Pololu Blog (Page 2)

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.

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!

One-sixth scale Mark 1 British Heavy Tank by Helen Lawson

Posted by Brandon on 6 November 2015
One-sixth scale Mark 1 British Heavy Tank by Helen Lawson

Helen Lawson designed and built a one-sixth scale Mark 1 British Heavy Tank replica that is a functional, radio controlled robot. The replica has been a work in progress for around three years and is now reaching completion. Helen designed the main chassis out of laser-cut wood and made other aspects of the chassis from aluminum and 3D printed parts.

One distinguishing feature of a MK 1 British Heavy Tank is the lack of a central turret. Instead, it has a sponson on each side. This proved challenging for Helen’s build since most electronics made for RC tanks only allow for a single gun and turret. To make the sponsons functional, Helen used a combination of an RC receiver, an RC switch with digital output, an RC switch with relay, a Micro Maestro servo controller, a few servos, and a Taigen gun flash unit. You can find more detailed information about this part of the system (including a wiring diagram and Maestro script) in her post on our forum. The images below show each side of one of the completed sponsons:

She also made a 3D-printed case for the Maestro (shown in the photo on the right) and a few of the other electronic components, which she made available on her Thingiverse page.

You can see a video of the robot in action on this Portsmouth Model Boat Display Team Armoured Division Facebook page, and even more information on her build, including many more pictures, in Helen’s forum thread at landships.net.

37D mm metal gearmotors with encoders and end caps

Posted by Ben on 3 November 2015
Tags: new products
37D mm metal gearmotors with encoders and end caps

Our 37D mm metal gearmotors now have fitted plastic end caps over their encoders that neatly protect the assembly and keep stray objects clear of the magnetic disc. The pictures below show the previous version (without end cap) next to one of the new ones:

The end cap is easily removable if you need to access the encoder or want a few more millimeters of clearance for your gearmotor, but there is a little bit of base plastic that will remain (as shown in the picture below), so removing the end cap does not quite make these new ones identical to the previous versions.

37D mm metal gearmotor with 64 CPR encoder (with end cap removed).

These gearmotors are available in six different gear ratios and with or without encoders, and we also carry the motor and encoder assembly by itself with no gearbox. The following table shows all of our 37D mm metal gearmotor options:

Gear Ratio No-Load
@ 12 V
Stall Torque
@ 12 V
Stall Current
@ 12 V

With Encoder

Without Encoder
1:1 11,000 RPM 5 oz-in 5 A motor without gearbox
19:1 500 RPM 84 oz-in 5 A 37Dx52L mm 37Dx52L mm
30:1 350 RPM 110 oz-in 5 A 37Dx52L mm 37Dx52L mm
50:1 200 RPM 170 oz-in 5 A 37Dx54L mm 37Dx54L mm
70:1 150 RPM 200 oz-in 5 A 37Dx54L mm 37Dx54L mm
100:1 100 RPM 220 oz-in 5 A 37Dx57L mm 37Dx57L mm
131:1 80 RPM 250 oz-in 5 A 37Dx57L mm 37Dx57L mm

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.

Brandon's mini sumo robot: Black Mamba

Posted by Brandon on 28 October 2015
Brandon's mini sumo robot: Black Mamba

Before I started designing my entry into this year’s LVBots mini sumo competition, I watched several videos of other competitions. I noticed a majority of the victories came from engaging the opponent from the side or back; a pattern I also noticed during the last LVBots mini sumo competition. For that competition, I made a robot that used a blade and sensors on the front and back of the robot (basically making the robot have two fronts and no back). However, my strategy in that competition was to roam the ring and search for the opponent, which I suspect increased the chances of the opponent engaging from a suboptimal angle. This time, I wanted to try having my robot spin in place looking for the opponent and striking once it was found. This ultimately resulted in my newest mini sumo robot, Black Mamba. For those unfamiliar, a black mamba is a snake with a reputation for being highly aggressive and is one of the longest and fastest-moving snakes in the world. A black mamba’s venom is highly toxic, and it is capable of striking at considerable range, occasionally delivering a series of bites in rapid succession. Black Mamba is also Kobe Bryant’s self-appointed nickname (yes, I am a Lakers fan). Continued…

HPCB micro metal gearmotors with extended motor shafts

Posted by Ben on 25 October 2015
Tags: new products
HPCB micro metal gearmotors with extended motor shafts

It has been a few months since we introduced our new high-power micro metal gearmotors with longer life carbon brushes. We now have them available with dual shafts, and we have made a corresponding update to our magnetic encoders to let them work with the larger terminals of the HPCB motors.

Magnetic Encoder Kit for Micro Metal Gearmotors (old version; not compatible with HPCB micro metal gearmotors).
Magnetic Encoder Kit for Micro Metal Gearmotors (HPCB compatible).

You might see similar-looking motors elsewhere, but no one comes close to our offering, from the quality of the gears to the variety of winding options to the selection of gear ratios, all in stock for shipment the day you order. By bringing together Pololu’s exclusive features of high-power windings, long-life carbon brushes, and encoders for closed-loop feedback control into a single package, these latest motors and encoders really demonstrate our continual investment in this popular form factor. With ten gear ratios available, from 10:1 through 1000:1, our total selection of micro metal gearmotors has grown to nearly 70 options:

Motor Type Stall
@ 6 V
@ 6 V
Stall Torque
@ 6 V

(Gearbox Only)

