legorobotics - Chapter 1: Parts and Sensors

Chapter 1: Parts and Sensors

Listen to first part of Chapter 1. Click here.

Engineering is a wide field covering many things from electronics to building structures. For robotics, we need to know a few basics in the beginning level. This foundation will give us a better grasp on challenges yet to come. Here are a few things that you should learn.

Amazing Robot Museum:

The Amazing Robot Museum - Take virtual field trip and learn about robots.

LEGO Parts: (for other robotic sets other than RCX or NXT you may move to "Gears")

Do you know which parts are shared between sets, which are Technic, which are Creator, which are Bionical, which are standard LEGO parts? You can look at all links below or choose one to learn about each part. Can you not only memorize the names of each part, but can you also identify which belong to your set?

PEERON.com parts reference

LEGO part reference<-- click this link for part sheet

WeirdRichard.com on parts part 1

WeirdRichard.com on parts part 2

Here is a build for a triangle. What parts can you identify?

Here is a build of a square. What parts can you identify?

Here is a build of a grid. What parts can you identify and how many of each would you need to build this?

Questions (something to probe kids with but not answer at this time):

1. What parts should we really memorize?

2. Why are friction and non-friction pins in their different lengths important?

3. Why are bushings of any length important?

4. Why are bricks with studs important?

5. Why are beams without studs (just holes) important?

6. Why are axles and flexible axles important?

7. Why are plates with studs important?

8. What's so important about sensors?

9. What's so important about the programming brick (RCX or NXT)?

10.What's so important about each gear?

From here on, we are going to find out why these parts are important.

Ask questions, look for ideas, or find troubleshooting tips:

ask Robohi <--- visit "For Educators" and look up topics (posts). There is more than one page of stuff. Make sure you are registered before trying to post something.

HIS Robotics Podcast

Work on this for day 1 ... (Have kids test each other on the parts)

-----------------------------------------------------

Brick Geometry:

Listen to part 2 of Chapter 1. Click here.

Brick Geometry movie<-- click this link for short movie

So, what's so important about Brick Geometry? Helps in the measurement of things and how to build something solid.
How many plates does it take to make one full brick height? 3 plates.
How would you create a solid support from something square? Use a traingle within the square frame.

Measuring with a beam with holes:

Use the longest beam with holes and measure things by holes. You can also measure things by studs, on top of a regular brick beam. This will allow you to know whether a space, that needs to be filled by a part, is can be filled by one or more parts. Measure the length of a bushing, you'll notice this is equal to one hole. Half a bushing is equal to half a hole. This can give more accurate info when building. The studs on a brick can help measure other bricks that is being used on your robot. This will help you create a solid robot.

Activity:

Take a piece of graph paper, fold into 4 quadrants, from left to right, up to down, label the first quadrant "Quadrant 1" (upper left hand corner) ... "Quadrant 4" (lower right hand). Now using a technic beam with holes, measure the width of one brick (color in, in the center of Quadrant 1, one block), now measure the length of the brick (color in, make this centered in Quadrant 3, the amount of blocks you measured - one hole equals one block), for Quadrant 4, color in the amount of blocks that will represent the top of the brick. Label each quadrant correctly with the correct representations, top for top view, side for side view, and front for front view. In quadrant 2 draw an angled 3D view of the brick as detailed as possible.

Expanded:

Get another sheet and measure, color, draw, label, each quadrant repeating the same steps as above but with a different part.

Ask questions, look for ideas, or find troubleshooting tips:

ask Robohi <--- visit "For Educators" and look up topics (posts). There is more than one page of stuff. Make sure you are registered before trying to post something.

HIS Robotics Podcast

Work on this for day 2 ... (discuss and/or take out a LEGO set and create shapes, letters, and simple structures with supports)

-----------------------------------------------------

Gears:

What are gears for? Gears are used to transfer energy from one point (input) to the next (output). Using one size to turn another size will give torque (power) or speed.

Lets understand FORCE + DISTANCE = TORQUE or SPEED.

Think of a wrench turning a nut. If one wants to turn a nut that is tough to turn, it is a good idea to hold near the butt of the wrench away from the head where the nut is. In this case, FORCE + DISTANCE = TORQUE. Like a 40 tooth gear, it has the distance and when force is applied, it can give more torque than an 8 tooth gear.

40 tooth gear compared to a wrench <-- click this link for short movie

An 8 tooth gear does not have that distance. This is like turning the wrench with one finger near the head where the nut is. You would be able to turn the nut quite fast with just your finger. The force, in this case, would allow for your wrench to turn the nut really quickly because there is barely any distance. So, FORCE + DISTANCE = SPEED in this case.

8 tooth gear compared to a wrench<-- click this link for short movie

In theory, if you go from big gear to small gear, this would give speed. If you go from small to big, you'll get torque.

