Skip to main content

HiTechnic Compass Sensor

OK, for some folks this may be old hat, but today was the first time I had a chance to play with one of the new sensors from HiTechnic. The HiTechnic sensors are skinned in a very nice-looking LEGOesque enclosure, replicating the look of the LEGO sensors but with a distinctive black endcap (I'm told this is also transparent to IR, so that IR-based sensors can share the same case components). The female port on the sensor is a mate to the LEGO-standard cables, offset catch and all, making wiring a snap (literally), and the piece pins on and feels exactly like it was made by LEGO (I'm rather surprised at this, actually; moulding pieces to this precision is no easy task). Currently you can use the NXT-G US sensor block to read the sensor, as it communicates with the NXT via I2C and this is the only "stock" NXT-G block that returns information from the sensor via I2C. But as consumers (and suppliers like HiTechnic) develop their own NXT-G blocks using the LabView Toolkit, I'm sure we'll see custom sensor blocks for these. Since the US sensor block returns only a single byte, the sensor returns the heading angle divided by two (currently; I think this is a limit of the NXT-G interface, not the sensor itself).

At BrickFest there was a wonderful demo of the compass sensors: put a compass-equiped robot on a turntable, and spin the turntable. While I watched this and commented on how great a demo it was... um... I never actually got a movie of it. So shoot me. To correct for this omission on my part, I decided to replicate the demo at home. I took a HiTechnic compass sensor and mounted it on JennToo, and then went ahead and wrote a program to keep the compass sensor pointed due south. The result is a fun and impressive robot that consistantly points in one direction (it's a $250+ compass... OK, I need to make something more practical someday).

The program itself is amazingly simple. No complicated corrections or difficult to figure out logic, the error signal (how much the heading differs from due south) is used to calculate the power on a Move block... essentially, that's it. Remember that the US sensor block here is not reading an US sensor , but actually the new compass sensor. Within the sensor block I do a compare to determine what direction to turn, and then the heading from the sensor (which is what comes out of the "distance" plug of the US sensor block... remember, we're "fooling" NXT-G into thinking the compass sensor is an US sensor) is used to figure out how fast to try to turn: the further away from the requested heading we are, the stronger we should try to drive the motors. The result is a very simple, understandable program, that is a lot of fun to watch run.

P.S.- I also have the Mindsensors compass to compare this with, and hope to report on that later. This is just the first non-LEGO sensor I've had to play with... and it looks like there will be plenty of toys in the future.

--
Brian Davis

Errata: a few points that I was either unclear on or just dead wrong:

(1) The sensor enclosures are actually made by LEGO, and supplied to HiTechnic, who then supply the internals and endcap. Thus, why it "feels" exactly like LEGO, and meshes with the LEGO wires: these parts are LEGO or LEGO-certified.

(2) The endcap on the compass sensor I showed is not made from the IR transparent material, but just black plastic (I've seen the IR cap and it's visually very similar). The IR transparent endcap will be used on sensors like the HiTechnic Bridge (which enables IR communication between the NXT & RCX)

I apologise for the incorrect or misleading information.

Popular posts from this blog

Celebrating MINDSTORMS with a Remix - Part 3

The ROBOTMAK3RS continued their celebration of the 25th Anniversary of MINDSTORMS through these Fall and Winter remix projects. Each ROBOTMAK3R was tasked with selecting one LEGO set of their choice and combining it with a MINDSTORMS set. Below are the five amazing models they came up with. Braill3 by Jerry Nicholls Braill3 is an EV3-based LEGO Braille bricks reader. This robot uses its fingertip, made from three touch switches, to read messages written using the LEGO Braille bricks and will speak out what it detected. If it sees a simple maths problem it will attempt to solve it and give the answer as well. To learn more about the process of creating this machine, read Jerry's blog . Braill3 can be viewed here . Set Review: The Braille Bricks set is well thought out. The ratios of the letters is suitable for general use and the addition of some punctuation and arithmetic operators is excellent. There is a card showing what bricks there are and their quantities, but no form of sort...

Celebrating MINDSTORMS with a Remix - Part 2

The ROBOTMAK3RS continued their celebration of the 25th Anniversary of MINDSTORMS through these summer and fall remix projects. Each ROBOTMAK3R was tasked with selecting one LEGO set of their choice and combining it with a MINDSTORMS set. Below are the five amazing models they came up with. Remote controlled material handle r by Jozua van Ravenhorst (aka Mr Jo) This remix combines the LEGO Technic Material Handler (42144) with MINDSTORMS EV3 (31313) It uses the power of pneumatic cylinders to move objects around. By using a bluetooth remote control, very precise movements can be made with this model. Touch sensors in the base chassis prevent the turret twisting the cables that go through the turntable to much. The program has several protections to prevent over pressurizing the system for each of the 3 individual pumps and valves that control the 2 booms and claws. The real version of this machine is mostly used in waste material sites to bring the material to machines that sort and...

Celebrating 25 Years of MINDSTORMS

In celebration of the 25th Anniversary of MINDSTORMS, we take a trip through history. Please also visit ROBOTMAK3RS Community every week as we highlight different projects all through 2023 in celebration of the anniversary. Some of the early history is based on the content shared by  Coder Shah  in our  MINDSTORMS EV3 Community Group . Some of the text and links may have been edited from his original posts for consistency and clarity.  1984 - Kjeld Kirk Kristiansen watched a TV program called "Talking Turtle," where MIT professor Seymour Papert demonstrated how children could control robot "turtles" using LOGO, a programming language he developed. 1988 - The collaboration between MIT and LEGO resulted in LEGO TC Logo in 1988, which allowed students to control LEGO models using computer commands. The video shows Papert demonstrating TC Logo. 1990 - LEGO TC Logo was hampered since the robots you built had to be tethered to a personal computer. LEGO and MIT...