Author Archives: Jan

New products: 1- and 31-channel QTR HD reflectance sensor arrays

via Pololu Blog

This week, we released what we expect to be the extremes of our new line of QTR HD reflectance sensor arrays, with two sizes of a single-sensor board on the small end and a massive 31-sensor array for the maximum size. This picture shows the relative sizes of the boards, along with some of the intermediate sizes we have available:

The QTR Reflectance Sensor Arrays are available in many different sizes.

We made the two single-sensor sizes because we could make good arguments for each one. Part of the point of doing a single-sensor board is to make it really small, so you can fit it into tight spaces. But “really small” means different things depending on the dimensions you care about. So we have one version that is only 5 mm (0.2") wide, with components on both sides of the PCB, and one version that is 7.5 mm (0.3") wide, with components on just one side. The 7.5 mm wide version is a little thinner and flatter because it doesn’t have parts on one side, can be used with a 3×1, single row connector, and costs slightly less because of the single-sided assembly.

QTRX-HD-01RC Reflectance Sensor, front and back views.

QTRX-MD-01A Reflectance Sensor, front and back views.

As I mentioned in some of my earlier posts (here and here) about this new line of sensor arrays, we are using two sensor types: more economical units we are calling “QTR”, and higher-performance units with lenses that we are calling “QTRX”. The main appeal of the QTRX sensors is that they can give the same readings at much lower IR emitter currents, which can really make a big difference for big sensor arrays. But if you crank up the current in those QTRX sensors, you can also get more distance. We did not do that on the QTRX arrays because the sensor modules leak light out the sides and interfere with each other when they are closely spaced, but with these single-channel boards, we are also making available the QTRX sensors with the higher 30 mA maximum emitter current, which allows for a range of up to about 8 cm (about 3 inches). We are calling these sensors QTRXL.

This video (taken with an old camera that does not have as much IR filtering as most newer cameras) shows the IR light leakage around the side of the QTRX sensor module:

I should point out that all of these new QTR modules offer variable brightness control by varying the current through the emitter using the control pin. However, if you want to take advantage of the maximum brightness and range, and have several sensors close to each other, you will need some barriers between them to prevent them from blinding each other (or just turn on one emitter at a time).

The 31-sensor arrays are huge! Well, at least compared to the tiny single-sensor boards.

QTRX-HD-31RC Reflectance Sensor Array.

The routing on those boards is quite complex because adjacent IR emitters are not just wired in series (because we want to have separate even/odd emitter control, plus the alternate density population options I discussed in this post), so we ended up having to go to a 4-layer PCB to route it. This did let us make the vertical dimension a little lower, so the board is just 16.5 mm tall, compared to the 20 mm board height for the versions with 15 and fewer sensors. The 31-channel board is also 0.062" (1.6 mm) thick, compared to the thinner 0.040" (1 mm) boards we use for the lower channel counts. You can compare all the dimensions of the various boards in the detailed dimension diagram (1MB pdf).

The sixteen new boards we released this week brings the total available in this new QTR HD product line to 40. You can see the options neatly summarized in the tables below to pick the best array for your application.

