Skip to content

Flash, FlashDevelop, AMFPHP and AMF Remoting – A Getting Started Guide

Introduction

Some months ago I began a project involving Flash for making visual representations of data.  The learning curve was steep at the beginning, mostly because of so much confusion between all of the Adobe (and formerly, Macromedia) products.  There’s Flash, ActionScript, Flex, AIR, ColdFusion, Director, and so on – and on top of that there are a small number of acronyms and catch terms such as AMF, RPC, FLA, SWF, MXML, to name a few…and what the heck does CS4 stand for?  I’d like to clarify a few of those things in this article, plus talk about a setup that works very well for me – Best of all, the setup I use is completely free (as in beer) and is also mostly open source.

Definitions

First of all, the difference between Flash and Flex is a little hard to explain but you already know what Flash is – it is the multimedia platform which had first become popular when owned by Macromedia, and is now continued by Adobe.  Flash was first designed for interactive (vector, primarily) animations, but has evolved in functionality, and is used for streaming media from YouTube, for instance.  Flex is essentially a framework built on top of Flash, and allows a programmer-style (rather than more of an animator) approach to creating Flash media.  There are in fact two versions of Flex, one is from Adobe and the other is open-source.  Flex targets the creation of applications rather than animations.  Since Flex is built on Flash, I tend to say ‘Flash’ when I (also) mean Flex. For a better explanation of the differences between Flash, Flex, and others, this article is very good: http://www.scottklarr.com/topic/39/adobe-air-vs-flash-vs-flex-vs-microsoft-silverlight/

Flash is well-suited for Internet applications and especially games, but seemed to be a good platform for data visualization and even user interfaces across the Net because it is designed around easy access to graphics rendering as well as distribution within websites.  Unlike Microsoft Silverlight, which serves a similar purpose, Flash is well-established, has a large community following, and has open source options.  Silverlight is definitely getting better and may surpass Flash in some technical aspects, but I chose Flash because it is more established, and Flash applications work well in Firefox, IE, and other browsers. Files with the FLA suffix are working files for Flash movies.  They can be produced by the Flash editor (Flash CS4, etc.  CS, by the way, stands for "Creative Suite" and seems to be a title which ties the core Adobe software together).  Flash movies can be written in ActionScript, or MXML (an XML-based markup language), or typically some combination of the two – ActionScript can be embedded within MXML, or various items such as buttons and text fields can be created directly through MXML. 

FlashDevelop is an Integrated Development Environment (IDE) which can create Flash movies and animations, and which I find useful and will talk about in the next section of this article. Once compiled a SWF (ShockWave Flash) file is created.  This is the end-user-visible, animation prone, Internet-ready file, and SWF files are played by the Flash player, either in stand-alone mode or typically within a web browser. In my project I needed a way of getting data from a database, and discovered what is called ‘AMF Remoting‘ or Remote Procedure Call (RPC) to tie Flash together with PHP, so that I could use PHP as a middle-man script to access an MSSQL database. AMF stands for ‘ActionScript Message Format,’ (see http://osflash.org/documentation/amf for a better description).  What it does is serialize Flash objects and send them along a network as a binary datastream, to be turned back into objects at the receiving end.  Compressing everything as a binary stream makes it a very efficient method for transport, and while AMF was originally a proprietary format (used by Flash and ColdFusion, another development platform which I don’t cover here), it has since been opened up and can be used in conjunction with ASP, PHP, and more.  So in other words, an object floating around in Flash can be squeezed into binary data, sent to a PHP script which receives it and translates it into an object in PHP and which can then be used within PHP.  The process works vice-versa too, of course.  Have a look at http://theflashblog.com/?p=414 for a good beginning explanation of AMF and more.

It is important to note that a Flash application has no knowledge of ‘who’ it is sending AMF information to or getting it from.  Objects are serialized with AMF0 or AMF3 encoding (AMF3 coincides with the release of ActionScript 3), then sent along to a receiving service of some sort.  Since I prefer usable platforms which are free and/or open source, I found AMFPHP and have had good luck with it.  AMFPHP creates native PHP objects out of the data (or tries to), and regular PHP scripts can then use those objects and do all the things that PHP does well, such as access databases and so-on.  AMFPHP can also send data back to Flash, which Flash receives and handles as an event, and can re-form the data into its own native objects as well.