If you go big to small and big to small again, this would give more speed. If you go from small to big and small to big again, you will get more torque.

The big gear, 40 tooth, and small gear, 8 tooth, is a 1:5 gear ratio. The small gear, 8 tooth, and big gear, 40 tooth, is a 5:1 gear ratio. If you had a 20 tooth gear and a 40 tooth gear, the ratio would be 1:2.

Understanding speed:

Person A = Takes large steps (large gear).

Person B = Takes small steps (small gear). Person B takes 1/4th the steps of Person A.

Without changes the length of each person's steps, how do you get Person B to keep up with Person A (Person A is moving 20 steps per minute)?

Without changing the length of steps again, how do you get Person A to keep up with Person B (Person B is moving 40 steps per minute)?

Story of speed:

A mother is walking her little child. The child has to take several little fast steps to keep up with mommy. If the mommy was the lead, her child has to put in more effort to keep up because the child covers less surface area than his mother. The mother would eventually have to lift, or drag her child to get her child to move faster. But if the child can keep up, look at the speed of that kid's legs. If the child was the lead, mother has to walk slower because she covers a lot of surface area than her child. But even if the child could pull mommy quickly, mommy has all the leverage - if you know what I mean.

Experiment for speed:

Take two wheels. One large and the other small. Roll both side by side. You'll find, if released at the same energy, that the smaller wheel will lose ground because it can't cover a large surface area like the large wheel. How much energy would it take to get the small wheel to keep up? If you were to keep both wheels moving at the same rate, what will it take for both wheels? What advantages and/or disadvantages are there for both wheels in this situation? Now, try this experiment with different kinds of tires.

Wheel circumference (this can be applied to gears):

Weirdrichard.com has a great lesson dealing with wheel circumference in math. Click here to access the site

Weirdrichard.com also has a lesson on calculating a wheels circumference. Click here to access the site

Ask questions, look for ideas, or find troubleshooting tips:

ask Robohi <--- visit "For Educators" and look up topics (posts). There is more than one page of stuff. Make sure you are registered before trying to post something.

HIS Robotics Podcast

Work on this for day 3 ... (review everything learned thus far)

-----------------------------------------------------

Watch 3 of the movies listed to learn a little more and review some things we've just covered.

Gear train: You'll notice that from one direction you have speed, and from the other you'll get a slow turn (it really represents torque).

Bevel gears: These gears are used for 90 degree angles. This allows for 90 degree energy transfers.

Gear angles: In a gear train, unusual sized gear(s) need to be angled properly in order for the teeth of both gears to affect each other.

Above are pictures of different gears, a rack, pulley, wheel, and gearbox. The black screw looking object above is the "Worm gear". This is like a tube with a thread (like a screw). Normally this is used to turn one of the above gears. Could be used for torque.

The other gear I'd like to mention is the slip gear. Usually white, with a grey center. Basically a 24 tooth gear with a sliding middle as to allow the slipping to prevent damage.

One more gear that requires three smaller gears within is the "Differential". This is normally used to keep two wheels to move at the same rate. Trust me there is a lot more to this gear than what I've just explained, but this is the basics on that.

Rack and pinion is a rack with teeth that allows for side to side movement. The pinion is usually the turn gear (one of the above round gears).

Pulley wheel, wheel that uses a rubber band or string. Although not a gear, it sometimes gets mentioned with gears. I am mentioning it here because it can be related to gears in that it transfers energy like a gear.

http://www.geocities.com/Baja/8205/gears.jpg

These are different gears used with many real world devices we commonly use.

This is used for? http://www.waterjets.org/waterjet_pictures/aluminum_gears.JPG

These gears are actually examples of what a waterjet cutter can do with aluminium. But, these could have a function for some mechanical device.

Try this test on gears and gadgets. from the Museum of Science

WeirdRichard.com has some great gear challenges

WeirdRichard.com on different types of gears

Remember this:

Even numbers of gears = input goes in one direction, while output goes in the opposite direction.

Odd number of gears = input and output always goes in the same direction.

If you access the bottom link, you'll noticed the mentioned gears on that site.

How Stuff Works - Gears:

Gear ratios- Great site to learn more about gears and gear ratios.

Tip: Check out Planetary Gears. Planetary Gears allow for lots of torque. Drills and electronic screw drivers use Planetary Gears. If it is possible to design this gearing system on your robotics set, your robot would have really good torque.

Pneumatics!: Sold as separate extended sets.

Weird Richard.com does it all. I love this site. Learn about Pneumatics here.