QTR sensors
2.9 V to 5.5 V; 30 mA max LED current(1); 5 mm optimal range
Board
width
Configuration Max board
current(2)
Max range Output
type
Name 1-piece
price
5.0 mm 1 sensor (HD)
32 mA 30 mm analog QTR-HD-01A $1.79
RC (digital) QTR-HD-01RC
7.5 mm 1 sensor (MD)
32 mA 30 mm analog QTR-MD-01A $1.61
RC (digital) QTR-MD-01RC
10.2 mm 4 mm × 2
32 mA 30 mm analog QTR-HD-02A $2.12
RC (digital) QTR-HD-02RC
17.0 mm 4 mm × 4
62 mA 40 mm analog QTR-HD-04A $3.26
RC (digital) QTR-HD-04RC
29.0 mm 8 mm × 4
62 mA 40 mm analog QTR-MD-04A $3.44
RC (digital) QTR-MD-04RC
4 mm × 7
125 mA 40 mm analog QTR-HD-07A $5.40
RC (digital) QTR-HD-07RC
61.0 mm 8 mm × 8
125 mA 40 mm analog QTR-MD-08A $6.39
RC (digital) QTR-MD-08RC
4 mm × 15
250 mA 50 mm analog QTR-HD-15A $10.82
RC (digital) QTR-HD-15RC
125.0 mm 4 mm × 31
495 mA 50 mm analog QTR-HD-31A $21.66
RC (digital) QTR-HD-31RC
QTRX sensors
2.9 V to 5.5 V; 3.5 mA max LED current(1); 10 mm optimal range
Board
width
Configuration Max board
current(2)
Max range Output
type
Name 1-piece
price
5.0 mm 1 sensor (HD)
5 mA 30 mm analog QTRX-HD-01A $2.17
RC (digital) QTRX-HD-01RC
7.5 mm 1 sensor (MD)
5 mA 30 mm analog QTRX-MD-01A $1.99
RC (digital) QTRX-MD-01RC
10.2 mm 4 mm × 2
5 mA 30 mm analog QTRX-HD-02A $2.88
RC (digital) QTRX-HD-02RC
17.0 mm 4 mm × 4
9 mA 40 mm analog QTRX-HD-04A $4.78
RC (digital) QTRX-HD-04RC
29.0 mm 8 mm × 4
9 mA 40 mm analog QTRX-MD-04A $4.96
RC (digital) QTRX-MD-04RC
4 mm × 7
17 mA 40 mm analog QTRX-HD-07A $8.06
RC (digital) QTRX-HD-07RC
61.0 mm 8 mm × 8
17 mA 40 mm analog QTRX-MD-08A $9.43
RC (digital) QTRX-MD-08RC
4 mm × 15
34 mA 50 mm analog QTRX-HD-15A $16.52
RC (digital) QTRX-HD-15RC
125.0 mm 4 mm × 31
68 mA 50 mm analog QTRX-HD-31A $33.44
RC (digital) QTRX-HD-31RC
QTRXL sensors
2.9 V to 5.5 V; 30 mA max LED current(1); 20 mm optimal range
Board
width
Configuration Max board
current(2)
Max range Output
type
Name 1-piece
price
5.0 mm 1 sensor (HD)
32 mA 80 mm analog QTRXL-HD-01A $2.17
RC (digital) QTRXL-HD-01RC
7.5 mm 1 sensor (MD)
32 mA 80 mm analog QTRXL-MD-01A $1.99
RC (digital) QTRXL-MD-01RC
1 Can be dynamically reduced to any of 32 available dimming levels.
2 With all LEDs on at max brightness setting.

Our introductory promotions are still going strong! Be one of the first 100 customers to use coupon code QTRINTRO and get any of these new sensors at half price! (Limit 3 per item per customer.)

New products: Robot Arm Kit for Romi (and also just the gripper)

via Pololu Blog

I’m super excited to announce our newest product, the Robot Arm Kit for Romi. The Romi arm is designed to mount to the back half of a Romi chassis with two fixed servos controlling the height and angle of the gripper through a nifty linkage system.

The Romi with Robot Arm and various electronics to enable RC control.

Side view of the Romi with Robot Arm and various electronics to enable RC control.

The gripper itself uses a micro servo with two parallel fingers or paddles that open and close through a rack and pinion arrangement. Here is a quick video demonstration of a Romi chassis with the arm attachment:

You can see the available range of motion in the drawings below:

Range of motion of the height of the Robot Arm for Romi.

Range of motion of the wrist tilt on the Robot Arm for Romi.

Range of motion of the gripper on the Robot Arm for Romi.

The kit ships with all mechanical parts, including special servos with a fourth wire for reading the position of the output shaft:

Contents of the Robot Arm Kit for Romi.

We are also making the gripper used on the arm available as a standalone Micro Gripper Kit with Position Feedback Servo. Here is a picture of the assembled gripper:

Fully assembled Micro Gripper with Position Feedback Servo.

Products like this arm kit, with many injection-molded components, are some of the most complicated and time-consuming products we make. As those of you who have followed our growth over the past decade are probably aware, we try to develop our more complete robot kits incrementally, starting with components like just a wheel or a motor bracket, and then using those components in the more integrated robots. For example, we came out with this line of wheels in 2010:

Pololu wheels with 90, 80, 70, and 60mm diameters in three colors: blue, red, and yellow.

The Romi and Balboa robots, which use those wheels, did not come out until 2016 and 2017.

Romi Chassis Kit – Blue.

One of the many possible configurations of the bumper cage on the Balboa 32U4 Balancing Robot.

If you look at the parts that go into just the gripper portion, you can see that each of the components is roughly as complicated as one of those wheels, and you can’t really do much with just one of those parts:

Contents of the Micro Gripper Kit with Position Feedback Servo.

So, a lot of work goes into designing these kits. We also do not machine the molds or do the injection molding in-house (we did that on the first few parts for the 3pi robot), so that adds a lot of delays compared to our electronics boards, which we make in the same building that we design them in. We do 3D print prototypes to maximize the chances that we get the designs right, but there are invariably little modifications that we end up having to make when the components are this complicated, which is why it takes us years to go from the initial idea to the released kit.

