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For the recent LVBots line following competition, my first instinct was to try to come up with some unique alternative design for a robot that would be competitive with the traditional differential drive robots. However, I knew the winning robot from the last LVBots line following competition (Mostly Red Racer) would be returning, and it had an impressive time to beat. I also remembered spending so much time designing and assembling the hardware for my last line following robot, that I ended up not having enough time to tune the PID coefficients and get the performance I was hoping for. After brainstorming a few ideas, I ended up deciding to keep it simple and make sure I had enough time to get a robot I was happy with, which I ultimately named “The Chariot” because of its shape. The Chariot ended up winning second place in the competition, which I was very happy with. Instead of focusing this blog post on how you can make your own version of The Chariot, I will try to explain my thought process throughout the design and build process, In other words, my hope is that after reading through this post, it will be clear why I chose the parts that I did. Continued…
New products: Stepper motors with lead screws, traveling nut, and mounting bracket for NEMA 23 stepper motors
|NEMA 17-size stepper motors with 18, 28, and 38cm lead screws.|
Since we started carrying the stepper motor with 28cm lead screw, we have routinely received requests for shorter and longer versions of it, so we are happy to announce that we are now carrying two additional versions: one with an 18 cm lead screw and one with a 38 cm lead screw. All three of the stepper motors with lead screw use the same NEMA 17-size stepper motor, which is also available without a lead screw.
All of the stepper motors with lead screw come with a traveling nut, also known as a carriage nut. This copper alloy nut features a mounting flange with four holes threaded for M3 screws to make it easy to integrate into your project. From time to time, we also get requests to make the traveling nut available for purchase separately, so we did! If you are interested in picking up some spare traveling nuts, more information can be found on the traveling nut’s product page.
We also have a new NEMA 23 stepper motor bracket as pictured above. Around eight months ago, we started carrying our stamped aluminum mounting bracket for NEMA-17 size stepper motors, and since then, we added a stamped aluminum NEMA 14 stepper motor bracket to our selection. We looked into getting similar aluminum bracket for NEMA 23-size stepper motors but ultimately decided to go with a more rigid 3mm-thick steel mounting bracket for NEMA 23 stepper motors. On this bracket, two steel supports are welded in the corner along the bend of the bracket to provide extra reinforcement.
Bruno Schneider posted the above video on our forum that showcases an automated ball path machine he made for last year’s advent season with his brother and father. The contraption uses a 24-channel Mini Maestro and is displayed in the window of his mother’s sewing shop. The machine is fun and impressive by itself, but the video (with accompanying sound effects) makes the project even more entertaining.
If you make or have made any festive projects using the Maestro or any of our other products, we would love to see them! You can post them in the comments below or in the Share Your Projects section of our forum, which is also a great place to browse for inspiration or ideas for a new project.
The people at Seewald Solutions posted about their Raspberry Pi-based robot they call ToyCollect. Inspired by the creator’s daughter, who hides her toys under the couch, the robot is controlled via Android and can be driven under the couch to allow the user to view the hidden toys via a Raspberry Pi camera module and retrieve them. Along with a Raspberry Pi, the ToyCollect robot uses a Zumo Chassis Kit, 100:1 Micro Metal Gearmotors HP, Qik 2sv1 Dual Serial Motor Controller, and a Zumo blade to push the toys. The video below shows the robot in action (in German; subtitles available):
For more information, including the source code and instructions for building your own ToyCollect robot, see the ToyCollect post on the Seewald Solutions website.
Our mini plastic gearmotors make great low-cost actuators for small robots, but they have one major shortcoming: they are not easy to mount (the offset versions have just one mounting hole and the 90° versions don’t have any). Well, today I am pleased to announce that we now have two mounting solutions!
These new plastic brackets, available in a wide version and a tall version, are designed specifically for our mini plastic gearmotors, with internal ridges that fit into recessed features on the gearmotors to hold them securely in place. Both brackets are compatible with all of our mini plastic gearmotors, and the two versions allow for different mounting orientations, some of which can be seen in the pictures below:
In some orientations, features of the mini plastic gearmotor cases prevent them from being flush with a flat mounting surface. To address this, we include a spacer plate with each bracket that fits between the gearmotor and the mounting surface in these orientations, keeping the motor level. If you look closely at the pictures above, you can see the spacer plate being used in three of them.
These new brackets are sold in pairs along with mounting hardware (two M3 screws and nuts per bracket).
See the product pages for additional information:
Our new stamped aluminum L-brackets are specifically designed for Sharp’s popular analog GP2Y0A02, GP2Y0A21, and GP2Y0A41 distance sensors, making it easy to mount them to your project in a variety of ways. The brackets are made of 0.8mm-thick aluminum, so they are light and bendable by hand if your application calls for something other than their default 90° angle, yet they are rigid enough to hold their position while in use.
