Wednesday, September 30, 2009

Have you ever done this?

I just spent two hours building. Not two hours trying things and taking them apart, two hours of putting bricks together just about as fast as I could. Many different sizes and shapes, parts I had to dig out. Then, half way through I thought of a much better idea how to build it. Now, I get to tear it all apart, sort it and put it all away and start over. *sigh*

Monday, September 28, 2009

More uses with the PF Motors

I really like PF motors. They have plenty of power, they are easy to mount, and the hollow shaft makes customizing a project a breeze. Everything I build uses the NXT, so I needed a way to control the PF motors. Enter the HiTechnic IRLink. But the problem is there is no direct way to the position of the shaft, such as “turn the shaft 270 degrees.” Well, there are a couple of ways to get around that.

The first way is to add some gearing and include a clutch gear. Then design your project so that it will hit some stops. When the stops are hit, the clutch gear will give and your actuator will end in the desired position. Reversing the motor will run the actuator the other way until the other stop is hit. This is analogous to using a pneumatic cylinder. Stopping the cylinder midway through the stroke is a challenge, so we mostly use it in the extended and retracted position. As you build and test, measure the time it takes to complete the cycle from one end to the other and write that into your program and add some additional time, say about 0.25 or .50 seconds.

Here is a short video showing an example of how that might work.

video

The second way again uses the IRLink sensor, but adds an RCX and a rotation sensor or a couple of touch sensors. The touch sensors would be used in the same manner as above, but the touch sensors would be used as the stop.

The IRLink makes use of the RCX and the PF motors, so you can get motor control and feedback while using only one port of the NXT! Imagine, using a single program, you can have 3 servomotors, 8 PF motors, 3 9V motors, 3 sensors on the RCX and 3 sensors on the NXT. If that is not enough power for you…..

Sunday, September 27, 2009

A New "The NXT Step" Blogger.

I am excited to say that I have been invited by the guys over at The NXT Step to be a permanent contributing blogger! It is an honor and I hope that I can live up to the very high standards that they have set. I look forward to being a part of what I feel is the best group of NXT experts on the net.

Friday, September 25, 2009

Friday's Robot Idea.

I love this idea, and I have been thinking about how to do it. It can be done in Lego.

A Box of Inspiration

I am always looking for inspiration. I look to others projects, videos, blogs and anything else I find interesting. Another way I find inspiration is spending time not working on a project, but on small details like gear assemblies and linear actuators. If I build something I like, I set it aside in a small tray that I store out of the way. It's a great way to solve problems when I just can't get a good answer. If I am stuck, I pull out the inspiration box.

Inspiration
(click to enlarge)

What I have shown is just a few I currently have on my building table. At times when I am stuck, I completely pull myself away from a project and work just on inspirations.

Click on any image to enlarge.

Wednesday, September 23, 2009

Pneumatic System Video

I have posted a video of all of the pneumatic components operating. See Pneumatic System Operated by Lego NXT.

Remotely Controlled Pneumatic Valves

I was ecstatic when I discovered this. For years we have wanted a way to control pneumatic valves with an RCX or a NXT. Here is a way to do it using only one port of the NXT!

Controlled "solenoid" pneumatic valves
(click to enlarge)

Using the great HiTechnic IRLink Sensor, you can operate the PF motors remotely. Since PF motors are relatively cheap and easy to come by, this gave me an idea. Can I design a system that uses PF motors to operate a pneumatic valve. The answer is yes.

The PF motor shaft is equipped with a 24 tooth cluch gear. That clutch gear turns a 40 tooth spur gear. In one of the outer holes of the spur gear is a piece that is connected to the valve lever throw. It is a rather simple construction that works great. This is the system by which I controlled the valve that operated the end effector of my Lego Flexpicker. It is very dependable. In fact, after I built and installed it, I often forgot about it functioning.

What is so great about this idea is that it can be controlled with a PF remote control as well as the HiTechnic IRLink sensor and up to eight valves can be controlled using only one port. With some creative building and blocking the signal at the right time, you can basically build a system where the sensor can control many more than eight valves.

Pneumatic Auxiliary Equipment

When building a pneumatic system, there are a few components that you may want to consider adding.

Auxiliary Components
(click to enlarge)

In this photo, I have shown a valve used as a pressure release valve, a manual pump, and three air tanks. I have shown them as a branch to the system instead of in line. Branches for components like this make it easier to add and work on certain problems.

The pressure release valve is used to release pressure when the system is not in use. A tube is attached to the center connection and when the system is pressurized, the lever is kept in the center position. Moving the lever either way releases pressure. Just remember to return the lever to the center position or else you will have a problem when trying to build pressure again. I don't like to store projects under pressure, so this allows me to quickly release pressure.

I like to build a manual pump into my systems. This is to have a way to quickly add pressure to the system to test actuators and other equipment in the system. It is not always necessary but can be convenient when it takes some work to get the compressor going.

