My Portfolio

Electric circuits

A basic electric circuit. The voltage source V on the left drives a current I around the circuit, delivering electrical energy into the resistor R. From the resistor, the current returns to the source, completing the circuit. An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task. The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics.

Electric power, like mechanical power, is represented by the letter P in electrical equations. The term wattage is used colloquially to mean "electric power in watts."

In direct current resistive circuits, electrical power is calculated using Joule's law:

In alternating current circuits, energy storage elements such as inductance and capacitance may result in periodic reversals of the direction of energy flow. The portion of power flow that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as real power (also referred to as active power). That portion of power flow due to stored energy, that returns to the source in each cycle, is known as reactive power.

A series circuit is the simplest circuit. The conductors, control and protection devices, loads, and power source are connected with only one path to ground for current flow. The resistance of each device can be different. The same amount of current will flow through each. The voltage across each will be different. If the path is broken, no current flows and no part of the circuit works. Christmas tree lights are a good example; when one light goes out the entire string stops working.

A parallel circuit has more than one path for current flow. The same voltage is applied across each branch. If the load resistance in each branch is the same, the current in each branch will be the same. If the load resistance in each branch is different, the current in each branch will be different. If one branch is broken, current will continue flowing to the other branches.

A series-parallel circuit has some components in series and others in parallel. The power source and control or protection devices are usually in series; the loads are usually in parallel. The same current flows in the series portion, different currents in the parallel portion. The same voltage is applied to parallel devices, different voltages to series devices. If the series portion is broken, current stops flowing in the entire circuit. If a parallel branch is broken, current continues flowing in the series portion and the remaining branches.

Plumbing

- (from the Latin plumbum for lead as pipes were once made from lead) is the skilled trade of working with pipes, tubing and plumbing fixtures for drinking water systems and the drainage of waste.

- is someone who installs or repairs piping systems, plumbing fixtures and equipment such as water heaters.

Water systems of ancient times relied on gravity for the supply of water, using pipes or channels usually made of clay, lead, bamboo or stone. Present-day water-supply systems use a network of high-pressure pumps, and pipes are now made of copper, brass, plastic, or other nontoxic material. Present-day drain and vent lines are made of plastic, steel, cast-iron, and lead. Lead is not used in modern water-supply piping due to its toxicity. The 'straight' sections of plumbing systems are of pipe or tube. A pipe is typically formed via casting or welding, where a tube is made through extrusion. Pipe normally has thicker walls and may be threaded or welded, where tubing is thinner-walled and requires special joining techniques such as 'brazing', 'compression fitting', 'crimping', or for plastics, 'solvent welding'.

Piping being placed for a sink.In addition to the straight pipe or tubing, many fittings are required in plumbing systems, such as valves, elbows, tees, and unions.

Plumbing fixtures are designed for the end-users. Some examples of fixtures include water closets (also known as toilets), urinals, bidets, showers, bathtubs, utility and kitchen sinks, drinking fountains, ice makers, humidifiers, air washers, fountains, and eye wash stations.

Plumbing equipment, not present in all systems, include, for example, water meters, pumps, expansion tanks, backflow preventers, filters, water softeners, water heaters, wrenches, heat exchangers, gauges, and control systems. Now there is equipment that is technologically advanced and helps plumbers fix problems without the usual hassles. For example, plumbers use video cameras for inspections of hidden leaks or problems, they use hydro jets, and high pressure hydraulic pumps connected to steel cables for trench-less sewer line replacement.

Copper piping system in a building with intumescent firestop being installed by an insulator, Vancouver, British Columbia, Canada.

• Potable cold and hot water supply
• Traps, drains, and vents
• Septic systems
• Rainwater, surface, and subsurface water drainage
• Fuel gas piping

Welding

- is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting theworkpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, but sometimes pressure is used in conjunction with heat, or by itself, to produce the weld.

- is a joining process in which a filler metal is melted and drawn into a capillary formed by the assembly of two or more work pieces. The filler metal reacts metallurgically with theworkpiece (s) and solidifies in the capillary, forming a strong joint.

- a printed circuit board. Soldering is a joining process that occurs at temperatures below 450 °C (842 °F). It is similar to brazing in the fact that a filler is melted and drawn into a capillary to form a join, although at a lower temperature. Because of this lower temperature and different alloys used as fillers, the metallurgical reaction between filler and work piece is minimal, resulting in a weaker joint. In a correctly made deposit the ripples produced on the bead will be uniform and the bead will be smooth no overlaps or undercuts.

1. CORRECT ELECTRODE SIZE

The correct choice of electrode size involves consideration of a variety of factors, such as the type, position, preparation of the joint, the ability of the electrode to carry high current values without injury to the weld metal or loss of deposition efficiency, the mass of work metal and its ability to maintain its original properties after welding, the characteristics of the assembly with reference to effect stresses set up by heat application, the practicability to heat treatment before and / or after welding, the specific requirement before and / or after welding, the specific requirements as to welding quality and cost of achieving the desired results.