An Environment Which Works for Me

I’ve already described most of the pieces necessary for the environment that I like using.  The main component which makes Flash programming rewarding is FlashDevelop. 

FlashDevelop

(FD) is an amazing free and open source IDE for writing ActionScript and Flex applications for Flash.  It will work alongside the Flash IDE for doing the programming behind the objects drawn in Flash and saved within a FLA file, or you can use it stand-alone as I do, and use fancier programming to create and position the objects within code.  FD works with .Net, and there is only a Windows version available.

Setting Up the Environment

So let’s get started actually putting all of the pieces together!

The Flash Player Itself

Well of course, in order to do anything with Flash, you need the player to play it….  I really only bring it up because Adobe actually offers a special debugger version of their player that could be quite useful.  I actually haven’t used it (FlashDevelop and a lot of trace statements have been enough so far), so I can’t say much about it, but I imagine if I spent some time on it, it would be invaluable for larger projects than what I need to do.  One minor point I should bring up, is that not all Flash movies out there are perfect…so with the debugger version you might get some annoying pop-up dialogs telling you in which way those movies are flawed, even if they don’t outright crash.

The download site is below.  Scroll down for debugger versions.  Choose carefully!  There are browser plug-in, standalone, and various other versions for different operating systems and browsers.  One nice thing is that you can have the stand-alone version running alongside the browser version, though.  It does no harm to install one on top of the other, except if I remember right it might complain when installing an old version on a new one.
http://www.adobe.com/support/flashplayer/downloads.html

Flex SDK

To compile anything with FD, you also need the Flex SDK:
Flex 3
Flex 4
You can check this ‘broken’ link in case a Flex 5 comes out before I edit this article…
http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex

At the time I’m writing this, Flex is up to version 4 as beta, so I would recommend the latest 3.4 release.  Flash player is at version 10 and may require Flex 4; check this out if you plan on programming for it.  Adobe’s download pages are confusing, if you search for Flex download, it seems you may pull up pages which link only to Adobe Flex, or the one I’ve linked to which also has the open source version, plus closed-source libraries to add into the open source version which gets it to the full closed source functionality…  It’s up to you what you want to do, but I suggest spending a few minutes poking around there to get a better understanding.  You can install the package upon download now, or wait until you have everything else you need, as is described next:

FlashDevelop

Download FD from the site:
http://www.flashdevelop.org/

Releases for download are listed in the Download forum thread.  When I first tried to get going, the installation was tricky for lack of understanding the different components.  Someone on the FD site was nice enough to post these directions for installing FD to me:

1. Make sure .NET is installed (it usually is)
2. Make sure Java is installed (it often is)
3. Download and extract the Flex SDK (latest milestone release is best)
4. Install the browser plugins from the Flex SDK’s runtimes directory
5. Run the external player (or associate if necessary) the external player in the runtime directory
6. Download and install FlashDevelop (I prefer the latest development version)
7. Configure the path to the Flex SDK and the external Flash player if necessary
8. Restart Windows (usually not necessary, but sometimes it helps)

In our case there is also:
9. Install and configure AMFPHP on a proper PHP server

AMFPHP

As described earlier, AMFPHP is a free, open source PHP service for handling AMF Remoting.  This enables the benefits of programming in both PHP and Actionscript using AutoComplete (code completion) in environments which support it, since you can work with the objects directly.  Binary serialization is also very fast, and AMF requires far less coding than previous methods of sending data to/from Flash (i.e., outdated methods such as wrapping data up into XML and sending that along, or using GET/POST methods with arrays).

Get AMFPHP here:
http://www.amfphp.org/

Setting it up AMFPHP is very easy (unzip it to the wwwroot directory and set permissions so it can be used); while using it may at first be a bit tricky.  Code you create for remoting will reside in the amfphp/services directory.  Base objects (as sent/received via AMF) belong in the amfphp/services/vo directory (VO stands for Value Object, and it seems the term has been replaced with ‘Data Transfer Object,’ or DTO)  VOs, reside under directories which match the package within Flash (PHP doesn’t natively support packages, but it can be emulated by PHP code).  Additionally, services can be tested to some degree using amfphp/gateway.php. 

