Segway Source code now available (dIMU and HiTechnic)

In the past few months I've been working on a renewed RobotC program for a LEGO MINDSTORMS NXT Segway.

The current program handles all balancing tasks in the background so you can make the Segway do what you want without worrying about balancing. It supports both the HiTechnic Gyro sensor and the new Dexter Industries dIMU. The complete source and instructions are available on my website.

The older ready to run NXT-G version of the program (only supports HiTechnic Gyro) is also still available.

Many of you have been asking for the source code, so here's a chance to study the balancing algorithm. You may use and edit the code as you like, but don't forget to link to the original code and give credit if you reshare your program.

Update: Just another example of what you could use the code for!

New Barometric sensor from HiTechnic

The relentless sensor makers of HiTechnic have released a new sensor for the NXT: the barometric sensor.
It can be used for measuring both the atmospheric pressure as well as its temperature. From the web page:

"The pressure value from the sensor is in 1/1000th of inch Mercury (inHg) and the temperature is in 1/10th degree Celsius. The NXT-G block allows the NXT to read the pressure in either inHg or hPa (hectopascals) and temperature in either Celsius or Fahrenheit degrees. Once adjusted for current conditions, the block can also calculate altitude in feet or meters."

As usual, HiTechnic also provides support for the new sensor in NXT-G as well as in RobotC.

By experience I'm positive that other NXT platforms like leJOS NXJ or NXC will integrate support soon, too.

New model from HiTechnic

HiTechnic have released the building instructions for a new model, this time a small go-kart. This go cart is controlled by a Power Functions remote, that sends commands to the HiTechnic IR-Receiver sensor which in turn communicates with the NXT.

It looks quick and I'm sure would be a blast to play with. Also a nice bonus that it can be built with both the 1.0 and 2.0 NXT sets :)

I Love how they get around not needing a differential (you'll have to watch the video to find out!)



More info here - http://www.hitechnic.com/models

**CORRECTION** The car uses the IR-Receiver, not the IR-Link as I had originally stated. My fault for writing this post late at night!

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Damien Kee
www.damienkee.com

Useful NXT-G Motor Block: Absolute position control

HiTechnic has released a new motor block that you can use in NXT-G. Here's an excerpt from the description found on the HiTechnic website.

Why the HiTechnic Motor PID Block?
This block is an alternative to the standard LEGO Motor Block. Unlike the Motor block, which when used with a duration of degrees or rotations, gives you relative control over the position of the motor, the PID Block is designed to give you absolute position control. With the standard Motor block, you might use it to go forward 45 degrees, go another 45 degrees, then go backward 90 degrees. Each time the motor turns an amount that is relative to the position that the block starts in. With the PID Block you specify an absolute position. For example, if you want the motor to go to position 45, you can pass in that value to the Set Point input of the PID Block and it will drive the motor to that position. If the motor starts at position 100, then it will go backward to 45; if it starts at 0 then it will go forward.

This type of control makes sense when your motor has a limited range of motion. For example, if you are using the motor to control the position of a robotic arm, you will likely want to make the arm go to a certain position and then have it do something. Since you may not want to keep track of the current position, it is often easier if you can just specify the position to go to. That is what this block lets you do. If you use the standard Motor block, then the direction and duration needed to get to a certain position will depend on the current position.

Here are some possible uses for the Motor PID Block:

- Steering mechanism on a car
- Linkage control system to follow the input from a sensor
- A selector mechanism for a sorter.
- A gripper mechanism that has multiple positions that you want to select between. Perhaps: Open, Closed, Crunch.
- A panning control mechanism where you want to accurately control the direction something is pointing.

Gus Jansson from HiTechnic demonstrates the block in the video below. Find more information and a download link here.

New sensors by HiTechnic: Angle and Magnetic

HiTechnic, one of the most active providers of 3rd party sensors for LEGO® MINDSTORMS, has published two new sensors: the Angle and the Magnetic sensor.

