Palace119 Power Tools

Airbrush Kit

Airbrush Makeup - A Natural New Look

What is the secret behind the flawless, seamless, makeup look of celebrities? Its not that they all have great skin and just shine naturally, but it is also not something that is out of reach of everyday folks either. If you asked them, they (may or may not) tell you that their makeup artist has an airbrush makeup machine. The time when this technology is only available exclusively with makeup artists and celebrities is over. These days with a home edition of airbrush makeup machine you can have a professionally done look in a jiffy, daily without the help of a makeup professional.

Do you dream of becoming the women and men that are on magazines covers? Have you ever pondered how certain women can look so beautiful at every second of the day? It isn't because that is how they naturally look. No, the celebrities get help. One of the biggest reasons that movie stars appear the way they do, is because they get airbrushed. But the good news is, the airbrush is no longer just the tool of the stars, it can be used from our home.

I was completely sick and tired of home remedies like applying toothpaste or papaya juice on my skin for my ever-increasing acne problem. My skin seemed like it would never be clear and nothing seemed to work on it. I even tried taking all the precautionary measures - believe me, not being able to have chocolate is like torture for a chocoholic like me. And the worst part is, it didn't really help.

Catherine Zeta Jones wears it. So does Jennifer Lopez. Why? Airbrush makeup creates a flawless face - almost as if you took your picture and ran it through Photoshop.

Here's how it works. A tiny amount of specialized foundation makeup is mixed with a few drops of water, and then sprayed onto the face with a wand. The result is a sheer, yet full coverage. You end up wearing less foundation, but with a flawless finish. It even hides under eye circles and rosacea.

This make-up is specifically designed to cover them up or hide their appearance on your skin, and it is important to purchase a formulation which correctly matches your complexion. If you get the wrong product your skin will have a discolored appearance when you apply it, and this will look quite strange and unnatural and actually draw the eye more to your scars than if you weren't using them at all. Additionally, you will also want to purchase a foundation which is water proof. This way, if water should come in contact with your skin, it won't be removed or run.

There are special foundations especially designed for airbrush application. Foundations, blush and eyes shadow can all be used when applying make up using the airbrush method. Traditionally, the makeup sponge and brush sufficed for applications of makeup. With newer, smaller and portable kits, airbrush cosmetics are slowly taking over from regular makeup for personal use at home.

A silent revolution is brewing in the world of makeup. Up until now not many people knew about this, and those who did know were mostly celebrities who show up with a flawless, camera-ready complexion. Everyone can use this revolutionary air brush make up now, not just celebrities.

The secret behind a flawless, seamless makeup coverage of a celebrity is air brush make up. Its similar to Photoshop except that it comes in a bottle. While this cutting edge makeup is great to wear when you attend the Oscars, It is light enough to be worn daily and long lasting.

With your big day fast approaching, here are some great wedding make up tips to ensure your make up stays as beautiful as the reason you're celebrating. One of the best wedding make up tips out there is to decide which look you want before the big day. Then, you can practice putting on your make up a couple times beforehand. With a few trial runs, you'll know exactly how to get the look your want and won't have to deal with everything the day of.

A similar situation arose when we were given a whole bunch of airbrush makeup machines as samples. She wanted to surprise her daughter with a gift of one, but wanted the absolute best, so she made me do the testing. It was actually really fun, and I got a few of the girls over for a weekend of makeup trials. Here's what happened.

The airbrush foundation wins hands down in the best foundation for shiny skin contest due to its quick drying, matte finish, and zero cacking properties which no conventional makeup can boast about. You also get the added advantage of hygienic application as only air and makeup touch your skin without redistributing the oil on your face, while the problem areas are covered and concealed to bring out a flawless and shine-free look.Some airbrush sets come with a finishing powder as well, to ensure that trouble spots stay shine free all day.

About the Author

Read about Skin Care Tips and also read about Fall Fashion Trends and Replica Purse

i am planing to buy a nail art airbrush kit. for $159 from ebay.?

i am planing to but a nail art airbrush kit. for $159 from ebay.
wanted to ask dose they rilly work...? and s it worth spendng this much for a nail kit.

http://cgi.ebay.com/NAIL-ART-PAINT-STENCIL-KIT-Airbrush-w-Compressor-System_W0QQitemZ190245190312QQcmdZViewItem?hash=item190245190312&_trkparms=72%3A552%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

I do custom paint, and use an airbrush everyday. I buy a lot of stuff from this company. Just not through ebay. Here's a link to their real website. http://www.airbrush-depot.com/ I don't know how familiar you are with airbrushes, but Iwata are the best around. These Master airbrushes are basically Iwata knockoffs. There are a bunch of companies selling these under different names. Airbrush Depot are the only ones that offer replacement parts at a reasonable price. I own a couple of these and they're actually nice guns. Especially for the price. If you were to buy the same model Iwata, It would cost you $180 for the airbrush alone. I love my Iwata's, but these guns are a close second.