Pneumatics in LEGO robotics is a system where pumps are used. The system uses a motor to pump air into a series of pipes connected to a switch and then to pumps. We can view this as hydraulics in a mechanical arm (from a digging machine). The next site gives a nice view and explanation of hydraulics. The site is How Stuff Works on Hydraulics.

http://www.howstuffworks.com/hydraulic.htm

Questions (lets start answering these questions):

1. What parts should we really memorize?

2. Why are friction and non-friction pins in their different lengths important?

3. Why are bushings of any length important?

4. Why are bricks with studs important?

5. Why are beams without studs (just holes) important?

6. Why are axles and flexible axles important?

7. Why are plates with studs important?

8. What's so important about sensors?

9. What's so important about the programming brick (RCX or NXT)?

10.What's so important about each gear?

Ask questions, look for ideas, or find troubleshooting tips:

ask Robohi <--- visit "For Educators" and look up topics (posts). There is more than one page of stuff. Make sure you are registered before trying to post something.

HIS Robotics Podcast

Work on this for day 4 ... (review everything learned thus far)

-----------------------------------------------------

What you should know about LEGOs and professionals in engineering:

Engineers around the world use LEGOs and the robotics system to produce minitures and/or models of things to help these professionals understand how something is going to work, or not work. The college of engineering offers courses on LEGO robotics for these upcoming engineers. LEGO robotics, unlike other kits, offers a cheaper and more expansive set.

History:

LEGO history

The Industrial Revolution

History of Inventions and Technology Timeline

Ask questions, look for ideas, or find troubleshooting tips:

ask Robohi <--- visit "For Educators" and look up topics (posts). There is more than one page of stuff. Make sure you are registered before trying to post something.

HIS Robotics Podcast

Work on this for day 5 ... (review everything learned thus far)

-----------------------------------------------------

Sensors:

This can be part of day 5 or day 6.

Let me introduce you to some sensors. Some belong to the RCX yellow brick and there are some that belong to the NXT white brick. You should take notice of what sensors you have in your kits or in your class. Pay special attention to the ones you have available to you.

All sensors are INPUTS and only one exception is made. The NXT motor/servo is a motor and rotation sensor at the same time, this can be plugged into the INPUT and OUTPUT. Other than that, all sensors are INPUTS only. Did I mention that except for one, all sensors are INPUTS only.

Warning! - Do not allow for Ultrasonic sensors, Sound sensors, and Light sensors to be tested at the same time and/or in a close vicinity if at the same time. Using the same sensors on different robots at the same time could throw off readings and how the robot reacts to its environment.

http://www.oreillynet.com/network/2000/05/22/graphics/2977.jpg - RCX

http://www.philohome.com/nxtmotor/code-wheel1.jpg - NXT serves as a motor/servo and a rotation sensor at the same time. This is the only device that can be plugged into an INPUT or OUTPUT.

Rotation sensor:

Used to allow for rotation control. The user is able to give commands, through programming, in degrees (as in angle) or the amount of rotations.

https://botballstore.org/catalog/images/Lego%20Light%20Sensor.jpg - RCX

http://www.euskalnet.net/kolaskoaga/irudiak/nxt/argisentsorea.jpg - NXT

Light sensor:

Used to sense white all the way to black. It can be set to give off a light, or to allow for light to dark to be detected, with direct or ambient lighting.

Warning: If you have the light sensor producing the light, you don't want ambient light to leak in and give the sensor another kind of reading. If you have the light off on the light sensor, you will need ambient or direct lighting to help your sensor detect different shades (white to black).

http://www-education.rec.ri.cmu.edu/multimedia/touchsensor2.jpg - RCX

http://www.active-robots.com/products/mindstorms4schools/

nxt-accessories/9843.jpg - NXT

Touch sensor:

Used to sense a push. The computer gets a feed back of "1" during a push. If there is no push, the computer gets a feed back of "0".

http://www.active-robots.com/products/lego/lego-spares/

tempsensor-750.jpg - RCX

Temperature sensor:

Used to sense different levels of temperature.

http://www.hitechnic.com/contents/media/Ultrasonic1.jpg - RCX

http://www.active-robots.com/products/mindstorms4schools/

menuthumbs/lego-accessories.jpg - NXT

http://www.hitechnic.com/contents/media/URpage2.gif - See how it works...

Ultrasonic sensor:

Used to detect bounce of ultrasonic sound to find a distance or whether there is an object in front of it.

http://www.kidtechnic.com/images/NXT/sensors/sound_LE.jpg - NXT

Sound sensor:

The sound sensor allows for the detection of sound at different levels. The limitation is comparible to human hearing measured in decibels (dba).

Sensors, in future projects, will be part of your main construction. During any "blue print", you will have to measure and plan out how these sensor(s) will fit.

You will encounter sensors in more detail in a later chapter. So, don't worry about details for now.

This can be part of day 5 or day 6.

===========================================

Book: