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In my last postI talked about the View feature of the brick that allows you to see what the sensors attached to the brick are reading. There is one important caveat regarding the light sensor that you need to be aware of. When you use the View to see what the light sensor is reading, it will likely range between for black and for white.

These are non-calibrated values. If you calibrate the light sensor which you shouldthese values will not change. That is, the View only shows non-calibrated values. In order to see the calibrated values, you have nxt robot light sensor not working write a small program to display the values the light sensor is reading. Or you can download one. The zip file also has a program that shows what the light sensor is reading.

Use this program to see the light sensor values if you use the program to calibrate the light sensor. I just learned of this last week. It would have helped me greatly when we were trying to diagnose problems with our light sensor last year. We ended up working around our problems. Hopefully, nxt robot light sensor not working understanding this caveat, you can avoid the confusion I had. My team only used View to find out if a sensor or motor is plugged into the correct port it is very hard to trace wires nxt robot light sensor not working their robots.

Other than than they find View to have no value. As you mention, View is a source of great confusion if you calibrate your light sensor. I think teams do themselves a disservice using View to program duration for a Move block.

The team may never learn the relationship between motor duration and move distance, or motor duration and turn angle. If your programs use motor duration you are also locked in to never changing your robot design. A change in wheel diameter or robot track distance between wheels invalidates all nxt robot light sensor not working programs. I think a much better solution is to learn how to convert linear distance measured in millimeters or inches into motor duration.

Write your own Move MyBlock that does the conversion, and write your programs using a tape measure. The biggest benefit, other than knowing a lot more about robotics, is that now your programs are protected against change.

Decide to use bigger wheels to go faster and save time? Just change the conversion factor inside the MyBlock, nxt robot light sensor not working all your programs magically work again. This is a very interesting idea. How do you give inputs to MyBlocks? What you describe here is a very good idea, but it is also very advanced. I believe most of the coaches that come here are rookie coaches, so sticking with degrees for their first year is a good way to get started.

They can move on to your more advanced methods which I would like to learn more about once they have a solid foundation. I found a simple tutorial on how to create MyBlocks with inputs as well as a very good detailed tutorial. I am a rookie coach. First I wanted to thank you for taking the time to share your experience in this blog.

But to your previous point, I agree that some of the techniques sometimes mentioned seem very advanced. What I always ask myself is how old are your team members Dean?

Thank you for your comment and your kind words. However, I have heard that the ideas that come from 6th and 7th grade teams have a leap in complexity and creativity.

We are using two light sensors to follow a line this year and I would say that she would not have been able to program it with my help without the experience of following a line with one light sensor last year. My advice is to stick with simple motor moves, sensor detections, loops, and myBlocks. My team last year did very well sticking to those foundations. My girls were all 8 when they started. They retired from FLL after last season and are mentoring a young all girl team this year.

Our team was different. We spent time doing things like writing video games or playing robot sumo. We built working generators out of LEGO. Remember the wave generator you had to build for Power Puzzle? Ours actually generated electricity.

We did lots of experiments. Most of what the girls built or wrote was never used in competition, but the concepts they learned were applicable. Our approach worked for us. The girls had fun while learning, and gained a lot of valuable life experience in the process. They are so comfortable with public speaking that they put on an FLL Orientation day at Boston Scientific all by themselves I was called out of town for work. The local FLL facilitator said the presentation was so well organized and informative that it is now the template for all future presentations.

And now my girls are passing on the lessons they learned. I am very happy. An observation on NXT light calibration. I am pretty certain this was true under NXT-G 2. It seems there is only one set of light calibration parameters used by the standard NXT calibration and sensor read blocks — so if you have multiple sensors they may behave differently from one another.

The team I coach is not using a color sensor; that may have its own calibration. About age appropriate programming: I think it depends on a blend of things — innate logic and math abilities, NXT programming experience esp. I agree that starting with bread and butter foundations is imperative.

For example the 9 and 10 year olds both have a strong sense of mechanical design — one did Jr FLL last year and learned a lot nxt robot light sensor not working that experience. Son the elder age 11 said he wanted to step away from mission programming nxt robot light sensor not working year after doing a lot of it for the past two years.

So the two younger ones and the other 11 year old are doing most of the mission programming, but they have a strong arsenal of utilities. She got in mostly for the research project. That being said, she is lead on one small mission for robot game and whether she admits it or not, she has a knack for dissecting problems. Remember folks, teamwork nxt robot light sensor not working as much as everything else and deserves just as much coaching support as research or game programming.

My understanding is that the color sensor works about the same as the light sensor, which is why they are allowing it this year. It has two modes; color and light.

The color mode reports a color index 1 for black, 2 for blue…. Unlike nxt robot light sensor not working light sensor there is no intensity or raw output. There is also no way to calibrate the light sensor mode. The lack of calibration and an intensity output make the sensor almost useless as a light sensor.

What I meant is that I read that the color sensor has no advantage over the light sensor in competition. So the organizers allowed it so you could use it as a light sensor.

I was answering the original question about how the color sensor differs from the light sensor. There are many knowledgeable people on the forums that could answer your question. My team of 10 year-olds are using three light sensors yes, we bought extras! This post 7 confirms my hunch. BTW, thank you for the pointer to the line follower design. The calibration code is VERY useful for my kids. They created separate calibration routines for each sensors and they keep these small code snipets as extra tools when going to a competition.

