20D mm metal gearmotor CB with long-life carbon brushes.

20D mm metal gearmotor CB with long-life carbon brushes and an extended motor shaft.

Magnetic Encoder Kit for 20D mm Metal Gearmotors assembled on a 20D mm metal gearmotor with extended motor shaft.

Last month when we introduced versions of our 20D gearmotors with long-life carbon brushes, we mentioned units with extended motor shafts were in the works. Well, I’m happy to announce that option is now available for both the 12V CB and 6V CB 20D gearmotors, making it possible to use them with encoders like our magnetic encoder kit. The following table shows our full selection of 20D gearmotors, which has now grown to 72 options:

Rated Voltage	Brush Type	Stall Current @ Rated Voltage	No-Load Speed @ Rated Voltage	Approximate Stall Torque @ Rated Voltage	Single-Shaft (Gearbox Only)	Dual-Shaft (Gearbox & Motor)
12 V	long-life carbon (CB)	1.6 A	570 RPM	26 oz-in	25:1 12V CB	25:1 12V CB dual shaft
			450 RPM	33 oz-in	31:1 12V CB	31:1 12V CB dual shaft
			225 RPM	58 oz-in	63:1 12V CB	63:1 12V CB dual shaft
			180 RPM	75 oz-in	78:1 12V CB	78:1 12V CB dual shaft
			140 RPM	85 oz-in	100:1 12V CB	100:1 12V CB dual shaft
			110 RPM	110 oz-in	125:1 12V CB	125:1 12V CB dual shaft
			90 RPM	130 oz-in	156:1 12V CB	156:1 12V CB dual shaft
			72 RPM	160 oz-in	195:1 12V CB	195:1 12V CB dual shaft
			57 RPM	200 oz-in	250:1 12V CB	250:1 12V CB dual shaft
			45 RPM	250 oz-in	313:1 12V CB	313:1 12V CB dual shaft
			36 RPM	290 oz-in	391:1 12V CB	391:1 12V CB dual shaft
			29 RPM	350 oz-in	488:1 12V CB	488:1 12V CB dual shaft
6 V	long-life carbon (CB)	2.9 A	590 RPM	22 oz-in	25:1 6V CB	25:1 6V CB dual shaft
			470 RPM	28 oz-in	31:1 6V CB	31:1 6V CB dual shaft
			230 RPM	54 oz-in	63:1 6V CB	63:1 6V CB dual shaft
			190 RPM	62 oz-in	78:1 6V CB	78:1 6V CB dual shaft
			150 RPM	72 oz-in	100:1 6V CB	100:1 6V CB dual shaft
			120 RPM	87 oz-in	125:1 6V CB	125:1 6V CB dual shaft
			93 RPM	110 oz-in	156:1 6V CB	156:1 6V CB dual shaft
			75 RPM	130 oz-in	195:1 6V CB	195:1 6V CB dual shaft
			60 RPM	170 oz-in	250:1 6V CB	250:1 6V CB dual shaft
			46 RPM	220 oz-in	313:1 6V CB	313:1 6V CB dual shaft
			37 RPM	260 oz-in	391:1 6V CB	391:1 6V CB dual shaft
			30 RPM	310 oz-in	488:1 6V CB	488:1 6V CB dual shaft
6 V	precious metal	2.9 A	590 RPM	22 oz-in	25:1 6V	25:1 6V dual-shaft
			470 RPM	28 oz-in	31:1 6V	31:1 6V dual-shaft
			230 RPM	54 oz-in	63:1 6V	63:1 6V dual-shaft
			190 RPM	62 oz-in	78:1 6V	78:1 6V dual-shaft
			150 RPM	72 oz-in	100:1 6V	100:1 6V dual-shaft
			120 RPM	87 oz-in	125:1 6V	125:1 6V dual-shaft
			93 RPM	110 oz-in	156:1 6V	156:1 6V dual-shaft
			75 RPM	130 oz-in	195:1 6V	195:1 6V dual-shaft
			60 RPM	170 oz-in	250:1 6V	250:1 6V dual-shaft
			46 RPM	220 oz-in	313:1 6V	313:1 6V dual-shaft
			37 RPM	260 oz-in	391:1 6V	391:1 6V dual-shaft
			30 RPM	310 oz-in	488:1 6V	488:1 6V dual-shaft