Air tanks are great because it is a great way to store energy. The more tanks you add into the system, the less often the compressor will cycle to regain pressure. I wish I had many more.

Pressure Switch

The pressure switch I have designed differs little from other designs. It uses a standard cylinder, a 9v electrical switch, and a few rubber bands.

Pressure Switch.
(click to enlarge)

One major benefit is that it is very easy to adjust tension. Currently there are four bands on it (two on each side). It is important to have similar tension on each side, so if you add a band to one side, a matching band should be added to the other side.

It can't be seen on this photo, but I added a shaft inside the throw lever and a 2x2 brick on top of the inside electrical connection. This was necessary so the bands wouldn't pull the lever so far that the pressurized cylinder wouldn't have problems starting to move the the throw lever.

Adjustment by adding bands should be done by observing the stress put onto the compressor motor and by making sure that the cylinders in the MOC are operating properly. If the compressor motor bogs down too much, you may want to remove some bands. If the cylinder is not able to move its load, you may want to add some bands.

High Power Pneumatic Compressor

There are bunches of Lego Technic compressors out there and some work well an others not so much. I would like to discuss a version of which I have had lots of success. Some may not like it because I modified a Lego piece (myself included), but in my opinion it was well worth it. It pumps out air like you wouldn't believe and can achieve high pressures in a hurry. This is the compressor I used when I built the Lego Flexpicker.


Compressor
(click to enlarge)

First, note that I used the most powerful motor. It is the RC Race Buggy motor (http://www.bricklink.com/catalogItem.asp?P=5292). I like it because it has the old style 9v connections which I can easily hook up to a 9v train regulator (http://www.bricklink.com/catalogItem.asp?P=2868b). This is necessary because as in real life, air compressors suck power in huge amounts. This system will eat batteries like they were M&Ms. The XL PF motor works too, but again the battery issue.

Using the train regulator obviously can't be done on mobile robots, so if you decide to use this on a wheeled or tracked robot, I seriously recommend using a dedicated battery box and having lots of spare batteries or keep the rechargables handy.

The manual pumps (http://www.bricklink.com/catalogItem.asp?P=2797c03) have to be modified, and for me this took a pair of needle nose pliers to remove the spring. I ruined the spring trying to take it off, but with with care it might be possible to take it off without stretching it.

It is important when building this compressor that the pumps are geared so that the pumps are 180 degrees out of phase with each other. This way, only one pump is compressing air at a time. Otherwise, the motor would have to work hard for a moment and then would have no resistance for a moment.

It is necessary to do some gearing and I used an 8:24 ratio. This gives plenty of power and speed. I also found that using the motor shaft nearest the end of the motor works best too as it has the highest gear ratio/lowest speed.

Tuesday, September 22, 2009

Technology Update

I have taken the next step in my blogging quest. I have purchased a new video recorder. I have built a couple of things, and will be posting very soon.

Friday, September 18, 2009

HELLO WORLD!

WELCOME TO TINKERNOLOGY!
Tinkernology is a blog that hopes to share years of experience of
building and programming with you.

My name is Chris. I have been a fan of Lego for about 20 years and a Mechanical Engineer for 12 years. I build Technic models and RCX and NXT robots.

I have built hundreds of MOCs, but one of my favorite parts of building is working through the details. By this I mean getting the gear ratio right, making the structure strong enough, making the MOC look right, making all the functions operate correctly and so on. Every complex assembly consists of several small functions. To make the large complex, you must understand each and every one of the small functions. That is what I plan to share; not necessarily the complete MOC, but the small parts that come together to make the creation.

When I build, I typically will build the same detail over and over, making changes until everything is just right. This has given me experience, and I want to share it with you. I don’t expect that I will show you ground breaking technology, but give you lots inspiration and ideas.

I have many topics that I want to share. Some of them are;
-Gearing, gearboxes, gear trains
-Sturdy building techniques
-Pneumatics
-Linkages
-Storage and building area ideas
-Physics and simple machines
-Building methodologies
-Motion and energy
-Engineering
-How to work with sensors
-Programming
-Unique building ideas
-My projects

I hope to post at least once a week, possibly more. I have tons of ideas for posts, so it may be a fast start.

I am an avid fan of robotics. Nearly every day I keep up on the state of the art robots. I spend time watching robot videos and reading robot blogs. I will share the interesting ones I find with you, so don’t expect every post to be purely Lego related. I look outside the Lego community for inspiration.

My current claim to fame is my Lego Flexpicker found on YouTube.



It has been featured on several blogs including MAKE magazine, Gizmodo, TechnicBricks, TheNXTStep, singularityhub, and industrialcontroldesignline.com. I plan share many of the building techniques and my experiences with you.


The first bit of advice I have for you, is to build, build, build! You can think all day about a project, but unless you try to build it you will never learn if it works or not.