2. CORRECT CURRENT

If current on equipment is too high or too low, you are certain to be disappointed in your weld. If too high, the electrode melts too fast and your molten pool is large and irregular, if too low, there is nor enough heat to melt the base metal and your molten pool will be small, will pile up, look irregular.

3. CORRECT ARC LENGTH

If the arc is too long or voltage too high the metal melts off the electrode is large globules which wobble from side to side as the arc wavers, giving a wide, spattered and irregular bead-with poor fusion between original metal and deposited metal. If the arc is too short, or voltage too low, there is not enough heat to melt the base metal properly and the electrode quite often sticks to the work, giving a high, uneven bead, having irregular ripples with poor fusion.

4. CORRECTTRAVEL SPEED

When your speed is too fast your pool does not last long enough, impurities an gas locked in. The bead in narrow and ripples pointed. When speed is too slow the metal piles up, the bead is high and wide with a rather straight ripple.

5. CORRECT ELECTRODE ANGLE

The electrode angle is of particular importance in fillet welding and deep groove welding. Generally speaking, when making a fillet weld, the electrode should be held so that ir bisects the angle between the plates (as shown at right) and is perpendicular to the line of weld, if under cut occurs in the verticle member, lower the angle of the arc and direct the arc toward the vertical member.

In arc welding an electrode is used to conduct current through a workpiece to fuse two pieces together. For an alternating current arc welder the welding electrode would not be considered an anode or cathode.

Correct and safe arc welding station.Welding can be a dangerous and unhealthy practice without the proper precautions; however, with the use of new technology and proper protection the risks of injury or death associated with welding can be greatly reduced.

Because many common welding procedures involve an open electric arc or flame, the risk of burns is significant. To prevent them, welders wear protective clothing in the form of heavy leather gloves and protective long sleeve jackets to avoid exposure to extreme heat, flames, and sparks.

The brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes inflammation of the cornea and can burn the retinas of the eyes. Welding goggles and helmets with dark face plates are worn to prevent this exposure and, in recent years, new helmet models have been produced featuring a face plate that self-darkens upon exposure to high amounts of UV light.

Welders are also often exposed to dangerous gases and particulate matter. Processes like flux-cored arc welding and shielded metal arc welding produce smoke containing particles of various types of oxides. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, many processes produce various gases (most commonly carbon dioxide and ozone, but others as well) that can prove dangerous if ventilation is inadequate. Furthermore, the use of compressed gases and flames in many welding processes pose an explosion and fire risk; some common precautions include limiting the amount of oxygen in the air and keeping combustible materials away from the workplace.

Certain welding machines which use a high frequency AC current component have been found to affect pacemaker operation when within 2 meters of the power unit and 1 meter of the weld site.

Types of laminators

Three types of laminators are used most often in digital imaging:

• Pouch laminators
• Heated roll laminators
• Cold roll laminators

Laminate film is generally categorized into these five categories:

• Standard thermal laminating films
• Low-temperature thermal laminating films
• Heatset (or heat-assisted) laminating films
• Pressure-sensitive films

- is a printing technique that uses a woven mesh to support an ink-blocking stencil. The attached stencil forms open areas of mesh that transfer ink as a sharp-edged image onto a substrate. A roller or squeegee is moved across the screen stencil, forcing or pumping ink past the threads of the woven mesh in the open areas.

A screen is made of a piece of porous, finely woven fabric called mesh stretched over a frame of aluminium or wood. Originally human hair then silk was woven into screen mesh; currently most mesh is made of man-made materials such as steel, nylon, and polyester. Areas of the screen are blocked off with a non-permeable material to form a stencil, which is a negative of the image to be printed; that is, the open spaces are where the ink will appear. The screen is placed atop a substrate such as paper or fabric. Ink is placed on top of the screen, and a fill bar (also known as a floodbar) is used to fill the mesh openings with ink. The operator begins with the fill bar at the rear of the screen and behind a reservoir of ink. The operator lifts the screen to prevent contact with the substrate and then using a slight amount of downward force pulls the fill bar to the front of the screen. This effectively fills the mesh openings with ink and moves the ink reservoir to the front of the screen. The operator then uses a squeegee (rubber blade) to move the mesh down to the substrate and pushes the squeegee to the rear of the screen. The ink that is in the mesh opening is pumped or squeezed by capillary action to the substrate in a controlled and prescribed amount, i.e. the wet ink deposit is proportional to the thickness of the mesh and or stencil. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate (called snap-off) leaving the ink upon the substrate surface. There are three common types of screenprinting presses. The 'flat-bed', 'cylinder', and the most widely used type, the 'rotary'. Textile items printed with multi-colour designs often use a wet on wet technique, or colors dried while on the press, while graphic items are allowed to dry between colours that are then printed with another screen and often in a different color after the product is re-aligned on the press. The screen can be re-used after cleaning. However if the design is no longer needed, then the screen can be "reclaimed", that is cleared of all emulsion and used again. The reclaiming process involves removing the ink from the screen then spraying on stencil remover to remove all emulsion. Stencil removers come in the form of liquids, gels, or powders. The powdered types have to be mixed with water before use, and so can be considered to belong to the liquid category. After applying the stencil remover the emulsion must be washed out using a pressure washer. Most screens are ready for recoating at this stage, but sometimes screens will have to undergo a further step in the reclaiming process called dehazing. This additional step removes haze or "ghost images" left behind in the screen once the emulsion has been removed. Ghost images tend to faintly outline the open areas of previous stencils, hence the name. They are the result of ink residue trapped in the mesh, often in the knuckles of the mesh, those points where threads cross. While the public thinks of garments in conjunction with screenprinting, the technique is used on tens of thousands of items, decals, clock and watch faces, balloons and many more products. The technique has even been adapted for more advanced uses, such as laying down conductors and resistors in multi-layer circuits using thin ceramic layers as the substrate.