Note: Stalling or overloading gearmotors can greatly decrease their lifetimes and even result in immediate damage. In order to avoid damaging the gearbox, we recommend keeping continuously applied loads under 50 oz-in (3.5 kg*cm) for the versions with precious metal brushes and under 70 oz-in (5 kg-cm) for the versions with carbon brushes (the ones with “CB” in the name). Stalls can also result in rapid (potentially on the order of a second) thermal damage to the motor windings and brushes, especially for motors like this that can deliver a lot of power for their size; a general recommendation for brushed DC motors is to limit continuous current to approximately 25% of the stall current.

Related products

Magnetic Encoder Pair Kit for 20D mm Metal Gearmotors, 20 CPR, 2.7-18V

Tomorrow is Cyber Monday and the final day of our sale; you can check out the Monday deals on our sale page now. The weekend deals are still active until midnight Pacific, so this is your chance to pick out what you want from those and what you want to get on Monday!

Our Black Friday/Cyber Monday Sale is nearing the halfway point; thank you to all of those who have already ordered! Today’s doorbusters are gone, but the rest of the daily specials are still active, and a lot more great deals are still coming your way, including the weekend deals we just released. We’re not doing any doorbusters Saturday and Sunday, just lots of extra discounts on big categories, so take your time looking around.

The weekend deals include two items we have never had on sale before: smart servos from XYZrobot and a 6DOF robot arm based on those servos. We recently released an Arduino library for the A1-16 smart servos and arm, making them especially easy to expand beyond their preconfigured sequences for use in your own advanced projects.

Our doorbusters will return starting at 6 AM on Cyber Monday, and rumor has it that might be a prime opportunity to snag one or two of our new Balboa balancing robots!

By the way, our friends at Adafruit are having their own Black Friday sale this weekend, with 15% off their entire catalog and 20% off their Feathers and accessories, plus free items for orders over certain amounts. You can find all the details on the Adafruit blog.

Twelve hours until the Black Friday doorbusters start!

You can check out Friday’s deals and doorbusters flyer on our sale page now; complete details will be available later tonight.

Thursday’s deals and doorbusters are now shown on our Black Friday sale page. It’s going to be a Zumo-themed day, with a big sale on the Zumo robots and kits as well as the motors you need to build them. Or you can take advantage of Thursday’s discounts on microcontroller and motor controller boards to build your own sumo bot! Like Wednesday, Thursday’s doorbusters start at 6:00 AM Pacific, and there will be many more deals available all day, including site-wide discounts and free items.

Please note that we will be closed Thursday, and have a happy Thanksgiving!

Some of my happiest memories of building Pololu, and therefore of my life, are of my friends Ben and Paul moving to Las Vegas to work on it with me. Ben was my best friend in high school, but we had not stayed in touch well after that. I met Paul at MIT, and he was involved with Pololu from the beginning, in 2000, and after he graduated, he visited Candice and me in Massachusetts and then in Las Vegas from time to time. Ben and I reconnected in late 2006, and he moved to Las Vegas shortly thereafter; Paul finally joined us (with his wife Fang) full time after the summer of 2007.

So we have been at this as a team for over ten years now. It’s long enough that it’s difficult to remember things being different. As I started writing this, I figured that our first Black Friday sale must have been in 2007, too. But apparently we did not have our first one until 2009 (though Ben pointed out, with a hint of resentment, that he might have been pushing for it sooner). I have happy memories of last-minute sale preparations and then staying up past midnight to watch the sales come in, wondering how long the doorbuster deals would last. Some years we were at home, instant-messaging each other; other years, we were at the office making sure everything worked as expected.

