Posts by Paul

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New MOSFET-based power switches

Posted by Paul on 23 September 2015

I am excited to announce four new general-purpose MOSFET-based power switches. But why is Pololu making something as seemingly basic as power switches?

Powering your project

One of the most basic requirements for any electronics project is a way to turn the power on and off.

For a typical project assembled on a breadboard, your first approach might naturally be to plug in some breadboard-compatible switch like this:

This will work okay in many situations, but if you start connecting motors or other high-power components like a Raspberry Pi, you will quickly reach the 300 mA limit of that little switch and melt it or worse. So, assuming that the rest of your project survived, the next step might be to upgrade to a beefier switch:

I use this one on a lot of projects; it feels really solid and can do 5 A. But it is not breadboard compatible, it is kind of big (more than one inch long), and flipping it takes a lot of force, all of which means more wiring and mounting issues to deal with. And then your project ends up not looking particularly modern – can you imagine a smartphone with one of those sticking out the side? We expect everything these days to be controlled by a tiny pushbutton, with software power features like auto-shutoff. Even my new car does not have the traditional mechanical keyswitch: those are getting rapidly replaced by intelligent software-controlled pushbuttons.

MOSFET-based power switches

With a modern power switch like the one on your phone, the pushbutton itself is only momentary and does not actually conduct the current that powers the device. Typically the button is just an input to a low-power microcontroller that activates MOSFETs as necessary to control power to the rest of the circuit. Programming a microcontroller is a fine approach to power management, but it is a difficult engineering challenge itself. What if you just want a component that does the job for you, like the switches pictured above? That’s where Pololu power switches come in.

Mini MOSFET Slide Switch with Reverse Voltage Protection, LV.
Mini Pushbutton Power Switch with Reverse Voltage Protection, SV.

Our power switches do MOSFET-based switching using simple electronic circuits; not having a built-in microcontroller means they are inexpensive and can work over a wide voltage range, for use in a variety of projects. Unlike many soft-power solutions, they are also designed to turn completely off – no current flows in the off state except whatever can leak through the transistors (around 10 nA or less).

We have been selling switches like these for a long time, both as discrete boards and incorporated into other products. As shown in the pictures above, we have two basic implementations:

  1. A slide switch that directly controls a MOSFET: the board stays permanently off or on depending on the state of the switch. (Used on the Zumo robots and the A-Star 32U4 Robot Controller.)
  2. A momentary button for push-on/push-off control, using a latching circuit. (Used on several Orangutan robot controllers and the 3pi robot.)

Block diagram of Pushbutton Power Switch with Reverse Voltage Protection.

The pushbutton version seems more modern and lends itself better to features like software shutoff, but using it on the 3pi demonstrates one potential disadvantage: if a 3pi crashes into something hard enough to rattle the batteries, the input voltage briefly drops to zero and turns off the switch, stopping the robot. You might consider this a feature, since it prevents further damage to an out-of-control robot. However, when we designed the Zumo, we knew that slamming into things would be standard practice, and a power shutdown in the middle of a sumo match could be disastrous. So our Zumo boards use the slide-switch method of power control.

The new Pololu power switches

Our older pushbutton power switches have long been in need of an upgrade, and now we have two new boards to replace them as well as two entirely new slide-switch versions. The boards have a greatly increased input voltage range: 2.2 V to 20 V on the LV versions or 4.5 V to 40 V on the SV versions, and there are a few other new features:

  • An additional MOSFET for reverse voltage protection. This helps protect your project against plugging in batteries or a power supply backwards, making a Pololu power switch a great first stage for your project. Please note that it can’t protect you against shorts that bypass the switch. (Ground connections through a benchtop power supply and a USB cable can cause problems, for example.)
  • Control pins that allow your microcontroller to turn the switch on and off. The simpler slide-switch versions just have a single input that turns the switch on, while our pushbutton switches provide inputs for latching the switch either on or off as well as an input (CTRL) that can assert either state.
  • Additional connection points so that you can connect your own button or switch (e.g. wire it to the outside of your case) in addition to the pre-installed one.

Note that the form factor is different and the current limits are lower than our older pushbutton power switches, so these are not drop-in replacements.

In summary, don’t be one of those people who has to plug and unplug wires to turn his project on and off. Take a look at the detailed specifications on product pages to select the right switch for your application!

Cable for Sharp GP2Y0A51SK0F analog distance sensors now available

Posted by Paul on 28 August 2015
Tags: new products
Cable for Sharp GP2Y0A51SK0F analog distance sensors now available

We are now finally carrying a cable for the Sharp GP2Y0A51SK0F Analog Distance Sensor 2-15cm. The GP2Y0A51SK0F, our shortest-range analog distance sensor, has a compact package with a unique JST ZH-style connector, so this cable will not work with any of our other distance sensors. The cable is 12 inches (30 cm) long, with wires that you can cut and terminate as necessary for your project.