At this time, do some searching to find sample remoting code to get yourself going on the coding end.  Eventually I may post a brief sample to illustrate using it.  This article may help:
http://www.joshuaostrom.com/2008/07/01/amfphp-class-mapping-primer-19-beta/

PHP Editing

For editing PHP files, I highly recommend PDT; PHP tools for Eclipse:
http://www.eclipse.org/pdt/

That’s a completely different tutorial and there are plenty of sites which can describe using it.  I like it because it is free and open source, and it works great for managing PHP projects, and it has excellent code completion for PHP.

Debugging

This guide wouldn’t be complete without mentioning debugging.  There are inherent challenges when doing something like Remoting, which make coding for it a bit precarious.  Finding the issues with a large amount of code or when new at the technique can be particularly difficult, and this is where a good debugging proxy can come in.  Specifically, Charles and ServiceCapture are two which can see remoting VOs and their data directly.  They essentially work by intercepting data sent down a network connection and displaying it in some human-readable format.

Charles was recommended by the AMFPHP website (if I remember correctly), and ServiceCapture was recommended directly to me, but there are others, some free and/or open source.  See, for example:
http://www.carehart.org/blog/client/index.cfm/2006/11/28/alternative_http_debugging_proxies

 

Conclusion

Hopefully this run-through is as useful to you as it would have been to me when starting up!  Good luck in your Flash Remoting endeavours.

Here are a few additional resources:

FlashDevelop help forums:
http://www.flashdevelop.org/community/

Another Getting Started article:
http://www.senocular.com/flash/tutorials/as3withmxmlc/

Flex code coloring schemes for FlashDevelop:
http://www.flashdevelop.org/community/viewtopic.php?f=10&t=2573
http://flashdevelop.org/community/viewtopic.php?t=2860

Posted in Article, Computers, How-To, Programming, Projects, Work. Tagged with , , , , , , , , .

By Ryan
August 29, 2009

No comments

Woodcarving

Woodcarving has been a hobby of mine since discovering that I could do it a number of years ago.  It is one of the rare things that came naturally to me; most of my other hobbies have taken years of work to get to any decent level of skill.  Most of my carvings end up as gifts for friends or family, although I am thinking more and more about making some to sell.

 Abstract
This is the first carving I made, and I titled it "Abstract."  It has a loose ball on the bottom corner, and a suspended ball in a cage, held by an arm of wood on the side.  I was very fortunate to find this piece of driftwood when I started, as it was very easy to carve and has a wonderful color and texture.  This piece is fragile, and has gotten dropped and so has a few parts which have been glued back together.

 On the Verge of Something
This one is titled "On the Verge of Something," because as I was carving it I kept feeling that it was going to become something else…yet it never quite got there.

Twist - Woodcarving
"Twist" is the title I gave to this piece.  There is a loose ball contained at the top.

Posted in Art, Projects.

By Ryan
February 14, 2009

No comments

Homebuilt laser!

Back to Ultracold Atomic Experiment

Of all the cool projects I’ve been involved in during my school career through my Physics career, I’ve got to say that getting to build a custom laser is the one I’m going to have the most fun talking about.  Not that it is the most interesting project ever…but come on, a home-built laser!  It should be a requirement for getting a Physics degree.

The laser light itself is supplied by a laser diode, this one is actually a commercial one used in DVD reader/recorder units.  The experiment requires the use of light locked to a 671nm wavelength, but this is not in the range of commonly available commercial lasers.  Laser diodes actually emit a range of frequencies around a central frequency, which can be shifted by heat and also stimulation of a particular frequency.  In fact by shining light at precisely the desired wavelength of light back onto the diode, this increases the diode’s emission at that one frequency, and can narrow the amount of light emitted at other frequencies.

The trick we will use in achieving a 671nm wavelength is to use a Littrow-mount feedback system.  Light from the laser is shined onto a diffraction grating, which reflects most of the light.  A small amount of light is reflected at precise angles based on its wavelength, (as is expected from the physics of diffraction gratings), and the grating’s first-order reflection is made to reflect back onto the laser diode.  By changing the orientation of the grating, a particular wavelength can be made to shine back onto the diode (again, this is explained by the basic science of diffraction gratings – like a shiny CD, wavelengths hitting a grating are reflected at angles proportional to their wavelength), and so select the desired wavelength to stimulate in the diode.