Even now, our Black Friday/Cyber Monday sale is probably the project Paul, Ben, and I work on together most intensely. There are of course others involved in getting ready for the sale, and there are lots of other projects the three of us all work on. But there’s a really hard deadline, which we typically do not have to deal with, which leads to late nights together. And preparing for the sale involves deciding which products we care about a lot and that we want to highlight, and since it’s our company, it’s our call on how much we want to push by offering products at or sometimes below cost, in the spirit of not only merchandising but also good fun. It’s a time to look back on the products we have released this year, and, as I am doing now, reminisce about Black Friday sales past.

(We do not recommend actually running a Balboa in the snow.)

I am giving this background not only to share some of what I am thankful for, but to give our customers and newer employees some understanding of our perspective and what goes into these sales. It’s personal. It’s something fun for me, a kind of reversal of the excitement of looking for good deals as a shopper on Black Friday. When I used to be more directly involved in getting things made and shipped, I would usually go to stores in the evening, to see what deals might be left that other shoppers weren’t interested in. In the past few years, I’ve had the luxury of doing some brick and mortar Black Friday shopping in the morning, though usually I’m still shopping for things like vacuum cleaners for Pololu at stores like Home Depot.

We listen to what our customers say, and we try to put something in our deals for everyone. Of course, part of the point is to offer some extreme discounts, so we limit the quantities and the durations on those deals. But we still try to set the limits such that the doorbusters will last at least a few hours, so if you care and try a little, they should be available. If you’re one of those people who don’t like waking up early or sorting through special offers, I remind you that we work hard to offer good prices to begin with, and we are offering discounts site wide for the duration of the sale. And if you are a student or parent who really had your heart set on a Zumo or Balboa robot for Christmas but miss out on the doorbuster for some reason, and that extra discount makes the difference in being able to afford it, let us know. We want deserving people to have these robots, and we’ll try to help you out.

Now, on to details about the sale this year, since we will be making some big changes from years past. In a break from past years, when we had a single set of doorbuster coupons that went active on the first day of the sale and the same items were on sale for the duration of the sale (Wednesday before Thanksgiving through Cyber Monday), we will have different door busters for different days. We have also upgraded our coupon system so that we can control the time they are active, not just the day, so that we can make doorbusters go active at a time more appropriate for our customers in the United States.

Our new free shipping system should allow many of the sale items to ship for free or at a low cost, which should make it practical to make several orders over the course of the sale. We might combine some orders into single shipments to reduce our shipping expenses, but please note that because of the volume of orders we get during the sale, we will not be able to accommodate requests to combine orders to reduce shipping charges.

I hope you get to spend the holidays doing things that bring meaning to your life, with the people you love.

Oh, and if you were expecting to see a preview of the sale, it’s up on the Black Friday/Cyber Monday sale page now. Keep checking back throughout next week as we reveal more great deals!

As Jan promised yesterday, our new dual motor drivers are now also available as Raspberry Pi expansion boards! The Dual G2 High-Power Motor Drivers for Raspberry Pi feature two discrete MOSFET H-bridges on a board designed to plug directly into a Raspberry Pi (Model B+ or newer), and they also include an integrated 5 V, 2.5 A switching step-down regulator that allows a single power supply to power both the motors and the Raspberry Pi. We provide a Python library for Raspberry Pi to make it easy to get started using the drivers.

Pololu Dual G2 High-Power Motor Driver 18v22 for Raspberry Pi.

Pololu Dual G2 High-Power Motor Driver 18v18 for Raspberry Pi.

