Pololu Blog (Page 27)
Welcome to the Pololu Blog, where we provide updates about what we and our customers are doing and thinking about. This blog used to be Pololu president Jan Malášek’s Engage Your Brain blog; you can view just those posts here.
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.
A few months ago, we introduced our new D24V5Fx buck (step-down) voltage regulator family with inaugural members offering fixed output voltages of 3.3 V, 5 V, 9 V, and 12 V, and now we have expanded that family by adding versions with fixed output voltages of 1.8 V, 2.5 V, 6 V, and 15 V.
We are particularly excited about this regulator family because of its wide operating voltage range, high efficiencies, and low dropout voltages, all in a compact 0.5″ × 0.4″ × 0.1″ (13 mm × 10 mm × 3 mm) form factor that is smaller than standard through hole linear regulators with DIP packages. For example, the picture below shows a D24V5Fx next to a 7805 voltage regulator in a TO-220 package:
These regulators operate at up to 36 V, making them especially useful in applications where there can be large variation in the input voltage, such as solar-powered systems or devices where power supply flexibility is a benefit. Since they are switching regulators, the efficiency is much higher than linear regulators when there is a big difference between the input and output voltage, and since they are synchronous, the efficiency is high even at light loads and low output voltages. As an example of the versatility of these regulators, the same D24V5F2 module can in one application be used to get 2.5 V from a 24 V battery and in another be an efficient way to add a 2.5 V node to a system that already has regulated 5 V. As the performance graph below shows, typical efficiency in the latter scenario is 90%, which could almost double battery life in portable systems when compared to linear regulators.
We consider the new D24V5Fx regulators to be next-generation alternatives to our D24V3Fx and D24V6Fx buck regulators, which have been some of our most popular products. In addition to having generally higher efficiencies (which in practice allow these 500 mA units to achieve maximum output currents comparable to our 600 mA D24V6Fx units), these new regulators have much lower dropout voltages (“dropout voltage” is the amount by which the input voltage must exceed the output voltage in order to ensure that the target output can be achieved). For example, the two graphs below show the dropout voltage of the new 5 V D24V5F5 compared to the older 5 V D24V6F5 and D24V3F5:
What this means for your project is broader operating ranges and longer battery life. For instance, a low-power 5 V system running on a 9 V battery can discharge it all the way to 5 V whereas the higher-dropout D24V6F5 regulator can only go to 6.5 V, and four-cell alkaline and five-cell NiMH packs (both with 6.0 V nominal voltages) become viable options.
Like the LPS331AP, the LPS25H provides pressure readings over a range of 260 mbar to 1260 mbar (26 kPa to 126 kPa), and this data can be used to calculate the sensor’s altitude. Our LPS25H carrier mounts the sensor on a 0.4″ × 0.8″ board (0.1″ shorter than our earlier LPS331AP carrier) that breaks out all of its pins, and as usual, we’ve included level shifters and a regulator to make it easy to use in a 5 V system. Continued…
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.
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.
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:
- Spin something really tiny and adorable.
- 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!
We are now carrying metal servo horns that work with Power HD’s ultra-high-torque HD-1235MG giant servos, which can deliver a whopping 560 oz-in (40 kg-cm) at 7.4 V. If you want to get the most power out of your HD-1235MG, I recommend substituting one of these anodized aluminum horns for the included plastic horns.
We are happy to announce two new Pololu distributors:
Sun Light Electronics Pte Ltd is an electronics supplier in Singapore that was founded in 1992. They specialize in “ICs and transistors”, but as you can see from their website, they now carry far more than that, including a large selection of hobby, robotics, and prototyping products.
Virtuabotix, in Colorado Springs, CO, is an electronics hardware manufacturer and distributor. They specialize in open-source hardware and have their own family of Arduino-compatible boards called Versalino. Virtuabotix also sells products through storefronts at Amazon, Newegg, and eBay.
See our growing list of almost 200 distributors to find one in your area.
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:
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
We are now carrying four exciting new sensors from Interlink Electronics:
- 0.25″-diameter circle, short tail force-sensing resistor (FSR)
- 0.6″-diameter circle, short tail FSR
- 1.4″ × 0.4″ force-sensing linear potentiometer (FSLP) strip
- 4.0″ × 0.4″ customizable-length FSLP strip
The two force-sensing resistors (or FSRs, for short) are short-tail versions of the small, circular FSRs we already carry, which allows them to be integrated into applications with tighter space constraints. These sensors act just like variable resistors that depend on the applied pressure, so you can put them into a simple voltage divider circuit and measure the force on them with a single analog-to-digital (ADC) microcontroller input.
0.6″-diameter short-tail force sensing resistor (FSR) next to a 0.6″-diameter FSR with a standard tail.
The two force-sensing linear potentiometers (or FSLPs) take the force-measuring functionality of FSRs and add in the ability to detect the location of the force, all while being an entirely passive component that is incredibly easy to use.
The two force-sensing linear potentiometers (FSLPs).
These FSLPs are exciting because they enable fun new touch interfaces, not only for you to interact with your project but for your project to interact with the world. We decided to make a quick demo for the Las Vegas Mini Maker Faire 2014 to show just how easy it was to do something cool with this sensor. The video at the top of this blog post shows the demo in action.
In the demo, a 4.0″×0.4″ FSLP is used with an Arduino Uno R3 to meassure the position and pressure of the user’s finger. (For applications where space is tight, smaller modules like our Arduino-compatible A-Star Micro can be directly substituted for the Uno.) Using the strip requires four connections to a microcontroller and one additional resistor. Two of the required connections must be analog inputs. Four connections for one sensor might seem like a lot to deal with, but step-by-step procedures in section 5 of the sensor’s integration guide (513k pdf) make it easy to get the sensor working, and the Arduino code used in this demo is available on github to help get you started. A diagram of the connections made between the sensor, Arduino, and LED strip in this demo are shown below.
The connections shown in the diagram also work with the shorter 1.4″×0.4″ FSLP (referred to as “standard FSLP” in the integration guide), though the pin numbers that correspond to each of the sensors outputs (SL, D1, and D2) are different for the two sizes of FSLP. The pin numbers for each FSLP can be seen in Figure 9 of the FSLP Integration Guide. In the guide the 4.0″×0.4″ FSLP is referred to as a “10 cm FSLP”.
Once the Arduino reads the position and pressure data from the sensor, it sends signals to a WS2812B addressable LED strip that control the number of LEDs that turn on and their color. The further along the strip your finger moves the greater the number of LEDs that light up, and the more pressure you apply the more the color of all the LEDs changes from blue to red.
To make the demo easy to transport and able to be left on all day, a 9V wall adapter was used to power the Arduino and 5V step-down regulator. The power connections from the regulator’s 5V output to the power input of the LED strip were also simplified by using a DC barrel jack to terminal block adapter and a DC barrel plug to terminal block adapter. The structure of the demo was laser cut from 1/8″ clear acrylic, and aluminum standoffs were used as spacers.
If you guys do something cool with our force-sensing linear potentiometers or resistors, we’d love to hear about it!