The zeroth-order reflection (essentially the mirror reflection off of the grating) is reflected from a mirror, then out parallel to the original beam path.  The grating and mirror are mounted as a unit on a swing-arm in front of the diode laser, so that rotation of the mirror/grating unit can be achieved by a piezo-electric unit.  This allows the first-order reflection to be locked onto the laser, while not (largely) affecting the attitude of the outgoing beam.

The parts I have made were all from plans which the professor in charge of the Ultracold Atoms Experiment obtained through a group he had worked with at Berkeley.  So producing the whole system was quite straight-forward and took about a week of actual work in total, once all the parts were together.

Bare laser mount

In the picture above, the diode mount is a modified lens mount with aluminum blocks attached to the front end (the laser emits to the left of the photo).  The aluminum block with an angled cut and Allen screws on top will hold the diffraction grating, and the aluminum bar it sits on holds the mirror, as seen below:

Laser, Grating, and Mirror

The laser diode itself is behind the bluish collimating lens, which can be adjusted by turning the threaded steel ring around it.  The black cylinder around this is a commercial diode mount, with a layer of "thermal goop" between it and a modified mounting unit, with more goop between it and the modified lens mount.  The thermal paste helps heat get to the laser diode efficiently.

Down the front of the laser

Laser and Base

The unit as seen above sandwiches a thermoelectric cooler (TEC, also known as a Peltier device), which acts as a "heat pump" when current is applied to it, by moving heat from one side of its body to the other (the red and black wires attach to it).  This is all attached to a massive (about 7-8 lbs.) brass block, and its mass and a rubber sheet below it help to dampen vibrations which might make their way through the optics table.  Everything sits inside a housing box, which is lined with Acoustiblock material to keep out sound vibrations traveling over the table.

Back to Ultracold Atomic Experiment

Posted in Experiment, Physics, Projects, Work.

By Ryan
January 26, 2009

1 comment

Ultracold Atomic Experiments

I have been working for some time with an Ultracold Atomic Experiment group at the University of Washington.  This has been one of my more enjoyable jobs, and has kept me busy machining parts, soldering together circuits, building lasers, taking pictures, and all sorts of other fun things.  The entire series of chambers is pulled to a very pristine vacuum – around 1E-10 torr or better.   Achieving such a good vacuum is a very involved and interesting process.  One of the steps is to heat the chamber walls to release embedded atoms so they can be pumped out; Below is a picture of the chamber wrapped in band heaters and other heating elements, which are each supplied power by one of the many variacs seen floating around the chamber.

Variacs!

The experiment will be trapping Lithium (Li) and Ytterbium (Yb) atoms, which get boiled off from separate ovens, slowed through Zeeman slowers, and combined into the central Magneto-Optical Trap, where they are further cooled by evaporative cooling until finally cold enough to settle into the lowest energy quantum state as a Bose-Einstein Condensate (BEC).  The projects I am or have been involved with include:

  • Create or Update Documentation for most projects
  • Data Acquisition Software and Hardware
    • Working with National Instruments Hardware and Software (interfaces with break-out boxes listed below)
    • Interfacing with Atticus/Cicero control software developed by a group at MIT
    • Digital Camera
      • Research and set-up of camera
      • Programming of User Interface
  • Construction of Electronics and Other Hardware
    • Diode Laser Lock Boxes
    • Lithium and Ytterbium Oven Control Units (Torture Units Li and Yb…)
    • 12 and 40 amp MOSFET switch boxes (BFW Housing Boxes)
    • Analog and Digital Isolation Break-Out Boxes
    • Enhancement Cavity Mode Lock Box
    • RF Driver boxes
    • 671nm Littrow-configuration laser
  • Create website for group
  • Take Photographs of experiment and lab
  • General Tasks
    • Troubleshoot/testing of various lab hardware and circuits
    • Organizing and maintaining electronics and other areas of lab (Research and purchase electronics parts)
    • Creating and now maintaining shared computer file system, software, and datasheets
  • Unicycle to Electronics Shop and back

Posted in Experiment, Physics, Projects, Work.