As far as the rest of the kit goes. I think it's a good deal. You'll have everything you need to get you started. I can't use those little compressors for the kind of work that I do, but I think it will be just fine for nail art. Here are a few links to get you started with your new airbrush.

http://www.howtoairbrush.com/ Lots of good lessons, and how to articles.

http://www.airbrushtech.net/ Great forum. Just sign up and start asking questions. A bunch of talented and friendly people here, that are always willing to help.

http://smartflix.com/store Instructional video rental. I'd suggest renting one of their beginner airbrush video's. You'll need to learn proper care and maintenance. If your airbrush isn't working right, neither are you.

If you have any other airbrush questions, don't hesitate to email me. I'm always glad to help. Good luck, and welcome to the wonderful world of airbrush.

Quick Change Airbrush Kit & Compressor

Chrome Vanadium

Chrome-Vanadium

Scanner Auto

Buy Scanner

There was a time when for every important document, book, articles or anything written or printed, we used to keep photo copies, but those were not long lasting and safe or in other words we can say that, keeping them at a safer place & taking care of them on the regular intervals seem pretty complicated, and as the time goes these copies loose their shine as well, then people really moved towards scanners.

Scanner is again an electronic auto functioning device that converts any printed or hand written document, images into digital file format by scanning them, which is now has become very popular because of its never lasting attitude, as in digital format you can keep a document in your computer's hard disc, any compact CD or DVD that is much safer way today, and when you need these documents to be printed, you don't need to carry original documents every time with you wherever you go, just keep them in any storage capacity device like pen drive, portable hard disc, compact disc or even mobiles now.

Today, You can see scanners are used their at every house, offices, malls, shopping centers and almost everywhere and for every purpose there are particular scanners have been invented, but the question is, how these scanners scan any object, it is done with the help of fixed sensor, there are two kind of sensors are used in scanners; Change-Coupled Device sensor (CCD) or Contact Image Sensor (CIS).

As it is been earlier stated that now for every purpose there is some special kind of scanner, the most used scanners are Flatbed Scanners, Sheetfed Scaners, Handled Scanners, Photo Scanners & Portable Scanners.

Flatbed scanners are bigger in size that will acquire your desktop space which is made of glass platen beneath a bright light supported by CIS or CSD sensor which helps out in scanning an object, with this kind of scanners you can scan anything including books, newspaper articles, photographs in standard or legal size page, you just need to put image on glass pane and scanner will scan the image clearly with the flash of light.

Sheetfed scanners are the scanners on which you need to insert the sheet manually in spite of putting it on some surface, it is smaller in size than flatbed scanners, it scans an object horizontally or vertically as this kind of slots are given only, but it can only scan a single page document not any book or any thicker object.

Handheld scanners are used more often at shopping centers to scan the price value of a product by dragging it above, but you need to make it stable to scan clearly otherwise it may distort the object image.

Photo Scanners are useful for them who are probably into the photography profession or the one who love doing it, this kind of scanners are higher price than any other type of scanners, but the clarity is just adorable, it has got a great resolution, it can also make your old pictures into fresh ones with the help of given software.

Portable scanners are the most compact scanners which are easy carrying, even there are few portable scanners a bit longer in shape than a cigarette lighter, so you can keep it in the pocket as well, but they are not high resistive and cannot scan whole the object at once, it scans text documents line by line, so consumes more time.

 

About the Author

Monty Alexander is a well known author and has written articles on ,Digital Camera , Hero honda Super Splender, Gifts store, Camera Batteries, Hero Honda Hunk, online shop and many other subjects.

how would you delete an avg email scanner banner from appearing on screen?

every now and again a banner pops up on screen saying avg e-mail scanner auto pop3:connecting to pop3.tiscali.co.uk.
it doesnt seem to be doing any harm but it can be annoying as it keeps coming and going.been in avg control centre and removed the email scanner but warning keeps popping up. have also uninstalled then installed avg but its still there. any ideas?

Use another anti virus - To limit the amount of times it pops up change the time your computer checks your mail

Full Auto Book Scanner - Featured on Hacked Gadgets

Ext Lot

Colon Cleanse Ultra Review - Colon Cleansing Free Trial

Colon cleansing is a big help in keeping us healthy and strong. It has helped us get rid of toxins as well as wastes that have accumulated in our body. There are a lot of colon cleansers that have emerged in our market today. Some may be effective some may not. Remember that not all colon cleansers are designed to fill in the specific needs of each individual. The important thing is that the colon cleanser will best work for you and safe for your body. Colon Cleanse Ultra is one of those colon cleansers that you can trust and you are assured that it is safe to use.

Click Here For Colon Cleanse Ultra Limited Free Trial!

If you think that all colon cleansers are one and the same, you are mistaken. Colon Cleanse Ultra does not only helps you get rid of toxins and lose weight but it also energizes you unlike other products that give you a drowsy and tired feeling.

It is composed of ingredients that help your body breakdown all that wastes and protects your colon against harmful substances that can lead to cancers which eventually causes death. It keeps the body healthy and strong. Giving you that clean feeling inside and out as well as leaving a felling of lightness.

Flatten that bulging stomach and have your way to that body hugging and fit figure you have been dreaming of all this time. Do not wait for the time wherein it will be hard for you to slim down. Obesity has been a big problem emotionally and physically. Do not wait for the time that fat will consume you before thinking of slimming down and cleaning your body system.

Think it over. If you want to live long, clean your body now, lose weight and be energized. Try the product Colon Cleanse Ultra now. They have a free trial which you can try out. Live happy, healthy and strong. Cleanse your colon now and live that healthy life.

