How to Make a Transistor Radio Essay Example for Free

How to Make a Transistor Radio Essay First a few safety precautions: * Never touch the element or tip of the soldering iron. They are very hot (about 400Â °C) and will give you a nasty burn. * Take great care to avoid touching the mains flex with the tip of the iron. The iron should have a heatproof flex for extra protection. An ordinary plastic flex will melt immediately if touched by a hot iron and there is a serious risk of burns and electric shock. * Always return the soldering iron to its stand when not in use. Never put it down on your workbench, even for a moment! * Work in a well-ventilated area. The smoke formed as you melt solder is mostly from the flux and quite irritating. Avoid breathing it by keeping you head to the side of, not above, your work. * Wash your hands after using solder. Solder contains lead which is a poisonous metal. If you are unlucky (or careless!) enough to burn yourself please read the First Aid section. Preparing the soldering iron: * Place the soldering iron in its stand and plug in. The iron will take a few minutes to reach its operating temperature of about 400Â °C. * Dampen the sponge in the stand. The best way to do this is to lift it out the stand and hold it under a cold tap for a moment, then squeeze to remove excess water. It should be damp, not dripping wet. * Wait a few minutes for the soldering iron to warm up. You can check if it is ready by trying to melt a little solder on the tip. * Wipe the tip of the iron on the damp sponge. This will clean the tip. * Melt a little solder on the tip of the iron. This is called tinning and it will help the heat to flow from the irons tip to the joint. It only needs to be done when you plug in the iron, and occasionally while soldering if you need to wipe the tip clean on the sponge. You are now ready to start soldering: * Hold the soldering iron like a pen, near the base of the handle. Imagine you are going to write your name! Remember to never touch the hot element or tip. * Touch the soldering iron onto the joint to be made. Make sure it touches both the component lead and the track. Hold the tip there for a few seconds and * Feed a little solder onto the joint. It should flow smoothly onto the lead and track to form a volcano shape as shown in the diagram. Apply the solder to the joint, not the iron. * Remove the solder, then the iron, while keeping the joint still. Allow the joint a few seconds to cool before you move the circuit board. * Inspect the joint closely. It should look shiny and have a volcano shape. If not, you will need to reheat it and feed in a little more solder. This time ensure that boththe lead and track are heated fully before applying solder. If you are unlucky (or careless!) enough to burn yourself please read the First Aid section. Some components, such as transistors, can be damaged by heat when soldering so if you are not an expert it is wise to use a heat sink clipped to the lead between the joint and the component body. You can buy a special tool, but a standard crocodile clip works just as well and is cheaper. Soldering Advice for Components It is very tempting to start soldering components onto the circuit board straight away, but please take time to identify all the parts first. You are much less likely to make a mistake if you do this! 1. Stick all the components onto a sheet of paper using sticky tape. 2. Identify each component and write its name or value beside it. 3. Add the code (R1, R2, C1 etc.) if necessary. Many projects from books and magazines label the components with codes (R1, R2, C1, D1 etc.) and you should use the projects parts list to find these codes if they are given. 4. Resistor values can be found using the resistor colour code which is explained on our Resistors page. You can print out and make your own Resistor Colour Code Calculator to help you. 5. Capacitor values can be difficult to find because there are many types with different labelling systems! The various systems are explained on our Capacitors page. Some components require special care when soldering. Many must be placed the correct way round and a few are easily damaged by the heat from soldering. Appropriate warnings are given in the table below, together with other advice which may be useful when soldering. What is solder? Solder is an alloy (mixture) of tin and lead, typically 60% tin and 40% lead. It melts at a temperature of about 200Â °C. Coating a surface with solder is called tinning because of the tin content of solder. Lead is poisonous and you should always wash your hands after using solder. Solder for electronics use contains tiny cores of flux, like the wires inside a mains flex. The flux is corrosive, like an acid, and it cleans the metal surfaces as the solder melts. This is why you must melt the solder actually on the joint, not on the iron tip. Without flux most joints would fail because metals quickly oxidise and the solder itself will not flow properly onto a dirty, oxidised, metal surface. The best size of solder for electronics is 22swg (swg = standard wire gauge). Soldering is defined as the joining of metals by a fusion of alloys which have relatively low melting points. In other words, you use a metal that has a low melting point to adhere the surfaces to be soldered together. Consider that soldering is more like gluing with molten metal, unlike welding where the base metals are actually melted and combined. Soldering is also a must have skill for all sorts of electrical and electronics work. It is also a skill that must be taught correctly and developed with