For more information, see the product page.

Paul's Wixel-based line following robot: Two Point Four

Posted by Paul on 18 August 2015
Tags: lvbots
Paul's Wixel-based line following robot: Two Point Four

Two Point Four was my entry in the LVBots 2015 line following competition, originally built for our 2013 contest but significantly rebuilt since then. I designed it to be simple, low-power, and lightweight, starting with its 2×AAA, 2.4 V nominal power supply, from which it gets its name. Continued…

New product: A-Star 32U4 Robot Controller with Raspberry Pi Bridge

Posted by Paul on 7 August 2015
New product: A-Star 32U4 Robot Controller with Raspberry Pi Bridge

I am excited to announce our new A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge, a general-purpose robot controller based on Atmel’s ATmega32U4 microcontroller.

This new robot controller is the latest model in our A-Star line of Arduino-compatible USB microcontroller boards. We started with the A-Star 32U4 Micro and have been gradually expanding the line, adding peripherals and various form-factor and voltage options, with the goal of eventually replacing our older Orangutan robot controllers. The Zumo 32U4 was a major step in that direction, since its controller board is essentially an A-Star 32U4 plus extra peripherals for motor control and sensing. But while the Zumo 32U4 is a complete robot kit, this board is for people who want to design their own robot.

The A-Star 32U4 Robot Controller LV includes most of the features of the A-Star 32U4 Prime LV, including an Arduino-compatible USB bootloader, an efficient step-up/step-down regulator, and handy peripherals like the buzzer and buttons, and it expands on the A-Star line by adding a pair of Texas Instruments DRV8838 1.8 A motor drivers, the same motor drivers as on the Zumo. All of the AVR’s GPIO lines are broken out, and we have included handy power and ground rails so you can easily connect lots of things like servos and sensors:

This board is well-suited for small robots that would have otherwise used an Orangutan controller like the SV-328 or SVP-1284. While we did not include an LCD like on the Orangutans, you can get far better display, monitoring, or data logging by making use of the Raspberry Pi connection, which I will talk about next.

Using the robot controller with a Raspberry Pi

The Raspberry Pi is a great board for an embedded project that needs serious computational power or connectivity. We have released a couple of Raspberry Pi motor driver boards over the past year, which give you a way to get started exploring robotics with your Raspberry Pi. But robotics projects tend to use a lot of analog sensors, timing-sensitive devices like servos, and other peripherals that are not compatible with the limited I/O capabilities of the Raspberry Pi. These types of things are what microcontrollers are designed for, so you can do a lot more if you pair your Raspberry Pi with a complete microcontroller board.

That’s why instead of using the standard Arduino form factor like the Prime, we built the A-Star 32U4 Robot Controller LV to double as a Raspberry Pi HAT:

A-Star 32U4 Robot Controller LV with Raspberry Pi Bridge on a Raspberry Pi Model B+.

The Robot Controller fits on top of a Raspberry Pi A+/B+/2, powers the Pi, and connects to it as an I²C slave device, giving you a bidirectional channel of communication between the two processors. We have broken out all of the GPIO of the Raspberry Pi, and there are a few general-purpose level-shifters included on the board to help you experiment with other communications protocols or interface other hardware to your system. We even include the EEPROM required by the HAT specification, though we have not found it to be particularly useful – we ship it blank and unlocked for you to experiment with.

For more information about the A-Star 32U4 Robot Controller LV, or to order, see the product page. You can also check out our open-source A-Star 32U4 Arduino library, which provides easy access to the main features of the Robot Controller, including its motor drivers; we will be adding examples showing I²C communication with the Raspberry Pi soon.

New distributors in Asia

Posted by Paul on 6 July 2015
Tags: distributors

To wrap up this round of distributor introductions, I would like to welcome the following new Pololu distributors in Asia:

NTREX, Inc. – Devicemart is an online electronics store in Incheon, South Korea, with a huge selection of components, prototyping equipment, robotics kits, 3D printers, PC components, and industrial supplies. We are excited to see that their Pololu category now lists hundreds of our parts. Devicemart is now our fourth Korean distributor.

Suzaku Lab, Ltd. is an online store based in Nara, Japan, specializing in robotics parts. Joining two other Japanese distributors, Suzaku is carrying an extensive selection of Pololu motion control boards, including the Jrk, Simple Motor Controller, and TReX lines as well as most of our stepper and DC motor driver breakout boards.

Coprime Pte Ltd, an electronics shop in Singapore, is now carrying Pololu products. We have not visited, but from the Facebook pictures of their storefront, it seems like Pololu parts are being displayed alongside an exciting array of other hobby electronics boards and parts. Coprime is our fourth Singaporean distributor and our second (!) located in Sim Lim Tower.