(Gearbox & Motor)
carbon brushes
1600 mA 3000 RPM 4 oz-in 10:1 HPCB 10:1 HPCB dual-shaft
1000 RPM 9 oz-in 30:1 HPCB 30:1 HPCB dual-shaft
625 RPM 15 oz-in 50:1 HPCB 50:1 HPCB dual-shaft
400 RPM 22 oz-in 75:1 HPCB 75:1 HPCB dual-shaft
320 RPM 30 oz-in 100:1 HPCB 100:1 HPCB dual-shaft
200 RPM 40 oz-in 150:1 HPCB 150:1 HPCB dual-shaft
140 RPM 50 oz-in 210:1 HPCB 210:1 HPCB dual-shaft
120 RPM 60 oz-in 250:1 HPCB 250:1 HPCB dual-shaft
100 RPM 70 oz-in 298:1 HPCB 298:1 HPCB dual-shaft
32 RPM 125 oz-in 1000:1 HPCB 1000:1 HPCB dual-shaft

(same specs as
HPCB above)
1600 mA 6000 RPM 2 oz-in 5:1 HP
3000 RPM 4 oz-in 10:1 HP 10:1 HP dual-shaft
1000 RPM 9 oz-in 30:1 HP 30:1 HP dual-shaft
625 RPM 15 oz-in 50:1 HP 50:1 HP dual-shaft
400 RPM 22 oz-in 75:1 HP 75:1 HP dual-shaft
320 RPM 30 oz-in 100:1 HP 100:1 HP dual-shaft
200 RPM 40 oz-in 150:1 HP 150:1 HP dual-shaft
140 RPM 50 oz-in 210:1 HP
120 RPM 60 oz-in 250:1 HP
100 RPM 70 oz-in 298:1 HP 298:1 HP dual-shaft
32 RPM 125 oz-in 1000:1 HP 1000:1 HP dual-shaft
700 mA 2200 RPM 3 oz-in 10:1 MP 10:1 MP dual-shaft
730 RPM 8 oz-in 30:1 MP
420 RPM 13 oz-in 50:1 MP
290 RPM 17 oz-in 75:1 MP 75:1 MP dual-shaft
220 RPM 19 oz-in 100:1 MP 100:1 MP dual-shaft
150 RPM 24 oz-in 150:1 MP
75 RPM 46 oz-in 298:1 MP
25 RPM 80 oz-in 1000:1 MP 1000:1 MP dual-shaft
low-power 360 mA 2500 RPM 1 oz-in 5:1
1300 RPM 2 oz-in 10:1
440 RPM 4 oz-in 30:1 30:1 dual-shaft
250 RPM 7 oz-in 50:1 50:1 dual-shaft
170 RPM 9 oz-in 75:1
120 RPM 12 oz-in 100:1 100:1 dual-shaft
85 RPM 17 oz-in 150:1
60 RPM 27 oz-in 210:1
50 RPM 32 oz-in 250:1
45 RPM 40 oz-in 298:1 298:1 dual-shaft
14 RPM 70 oz-in 1000:1 1000:1 dual-shaft

You can see all ten of the new versions below, and if there are any versions we do not yet have that you would like to see us carry, let us know in the comments!

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:

Motion tracking skeleton at Cedar Gables Inn

Posted by Amanda on 20 October 2015

Forum user Ken constructed a spine-chilling Halloween project that is featured at the Cedar Gables Inn Bed and Breakfast in Napa, California. His project is based on Brandon’s Motion Tracking Skull Halloween prop, but instead of just using a head-turning skull, Ken used a full-scale skeleton body to complete the creepy look.

Motion tracking skeleton at the Cedar Gables Inn.

Just like in Brandon’s example, Ken used two Sharp GP2Y0A60SZ analog distance sensors to detect objects (or humans) and a Micro Maestro servo controller to read the output values from the sensors and control the servo that moves the head. Ken improved on Brandon’s code by returning the skeleton’s head to its starting position after a short delay so the skeleton wouldn’t stare rudely at the inn’s guests.

For more information about Ken’s Halloween project, see his forum post, and if you happen to be in the Napa Valley area this Halloween, stop by the Cedar Gables Inn and check it out in person!

In case you missed it, we have Maestros and Sharp distance sensors on sale right now as part of our Polo-BOO! Halloween Sale. The sale ends in less than two days, so if you want to try doing a project like this, now is the time to get started!

Sumo ring border angle detection

Posted by David on 8 October 2015
Tags: lvbots
Sumo ring border angle detection

My robot from the last LVBots mini-sumo competition has a feature which I think is pretty interesting and sets it apart from a lot of other robots: when it detects the border of the sumo ring, it measures the angle of the border and uses that information to try to get to the center. Continued…

Polo-BOO! Halloween Sale

Posted by Ben on 7 October 2015

Halloween is just around the corner, but there is still time for you makers out there to build terrifying interactive props and amazing costumes, and we want to help. From now through October 21, we are having a sale on servos and servo controllers, proximity sensors, programmable microcontroller boards, power supplies, and more – all the products you might want to bring your creepy creations to life. See the sale page for more details and the full list of products.

If you need some inspiration, check out our sample Halloween projects, and as always, we would love to hear about anything cool you make with our products; we might feature it on the blog!

New Products

Scooter/Skate Wheel 100×24mm - Black
100:1 Metal Gearmotor 37Dx73L mm with 64 CPR Encoder
19:1 Metal Gearmotor 37Dx68L mm with 64 CPR Encoder
70:1 Metal Gearmotor 37Dx70L mm with 64 CPR Encoder
Big Pushbutton Power Switch with Reverse Voltage Protection, MP
Pololu 7.5V, 2.4A Step-Down Voltage Regulator D24V22F7
0.1" (2.54mm) Crimp Connector Housing: 2x17-Pin 5-Pack
Pololu Zumo T-Shirt: Charcoal Gray, Adult L
75:1 Micro Metal Gearmotor HPCB with Extended Motor Shaft
Free Elektor magazine November/December 2015
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