Click Here For Colon Cleanse Ultra Limited Free Trial!

About the Author

This author writes about Colon Cleanse Ultra Review and Colon Cleansing Free Trial.

I own a 2005 Chevy Colorado ext. cab with 67k mi. Should I trade it for a 2002 Honda CR-V AWD with 140k mi?

I own (out-right) a 2005 Chevy Colorado ext. cab Z71 with 67k mi. Should I trade it for a 2002 Honda CR-V AWD with 140k mi (one-owner)? I've owned a CR-V before and really like them. I have a bad habbit of trading cars a lot though. I'd like to find the perfect all-arounder to keep for some time. My truck is worth about $7k and for that money I am having trouble finding a good CR-V without a ton of miles or very old. I'd like to be able to put stuff inside the vehicle and also carry more than 2 people. The truck has been handy, but shouldn't be needing it much more...the wife owns a truck too.

Absolutely not. You have at least 100,000 good miles left on the Chevy but only 60,000 miles tops left on the Honda.

Updated Google Translate Firefox Ext. 25 languages alt fixed

Self Adjusting

Back Pain Relief: How To Self Adjust Your Collarbone Example

Torque Angle

Dynamic Analysis of Stepper Motor Mechanism

A force of one pound will accelerate a mass of one slug at one foot per second squared. The same relationship holds between the force, mass, time and distance units of the other measurement systems. Most people prefer to measure angles in degrees, and the common engineering practice of specifying mass in pounds or force in kilograms will not yield correct results in the formulas given here! Care must be taken to convert such irregular units to one of the standard systems outlined above before applying the formulas given here!

 

Statics

For a motor that turns S radians per step, the plot of torque versus angular position for the rotor relative to some initial equilibrium position will generally approximate a sinusoid. The actual shape of the curve depends on the pole geometry of both rotor and stator, and neither this curve nor the geometry information is given in the motor data sheets I've seen! For permanent magnet and hybrid motors, the actual curve usually looks sinusoidal, but looks can be misleading. For variable reluctance motors, the curve rarely even looks sinusoidal; trapezoidal and even assymetrical sawtooth curves are not uncommon.

 

For a three-winding variable reluctance or permanent magnet motors with S radians per step, the period of the torque versus position curve will be 3S; for a 5-phase permanent magnet motor, the period will be 5S. For a two-winding permanent magnet or hybrid motor, the most common type, the period will be 4S, as illustrated in Figure 2.1:

 

Figure 2.1

Again, for an ideal 2 winding permanent magnet motor, this can be mathematically expressed as:

T = -h sin( ((/2) / S)  )

Where:

T -- torque

h -- holding torque

S -- step angle, in radians

 = shaft angle, in radians

But remember, subtle departures from the ideal sinusoid described here are very common.

The single-winding holding torque of a stepping motor is the peak value of the torque versus position curve when the maximum allowed current is flowing through one motor winding. If you attempt to apply a torque greater than this to the motor rotor while maintaining power to one winding, it will rotate freely.

 

It is sometimes useful to distinguish between the electrical shaft angle and the mechanical shaft angle. In the mechanical frame of reference, 2 radians is defined as one full revolution. In the electrical frame of reference, a revolution is defined as one period of the torque versus shaft angle curve. Throughout this tutorial,  refers to the mechanical shaft angle, and ((/2)/S) gives the electrical angle for a motor with 4 steps per cycle of the torque curve.

 

Assuming that the torque versus angular position curve is a good approximation of a sinusoid, as long as the torque remains below the holding torque of the motor, the rotor will remain within 1/4 period of the equilibrium position. For a two-winding permanent magnet or hybrid motor, this means the rotor will remain within one step of the equilibrium position.

 

With no power to any of the motor windings, the torque does not always fall to zero! In variable reluctance stepping motors, residual magnetization in the magnetic circuits of the motor may lead to a small residual torque, and in permanent magnet and hybrid stepping motors, the combination of pole geometry and the permanently magnetized rotor may lead to significant torque with no applied power.

 

The residual torque in a permanent magnet or hybrid stepping motor is frequently referred to as the cogging torque or detent torque of the motor because a naive observer will frequently guess that there is a detent mechanism of some kind inside the motor. The most common motor designs yield a detent torque that varies sinusoidally with rotor angle, with an equilibrium position at every step and an amplitude of roughly 10% of the rated holding torque of the motor, but a quick survey of motors from one manufacturer (Phytron) shows values as high as 23% for one very small motor to a low of 2.6% for one mid-sized motor.

 

 

Half-Stepping and Micro stepping

 

So long as no part of the magnetic circuit saturates, powering two motor windings simultaneously will produce a torque versus position curve that is the sum of the torque versus position curves for the two motor windings taken in isolation. For a two-winding permanent magnet or hybrid motor, the two curves will be S radians out of phase, and if the currents in the two windings are equal, the peaks and valleys of the sum will be displaced S/2 radians from the peaks of the original curves, as shown in Figure 2.2:

 

Figure 2.2

This is the basis of half-stepping. The two-winding holding torque is the peak of the composite torque curve when two windings are carrying their maximum rated current. For common two-winding permanent magnet or hybrid stepping motors, the two-winding holding torque will be:

h2 = 20.5 h1

where:

h1 -- single-winding holding torque

h2 -- two-winding holding torque

 

This assumes that no part of the magnetic circuit is saturated and that the torque versus position curve for each winding is an ideal sinusoid.

 

Most permanent-magnet and variable-reluctance stepping motor data sheets quote the two-winding holding torque and not the single-winding figure; in part, this is because it is larger, and in part, it is because the most common full-step controllers always apply power to two windings at once.

 

If any part of the motor's magnetic circuits is saturated, the two torque curves will not add linearly. As a result, the composite torque will be less than the sum of the component torques and the equilibrium position of the composite may not be exactly S/2 radians from the equilibria of the original.

 

Microstepping allows even smaller steps by using different currents through the two motor windings, as shown in Figure 2.3:

 

Figure 2.3

For a two-winding variable reluctance or permanent magnet motor, assuming nonsaturating magnetic circuits, and assuming perfectly sinusoidal torque versus position curves for each motor winding, the following formula gives the key characteristics of the composite torque curve:

h = ( a2 + b2 )0.5

x = ( S / (/2) ) arctan( b / a )

Where:

a -- torque applied by winding with equilibrium at 0 radians.

b -- torque applied by winding with equilibrium at S radians.

h -- holding torque of composite.

x -- equilibrium position, in radians.

S -- step angle, in radians.

 

In the absence of saturation, the torques a and b are directly proportional to the currents through the corresponding windings. It is quite common to work with normalized currents and torques, so that the single-winding holding torque or the maximum current allowed in one motor winding is 1.0.

 

Friction and the Dead Zone

 

The torque versus position curve shown in Figure 2.1 does not take into account the torque the motor must exert to overcome friction! Note that frictional forces may be divided into two large categories, static or sliding friction, which requires a constant torque to overcome, regardless of velocity, and dynamic friction or viscous drag, which offers a resistance that varies with velocity. Here, we are concerned with the impact of static friction. Suppose the torque needed to overcome the static friction on the driven system is 1/2 the peak torque of the motor, as illustrated in Figure 2.4.

 

Figure 2.4

The dotted lines in Figure 2.4 show the torque needed to overcome friction; only that part of the torque curve outside the dotted lines is available to move the rotor. The curve showing the available torque as a function of shaft angle is the difference between these curves, as shown in Figure 2.5:

Figure 2.5

Note that the consequences of static friction are twofold. First, the total torque available to move the load is reduced, and second, there is a dead zone about each of the equilibria of the ideal motor. If the motor rotor is positioned anywhere within the dead zone for the current equilibrium position, the frictional torque will exceed the torque applied by the motor windings, and the rotor will not move. Assuming an ideal sinusoidal torque versus position curve in the absence of friction, the angular width of these dead zones will be:

d = 2 ( S / (/2) ) arcsin( f / h ) = ( S / (/4) ) arcsin( f / h )

where:

d -- width of dead zone, in radians

S -- step angle, in radians

f -- torque needed to overcome static friction

h -- holding torque

 

The important thing to note about the dead zone is that it limits the ultimate positioning accuracy! For the example, where the static friction is 1/2 the peak torque, a 90° per step motor will have dead-zones 60° wide! That means that successive steps may be as large as 150° and as small as 30°, depending on where in the dead zone the rotor stops after each step!

 

The presence of a dead zone has a significant impact on the utility of microstepping! If the dead zone is x° wide, then microstepping with a step size smaller than x° may not move the rotor at all. Thus, for systems intended to use high resolution microstepping, it is very important to minimize static friction.

 

Dynamics

Each time you step the motor, you electronically move the equilibrium position S radians. This moves the entire curve illustrated in Figure 2.1 a distance of S radians, as shown in Figure 2.6:

 

Figure 2.6

The first thing to note about the process of taking one step is that the maximum available torque is at a minimum when the rotor is halfway from one step to the next. This minimum determines the running torque, the maximum torque the motor can drive as it steps slowly forward. For common two-winding permanent magnet motors with ideal sinusoidal torque versus position curves and holding torque h, this will be h/(20.5). If the motor is stepped by powering two windings at a time, the running torque of an ideal two-winding permanent magnet motor will be the same as the single-winding holding torque.

It shoud be noted that at higher stepping speeds, the running torque is sometimes defined as the pull-out torque. That is, it is the maximum frictional torque the motor can overcome on a rotating load before the load is pulled out of step by the friction. Some motor data sheets define a second torque figure, the pull-in torque. This is the maximum frictional torque that the motor can overcome to accelerate a stopped load to synchronous speed. The pull-in torques documented on stepping motor data sheets are of questionable value because the pull-in torque depends on the moment of inertia of the load used when they were measured, and few motor data sheets document this!

 

In practice, there is always some friction, so after the equilibrium position moves one step, the rotor is likely to oscillate briefly about the new equilibrium position. The resulting trajectory may resemble the one shown in Figure 2.7:

 

 

 

 

Figure 2.7

 

Here, the trajectory of the equilibrium position is shown as a dotted line, while the solid curve shows the trajectory of the motor rotor.

