Snap switch

Manual and Magnetic Starters Manual motor starters are operated by hand. The simplest type of manual starter is a snap switch with no overload protection, used only for motors of 1,492 kW (2 hp) and smaller, usually single-phase motors with integral overload protection. 

There are many thousands of outstanding applications where plastics are used in electrical designs. The designers imaginations have excelled in developing new plastic products. An example is the folded membrane and snap switches in controlling electronic devices. 

The very low storage temperature and low operating temperature specifications (see Section 4.3 below) also required dedicated design features because many of the components, such as the pumps and processors, cannot operate at very low temperatures. Because of this limitation there were added to several components cold start heaters controlled by snap switches. Further, an industrial temperature grade microprocessor was used in the SDU. With the snap switches the cold start heaters can come on when the power is applied at less than about 32°F/0°C. The snap switches cut off the cold start heaters and apply power to the full CBMS II system once their setpoint temperature is reached. 

Vibrator on-off switch. Turns the vibrator on or off. It s a spring-return switch so you must hold the switch in the on position. Let go, and it snaps off. 

A type of material known as shape memory alloy (SMA) can perform this trick. SMAs are more complicated than electrorheological fluids and the other smart materials previously described in this chapter. An SMA does not only react or respond to environmental conditions, it also has a memory that enables it to return to a specific structure, or sometimes switch between two different structures. After the material has been set, it can recover from a deformation that would be permanent in other materials. When the temperature is raised by an amount that depends on the specific material, it snaps back into shape automatically. The memory is based on phase transitions, as described in the sidebar on page 120. 

The switch used here is an excellent switch, however we would have preferred a tighter dead band of about 2 psi, or possibly a variable dead band for more flexibility. However, many switches with variable dead bands contain mercury, which we wanted to avoid. Plus, we wanted a snap action switch, and they were only available with a fixed dead band version. 

This particular brand is hermetically sealed, which was an important consideration because of the switch s proximity to the tank. Also, the snap action switches in this model were potted (sealed). This in itself does not provide an appropriate level of safety, but since the system uses a low current, low voltage signal, we considered the switch to be adequate for our needs and safety concerns. Of course we cannot advise the use of such equipment. Any switches used in a system must meet the standards of your area AHJ. 

Pressure switch, hermetically sealed, fixed dead band, snap action, stainless steel. Dwyer Instruments Mercoid switch DS7341- 153-23E 1... 

DNase I stock solutions are stored at -2O C (1 mg/ml) in 5- xl aliquots (each aliquot is used once). Variation in the activity of DNase I preparations is often observed and the exact amount needed to introduce the desired number of nicks should be determined for each enzyme batch. Sometimes template switches occur which will result in snap-back structures (zero-binding nucleic acid), which remain S, nuclease-resistant upon denaturation. Rigby et al. (1977) suggested that this effect was due to a differential loss of 5 - 3 exonuclease activity upon storage leading to a displacement of the nicked strand and a template switch from the complementary... 

Figure 6.20 shows the snapping microlenses reported by Holmes [17]. If a trigger mechanism was used to develop critical stress in all shells simultaneously, the entire surfaces of shells would change curvature. One way to achieve this switching of multiple lenses from convex to concave was by exposing the responsive surface to oxygen plasma treatment. 

My son s early model Speak Spell had given him what seemed to be hundreds of hours of enjoyment when one day the enter key broke off at its plastic hinge. But since Stephen could still fit his small finger into the buttonhole to activate the switch, he continued to enjoy the smart, if disfigured, toy. Soon thereafter, however, the E key snapped off, and soon the T and O keys followed suit. Although he continued to use the toy, its keyboard soon became a maze of missing letters and, for those that were saved from the vacuum cleaner, taped-on buttons. 

Albeck, J.G., Burke, J.M., Spencer, S.L., Lauffenburger, D.A., and Sorger, RK. 2008b. Modeling a snap-action, variable-delay switch controlling extrinsic cell death. PLoS Biol 6 2831-2852. 

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