As with the Arduino shield (or standalone) versions, two different PCBs are used for these drivers: the black board has 5×6 mm MOSFETs and the red board has 3×3 mm MOSFETs. Again, each board is available with 30 V or 40 V MOSFETs for a total of four options:

	Dual G2 High- Power Motor Driver 18v22 for Raspberry Pi	Dual G2 High- Power Motor Driver 18v18 for Raspberry Pi	Dual G2 High- Power Motor Driver 24v18 for Raspberry Pi	Dual G2 High- Power Motor Driver 24v14 for Raspberry Pi
Absolute max input voltage:	30 V		36 V*
Max nominal battery voltage:	18 V		28 V
Max continuous current per channel:	22 A	18 A	18 A	14 A
Default active current- limiting threshold:	60 A	50 A		40 A
Available with connectors installed?	No	Yes	No	Yes

* 40 V if regulator is disconnected

Unlike the Arduino, the Raspberry Pi does not have analog inputs, so there isn’t an easy way to do current sensing with these boards. However, the current sensing pins are exposed for advanced users who might want to add an external ADC or otherwise make use of the current sense feedback.

Until now, our motor driver offerings for the Raspberry Pi have been limited to our dual MC33926 and DRV8835 add-on boards, which handle much less current. One of our other favorite integrated motor drivers, the VNH5019, would have been a nice step up in power from the MC33926, but it has one big downside…literally. Its footprint measures around 17 mm by 19 mm, and you can see that on our dual VNH5019 Arduino shield, the two driver ICs take up most of the width of the board:

Pololu dual VNH5019 motor driver shield for Arduino.

We try to make our Raspberry Pi expansion boards conform to the HAT (Hardware Attached on Top) mechanical specification when we can, and that spec recommends including a slot in the middle of the board to accommodate a flex cable plugging into the Raspberry Pi’s camera connector.

Raspberry Pi HAT mechanical specification drawing.

Combined with the cutout for the other flex connector, this space limitation means that it would be difficult—if not impossible—to make a VNH5019 motor driver expansion board for the Raspberry Pi that is not annoyingly obstructive. So we are excited that the G2 design, with its discrete MOSFET H-bridges, provided enough layout flexibility for us to create these high-power dual motor driver expansions without making such compromises. We hope that they will open up new possibilities for bigger and more powerful Raspberry Pi robots!

Related products

	Pololu Dual G2 High-Power Motor Driver 18v18 for Raspberry Pi (Partial Kit)
	Pololu Dual G2 High-Power Motor Driver 18v18 for Raspberry Pi (Assembled)
	Pololu Dual G2 High-Power Motor Driver 24v14 for Raspberry Pi (Partial Kit)
	Pololu Dual G2 High-Power Motor Driver 24v14 for Raspberry Pi (Assembled)
	Pololu Dual G2 High-Power Motor Driver 18v22 for Raspberry Pi (Partial Kit)
	Pololu Dual G2 High-Power Motor Driver 24v18 for Raspberry Pi (Partial Kit)

We sell a lot of motor drivers, which makes sense since you usually need motors to build robots, and motor drivers tend to be the kind of product you cannot really build yourself on a breadboard. One of our more popular products is the dual VNH5019 shield for the Arduino:

Pololu dual VNH5019 motor driver shield, assembled and connected to an Arduino Uno R3.

That product is based on ST’s massive VNH5019 motor driver chip, which is a successor to the VNH3SP30 driver we initially started selling back in 2005:

Older version of the High-Current Motor Driver Carrier.

When I first heard of the chip (at one of the first LVBots meetings), it seemed like someone must have misremembered the spec since it was inconceivable for a single integrated chip to deliver 30 amps. And to some extent, that was valid—you would have to do a lot of extra thermal management work to get 30 A out of that chip without it overheating. But the chip really could do in excess of 10 A, which was still amazing; the real limitation was in voltage, especially if you tried to use PWM at any moderate frequency. The VNH2SP30 was better about PWM frequency, letting us get to 20 kHz, but it had an upper operating limit of 16 V. The VNH5019 raised this to 24 V, getting us tantalizingly close to the 24V rail many would like to use. The problem is that 24 V is the limit, and we really need to be able to operate higher than that to account for the usual variations in nominally 24V power setups.