 

Resonance

 

The resonant frequency of the motor rotor depends on the amplitude of the oscillation; but as the amplitude decreases, the resonant frequency rises to a well-defined small-amplitude frequency. This frequency depends on the step angle and on the ratio of the holding torque to the moment of inertia of the rotor. Either a higher torque or a lower moment will increase the frequency!

 

Formally, the small-amplitude resonance can be computed as follows: First, recall Newton's law for angular acceleration:

 

T = µ A

Where:

T -- torque applied to rotor

µ -- moment of inertia of rotor and load

A -- angular acceleration, in radians per second per second

We assume that, for small amplitudes, the torque on the rotor can be approximated as a linear function of the displacement from the equilibrium position. Therefore, Hooke's law applies:

T = -k 

where:

k -- the "spring constant" of the system, in torque units per radian

 -- angular position of rotor, in radians

We can equate the two formulas for the torque to get:

µ A = -k 

Note that acceleration is the second derivitive of position with respect to time:

A = d2/dt2

so we can rewrite this the above in differential equation form:

d2/dt2 = -(k/µ) 

To solve this, recall that, for:

f( t ) = a sin bt

The derivitives are:

df( t )/dt = ab cos bt

d2f( t )/dt2 = -ab2 sin bt = -b2 f(t)

Note that, throughout this discussion, we assumed that the rotor is resonating. Therefore, it has an equation of motion something like:

 = a sin (2 f t)

a = angular amplitude of resonance

f = resonant frequency

This is an admissable solution to the above differential equation if we agree that:

b = 2 f

b2 = k/µ

Solving for the resonant frequency f as a function of k and µ, we get:

f = ( k/µ )0.5 / 2

 

It is crucial to note that it is the moment of inertia of the rotor plus any coupled load that matters. The moment of the rotor, in isolation, is irrelevant! Some motor data sheets include information on resonance, but if any load is coupled to the rotor, the resonant frequency will change!

In practice, this oscillation can cause significant problems when the stepping rate is anywhere near a resonant frequency of the system; the result frequently appears as random and uncontrollable motion.

 

Resonance and the Ideal Motor

 

Up to this point, we have dealt only with the small-angle spring constant k for the system. This can be measured experimentally, but if the motor's torque versus position curve is sinusoidal, it is also a simple function of the motor's holding torque. Recall that:

 

T = -h sin( ((/2)/S)  )

The small angle spring constant k is the negative derivitive of T at the origin.

k = -dT / d = - (- h ((/2)/S) cos( 0 ) ) = (/2)(h / S)

Substituting this into the formula for frequency, we get:

f = ( (/2)(h / S) / µ )0.5 / 2 = ( h / ( 8 µ S ) )0.5

Given that the holding torque and resonant frequency of the system are easily measured, the easiest way to determine the moment of inertia of the moving parts in a system driven by a stepping motor is indirectly from the above relationship!

µ = h / ( 8 f2 S )

For practical purposes, it is usually not the torque or the moment of inertia that matters, but rather, the maximum sustainable acceleration that matters! Conveniently, this is a simple function of the resonant frequency! Starting with the Newton's law for angular acceleration:

A = T / µ

We can substitute the above formula for the moment of inertia as a function of resonant frequency, and then substitute the maximum sustainable running torque as a function of the holding torque to get:

A = ( h / ( 20.5 ) ) / ( h / ( 8 f2 S ) ) = 8 S f2 / (20.5)

Measuring acceleration in steps per second squared instead of in radians per second squared, this simplifies to:

Asteps = A / S = 8 f2 / (20.5)

Thus, for an ideal motor with a sinusoidal torque versus rotor position function, the maximum acceleration in steps per second squared is a trivial function of the resonant frequency of the motor and rigidly coupled load!

For a two-winding permanent-magnet or variable-reluctance motor, with an ideal sinusoidal torque-versus-position characteristic, the two-winding holding torque is a simple function of the single-winding holding torque:

 

h2 = 20.5 h1

Where:

h1 -- single-winding holding torque

h2 -- two-winding holding torque

Substituting this into the formula for resonant frequency, we can find the ratios of the resonant frequencies in these two operating modes:

f1 = ( h1 / ... )0.5

f2 = ( h2 / ... )0.5 = ( 20.5 h1 / ... )0.5 = 20.25 ( h1 / ... )0.5 = 20.25 f1 = 1.189... f1

This relationship only holds if the torque provided by the motor does not vary appreciably as the stepping rate varies between these two frequencies.

In general, as will be discussed later, the available torque will tend to remain relatively constant up until some cutoff stepping rate, and then it will fall. Therefore, this relationship only holds if the resonant frequencies are below this cutoff stepping rate. At stepping rates above the cutoff rate, the two frequencies will be closer to each other!

 

 

Living with Resonance

 

If a rigidly mounted stepping motor is rigidly coupled to a frictionless load and then stepped at a frequency near the resonant frequency, energy will be pumped into the resonant system, and the result of this is that the motor will literally lose control. There are three basic ways to deal with this problem:

 

Controlling resonance in the mechanism

 

Use of elastomeric motor mounts or elastomeric couplings between motor and load can drain energy out of the resonant system, preventing energy from accumulating to the extent that it allows the motor rotor to escape from control. Or, viscous damping can be used. Here, the damping will not only draw energy out of the resonant modes of the system, but it will also subtract from the total torque available at higher speeds. Magnetic eddy current damping is equivalent to viscous damping for our purposes.