By Ryan
January 8, 2009

No comments

Company List for Motion Control Parts

 Back to Motion Control home

A short list of companies from which to purchase parts for motion control.

Digi-Key:
www.digikey.com
A very large assortment of electronics.  Their site, however, is entirely text-based–so if you know what your part looks like but don’t know what it’s called, this is a tough place to find it!  They do have links to pages of their catalog in PDF format–a really inefficient way to search for parts…

Jameco:
www.jameco.com
Nice selection of parts, and a nice-looking Internet store.  Good search engine, nice product pics, and low prices.  The site was very slow at one time.  WATCH OUT–items are priced by the part, but Jameco sometimes doesn’t sell individuals–it’ll say ’sold in quantities of XX’.

Alltronics:
www.alltronics.com
Specializes in purchasing and reselling surplus electronics and gadgets. Their prices are very low, and while they have a decent picture and description for pretty much everything they sell, I can’t say their site is altogether easy on the eye. What’s nice though is that basically the entire site-map is in the index on the left side of their site, which is also searchable.  They tend to have lot of unique items that come and go.  The best part about Alltronics is how they charge for shipping–they actually weigh your order and then charge only the exact amount.  $15-order minimum.

Newark:
www.newark.com
Very nice-looking site.  No actual pictures of items, but many items have (extremely small) illustrations or documentation in PDF format.

Radio Shack:
www.radioshack.com
Highly overpriced, and their stock in most electronic components is dwindling (at least in my area).  Buy here only if you need a local place to go, if you need low quantities of a (common) part right away, or if you need something at some odd day of the week.

Allegro:

The manufacturer of the UCN 5804 chips.


Groups:

FIRST
Seattle Robotics Society


Misc:

eBay:

Search under "step* motor." Smaller steppers (Nema 17 and 23–the 5804 can’t handle larger) should be available for <$5.

 

 

Posted in Article, How-To, Projects. Tagged with , , .

By Ryan
January 6, 2009

1 comment

Parts list for beginning motion control

 Back to Motion Control home.

This list was compiled quite a few years ago in conjunction with and for Bruce Shapiro and his course, ‘From Bits, to Bytes…to Bots‘.

It is intended to aid in finding all of the right parts quickly and cheaply, through each phase of learning control via a computer parallel port.

How much will you spend? Depending on how good you are at scrounging, plan on at least $30, though if you’re stocking up on decent motors it may be closer to $80!

The_Parallel_Cable
LEDs
Resistors
The Chips

The Motors
MISC

Who are we ‘promoting’?
A list of companies listed here, and a few organizations.

The Parallel Cable:
www.digikey.com
www.jameco.com
Needed to interface the circuit to the printer port. Unfortunately, no ready-made male 25-pin to 26-pin socket exists (that I know of). You may be able to order them custom-made, or make them yourself using parts
from Digikey or Jameco:

PARTS: JAMECO $ DIGIKEY $
 
25 pin IDC D-sub male connector 12335 1.89 ? ?
26 pin IDC socket connector 138333 0.42 ? ?
25 conductor flat cable 105697 6.29  (10 Ft) ? ?

Bruce says:
"The press-fit connectors are easy to use, but take some practice. Make sure you check the alignment BEFORE pressing the two halves slowly in a vice."

top

LEDs:
www.alltronics.com
Individual LEDs are probably the easiest to find part. These are cheap and usually run at 1.5, 3, or 5 volts. Too much voltage can pop them, so careful!

The bar graph LED is a little more difficult to find.  I got one for just over $3 at Radio Shack (the only part they had that I needed…)  I know Alltronics sells them, but am not sure the catalog number…

PARTS: ALLTRONICS $ DIGIKEY $
 
10-digit Bar Graph LED ? ? ? ?

top


Resistors:
www.jameco.com
www.digikey.com
Resistors are actually easier to come across than LEDs, but finding the right one is sometimes a task.  In order to protect the parallel port while plugging wires into it, we suggest using a very high resistor value–up to 1K.

Bruce writes:
"…the resistor value I use is 1K.  This limits the current through the LED’s to <5ma, which can be kind of dim– but I wanted to make sure that I wasn’t straining the output capabilities of the port.  So far, I’ve used many tens of laptops, and have never had a problem with a parallel port.