Explore Labs is an open-source electronics company in Jodhpur, India that has been writing tutorials and selling and designing boards since around 2011 (they are growing and recently rebuilt their website, so some old content is unavailable). They publish their hardware designs on GitHub and sell them on their site along with Arduino, Raspberry Pi, the Intel Edison, kits from 3D Robotics, and now Pololu parts.

Tanna Educational Services, another new Indian distributor in Rajkot, Gujarat, offers training services on topics including embedded development and also sells microcontroller-related boards, kits, and components on their website. Their Pololu category contains various regulators and motor drivers, several sensors, the Wixel, our USB AVR Programmer, and more. Tanna and Explore Labs bring us to a total of five Indian distributors.

See the full list of over 200 distributors to find one in your area.

New distributors in South America

Posted by Paul on 16 June 2015
Tags: distributors

Continuing with our belated new distributor introductions, we are happy to welcome these six new Pololu distributors in South America:

Baú da Eletrônica is a new Pololu distributor in São Paulo, Brazil. Check out their Pololu category for the 3pi Robot, Zumo, and more.

BUILDBOT, also in São Paulo, is now carrying the 3pi and Zumo as well as a variety of Pololu sensors, relay modules, and mechanical parts.

FILIPEFLOP is yet another new distributor in Brazil (bringing the total to eight), located in the city of Florianópolis. Make sure to check out their blog, which is full of useful-looking tutorials.

IMPORTRONIC, a robotics and electronics store in Quito, Ecuador, now features a Pololu category with a selection of our popular motors and servos., in Lima, Peru, carries a large selection of electronics parts. Search for Pololu on their site to find our 3pi and Zumo, Arduino and Raspberry motor drivers, the Arduino-compatible A-Star Mini, and more.

Eneka is a new distributor with an interesting history. The store was founded by four brothers as a radio assembler/installer in Paris, France, and moved to Montevideo, Uruguay, in 1936 due to the deteriorating situation in Europe. Since then, they have become a distributor of electronics equipment and components, and they recently started adding robotics to their product line. Our first distributor in Uruguay, Eneka carries a number of Pololu parts including voltage regulators, sensors, motors, and wheels.

See the full list of over 200 distributors to find one in your area.

New distributors in Europe

Posted by Paul on 4 June 2015
Tags: distributors

Continuing to catch up on our new distributor introductions, we are excited to welcome these new European distributors:

Transfer Multisort Electronik (TME) is an electronics distributor based in Łódź, Poland, with local offices in six countries around Europe and a catalog of 145,000 products. Their robotics category is now full of Pololu products. Scroll down to the end of this post for a video of their warehouse, including an impressive 23-meter-high automated storage rack.

GoTronic runs an online store with a physical storefront in Blagny, France, near the Belgian border. They have been in business since 1990 and sell all kinds of robotics parts and kits and electronics components. Search for “Pololu” to find wheels, motors, the Zumo Robot Kit for Arduino, Maestros, motor drivers, and more.

OM ELECTRONIQUE is an electronics shop and online store located in Grenoble, France, selling all kinds of electronics items from audio/visual equipment to robotics parts. You can check out their two-page Pololu category.

MCHobby – Microcontroleur Hobby is an online electronics store operating out of Waterloo, Belgium. They have put a huge amount of effort into supporting customers in France and Belgium with detailed French-language documentation for the products they carry. For examples, check out their Zumo page or this DRV8825 carrier tutorial.

Flikto Elektronik distributes our products alongside items from places like Adafruit, Arduino, and Sparkfun. Located in Cologne, Germany, they offer same-day, low-cost shipping throughout Europe, including free shipping within Germany for orders over €50. is a shop run by Pieter Floris in Breda, Netherlands, distributing all kinds of “electronic thingies”. They are carrying a variety of Pololu products including motors, motor drivers, Maestro servo controllers, and the zumo Robot for Arduino. I noticed that they also offer something I have not seen at other places: a €5.00 soldering service to help people without soldering experience.

SPACE d.o.o. is a hobby shop located on the grounds of the Belgrade Fair complex in Serbia, now carrying Pololu parts including the 3pi and Zumo Robot for Arduino.

MechaDroid is a new electronics and robotics shop in Cham, Switzerland, selling Pololu motors, motor drivers. and more.

Now, here is that cool video of TME’s warehouse:

See the full list of over 200 distributors to find one in your area.

Memorial Day weekend sale

Posted by Paul on 22 May 2015

Memorial Day weekend sale

We are having a big Memorial Day sale now through Monday, with discounts on over 600 products when you use the coupon code MEMORIALDAY15. Stock up on robot parts now so you can build cool things all summer long! Note that we will be closed on Monday, so orders will not ship until Tuesday, May 26.

