmotors are even smaller (and much lighter) than our popular micro metal gearmotors.

26:1 sub-micro plastic planetary gearmotor next to a micro metal gearmotor and a LEGO Minifigure for size reference.

Our sub-micro plastic gearmotors are available in two gear ratios: 26:1 and 136:1. Click on those ratios to learn more about each motor!

Motor accessories

While there are no mounting holes, their cylindrical bodies makes them perfect for snapping into 1/4″ (6 mm) fuse clips, and their small scale makes it easy to affix them with tape or glue. We are also now carrying tiny 14 × 4.5 mm wheels, which are compatible with the sub-micro plastic gearmotor output shafts.

26:1 sub-micro plastic planetary gearmotor being held by a 1/4″ (6 mm) fuse clip.
Sub-micro plastic planetary gearmotor with a 14×4.5mm wheel.

But, Jon, what can I do with such a tiny, adorable motor?

I’m glad you asked! The way I see it, you really only have two options:

  1. Spin something really tiny and adorable.
  2. Make something tiny and adorable like this line follower made by Pololu engineer Kevin (blog post coming soon!):

I’m just kidding; there are definitely plenty of interesting things that can be made with these motors. We can’t wait to see what you use these motors for!

Custom optical encoder signal processing board for the Zumo

Posted by Jon on 16 May 2014

Erich, a professor at the Lucerne University of Applied Sciences and Arts in Switzerland, posted to our forum about a circuit he designed for the robots he’s building based on our Zumo chassis for his embedded system programming course. His Zumos are retrofitted with our micro metal gearmotors with extended backshafts and optical encoder board. The custom circuit he designed converts the analog output of our optical encoder boards to digital waveforms, which makes them more easily interpreted by microcontrollers and other devices. His board uses a Digital-to-Analog Converter (Microchip’s MCP4728) and four op-amps (Microchip MCP6004) to generate the modified quadrature output. The DAC can be controlled directly over I²C and can be calibrated automatically. After verifying that it works, Eric ordered a bunch more boards to use in his course:

One of Erich’s fully soldered optical encoder boards with attached 3-tooth wheel.
This oscilloscope capture compares the processed encoder output (top) with the raw output voltages of the optical encoder board (bottom).
A bunch of signal processing PCBs!
Erich’s optical encoder signal processing board with components populated.

We look forward to seeing how they work with the Zumos!

You can read more about Erich’s signal processing boards on this blog post from his website. You can follow the progression of the robots used in his course by visiting these forum posts:

March 2013: Zumo Robot with FRDM-KL25Z Board

September 2013: Zumo Robot with Pololu Plug-in Modules

October 2013: Zumo Robot with Pololu Plug-in Modules, assembled

December 2013: Zumo Tournament Videos

New product: Advancer Technologies Muscle Sensor v3

Posted by Jon on 29 April 2014
Tags: new products

Looking for a way to pump up your next project? Let the Muscle Sensor v3 from Advancer Technologies do the heavy lifting!

This small, easy-to-use, 1″ × 1″ board measures muscle activation via electric potential; this is referred to as electromyography (EMG). The sensor measures, filters, rectifies, and amplifies the electrical activity of a muscle; as the muscle flexes, the output voltage increases, resulting in a simple analog signal that can easily be read by any microcontroller with an analog-to-digital converter (ADC), such as our A-Star or an Arduino.

Muscle Sensor v3 with included hardware.

The engineers here were pretty excited to play with these when we got our first samples, as many of us hadn’t used anything like it before. While thinking of various ways to test the sensor, a few of us remembered this ridiculously awesome video of Terry Crews making music with his muscles. (Gets me every time! #MuscleEnvy.) Without getting ahead of ourselves, we decided to try something much quicker and more straightforward with some of our electronics.

In the demonstration video at the beginning of this post, you can see the muscle sensor in action as it measures the muscle activity of my bicep. The demo uses the muscle sensor with a Maestro servo controller to update the position of a hobby RC servo based on how hard I flex. The setup was very simple; the analog output signal from the muscle sensor is connected directly to channel 0 on the Maestro, and the two boards share a common ground. The muscle sensor is powered by two 1S LiPo batteries and the Maestro and servo (connected to channel 1) are powered from a separate 6 V battery pack.

Here I am modeling the correct placement of electrodes on my bicep for the Muscle Sensor v3.

The Maestro script we used is very similar to the “Using an analog input to control servos” example script provided in the Maestro user’s guide with a couple of modifications. We changed the scaling of the input channel (since our signal was from 0 V to 3.7 V) as well as the channel numbers to match our setup. The whole script is only a few lines long:

# Sets servo 1 to a position based on the analog input of the Muscle Sensor v3.
begin
  0 get_position       # get the value of the muscle sensor's signal connected to channel 0
  6 times 4000 plus    # scale it to roughly 4000-8092 (approximately 1-2 ms)
  1 servo              # set servo 1 accordingly
repeat

We can’t wait to see all of the amazing things you come up with when you engage your brain (and your muscles) with this sensor!