Similar to the rotation sensor built into the NXT servo motors, the angle sensor measures axle rotation position and rotation speed; while the rotation sensor is located on the motor's axle, though, the angle sensor  can be directly attached to the axle in question, hence does not suffer from inaccuracies that arise from friction or gear slopes. It thus is apt to be more reliable on models where this is a critical factor.
Another very nice feature is that it keeps measuring the angle even when unplugged or not powered; so there's no need for re-calibration between power cycles.

The magnetic sensor is a single-axis magnetometer and is able to detect and measure magnetic fields that exist around the sensor.

Finding a ball

For my actual project, a soccer-playing NXT robot, I've started with a prototype that is capable of finding a ball that broadcasts infrared signals; on that behalf it uses the IR Seeker Sensor by HiTechnic :



The programmed with leJOS NXJ, the Java platform for LEGO® MINDSTORMS NXT; working with it again revealed to me how powerful and elegant, yet easy to use leJOS has become by now.

HiTechnic SMUX blocks

Just got a note from the guys at HiTechnic that they have now released the NXT-G blocks for their SMUX

Each block looks just like the original, but with the addition of a small triangle up in 'Port' section.  Once you choose which port your SMUX is connected to, you can then choose what port within the SMUX that particular sensor is connected to.

They have a fantastic write up on their blog at:

http://www.hitechnic.com/blog/smux/smux-nxt-g-blocks-now-available/

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Damien Kee
www.damienkee.com

HiTechnic Balancing the HTWay

Sweet! HiTechnic's turn with HTWay ... a two-wheeled, self-balancing, Segway like marvel with a nice added feature...Power Functions remote control! At this point the HTWay requires a HiTechnic Gyro Sensor, a HiTechnic IRReceiver, and a LEGO Power Functions IR Remote Control. Programs for both NXT-G 2.0 and NXC are available. With the integrated wheel-size setting menu users have an interesting option. The provided programs can also be altered for exchange or integration of different sensors to fit specific needs.

HiTechnic has posted HTWay's detailed instructions (including building/ programming steps) and a nice back-history of self-balancing pBricks from the beginning. Be sure to see the video!

I've always loved the way 'AllTheseWays' look like nothing is happening when they are performing at their best...for me anyway...just standing there.

Chris

Using the EOPD sensor to measure distance

On the HiTechnic website, Gus Jansson has published an interesting article on how to use the HiTechnic EOPD sensor as an accurate distance measuring sensor. You can read it by following this link. (Thanks to Xander for the link.)

Color Sensor Comparision

Philo has just put up a really well-done comparison of two of the color sensor that are currently available for the NXT. The first is the official one from LEGO, included in the V2 NXT kit, while the second is the HiTechnic V2 color sensor which can be purchased separately. I'm not going to bother summarizing Philo's excellent presentation too much, because reading it is an education in itself - not just on how the sensors "perform", but on how to compare sensors properly: developing tests, and understanding the results. Please read his page for the whole scoop. A dirt-simple summary is both have strong points, with the HiTechnic one being amazing at detecting multiple colors and handling challenging ambient light conditions, and the LEGO one (by virtue of using the rapidly-reading AtoD converter on-board the NXT) being much faster (probably important for line-following, for instance).

Thank you Philo for doing comparisons like this - and please read his summary, it really is excellent.

HiTechnic Experimenter's Kit A & Solderless Prototype Sensor Board

The wonderful folks over at HiTechnic have released a new offering that will interest electronics beginners, science teachers, and advanced tinkerers with a very cool way to play, learn, and create! HiTechnic's Experimenter's Kit A with the Solderless Phototype Sensor Board will enable you to go far beyond what LEGO has in mind for the NXT. The HiTechnic Experimenter's Kit A is a clean and easy way to integrate the LEGO MINDSTORMS NXT with the world of homebrew electronics and circuits while keeping your NXT warranty intact. Crack into the potential of the NXT without cracking the NXT! Control something with the NXT...Have something control the NXT! Prototype the next big 3rd-party sensor! Bend the NXT, some circuits, and your mind!