We are at least sticking to our incremental product release approach as far as integration with electronics goes: at the time of the Romi arm attachment release, we do not have a specific solution for controlling the robot, which we will be working on next. Therefore, this kit is currently intended for advanced users who are comfortable powering and controlling several servos on their own.

As with all of our new product releases this year, we are offering substantial introductory discounts for the first customers to try out our new designs. You can use coupon code ROMIARMINTRO to get the whole arm for just $49 and code GRIPPERINTRO to get just the gripper for only $13. Each coupon is limited to 100 uses and 3 units per customer.

New products: more new QTR HD sensor arrays by student engineering interns

via Pololu Blog

All the student engineering interns we had over the summer from out-of-town colleges are headed back to school, so I get to announce the release of products they worked on over the summer. The new QTR sensors we are releasing today include the 15-channel version laid out by seventeen-year-old Chris H.

Hadouken! (2018 summer engineering intern Chris couldn’t come up with a clever pun to use for this picture of him posing with a circuit board he designed.)

You can see more about our new line of QTR reflectance sensor arrays in the first blog post I wrote about them a few weeks ago. One cool design and manufacturing aspect I did not mention then is that we designed these boards so that they could be populated at various densities. For example, that lets us make an 8-channel version with 8 mm sensor pitch on the same board that also works as a 15-channel array with 4 mm sensor pitch:

QTRX-MD-08RC Reflectance Sensor Array.

Here are some diagrams showing some of the thought that went into the soon-to-be released 31-channel version, which can also be populated to be an 8 mm pitch, 16-sensor array; a 12 mm pitch, 11-channel array; and a 20 mm pitch, 7-channel array:

Diagram of emitters and drivers on a QTR-HD-31x sensor array board with all sensors populated.

Diagram of emitters and drivers on a QTR-HD-31x sensor array board with 1/2 sensors populated.

Diagram of emitters and drivers on a QTR-HD-31x sensor array board with 1/3 sensors populated.

Diagram of emitters and drivers on a QTR-HD-31x sensor array board with 1/5 sensors populated.

With so many combinations of sensor types and output circuits, we won’t make every one of the possible arrangements a stock product, but the idea is that if you have an application where a particular sensor pitch is ideal for you, we can quickly make some for you without having to lay out new PCBs.

We expect eight channels on an 8 mm pitch to be a popular variant, so those will be stock products. We have also added the corresponding 4-channel version (using the same boards used for the full-density, 7-channel product), so this new product announcement covers twelve new stock sensor arrays:

QTRX-HD-15RC Reflectance Sensor Array.

QTRX-MD-08RC Reflectance Sensor Array.

QTRX-MD-04RC Reflectance Sensor Array.

Our introductory promotions are still going strong! Be one of the first 100 customers using coupon code QTRINTRO and snag any of these new sensors at half price! (Limit 3 per item per customer.)

New products: U3V70x high-current boost voltage regulators

via Pololu Blog

Today we are finally releasing our new U3V70x family of boost regulators, which are now our highest-current boost regulators. (I said “finally” because we have had the boards designed for over six months, but we just finally received the main ICs for our production builds even though I ordered them last year.) Besides supporting the most current of any of our boost regulators, we also have an adjustable version with a multi-turn trimmer potentiometer, which makes setting the output voltage to a particular value much easier than when the whole output voltage range is represented by the 250 degrees or so of a single-turn pot. The regulators operate with input voltages down to 2.9 V, and the adjustable output version can be set to an output in the range of 4.5 V to 20 V. Talking about the current on boost regulators is tricky since it’s so dependent on input and output voltages, so it’s best to just show you a few performance graphs:

Typical efficiency of Step-Up Voltage Regulator U3V70x, Vout = 12V.

Typical maximum continuous output current of Step-Up Voltage Regulator U3V70x.

For those who don’t need adjustability (that multi-turn pot is expensive!), we offer fixed-voltage versions in six standard voltages:

We can also make customized fixed versions for you with other voltages between 4.5 V and 20 V.

Comparison of the newer U3V70A boost regulator (top) to the older U3V50ALV (bottom).

It’s exciting that these new regulators are smaller than what used to be our highest-power boost regulator (the U3V50x family) despite handling more current. One way we kept the size smaller is by using only ceramic capacitors. One consequence of that is that the new regulator outputs are slightly noisier, so if that is important for your application, you might want to add some external capacitors to further smooth out the voltage. The older design also supports a higher maximum output voltage, so if you need more than 20 V, our U3V50F24 fixed 24 V and U3V50AHV adjustable 9 V to 30 V units are still our highest-power options.

