Posts by Jon

You are currently viewing a selection of posts from the Pololu Blog. You can also view all the posts.

Video: MyoWare Muscle Sensor demonstration with Maestro servo controller

Posted by Jon on 6 November 2015

I got your torque right here ;)

Now that we are carrying Advancer Technologies’ MyoWare Muscle Sensor, it is time to update our demonstration video! I’ve had two whole years to add some mass to my biceps (during which time I continuously worked on those bad boys for a grand total of four weeks), and now I can proudly present to you these sick gains.

The demonstration is basically a redo of the original muscle sensor demo with the new sensor, except for a few small differences (honestly, my biceps are not that much bigger). In this setup, a 6-channel Maestro reads the muscle sensor’s analog voltage output and commands the position of a Power HD servo. The Maestro’s +5 V (out) pin supplies power to the MyoWare Muscle Sensor, and the servo and Maestro are powered by 4 rechargeable AA batteries. On a personal note, I found it really satisfying to use a single power source for this demonstration, which is not something you can do with the previous version of this muscle sensor, as it requires two supplies. (Be sure to check out the MyoWare Muscle Sensor’s product page to read about more ways the new muscle sensor improves upon the older version!)

This Maestro script is slightly more interesting than the script in the last demo, since the servo’s default direction of rotation was the opposite of the motion for a bicep curl (and we were already quite happy with the servo’s orientation with respect to my arm for the planned video footage). To get around this, and make the servo arm movement match the position of my arm during a bicep curl, I did some basic math and came up with an equation that you can see in the code below:

# Sets servo 1 to a position based on the analog input of the MyoWare Muscle Sensor.
  8000            # put this value on the stack (for why, see line 5)
  0 get_position   # get the value of the muscle sensor's signal connected to channel 0
  4 times minus    # y = -4x + 8000 , which is an equation we use to deal with the servo's 
                   # default direction of rotation and scale the Maestro's Target 
                   # value to roughly 4000-8000 (approximately 1-2 ms)
                   # which is the range of servo pulses that corresponds
                   # to the motion we want.
  1 servo          # set servo 1 accordingly

You can, of course, use other devices to read the analog voltages from the MyoWare Muscle Sensor. If you have not already, you might try using one of our A-Stars!

If you have a project that uses the MyoWare Muscle Sensor, we would be pumped to hear about it!

New product: MyoWare muscle sensor and electrodes

Posted by Jon on 30 October 2015
Tags: new products
New product: MyoWare muscle sensor and electrodes

We are pumped to announce that we are now carrying Advancer Technologies’ MyoWare Muscle Sensor!

This sensor features a number of improvements over the older Muscle Sensor v3 including single-supply operation (no need for a negative voltage supply) and built-in snap connectors for electrodes. Other new features include a raw EMG output, reverse power protection, a power switch, LED indicators, and two mounting holes.

For a fun example that shows how you could use the muscle sensor, take a look at this blog post, which uses one of our Maestros to monitor a bicep while it is flexing, and command a servo to imitate the motion with a tiny cardstock version of He-Man’s arm. (Note that the project uses the older Muscle Sensor v3, not this new product.) You can also head on over to Advancer Technologies’ website for more project ideas.

The MyoWare Muscle Sensor does not ship with electrodes; they are available separately in packs of six.

Prototyping hexapod motion with a Maestro USB servo controller

Posted by Jon on 23 October 2015
Prototyping hexapod motion with a Maestro USB servo controller

Chris Barlow posted this interesting write-up about how he is using the USB connection of a Mini Maestro servo controller to prototype motion control for his hexapod robot. He has been going over the build in detail on his blog, so check it out over there, and be sure to take a look at this short video below:

Zippy: an Arduino Nano-based balancing robot

Posted by Jon on 3 September 2015

Zippy is an RC balancing robot created by Larry McGovern. It uses an Arduino Nano to read pulses from an RC receiver and accelerometer and gyroscope data from an MPU6050. After processing that information, the Nano commands two ST motor driver development boards, which each control a 30:1 37D mm gearmotor with encoder. The whole system is powered by a 3S LiPo (brand: Zippy, of course!). You can watch Zippy scoot around on pavement below:

In the video description, Larry mentions that he modeled Zippy after the Balanduino robot, but we would like to highlight one noticeable difference: he used his own pair of wheels, which are mated to the output shaft of his gearmotors with our 6mm scooter wheel adapters! I had a major role in designing these, so on a personal note, it is especially exciting to see someone get a good use out of them. (It also looks like our stamped aluminum L brackets are used to mount the motors.)