The appropriate bracket for your project depends on the specifics of how you would like to mount it. For example, if you want a low-profile installation on a horizontal surface, the parallel bracket (pictured above on the left) is a good choice. For a low-profile installation off of a vertical surface, the perpendicular bracket (pictured above on the right) might be most appropriate. The multi-option bracket (pictured above in the center) allows the sensor to be mounted to either face, so it supports both perpendicular and parallel orientations, and the long slots offer a lot of flexibility in sensor placement relative to the mounting surface.
See the product pages for additional information:
- Bracket Pair for Sharp GP2Y0A02, GP2Y0A21, and GP2Y0A41 Distance Sensors – Perpendicular
- Bracket Pair for Sharp GP2Y0A02, GP2Y0A21, and GP2Y0A41 Distance Sensors – Parallel
- Bracket Pair for Sharp GP2Y0A02, GP2Y0A21, and GP2Y0A41 Distance Sensors – Multi-Option
Our family of Mini Plastic Gearmotors is growing! We have added HP versions with more powerful motors for increased torque and speed, and we are now carrying versions with extended motor shafts intended for use with custom encoders for motor speed and position feedback. (These extended-shaft versions are not compatible with the magnetic encoders we just released for our Micro Metal Gearmotors; we will have a similar encoder solution for these plastic gearmotors at some point, but for now we are offering them for people who want to make their own encoders.) The following table shows the current state of our Mini Plastic Gearmotor family:
@ 4.5 V
@ 4.5 V
@ 4.5 V
90° output + motor shaft
offset output + motor shaft
|1250 mA||150 RPM||25 oz-in||120:1 mini HP||120:1 mini HP||120:1 mini HP||120:1 mini HP|
|low-power||800 mA||120 RPM||20 oz-in||120:1 mini||120:1 mini||120:1 mini||120:1 mini|
|80 RPM||30 oz-in||180:1 mini||180:1 mini|
We are particularly excited about these gearmotors because they offer a great combination of performance and affordability; don’t be surprised if you find these motors in some of our future robots and robot kits! For more information about all of these gearmotors, see our Mini Plastic Gearmotors category.
If you read Grant’s Creepy eyes Halloween prop post, then you already know that several of us here at Pololu are working on Halloween projects. I based my project on a motion tracking Halloween prop tutorial by Jason Poel Smith that I saw last year on the Make magazine website. The concept is simple: make a Halloween prop mysteriously follow an unsuspecting person as they walk by. The tutorial by Jason Smith uses photoresistors to track a person by detecting their shadow and moving a servo with a Halloween prop attached to it. This works well, but there are a few things that I thought could be improved. Continued…
Pololu forum member spiked3 recently shared a sophisticated robot he made called RoboNUC. It uses a Netduino and a LIDAR module and was intended to help him learn simultaneous localization and mapping (SLAM). SLAM is a technique used to map an unknown environment and keep track of the device’s location within the environment. Using SLAM, the robot is able to characterize the surrounding areas without needing to physically navigate them. RoboNUC uses our 1″ plastic ball caster, and the acrylic chassis was laser cut using our custom laser cutting service.
Last week, Jon mentioned how several of the mechanical engineers here at Pololu were assigned a simple board to develop. Well, our new Breakout Board for microSD Card is the first board that I designed!
Electrically, this board is pretty basic. It breaks out all of the connections available on a microSD card into two rows of 0.1″-spaced pins for easy prototyping use with standard perfboards, solderless breadboards, and 0.1″ connectors. We tried to arrange the pins in a convenient order by placing all of the pins needed for SPI mode on one side of the board (along with the card detect pin). What makes this board interesting mechanically is that it is the first of our products to use a connector for a microSD card. The push-push type connector is positioned so that when a microSD card is fully inserted, it protrudes slightly beyond the edge of the board to allow easy access to the card. The integration of our electrical and mechanical procedures allows us to make 3D models such as the one below to help support our products. We currently use models like this in the dimension diagrams we publish for our boards, but we hope to eventually make the models themselves available too.
|Breakout Board for microSD Card rendered in Solidworks.|
Integration with 5 V systems
There are no other components on the board aside from the microSD card connector. Since standard microSD cards use 3.3 V logic, no extra considerations need to be taken to use it with a 3.3 V microcontroller, but signal conditioning is required for use with 5 V microcontrollers. We did some tests using our 4-channel level shifter and an Arduino Uno to read and write from a microSD card using the Arduino SD library, and we had successful results; however upon closer inspection, we noticed the level shifter did not have time to shift the 3.3 V signals all the way up to 5 V, so this setup only worked because the Arduino Uno registered 3.3 V as a high signal. With a 5 V microcontroller that accepts a 3.3 V signal as high, the microSD card outputs can be connected directly to the microcontroller, and the microcontroller’s 5 V outputs can be shifted to 3.3 V using a simple voltage divider. We found the resistor values needed to be fairly low – we settled on 500 Ω and 1 kΩ resistors. Since we used the standard Arduino SD library, our tests were done at SPI speeds of 4 MHz. In systems operating at higher speeds or with more stringent logic voltage requirements, it might be necessary to use a buffer IC or other high-speed level-shifting solutions.
For more information about this breakout board, see its product page.