A macro photo of a screenprint with a photographically produced stencil. The ink will be printed where the stencil does not cover the substrate. There are several ways to create a stencil for screenprinting. A method that has increased in popularity over the past 70 years is the photo emulsion technique:

1. The original image is created on a transparent overlay such as acetate or tracing paper. The image may be drawn or painted directly on the overlay, photocopied, or printed with an inkjet or laser printer, as long as the areas to be inked are opaque. A black-and-white positive may also be used (projected on to the screen). However, unlike traditional platemaking, these screens are normally exposed by using film positives.
2. A screen must then be selected. There are several different mesh counts that can be used depending on the detail of the design being printed. Once a screen is selected, the screen must be coated with emulsion and let to dry in the dark. Once dry, the screen is ready to be burned/exposed.
3. The overlay is placed over the emulsion-coated screen, and then exposed with a light source containing ultraviolet light in the 350-420 nanometer spectrum. The UV light passes through the clear areas and create a polymerization (hardening) of the emulsion.
4. The screen is washed off thoroughly. The areas of emulsion that were not exposed to light dissolve and wash away, leaving a negative stencil of the image on the mesh.

- can reproduce images with a high level of detail, and can be reused for tens of thousands of copies. The ease of producing transparent overlays from any black-and-white image makes this the most convenient method for artists who are not familiar with other printmaking techniques. Artists can obtain screens, frames, emulsion, and lights separately; there are also preassembled kits, which are especially popular for printing small items such as greeting cards. Another advantage of screenprinting is that large quantities can be produced rapidly with new automatic presses, up to 1800 shirts in 1 hour.

- the most common ink used in commercial garment decoration. Good colour opacity onto dark garments and clear graphic detail with, as the name suggests, a more plasticized texture. This print can be made softer with special additives or heavier by adding extra layers of ink. Plastisol inks require heat (approx. 150°C (300°F) for many inks) to cure the print.

- these penetrate the fabric more than the plastisol inks and create a much softer feel. Ideal for printing darker inks onto lighter coloured garments. Also useful for larger area prints where texture is important. Some inks require heat or an added catalyst to make the print permanent.

- relatively new breed of ink and printing with the benefits of plastisol but without the two main toxic components - soft feeling print.

- used to print lighter colours onto dark background fabrics, they work by removing the dye in the garment – this means they leave a much softer texture. They are less graphic in nature than plastisol inks, and exact colours are difficult to control, but especially good for distressed prints and underbasing on dark garments that are to be printed with additional layers of plastisol.

- consists of a glue printed onto the fabric and then foil or flock (or other special effect) material is applied for a mirror finish or a velvet touch.

- metallic flakes are suspended in the ink base to create this sparkle effect. Usually available in gold or silver but can be mixed to make most colours.

- similar to glitter, but smaller particles suspended in the ink. A glue is printed onto the fabric, then nanoscale fibers applied on it. Expanding ink (puff) an additive to plastisol inks which raises the print off the garment, creating a 3D feel.

- again a glue is printed in the shape of the design, to which small plastic beads are then applied – works well with solid block areas creating an interesting tactile surface.

- artwork is created and then separated into four colours (CMYK) which combine to create the full spectrum of colours needed for photographic prints. This means a large number of colours can be simulated using only 4 screens, reducing costs, time, and set-up. The inks are required to blend and are more translucent, meaning a compromise with vibrancy of colour. Gloss a clear base laid over previously printed inks to create a shiny finish. Nylobond a special ink additive for printing onto technical or waterproof fabrics.

Another solvent based ink, but you can almost see your face in it.

Suede is a milky coloured additive that is added to plastisol. With suede additive you can make any colour of plastisol have a suede feel. It is actually a puff blowing agent that does not bubble as much as regular puff ink. The directions vary from manufacturer to manufacturer, but generally you can add up to 50% suede additive to your normal plastisol.