As far as I know, there is no integrated circuit that can deliver over ten amps at 24 V nominal (i.e. at least 30 V max); for that kind of power, you need to go to H-bridges with discrete MOSFETs. We have had those as stand-alone products for a while, too. But those still leave you with a lot of wiring to do if you want to drive two motors, which is typically the minimum for a mobile robot. The new product family we just released makes that easy by providing two high-power motor drivers in one Arduino shield-type package:

Pololu Dual G2 High-Power Motor Driver 24v18 Shield for Arduino.

Pololu Dual G2 High-Power Motor Driver 24v14 Shield for Arduino.

As you can see from the pictures, the main difference in these Dual G2 High-Power Motor Driver Shields is in the MOSFETs: the white boards have larger, 5×6mm MOSFETs, and the blue boards have smaller, 3×3mm MOSFETs. These correspond to the two versions of the individual drivers:

Pololu G2 High-Power Motor Driver 24v21 and 24v13.

(The higher-power version on the left has the MOSFETs on the back side of the board.) We also offer each board with 30V and 40V MOSFETs, for four total options. The new dual motor drivers perform similarly to our single-channel G2 units, and like the single channel carriers, all of these dual drivers feature current sensing and an adjustable current limit that could be used to detect and protect against stall conditions. These are the individual performance points:

	Dual G2 High- Power Motor Driver 18v22 Shield	Dual G2 High- Power Motor Driver 18v18 Shield	Dual G2 High- Power Motor Driver 24v18 Shield	Dual G2 High- Power Motor Driver 24v14 Shield
Absolute max input voltage:	30 V		40 V
Max nominal battery voltage:	18 V		28 V
Max continuous current per channel:	22 A	18 A	18 A	14 A
Default active current- limiting threshold:	60 A	50 A		40 A
Current sense output:	10 mV/A	20 mV/A

For drivers like these, power (heat) dissipation is generally the limiting factor. The copper area around the MOSFETs on both the white and blue versions of the drivers are about the same, so the lower-current blue units perform better then their smaller single channel G2 counter-parts, while the higher current white drivers do worse than the smaller single channel G2 carriers (which also use four layer PCBs for better performance). The power ratings we provide are the maximums without additional heat sinking or air flow and at room temperature. Please note that the boards will be extremely hot at those maximum currents, and the available current will be lower if the ambient temperature is higher.

Since many Arduino boards do not support higher input voltages, the new dual drivers also incorporate a 1A switching regulator so that a single higher-voltage supply can power the motors and Arduino. We have an Arduino library to help you get up and running quickly. And for those who want to use the board without an Arduino, all of the motor control connections are also brought out to a row of 0.1″ headers on one side of the board.

(And for those of you wanting to use this kind of driver with a Raspberry Pi, we have a Raspberry Pi HAT form-factor version coming soon!)

Related products

	Pololu Dual G2 High-Power Motor Driver 18v22 Shield for Arduino
	Pololu Dual G2 High-Power Motor Driver 18v18 Shield for Arduino
	Pololu Dual G2 High-Power Motor Driver 24v18 Shield for Arduino
	Pololu Dual G2 High-Power Motor Driver 24v14 Shield for Arduino

I am excited to announce our new product, the Pololu P-Star 45K50 Mini SV, which is the second member of our P-Star family of programmable controllers based on the PIC18 microcontrollers from Microchip. The P-Star 45K50 Mini SV features a user-programmable PIC18F45K50 microcontroller (32 KB of flash, 2 KB of RAM, full-speed USB), a USB bootloader, and a switching step-down regulator that allows it to be powered from 5 V to 36 V.

The P-Star 45K50 Mini SV is very similar to the smaller P-Star 25K50 Micro, but is bigger and better, with 11 more I/O pins (for a total of 30), a more capable 5 V regulator, and several other additional features. The table below lists the main differences between the two P-Stars:

P-Star 25K50 Micro (top) and P-Star 45K50 Mini SV (bottom).