 

Figure 2.8 illustrates the use of elastomeric couplings and viscous damping in two typical stepping motor applications, one using a lead screw to drive a load, and the other using a tendon drive:

 

Figure 2.8

In Figure 2.8, elastomeric moter mounts are shown at a and elastomeric couplings between the motor and load are shown at b and c. The end bearing for the lead screw or tendon, at d, offers an opportunity for viscous damping, as do the ways on which the load slides, at e. Even the friction found in sealed ball bearings or Teflon on steel ways can provide enough damping to prevent resonance problems.

 

Controlling resonance in the low-level drive circuitry

 

A resonating motor rotor will induce an alternating current voltage in the motor windings. If some motor winding is not currently being driven, shorting this winding will impose a drag on the motor rotor that is exactly equivalent to using a magnetic eddy current damper.

 

If some motor winding is currently being driven, the AC voltage induced by the resonance will tend to modulate the current through the winding. Clamping the motor current with an external inductor will counteract the resonance. Schemes based on this idea are incorporated into some of the drive circuits illustrated in later sections of this tutorial.

 

Controlling resonance in the high-level control system

 

The high level control system can avoid driving the motor at known resonant frequencies, accelerating and decelerating through these frequencies and never attempting sustained rotation at these speeds.

 

Recall that the resonant frequency of a motor in half-stepped mode will vary by up to 20% from one half-step to the next. As a result, half-stepping pumps energy into the resonant system less efficiently than full stepping. Furthermore, when operating near these resonant frequencies, the motor control system may preferentially use only the two-winding half steps when operating near the single-winding resonant frequency, and only the single-winding half steps when operating near the two-winding resonant frequency. Figure 2.9 illustrates this:

 

Figure 2.9

 

The darkened curve in Figure 2.9 shows the operating torque achieved by a simple control scheme that delivers useful torque over a wide range of speeds despite the fact that the available torque drops to zero at each resonance in the system. This solution is particularly effective if the resonant frequencies are sharply defined and well separated. This will be the case in minimally damped systems operating well below the cutoff speed defined in the next section.

 

Torque versus Speed

 

An important consideration in designing high-speed stepping motor controllers is the effect of the inductance of the motor windings. As with the torque versus angular position information, this is frequently poorly documented in motor data sheets, and indeed, for variable reluctance stepping motors, it is not a constant! The inductance of the motor winding determines the rise and fall time of the current through the windings. While we might hope for a square-wave plot of current versus time, the inductance forces an exponential, as illustrated in Figure 2.10:

 

Figure 2.10

               

The details of the current-versus-time function through each winding depend as much on the drive circuitry as they do on the motor itself! It is quite common for the time constants of these exponentials to differ. The rise time is determined by the drive voltage and drive circuitry, while the fall time depends on the circuitry used to dissipate the stored energy in the motor winding.

At low stepping rates, the rise and fall times of the current through the motor windings has little effect on the motor's performance, but at higher speeds, the effect of the inductance of the motor windings is to reduce the available torque, as shown in Figure 2.11:

 

Figure 2.11

The motor's maximum speed is defined as the speed at which the available torque falls to zero. Measuring maximum speed can be difficult when there are resonance problems, because these cause the torque to drop to zero prematurely. The cutoff speed is the speed above which the torque begins to fall. When the motor is operating below its cutoff speed, the rise and fall times of the current through the motor windings occupy an insignificant fraction of each step, while at the cutoff speed, the step duration is comparable to the sum of the rise and fall times. Note that a sharp cutoff is rare, and therefore, statements of a motor's cutoff speed are, of necessity, approximate.

The details of the torque versus speed relationship depend on the details of the rise and fall times in the motor windings, and these depend on the motor control system as well as the motor. Therefore, the cutoff speed and maximum speed for any particular motor depend, in part, on the control system! The torque versus speed curves published in motor data sheets occasionally come with documentation of the motor controller used to obtain that curve, but this is far from universal practice!

 

Similarly, the resonant speed depends on the moment of inertia of the entire rotating system, not just the motor rotor, and the extent to which the torque drops at resonance depends on the presence of mechanical damping and on the nature of the control system. Some published torque versus speed curves show very clear resonances without documenting the moment of inertia of the hardware that may have been attached to the motor shaft in order to make torque measurements.

 

The torque versus speed curve shown in Figure 2.11 is typical of the simplest of control systems. More complex control systems sometimes introduce electronic resonances that act to increase the available torque above the motor's low-speed torque. A common result of this is a peak in the available torque near the cutoff speed.

 

About the Author

Assistant professor in lord venkateswara engineering college.I am doing phd in sathyabama university, Tamil Nadu,India.

How does torque change as the motor shaft rotates on a DC Motor?

I need to know how torque changes throughout one full 360 degree rotation of the armature/shaft of a DC motor. (Torque vs. Angle Position)

To answer this you have to specify how many poles there are on the motor. The result on a 2 pole motor is much different from a 12 pole.

BMR Adjustable Torque Arm Pinion Angle How To

Air Caulking

Raleigh Air Conditioning-How To Get The Best Usage From Your System

It is summer time and the heat is on!  Not inside your home of course, but the warmer temperatures are going to be here for the next several months and you want to be prepared.  Your air conditioner is going to be running most of the time in order to cool your home and make it a bearable place to occupy through the season.