Jon's line following robot: Usain Volt 2.0

Posted by Jon on 4 May 2015
Jon's line following robot: Usain Volt 2.0

Like other developers and engineers here, I made a robot for the LVBots Line Following Contest. This post describes my robot, Usain Volt 2.0, and details some of what I was thinking when I designed it. If you want to know more about the competition rules and how it was judged, see the LVBots line following rules. Continued…

Maestro-controlled Spider Dress 2.0 at CES 2015

Posted by Jon on 9 January 2015
Maestro-controlled Spider Dress 2.0 at CES 2015

This week at the Consumer Electronics Show, some of our engineers got to see Spider Dress 2.0, which was being exhibited by its designer, Anouk Wipprecht, at the Intel booth. The dress is designed to react to invasions of the wearer’s personal space with threatening insect-like legs controlled by servos. Two Maxbotix proximity sensors are used to detect movement, and two 12-channel Maestro servo controllers  (one under each shoulder pad) control the response of the legs. The whole dress is controlled by an Intel Edison.

Anouk hanging out in the personal space of Spider Dress 2.0 at CES 2015.
A nook under each shoulderpad holds a 12-channel Maestro servo controller.

Anouk explains the dress in detail in this video, which was produced by Make, and features a brief cameo by yours truly:

You can learn more about Spider Dress 2.0 in this Make article, and about Anouk and her work by visiting her website.

Khan Academy interactive continuous rotation servo demo

Posted by Jon on 28 November 2014
Khan Academy interactive continuous rotation servo demo

Khan Academy user mbbackus created a demo that allows users to visualize the effects of sending different pulse widths to the SM-S4303R and Parallax continuous rotation servos. (You can use the up and down arrow keys to change the pulse width, and more instructions can be found as comments in the code.)

For those who are interested, you can learn more about standard RC servo pulses in this series of blog posts about hobby servos.

You can see the demo on its Khan Academy page.

New products: Pololu T-shirts

Posted by Jon on 21 November 2014
Tags: new products

We have a new batch of T-shirts available, just in time for winter! These shirts are very similar to the ones we released in 2012, featuring a printed circuit board (PCB) design in the shape of the Pololu logo on the front and the Pololu slogan “Engage Your Brain” on the back.

The shirts are available in a variety of youth and adult sizes, and this time we have two new colors available in addition to our standard royal blue: cardinal red and charcoal gray.

You can find our full selection in our T-shirts category.

Raspberry Pi-controlled chicken coop

Posted by Jon on 6 November 2014
Raspberry Pi-controlled chicken coop

Forum user bennard posted about his WiFi-enabled chicken coop, which uses a Raspberry Pi to monitor and log data about its environment, serve a web page, send emails, and open and close the coop door. The system has sensors for detecting temperature, humidity, motion, and light, and includes a 50W solar panel and solar charge controller for recharging its batteries. The automated door is a hinged piece of wood that is connected to a linear actuator (via this mounting bracket) and controlled by a jrk 21v3 motor controller.

You can learn more about bennard’s project in his forum post.

Ascending/descending spider

Posted by Jon on 16 October 2014
Ascending/descending spider

This animated spider prop takes a traditionally static Halloween display to new heights! The setup is simple: a Maestro servo controller and a continuous rotation servo raise and lower a spider with the help of a limit switch. Continued…

New Products

Pololu 5V, 2.5A Step-Down Voltage Regulator D24V22F5
RoboClaw 2x7A Motor Controller (V5)
Big Pushbutton Power Switch with Reverse Voltage Protection, HP
Free Elektor magazine November/December 2015
100:1 Metal Gearmotor 37Dx73L mm with 64 CPR Encoder
Scooter/Skate Wheel 70×25mm - Black
Pololu Zumo T-Shirt: Royal Blue, Adult L
Pololu 3.3V, 2.6A Step-Down Voltage Regulator D24V22F3
Big Pushbutton Power Switch with Reverse Voltage Protection, MP
298:1 Micro Metal Gearmotor HPCB with Extended Motor Shaft
Log In
Pololu Robotics & Electronics
Shopping cart
(702) 262-6648
Same-day shipping, worldwide
Shop Blog Forum Support
My account Comments or questions? About Pololu Contact Ordering information Distributors