The SIP resistor network is carried by Digikey and Jameco  — Jameco #97877.  Just remember to place it with the common lead connected in the right spot (grounded)."

If you are not sure how to read resistor color bands, there is a little tutorial here.

Single Resistors
Any place that sells electronics components will have

SIP (Single In-line Resistors

PARTS: JAMECO $ DIGIKEY $
 
SIP resistor network 97877 2.60 (10) ? ?

top

The Chip(s):
www.alltronics.com
www.newark.com

PARTS: Alltronics $ Newark $
 
UCN5804B 93I002 4.50 09F1557 4.50

top

The Motors:

www.alltronics.com
www.newark.com
www.ebay.com

NOTE:
Currently Alltronic’s site has the amperage for their 6-wire unipolar stepper (22M010) wrong. It claims 0.35 V, but the motor actually requires 1.35 V.

Bruce writes:
"The power supply needs to give 5V for the 5805 chip, and the voltage of your stepper (12V in my case). You can use a single 12V supply, and then use a 5V regulator (7805, or 78L05) to get the 5V. The 5804 chip can handle up to ~35V (check this) and ~1.2 amps / phase). Your motor will have to stay within these bounds. Unipolar means that electricity flows through the motor’s windings in only one direction. 5, 6, and 8 lead motors will allow this configuration. Check out one of the many stepper motor tutorials on the net to understand this. Bipolar drives result in more power, but require more electronic sophistication. I have not found a single chip like the 5804 that will take step and direction signals and output directly to a bipolar (4-wire) motor.

"One source for a stepper to use can be found in old floppy drives. The key features are: 5,6,or 8 wires; rated voltage <35, and rated amperage <1.2. Jameco lists a few, but the ones they have that are <$10 are ‘coarse’ — meaning they have a step angle of 7.5 degrees. These will work– but I like really smooth motion (look for 200 steps/rev or 1.8 degrees).

You may have to scrounge for the ‘perfect’ one of these!"

top

MISC:
Still looking for resources regarding power supplies, and a way to connect one to a breadboard.

top

Good luck in your motion control endeavors!

 

Posted in How-To, Projects. Tagged with , , .

By Ryan
January 6, 2009

No comments

Getting Started With Motion Control

Motion Control

Companies

Parts

Outer Links:

http://www.taomc.com/

http://www.taomc.com/bits2bots/

Posted in Article, Projects. Tagged with , .

By Ryan
January 6, 2009

2 comments

Michelson Interferometer – Part 2

This is the portion of my physics group project report that I wrote.

Interferometer Page 1

Measuring Static Frictional Forces using Interferometry

Interferometer Setup
Fig. 1:  Interferometer Setup and Labels
Fringes from Michelson Interferometer
Fig. 2:  Interferometer Fringes

Introduction

It is often not understood that even when dealing with static friction, application of less-than-critical sheering forces (that is, forces which do not cause breaking of static friction) creates an actual displacement between an object and the surface it rests on. The amount of movement is typically very small and barely if at all visible (displacement can be large enough to be seen when, for example, the surface is a rubber mat). When the sheering force is let off, static friction becomes a restoring force, returning the objects to its original position respective to the surface. This restoring force can be thought of as spring tension, and in this thinking ought to be proportional to object displacement.

This experiment sought to verify the linear F = k x relationship of static frictional forces between various materials at less-than-critical sheering forces. Very precise measurements of displacement were measured using a Michelson-type interferometer. The results showed a definite linear relationship between applied force and displacement of the test object for Styrofoam and particleboard surfaces.

Procedure

The first goal achieved was forming the ‘fringing’ patterns with the interferometer. The basic setup follows the Michelson interferometer design.

As shown in Fig. 1 , the beam emitted by the Laser (while a laser pointer is shown, a HeNe laser was used for actual collection of data) passed through one or two Lenses . The Lenses simply made the laser beam diverge and created a larger beam for viewing. The beam then hit the Beam Splitter , separating into two partial beams. Each partial beam bounced from a mirror back onto the beam splitter so that they overlapped and projected as a spot of light on a viewing surface (in the direction of the sheet of paper in Fig. 1). The Reference Mirror held a fixed position and created a reference beam. The Test Mirror was attached to a movable Test Block , and the surface under the block could be changed.