As with all our new products this year, we are offering a special introductory promotion. You can get up to three of each version for just $9 (which is an especially good deal for the adjustable regulator!), limited to the first 100 customers using coupon code U3V70XINTRO .

New product: high-density QTR reflectance sensor arrays

via Pololu Blog

I am excited to announce the first of a new line of reflectance sensor arrays that feature a high-density 4-mm pitch and dimmable IR emitter brightness control. In addition to versions with our familiar IR emitter/phototransistor pair modules without lenses, which we will keep calling “QTR,” we have versions with a higher-performance sensor with lenses on the IR emitter and phototransistor, which we are calling “QTRX.” These higher-performance sensors allow similar performance at a much lower IR LED current, which can really start adding up at higher channel counts. (High-brightness, “QTRXL” versions of these boards are coming soon, too.)

These new sensor arrays also feature LED brightness control that is independent of the supply voltage (which can be 2.9 V to 5.5 V) and separate controls for the odd-numbered LEDs and the even-numbered LEDs, which gives you extra options for detecting light reflected at various angles. As with our older QTR sensors, we are offering these in “A” versions with analog voltage outputs and “RC” versions that can be read with a digital I/O line on a microcontroller by first setting the line high and then releasing it and timing how long it takes for the voltage to get pulled to the logic low threshold:

Schematic diagrams of individual QTR HD sensor channels for A version (left) and RC version (right).

This announcement therefore covers four total new products:

As with all our new products this year, we are offering a special introductory promotion, and this one is for half off up to three of each sensor type, limited to the first 100 customers using coupon code QTRHD07INTRO .

New product: Raspberry Pi 3 Model B+

via Pololu Blog

We are now carrying the Raspberry Pi 3 Model B+. The Raspberry Pi is a popular credit card-sized computer that can run ARM Linux distributions. The Raspberry Pi 3 Model B+ has many performance improvements over the Pi 3 Model B including a faster CPU clock speed (1.4 GHz vs 1.2 GHz), increased Ethernet throughput, and dual-band WiFi. It also supports Power over Ethernet with a Power over Ethernet HAT.

This comparison chart shows some of the improvements in the Raspberry Pi over the years:


Raspberry Pi Model B

Raspberry Pi Model B+

Raspberry Pi 2 Model B

Raspberry Pi 3 Model B

Raspberry Pi 3 Model B+
CPU: BCM2835 BCM2836 BCM2837 BCM2837B0
CPU cores: 1 4
CPU speed: 700 MHz 900 MHz 1.2 GHz 1.4 GHz
RAM: 512 MB 1 GB
Ethernet: Yes
WiFi: No 2.4 GHz 802.11n 2.4 GHz & 5 GHz 802.11b/g/n/ac
Bluetooth: No 4.1 4.2
Bluetooth Low Energy: No Yes
HDMI: Yes
Analog video: Yes Yes1
SD socket: SD microSD
Onboard regulators: linear switching
Expansion header pins: 26 40
USB ports: 2 4
Mounting holes: 2 4
Dimensions2: 3.35″ × 2.2″ × 0.8″
Weight3: 40 g 42 g 50 g

1 Audio and analog video provided by a single four-pole 3.5 mm jack. This 3.5 mm jack also has its own dedicated low-noise power supply for improved audio.
2 Length and width measurements are for the PCB only; several of the connectors extend past the edge of the board.
3 Weight does not include microSD cards.

The Raspberry Pi 3 Model B+ maintains compatibility with the HAT (hardware attached on top) standard, and it works with our large selection of Raspberry Pi motor drivers and robot controllers.

We also offer two mobile robot platforms ready for expansion with the Raspberry Pi: the Balboa 32U4 Balancing Robot Kit and the Romi chassis using the Romi 32U4 Control Board.

Like many sites selling Raspberry Pis, we do not have any special source or price for these, and we are just carrying them for the convenience of customers who are interested in our products that work with the Raspberry Pi. To limit our losses without resorting to the “limit one per customer” kind of restrictions on other sites, we for the first time implemented reverse price breaks on our site, meaning the price per unit goes up as the quantity goes up:

Reverse price breaks on the Raspberry Pi 3 Model B+

I am not very excited about these kinds of restrictions, so we were close to not offering the new Raspberry Pis at all. I hope that it will prove to be useful or convenient for at least some of you, and those looking for larger quantities can shop around for a better source. I am interested in what customers think, so please share your thoughts. Are the reverse price breaks annoying? Is it better to offer this than nothing at all?