	P-Star 25K50 Micro	P-Star 45K50 Mini SV
Microcontroller:	PIC18F25K50	PIC18F45K50
User I/O lines:	19	30
Analog inputs:	14	25
Reset button:
Operating voltage:	5.5 V to 15 V	5 V to 36 V
Regulator type:	linear	switching step-down
Regulated current:(1)	100 mA	500 mA
Auxiliary 3.3 V regulator:
Dimensions:	1″ × 0.6″	2.0″ × 0.7″

1 These values are rough approximations for comparison purposes. Available current depends on input voltage, current consumed by the board, ambient conditions, and regulator topology.

Although we have been using PIC microcontrollers since our very first product, these two P-Stars are our first products where the PIC microcontroller can be programmed by the user. You can program the P-Star in C or assembly with the MPLAB X IDE, or you can use Microchip’s new online IDE, MPLAB Xpress. The P-Star User’s Guide has instructions for getting started with those environments.

You can load programs onto the P-Star via its proprietary USB bootloader using our open source software that is available for Windows, Linux, and Mac. The bootloader uses 8 KB of flash memory, leaving 24 KB for the user. Alternatively, an ICSP programmer can erase the bootloader and access the full 32 KB of program memory. (Since the bootloader is not recoverable, we recommend this option only for those who are comfortable programming exclusively with an external programmer.)

Both P-Star boards feature a precision 16 MHz crystal, a USB Micro-B connector, and three user-controllable LEDs. A voltage regulator and power selection circuit allow the board to be powered from either USB or an external voltage source.

P-Star 45K50 Mini SV pinout diagram.

Compared to the popular ATmega32U4 microcontroller, the PIC18F25K50 and PIC18F45K50 have nearly the same performance and memory capacity, but these PICs also have some compelling features that are missing on the AVR. For example, they use the PIC18 architecture, which has two interrupt priority levels: interrupts can be assigned to either level, and a high-priority interrupt routine can run during a low-priority one. This powerful feature is what enables our Maestro servo controllers to generate precise servo signals while still using low-priority interrupts to assist with serial communication and other tasks. Unlike the ATmega32U4, these PICs can operate at full speed down to 2.7 V (though the brown-out reset on the P-Star is activated at 2.85 V by default).

P-Star 45K50 Mini SV, bottom view.

P-Star 45K50 Mini SV on a breadboard, shown with a vertical 5-pin ICSP programming header installed.

The PIC18F25K50 and PIC18F45K50 also feature a 5-bit digital-to-analog converter (DAC), which is a handy feature not available on many 8-bit microcontrollers. We use that DAC to set the stepper motor current limit on our Tic stepper controllers, where the PIC18F25K50 serves as the main processor.

A 3 kHz triangle wave generated by the 5-bit digital-to-analog converter (DAC) on the P-Star 25K50 Micro.

For more information, check out the P-Star 45K50 Mini SV page.

Related products

	P-Star 25K50 Micro
	P-Star 45K50 Mini SV

I am excited to announce our new product, the Tic T834 USB Multi-Interface Stepper Motor Controller. The Tic T834 is the second member of the Tic family of USB stepper motor controllers. It incorporates a TI DRV8834 driver, can operate from 2.5 V to 10.8 V, and can deliver up to approximately 1.5 A per phase without a heat sink or forced air flow.

Like the Tic T825, the Tic T834 makes basic speed or position control of a stepper motor easy, with support for six high-level control interfaces:

• USB for direct connection to a computer
• TTL serial operating at 5 V for use with a microcontroller
• I²C for use with a microcontroller
• RC hobby servo pulses for use in an RC system
• Analog voltage for use with a potentiometer or analog joystick
• Quadrature encoder input for use with a rotary encoder dial, allowing full rotation without limits (not for position feedback)

Tic T825 and T834 USB Multi-Interface Stepper Motor Controllers.

The Tic T834 is available with connectors soldered in or without connectors soldered in.

Related products

	Tic T834 USB Multi-Interface Stepper Motor Controller (Connectors Soldered)
	Tic T834 USB Multi-Interface Stepper Motor Controller