HiTechnic has added The Experimenter's Kit Handbook…a fantastic guide full of detailed step-by-step projects teaching beginner electronics and sensor prototyping on the included Solderless Breadboard. This handbook provides a wonderful way for Mindstormers to learn about electronics and have fun at the same time. They have included enough components to build 8 experiment projects detailed in the Experimenter’s Kit Handbook, every one providing many different educational aspects of user electronics. Each chapter of the handbook explains how to identify the components, construct the project’s circuit, and run an example program. Programming examples and custom blocks for NXT-G, LabVIEW, NXC, and RobotC are available for each project.

The real treat is that this kit allows experimenters to design and build custom circuits and sensors to interact with the NXT through a normal cable connection. If you create something worth saving permanently, try their Solderable Prototype Board.

Take a Look! The Experimenter’s Kit A Handbook and sample programs are available for download here. Look through it and let the ideas flow! If you create something, send me some details and I'll post it to the blog.

I’m in the process of reviewing this kit and going beyond the kit projects by spinning it through a few of my own dark experiments and homebrews. In the coming months I’ll show off what’s being twisted in my own secret lab. (covert photo..)

Christopher R. Smith
Littlehorn

New Products From HiTechnic

There were several very nice surprises in the new LEGO Education catalog. Besides WeDo, there are three gems from HiTechnic. The first is a simple touch sensor multiplexer for the NXT. The idea is that by combining multiple touch sensor on one input port (but giving each a slightly different resistance), you can detect not only when one is pressed but which one is pressed. This was something that was commonly done with the RCX, but there hadn't been a commercial product to do it as yet for the NXT: it appears HiTechnic has stepped up and filled that gap. Four touch sensors can share a single input port on the NXT, greatly expanding the number of touch sensors you could use (at least 16; enough to build a simple keyboard, perhaps). The square "bumps" on the housing are spaced so that a studless beam nestles neatly between them, allowing you to "clamp" or "bracket" the housing in place (without going to the trouble of LEGO-certified pinholes etc.). The NXT-G block (downloadable from HiTechnic) is also well-designed, with a lot of careful thought into how to make using this sort of system as easy as possible, while still allowing the user a huge range of combinations. At $29 (without the extra touch sensors), it's not a bad price either, and you can buy it from LEGO Ed as a package with extra touch sensors for $98. One caution: this will only multiplex touch sensors, not other types.

The other interesting thing is the Tetrix system, designed to be used in FTC and based on the NXT brick. Tetrix uses metal pieces in place of some LEGO elements, but more interesting for many of us is that it uses true servos. It turns out both the servo controller and the DC motor controller are built by HiTechnic, and can be bought individually from LEGO Ed. At $80 each (either version), these aren't cheap, but they are at least now available... and very tempting. The catalog says you can daisy-chain up to four units off a sensor port (not a motor port), and they have their own battery connections so the power driving the DC motors and servos is not coming from the NXT, but from supplementary battery systems. Ideal for powerful motors, and this can greatly expand the number of motors potentially under control (I might end up with something like this for HALE-style, light-weight missions that still need a lot of actuators, for example). These elements do not have (to my knowledge) any NXT-G blocks for them (and they are currently sold only through LEGO Ed), but that makes sense in that FTC generally uses ROBOTC or LabVIEW or similar... and I'd be surprised if it wasn't at least possible to interface them down to NXT-G (it's all the same hardware, so at most it might be a firmware issue). Other interesting robotics products are DC motors, motor encoders, servos, LEGO "hardpoint" connectors (allowing the LEGO elements to interface with the Tetrix metal pieces), as well as lots of other hardware). Take a look.

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Brian Davis