You want to keep the cool air inside and the warmer air outside.  Poor insulation can result in your cooled air escaping which causes your air conditioner to work harder and thus generates a higher energy bill.  The most common ways that air escapes is through windows, doors and the attic.  Of course making sure they are closed is a start; however, air can seep through any gaps surrounding your doors and windows as well as through the attic.

Proper insulation is important for getting the best results out of your air conditioner.  If there are ways in which cool air is leaving and the warm air is seeping inside, then your unit will be working overtime and may not produce the desired results, those of keeping your home cool. You can remedy this by implementing a few simple solutions.

Windows

With windows, air can escape from around the pane.  Some people choose to replace older windows with newer, energy efficient models that save them money on their energy bills both during the winter as well as the summer. If you're not going to replace those drafty windows you can find a much less expensive method of insulating them and preventing cool air from escaping.

Once you locate any air leaks in your windows, you can determine how you want to eliminate the problem.  You can re-caulk windows that have older caulking that is missing or broken, or you can replace old weather stripping. For decorative alternatives, you can hang curtains made of heavy fabric that will block the hot air from coming into the house.

Doors

Providing insulation for your doors is even easier than for your windows.  Inspect the doors in your home and check to see if there is a gap between the floor and the bottom of the door.  Air could easily escape through this area and you can utilize a simple remedy to prevent air leakage. You can purchase, or make, what is known as a door snake which is simply a tube of fabric that contains pellets and is placed on the floor in front of the gap to keep air from coming through or from escaping.

Attics

Inadequate insulation in your attic will result in heat seeping through your ceiling.  If you're not sure about the insulation of your attic you should contact a professional to come and inspect it for you.  They can determine the best method of correcting the problem and may be able to install cellulose insulation which provides additional benefits such as pest control, sound proofing and doesn't take much time or cause any inconvenience.

It is well worth the effort to make sure that your home has adequate insulation. You can save money on your energy bills and enjoy the cooler temperatures in your home provided by your air conditioning unit.

About the Author

Are you looking for someone to service your Raleigh Air conditioning that is both honest and affordable? Vernon Gantt of Ask Expert Express has provided quality repair, service and education to Raleigh since 1967. For more information, visit http://www.askexpertexpress.com/.

For the Crosman R34 Soft Air Rifle automatic or semi atomatic or single shot?

by single shot i mean caulking it each time

It's automatic.

Air Sealing and Caulking Walls

Aluminum Stand

Aluminum Christmas Trees and a Stroll Down Memory Lane!

Now that I'm officially a senior citizen, I find myself strolling down memory lane more than ever before.  I'm also more aware of just how much our world has changed since we were kids dashing to the first McDonalds in our town.  You could buy a hamburger for just 15 cents!  Like those burgers, many of the things we enjoyed years ago are no longer with us.

In high school, my friends and I would anxiously await Friday nights. Four of us boys, with our crew cuts and Jimmy Smith's duck tail, would pile into Jimmy's 1957 Chevrolet and go to the local drive-in movie. 
 
We would park 3 rows to the right and 4 to the back of the concession stand so we could see any unattached girls as they went to get popcorn and a Coke.  We thought we were slick back then as we would race to the concession stand to try and meet girls that we thought were worthy of our attention.
 
Sometimes during my late teen years, Aluminum Christmas Trees became a trend that my parents thought would solve the problem of dry evergreen needles on the floor.  Until that time we had always cut our Christmas tree from the woods that was only a mile from our house. 

My first year in college, I remember returning home for the Christmas holiday, horrified to see a glistening gigantic shredded roll of aluminum foil shaped into a tree, standing in a corner of the living room.  I was shocked when I saw it occupying the space that had been dedicated to a freshly cut aromatic cedar trees.
 
 Thankfully that fad came and went in just a couple of years, then we moved on to fake green trees with little bottles of aerosol spray that was guaranteed to smell like a fresh cut cedar or spruce tree.
Whatever happened to television test patterns that would suddenly appear on the screen at the stroke of midnight?  As strange as it seems, there was something comforting to us insomniacs about staring at that immovable page emanating from the picture tube as if it held the secret to the universe!  It's quite possible it did, but whatever its message, it went over my head.

There were some things that were so far ahead of their time, that it seems incomprehensible that they're gone.  In an era in which people really loved their cars, the Studebaker was in a class of its own.
 
While my friends proclaimed the delight of owning their '57 Chevys and Fords, my 1953 Studebaker Starliner was my pride and joy!  That car looked like it was going fast even when it was standing still!  Besides being a great automobile, it set you apart from the rest of the crowd.  Not everyone owned a Studebaker!

Do you remember the 5 cent Coca-Cola?  When I was a kid in the summertime, I'd walk to the small grocery store about a mile from the house, pulling my red Radio Flyer behind me.  I would buy a case of Cokes and a half block of ice. 

I had extended the sides of the wagon 6 inches taller so I could chip up the ice and pour it in the wagon; then I would lay the bottles of Coke on the bed of ice.  I walked another mile to a housing development being built close to town.  There, in the Alabama heat I would sell that case of Coca-Colas to weary carpenters, masons and painters for 15 cents each, or two for a quarter.  I sold out every day.