For more information, including all of the sale items, see the sale page.

New high-current stepper driver carrier with SPI: AMIS-30543

Posted by Paul on 21 May 2015
Tags: new products
New high-current stepper driver carrier with SPI: AMIS-30543

This new board is a Pololu carrier for ON Semiconductor’s AMIS-30543 Micro-Stepping Motor Driver, which is a high-performance stepper motor driver with advanced features not found on our other stepper motor driver carriers.

AMIS-30543 stepper motor driver carrier, bottom view with dimensions.

The Pololu AMIS-30543 Stepper Motor Driver Carrier breaks out all of the important pins of the driver onto breadboard-compatible 0.1"-spaced pins, with optional terminal blocks for the power and motor connections and mounting holes for a more robust setup. Our board supplies reverse protection and all the necessary circuit components for interfacing to a microcontroller.

The AMIS-30543 is rated up to 30 V and 3 A, but (as with other stepper drivers) the current rating is a theoretical maximum assuming excellent cooling. Using our board at room temperature without a heatsink, the chip can practically supply about 1.8 A per coil, more than any of our other stepper motor driver carriers.

The SPI interface of the AMIS-30543 provides many exciting features: it lets you configure microstepping (down to 1/128-step), set the current limit, select voltage slopes, change direction, disable the outputs or put the driver to sleep, monitor the micro-step position and errors, and more. Please note, however, that you cannot step the motor over SPI.

Many of our customers have asked for software current limit control, since it allows better power management. For example, consider that stepper motors counter-intuitively use their maximum current when stopped, even if there is no holding torque required. This wastes a lot of power and generates undesirable heat in the drivers and motors. In a typical application like a 3D printer, where you don’t need much holding torque, you would want to reduce the current limit to a low value during pauses. You might use a higher limit (above the continuous limit) when accelerating and an intermediate value for constant-speed motion. The SPI current limit control on the AMIS-30543 lets you do all of this in your code.

Another advanced feature is the SLA (speed and load angle) output that indicates the level of the back-EMF voltage of the motor. This is an analog signal that can be used for stall detection or closed-loop control of the torque and speed:

AMIS-30543 stepper motor driver SLA output (green) and motor output (blue).

It is easy to get started using our Arduino library on GitHub, which provides basic functions for configuring and operating the driver as well as access to many of the advanced features. Please visit the product page for a detailed description, wiring diagrams, the AMIS-30543 datasheet, and more.

More new distributors

Posted by Paul on 21 May 2015
Tags: distributors

Core Electronics, in Adamstown, New South Wales, joins five other distributors in Australia and carries a wide variety of electronics parts for the maker community. Like fellow Australian distributor Little Bird Electronics, they take the approach of listing almost all of our products for sale, with shipping times depending on their on-site stock. This means that if you are in Australia and want some relatively obscure Pololu product like our Wires with Pre-crimped Terminals 2-Pack M-M 60" Purple you can get it without worrying about international shipping charges.

Studica, Inc. is a distributor of educational products, based in New York, with offices in Canada, Brazil, UK, Italy, Greece, Denmark, Hungary, and Australia. You can browse their entire Pololu category, which mainly includes our complete robots and robot kits.

CrustCrawler Robotics is a manufacturer of robotic arms, grippers, ROV parts, and walking robots in Gilbert, Arizona, USA. CrustCrawler – now our nearest distributor – is carrying our Maestro servo controllers, which they also include as a standard controller with some of their arm configuations.

We are happy to add BC Robotics Inc. to our list of Canadian distributors. BC Robotics is a distributor and manufacturer of electronic kits and parts that also helped found Makerspace Nanaimo just a block away from their office in Nanaimo, British Columbia. BC Robotics carries a variety of Pololu products and offers several flat-rate shipping options throughout Canada. Fun fact: their location in Nanaimo makes BC Robotics our westernmost distributor!

See the full list of over 200 distributors to find one in your area.

New Products

Mini MOSFET Slide Switch with Reverse Voltage Protection, SV
Mini Pushbutton Power Switch with Reverse Voltage Protection, LV
9mm Electromagnetic Buzzer: 40Ω, 4-6V, Top Opening
47:1 Metal Gearmotor 25Dx52L mm MP 12V
3-Pin Female JST ZH-Style Cable (30cm) for Sharp GP2Y0A51 Distance Sensors
Pololu Wheel for FEETECH FS90R Micro Servo, 60×8mm Pair - Black
Zumo 32U4 Robot (Assembled with 100:1 HP Motors)
Zumo 32U4 Robot (Assembled with 50:1 HP Motors)
4.4:1 Metal Gearmotor 25Dx48L mm HP 12V
Mini MOSFET Slide Switch with Reverse Voltage Protection, LV
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