Engineers can choose from many different sensors on the market today to measure all types of phenomena. These devices are produced by a wide variety of different suppliers. To help you get a better “sense” (no pun intended) of what is available we are developing a series of articles focusing on the sensor technologies, parts, and solutions of key suppliers. This article will focus on Parallax, Inc., which supplies positioning and specialized sensors through Hotenda. Parallax is a unique company in that in addition to sensors, for more than 25 years Parallax has turned out high-quality robotics, BASIC Stamp microcontrollers (so named because it is small in size, like a postage stamp) microcontroller development tools, LCDs, AppKits, and small single-board computers that are used by electronic engineers, educational institutions, and hobbyists.
However, even by just limiting our discussion to sensor solutions, Parallax is noteworthy in that it addresses a specific application area, robotics, providing proximity sensors, tilt sensors, motion sensors, and accelerometers.
In the past eight years, based on its successful release of its P8X32A Propeller microcontroller, Propeller Assembly Language, and SPIN interpreter technologies, the company has made a name for itself as a commercial sensor provider in addition to being an educational/hobby player.
Parallax sensors include proximity, tilt, motion, accelerometers, and infrared; these are sometimes combined in inexpensive kits that are easily ordered for both classroom projects as well as commercial development.
Notable parts and kits
The Parallax 4-Directional Tilt Sensor (part #28036) is an accelerometer replacement when applications do not need precise angular feedback, such as for robotic movement, alarm systems, tilt sensing for remote controls, and rotating display adjustment. Used in smartphones and digital cameras, these devices provide an inexpensive means to adjust the screen display when the device itself is rotated.
Featuring small 6-pin DIP packaging with breadboard-friendly 0.1 in. pin spacing, they easily communicate with any microcontroller and provide positional feedback in four directions.
The tilt sensor (Figure 1) includes one IR LED, two phototransistors, and a small ball that moves when the sensor rotates. Depending on the orientation of the sensor, the two phototransistors will output high or low signals depending whether light is detected or not. New locations are triggered when the sensor is rotated roughly 30° toward the new position.
Figure 1: When the sensor is lying flat and only acted on by g-forces, the cylinder is in Location C. Upon startup and when lying flat, the sensor remains in the last location before shutdown. Once movement is detected, the sensor will respond normally.
The Parallax PING))) Ultrasonic Sensor (Figure 2) is an inexpensive and easy way to provide distance measurement between moving and stationary objects. Robotics is a major application, but the sensor also is used in security systems.
Figure 2: The PING))) Ultrasonic Sensor is used for robotics and security applications.
The sensor measures distance using sonar as an ultrasonic pulse is transmitted, and distance to target is computed based on time for an echo return. Output from the PING))) sensor is a variable-width pulse that corresponds to the distance to the target.
PING))) provides precise, noncontact distance measurements within a 2 cm to 3 m range. The ultrasonic measurements work in any lighting condition, important when used for an infrared object detector application. Pulse-in/-out communication requires one I/O pin, and a burst indicator LED shows measurement in progress. No soldering is required. A 3-pin header makes it easy to connect to a development board, directly or with an extension cable.
Applications include security systems, interactive animated exhibits, parking assistant systems, and robotic navigation.
The Parallax Sound Impact Sensor
(part #29132) is used to both add noise control and respond to loud noises. An on-board microphone enables the sensor to detect decibel-level changes, triggering the sending of a high pulse through the signal pin. This change can be read by an I/O pin of any Parallax MCU.
Features include a detection range up to 3 m, an on-board potentiometer that provides an adjustable range of detection, a 3-pin SIP header ready for breadboard or through-hole projects, and a built-in series resistor for compatibility with the Propeller MCU, as well as other 3.3 V devices.
Applications include noise-activated alarm systems, holiday animated props, and robotic control.
Parallax is perhaps best known for its educational kits; here are some examples of the types that are available. The first is an Infrared Line Follower Kit
(part #28034) that provides eight infrared emitter and receiver pairs for high-precision line-following applications.
IR frequency generation is accomplished onboard using an ICM7555 chip. The user only reads the state of each IR receiver to detect white or black surfaces. An enable pin puts the Infrared Line Follower into low-power mode.
Features include compatibility with both the Boe-Bot and Stingray robots from Parallax, an onboard 3 V regulator for easy use with Propeller-powered robots, easy to adjust 38 to 43 kHz IR frequency using an onboard potentiometer, onboard LEDs for instant line-detection communications, and high immunity to ambient lighting conditions.
Applications include line following, maze navigation, robotic contests, detect line stripe width, and edge detection.
The SumoBot Kit
(Figure 3) was introduced in the U.S. by Seattle Robotics Society member Bill Harrison, who organized some of the first U.S. robot Sumo tournaments. Today, the SumoBot is considered an intermediate robotic project that teaches the following concepts:
Figure 3: The SumoBot Kit.
- Interaction between mechanical and electrical systems, and the ability to tune hardware or adjust software to obtain desired results
- Intermediate programming skills with the BASIC Stamp 2 microcontroller
- Variable aliasing, general sound programming practices, constant/variable definitions that allow for program customization in just a few places rather than throughout an entire program
To get students interested in and excited about the fields of engineering, mechatronics, and software development as they design, construct, and program an autonomous robot, Parallax has developed the Boe-Bot kit
offering a series of hands-on activities and projects using the Parallax Boe-Bot robot (Figure 4). Its name comes from the Board of Education carrier board that is mounted on its wheeled chassis.
Figure 4: The Boe-Bot Kit.
Parallax is interesting on the competitive front, too. Certainly there are other players in the tilt, infrared, proximity, and other sensor areas the company serves. However, given Parallax’s focus on the robotics, educational, and hobby markets, it has few direct competitors. This will change as the company becomes more entrenched in commercial markets, and it will most likely be seen as direct competition by established suppliers in some sensor categories. However, for that to happen the marketplace will have to draw a distinction between Parallax products aimed at traditional sensor markets and those it has designed for more than 25 years to inspire students, such as the robotics kits that are extremely inexpensive to purchase. On the other hand, if the source of competition is other hobby kits in hobby stores, Parallax has the advantage. In most cases, competing suppliers do not have the same serious engineering reputation provided by Parallax.
For more information on the parts discussed in this article, use the links provided to access product information pages on the Hotenda website.