Pololu Blog (Page 54)
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.
Get FREE copies of Circuit Cellar magazine’s May issue and Elektor magazine’s May issue with your order, while supplies last. To get your free issues, enter the coupon codes CIRCUIT0514 and ELEKTOR0514 into your shopping cart. The magazines will add 6 ounces and 7 ounces, respectively, to the package weight when calculating your shipping options.
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 with 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!
We are happy to welcome GarageLab as a Pololu distributor! GarageLab, located in Doral, FL, is the US branch of our Brazilian distributor Laboratório de Garagem. They carry a wide range of Arduino, microcontroller, and robotics-related products, including their very own Arduino-compatible Garagino.
For distributors in your area, you can check out our complete list of almost 200 distributors.
Inevitably, if you work with electronics long enough, you will encounter a wire that is too long, too insulated, or too connected (to the wrong thing), and while you might be able to MacGyver your way out of the situation with a pair of scissors or a suitably hardy set of teeth, nothing beats a good wire stripper. With that in mind, we set off in search of some good, basic wire strippers that would get the job done well without breaking the bank. Our favorites were a set of multi-purpose wire strippers and cutters that feature comfortably curved and cushioned grips and a nose that can be used as pliers. One version works with 10 to 20 AWG wires and another works with 20 to 30 AWG wires. (The stripping holes are labeled with the gauge of solid-core wire for which they are intended; for stranded wire, use the next larger hole.)
Let’s Make Robots user rhughes posted about MiniTrack, his custom-built tracked robot that features the ability to drive on each of its three sides. It uses our 30T track set and an extra pair of our 42×19mm sprockets. The tracks are driven by a pair of medium power 150:1 micro metal gearmotors, which are controlled by a DRV8833 dual motor driver carrier. MiniTrack also uses two Sharp GP2Y0D805Z0F digital distance sensors for object avoidance:
You can find pictures of various stages of the assembly of this robot and learn what else was involved in making it inside rhughes’s post.
We recently released the A-Star 32U4 Micro, an Arduino-compatible ATmega32U4 breakout board intended to be cheap enough to go into (and stay in) almost any project. To help our customers put A-Stars in everything, we are announcing a new, limited-time offer: on any order over $100, you can get a free A-Star 32U4 Micro with coupon code FREEASTAR.
Taking advantage of this deal? What are you planning to use your A-Star for? Please tell us about your project in the comment section.
LVBots is a robotics club that has been meeting at the Pololu office in Las Vegas, Nevada for almost ten years. Our meetings are open to all ages and skill levels, and everyone is encouraged to bring their projects to share – even projects that are not capable of flying hundreds of feet into the air. Do you live in the area, or are you passing through? Check out our schedule and join us!
The Las Vegas Mini Maker Faire 2014 was on April 5th, and as you might have heard, we had a booth there with demos of our products. For more about the faire and a video, see my previous blog post. This post details the Simple Motor Controller and Sharp analog distance sensor demo that we brought. The demo was popular at the faire with both kids and adults, and though it is simple, it is a great tool for showing those who are just getting interested in robotics what one of the first steps to building a robot might look like. Continued…