More difficult was developing the apparatus to precisely add and measure sheer force to the Test Mirror. The resulting design is shown in Fig. 3 (NOTE–Figure 3 isn’t here yet). The end of a Fishing Line was attached to a hook on back of the Test Block . The Line passed through the two Static Pulleys and terminated at the Force Probe . The Moveable Pulley could then be pushed into the Fishing Line, causing a Tension felt equally by both the Force Probe and Test Block. It should be noted that the Test Block and Force Probe were adjusted carefully so that they were directly aligned with the Fishing Line. In this way, the Pulley system ensured that only the desired vector component of force was applied to the Probe and Block.  When everything was secured properly, this system worked remarkably well and tension could be applied and held fairly precisely by hand.

A computer captured data directly from the calibrated Force Probe. To take a data run, the apparatus was first adjusted so little or no force acted on the Test Mirror and Force Probe. The state (bright or dark) of the central dot (see Fig. 2) was noted, the force was captured and 0 was entered as the fringe number. The Moveable Pulley was then pushed into the Fishing Line until the central dot grew into a ring with its alternate state in the center. The force was again captured and entered as fringe # 1. For example, in Figure 2, the initial central dot is red. If tension were applied to the Test Block, it would grow into a ring with a dark spot in its center. The dark spot becomes the new central dot, and was counted as one fringe when it became the same size as the original bright spot.

This process was repeated for multiple surfaces, and for most runs it was verified that as tension was let off the same number of fringes disappeared as had previously appeared. For the final run of a surface, the attempt was made to capture data until holding the Moveable Pulley became too difficult or the static friction bonds were broken and the Test Mirror slid out of position.

Interferometer Page 1

 

Posted in Article, Experiment, How-To, Physics, Projects, Work. Tagged with , .

By Ryan
January 6, 2009

2 comments

Projects

Projects page

Posted in Projects.

By Ryan
January 1, 2009

Comments Off

Michelson Interferometer Part 1

This article describes the physics project I was involved in.

Interferometer page 2

Interferometry: Measuring Displacement on a Molecular Level

Our project is to very precisely measure static frictional forces between various materials. The high precision comes in using a Michelson-type interferometer.

Interferometer Setup
Fig. 1:  Interferometer Setup and Labels
Fringes from Michelson Interferometer
Fig. 2:  Interferometer Fringes

An interferometer overlaps two beams of same-frequency laser light. This creates an interference pattern due to the wave nature of light (Fig. 2). A laser pointer is shown above (Fig. 1), which is replaced by a Helium-Neon laser for the actual experiment, in order to gain more significant digits for the wavelength. As shown, the beam is first passed through two lenses. The only purpose for this is to make the laser beam diverge and ultimately create a larger beam for viewing. After the lenses, the beam is split into two partial beams using a half-silvered mirror (a beam splitter). Each partial beam is bounced from a mirror back onto the beam splitter so that they overlap and project as a spot of light on a viewing surface (in the direction of the sheet of paper in Fig. 1). One mirror holds a fixed position and creates a reference beam. The other test mirror is attached to a movable block. The surface under the block can be changed, and a measured force can be applied to it. Static frictional forces act to hold the block in place, but not without allowing some movement. When the force is let off, the block returns to its original position as if held in place by springs.

The interference pattern formed has the appearance of tree rings, with alternately bright and dark circles. What we are interested in is the central ‘dot’ which may be initially bright or dark. When the test mirror is shifted forwards or backwards, the central dot will grow or shrink. Assuming the central dot was initially bright, as it grows it will turn into a ring and a dark dot will appear at its center. As this dark spot grows, it also turns into a ring with a bright spot at its center, this pattern alternating. As the test mirror is shifted back to its original position, the rings will converge into alternately colored central dots. The appearance of each alternate-color dot corresponds to the test mirror having shifted its position by a quarter-wavelength of light – that is, 1/4 of 632.8 nanometers for the Helium-Neon laser ultimately used. This is roughly just over 1,100 times the diameter of a carbon atom!

Interferometer page 2

 

Posted in Article, Physics, Projects. Tagged with , , .

By Ryan
January 1, 2009

2 comments