Many of us thought that 25 cents a gallon gasoline was far too much to spend for fuel. There's a country song somewhere which was written by someone who was obviously a philosophical genius.  The line that I'll always remember is "When gas was 25 cents a gallon, love was only 50 cents away."

Whatever happened to flashbulbs, Timmy and Lassie, Bryllcreme, The Ozzie and Harriet Show and metal ice cube trays that either made the ice break free or cause the lever to bend.  Everyone remembers the Burma Shave signs on the side of a two-lane road.  Where have all these things gone?  Where ever they are, I miss them!

About the Author

Bob Alexander is well experienced in outdoor cooking, fishing and leisure living. Bob is also the author and owner of this article. Visit his sites at:
http://www.redfishbob.com
http://www.bluemarlinbob.com

Will putting aluminum foil underneath my laptop help keep it cool?

I heard that aluminum absorbs heat (supposedly they make aluminum computer stands, but I don't want that).

Is it true?

An aluminum foil heatsink. Interesting. The foil wouldnt do anything in the way of dissipating the heat.

They make laptop cooling systems, check em out.

iClooly Aluminum Stand for iPhone 3G/3GS

Bit Tool

drill SQUARE HOLES Japanese form tool

Gun Holder

How to Load Inks and Price Gun Labels into a Samark 26

Here is an indepth guide to loading your Samark 26 pricing and labeling gun: -

Whilst holding your Samark 26 pricing and labeling gun in your left hand, open the machine in the following three places:

1) Pull the reel holder back towards the handle
2) Pull the straight bottom cover, out
3) Pull the internal platen flap down

With your roll of labels lightly pinch about 15cms of label strip into a ‘V’ shape. Place the roll of labels clockwise onto the holder and close the holder in an upward direction.

Thread your labels diagonally through the Samark 26 pricing and labeling gun leaving about 10cms extending from the price gun.

Close the internal platen, and hold this down firmly with your fingers, whilst operating the handle of the machine several times, your labels will start to feed through the price gun.

Continue to operate the handle until the label strip extends beyond the edge of the bottom cover.  Fold the label strip straight back towards the handle and close the bottom cover.

To check that the Samark 26 pricing and labeling machine has been loaded properly, ensure that the label strip is extending from the pricing and labeling machine in a straight line, squeeze the handle firmly and your labels will appear printed and ready to promote your product, you can now price up and label quickly and efficiently.

It is very easy to change the digits in your Samark 26 pricing and labeling gun, select the column to be altered by lining the orange arrow with the print column and turning the knob to the desired digit. Do not dial beyond the yellow figures.

To change the Samark 26 pricing and labeling gun ink roller, squeeze the handle half way and the roller will protrude at the front of the gun, grasp the roller arm firmly.

Slide the roller off to the right or left and replace it with Samark 26 ink roller then gently allow the roller arm to return.  

Your Samark 26 pricing and labeling machine is now completely ready to begin its hard work.

About the Author

Jenwa is an Industry Expert in Pricing and Labeller Guns. To know more visit http://www.thepricegunshop.co.uk/

Who agrees with US Attorney General, Eric Holder, in regards to curbing America's gun laws to better Mexico?

http://www.youtube.com/watch?v=NAD2eJD5Xbo

Since when do we think it's fine to stomp on our Constitution to benefit another country?

Any idea what our founding fathers would say on the matter?

@RIPGOP

"The founding father's would not agree with the gun industry arming the drug cartels in Mexico. I'm SURE of that."

Let me explain something to you pal... these Mexican drug cartels are using FULL-AUTO AR-15s. Those are military weapons. The civilian gun industry does not even manufacture these.

If you buy an AR-15 at a Wal-Mart or something, it does not have the same type of barrel. Even if you modify it to fire full auto, you will only put about 50 rounds through the thing before that rifle becomes unusable.

Furthermore, the drug cartels are using fragmentation grenades. I don't know where those are coming from, but it ain't Wal-Mart!

Curtailing the 2nd amendment-protected rights of free US citizens has NOTHING WHATSOEVER to do with "Mexican drug gangs." Those weapons are coming from somewhere else (quite possibly from criminal elements within our own government and military -- the same people who want us disarmed!)

Also, I should add that the US and Mexican governments ship far more drugs across the border than these cartels they are supposedly "fighting." They don't want to stop the trafficking, they want to wipe out their competition.

Read up about the drug war. It's one of the biggest criminal scams in history. Now the people running it have the audacity to try to use their engineered crises as an excuse to disarm the population? Not happening.

By the way, I think if you told the founders that there was an all out war going on right across the border, they would probably demand that all citizens in the area acquire MORE firearms, and make the necessary preparations to defend their homes and towns if the violence spills across the border (which it already HAS, on multiple occasions.)

If the colonists who fought our revolution were alive today, this whole thing would have been over as soon as it began, and no criminal cartel or foreign troops would dare to come within 200 miles of our border!

And any discussion of disarming Americans would be met with immediate revolt (because the founders understood that any government that wishes to disarm its people is the enemy of its people.)

The Back Up Bedside Gun Rack Commercial -- BACKUP