As a follow up to my previous post. Here is the solution to dealing with single calibration for multiple light sensors e. E-mail will not be published required. Notify me of follow-up comments by email. Notify me of new posts by email.

Home About Contact Me. I have been a Lego League coach since This year, I wanted to document the season to give rookie coaches a resource to help them through to competition. The process can be intense, but it can also be a lot of fun for you and your team. I hope to cover enough through my posts, but if I leave anything out, please feel free to leave a comment, or contact me. Dean Hystad Oct 26, at Thanx for the info, Dean.

Florian Oct 28, at Florian Thank you for your comment and your kind words. Nxt robot light sensor not working Hystad Oct 29, at

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During bluetooth communication there is usually a short lag between each command transmission. This lag can be expected to not exceed 30ms at most, as stated in the official Mindstorms protocol documentation. From time to time however a significantly higher lag can be observed.

A packet will then be delayed up to 10 seconds this behaviour has only been verified when using Windows. The causes for this are likely to originate in the bluetooth stack or protocol itself and have yet to be closer examined. They seem to depend on the bluetooth signal strength, the used adapter model, the battery power of the robot and the system specification of the host computer.

When such a packet loss happens, the robot cannot be controlled during this time, e. That is why you should try to specify a certain tacho limit for the motor using NXTMotor. That way the motor will automatically stop at the correct position, even if the delay happens at the wrong time. Fact is that we are experiencing a timeout period whose length can be adjusted.

The default setting is 2 seconds, which reduces this period to a tolerable length. You can experiment with lower values, however do they have a drawback: Too short timeout periouds might cause real packet loss, meaning that data will actually be lost because the bluetooth stack cannot retransmit the lost data in time. This usually results in error messages or strange warnings "trying to collect a packet that was not requested".

Best performance depends on many factors, and the effects are unfortunately not always reproducable. See also section "Tutorial: The NXT light sensor measures brightness, actively or passively. Unfortunately, the detected intensity depends on the wavelength of the light and is not a linear function. Commonly spoken, warm light like sunlight or that produced by light bulbs results in a higher intensity, whereas cold light such as from neon lamps or white-blue LEDs only gets detected with lower intensity.

Hence a common problem is that daylight cannot be compensated by artifical light in such a way, that repeated measurements always yield the same values. So how do we cope with this? If a robot should be able to work in all scenarios with different illumination, there are mainly two possibilities:.

Either the program requests a reference each time it is started, i. This is basically a calibration process, that might even be supported by future NXT firmware versions an according datafield is already reserved.

The other way is to take the surrounding light into account: Measure the daylight or artificial light of the environment. This brightness can then be used to calculate the real brightness using the value obtained from the sensor. Maybe the easiest way is to make sure the robot always operates in similar illuminated situations.

Please note that multiple ultrasonic sensors in one room or on one NXT could influence each other. First of all you need surfaces that reflect ultrasound. Not suitable are usually things with very soft surfaces, especially cloth or fur-like structures. One of the most important things to consider is the angle the sensor is facing towards the object: Round surfaces, just like bottles, are extremly difficult to outline accurately.

They reflect the ultrasonic impulses in too many directions, hence you get echos of imaginary objects that are not really there. The spreading of the ultrasonic sensor is very wide anyway: It is probably best to stick to flat, hard, big objects at first. This section does not apply when using the NXTMotor class! The NXT motors have a certain way they always try to reach the most accurate position. This may lead to some unexpected effects. It only happens when using a certain rotation limit specified by TachoLimit.

Imagine you want to rotate a motor degrees. As you set a relatively high power, and a certain rotational moment is involved, the motor will turn further than its set angle limit.

Basically at the exact position of , the power will be turned off, leaving the motor spinning in coast mode until it comes to a stop. Let us just imagine this would be at degrees. The motor now "remembers" that is has just turned degrees too much.

The next time, when you issue another "rotate by " command, what do you expect? The motor keeps an internal memory of cumulative commands containing angle limits. This means, when you send the second "move " command, the internal sum is now at This is the new target to be reached.

In this case it does not matter that you start at already. The motor "realizes" that there are only degrees missing until To put it another way, if the motor is off by degrees one time, it will try to correct it the next time. This results in periodic movements that are "too far" or "too short", depending on what you send, and what you expect. Do not turn any motors by hand while the NXT is still turned on, unless you know exactly what you are doing. If the internal counters do not get reset properly, the NXT motor will try to "correct" these changes you made by hand the next time it receives a command containing an angle limit.

For driving robots, the regulation mode "synchronization" is very handy to drive straight lines or curves parameters SyncToMotor and TurnRatio of DirectMotorCommand. When sending multiple commands to synced motors, e. It has been found that these problems can be fixed by calling the following functions inbetween the different track sections:. For better performance especially when using USB connections on slow machines , it is recommended to run this toolbox function:.

For more details, see help section "Optimizing Performance". It can also help when you want to trace certain conditions leading to errors, or when you're experiencing timeout problems. To enable debug messages inside the command window, just type:.

The complexer the functions get, the longer those error messages will be. Most of the time, they are the best clue you have in order to find out what went wrong. It can be a bit confusing when all those red words take up lots of space inside your command window, or when errors repeatedly occur again and again.

Note that your command history will not be touched by this. The last results from your command window will be cleared however. It can be amazing how clean an error message suddenly looks when starting the program again in an empty command window