practice. This tutorial will cover the most common types of soldering required for electronics work. This includes soldering components to printed circuit boards and soldering a spliced wire joint. Soldering Equipment The Soldering Iron/Gun The first thing you will need is a soldering iron, which is the heat source used to melt solder. Irons of the 15W to 30W range are good for most electronics/printed circuit board work. Anything higher in wattage and you risk damaging either the component or the board. If you intend to solder heavy components and thick wire, then you will want to invest in an iron of higher wattage (40W and above) or one of the large soldering guns. The main difference between an iron and a gun is that an iron is pencil shaped and designed with a pinpoint heat source for precise work, while a gun is in a familiar gun shape with a large high wattage tip heated by flowing electrical current directly through it. For hobbyist electronics use, a soldering iron is generally the tool of choice as its small tip and low heat capacity is suited for printed circuit board work (such as assembling kits). A soldering gun is generally used in heavy duty soldering such as joining heavy gauge wires, soldering brackets to a chassis or stained glass work. You should choose a soldering iron with a 3-pronged grounding plug. The ground will help prevent stray voltage from collecting at the soldering tip and potentially damaging sensitive (such as CMOS) components. By their nature, soldering guns are quite dirty in this respect as the heat is generated by shorting a current (often AC) through the tip made of formed wire. Guns will have much less use in hobbyist electronics so if you have only one tool choice, an iron is what you want. For a beginner, a 15W to 30W range is the best but be aware that at the 15W end of that range, you may not have enough power to join wires or larger components. As your skill increases, a 40W iron is an excellent choice as it has the capacity for slightly larger jobs and makes joints very quickly. Be aware that it is often best to use a more powerful iron so that you dont need to spend a lot of time heating the joint, which can damage components. A variation of the basic gun or iron is the soldering station, where the soldering instrument is attached to a variable power supply. A soldering station can precisely control the temperature of the soldering tip unlike a standard gun or iron where the tip temperature will increase when idle and decrease when applying heat to a joint. However, the price of a soldering station is often ten to one hundred times the cost of a basic iron and thus really isnt an option for the hobby market. But if you plan to do very precise work, such as surface mount, or spend 8 hours a day behind a soldering iron, then you should consider a soldering station. The rest of this document will assume that you are using a soldering iron as that is what the majority of electronics work requires. The techniques for using a soldering gun are basically the same with the only difference being that heat is only generated when the trigger is pressed. Solder The choice of solder is also important. There several kinds of solder available but only a few are suitable for electronics work. Most importantly, you will only use rosin core solder. Acid core solder is common in hardware stores and home improvement stores, but meant for soldering copper plumbing pipes and not electronic circuits. If acid core solder is used on electronics, the acid will destroy the traces on the printed circuit board and erode the component leads. It can also form a conductive layer leading to shorts. For most printed circuit board work, a solder with a diameter of 0.75MM to 1.0MM is desirable. Thicker solder may be used and will allow you to solder larger joints more quickly, but will make soldering small joints difficult and increase the likelihood of creating solder bridges between closely spaced PCB pads. An alloy of 60/40 (60% tin, 40% lead) is used for most electronics work. These days, several lead-free solders are available as well. Kester 44 Rosin Core solder has been a staple of electronics for many years and continues to be available. It is available in several diameters and has a non-corrosive flux. Large joints, such as soldering a bracket to a chassis using a high wattage soldering gun, will require a separate application of brush on flux and a thick diameter solder of several millimeters. Remember that when soldering, the flux in the solder will release fumes as it is heated. These fumes are harmful to your eyes and lungs. Therefore, always work in a well ventilated area and avoid breathing the smoke created. Hot solder is also dangerous. It is surprisingly easy to splash hot solder onto yourself, which is a thoroughly unpleasant experience. Eye protection is also advised. Preparing To Solder Tinning The Soldering Tip Before use, a new soldering tip, or one that is very dirty, must be tinned. Tinning is the process of coating a soldering tip with a thin coat of solder. This aids in heat transfer between the tip and the component you are soldering, and also gives the solder a base from which to flow from. Step 1: Warm Up The Iron Warm up the soldering iron or gun thoroughly. Make sure that it has fully come to temperature because you are about to melt a lot of solder on it. This is especially important if the iron is new because it may have been packed with some kind of coating to prevent corrosion. Step 2: Prepare A Little Space While the soldering iron is warming up, prepare a little space to work. Moisten a little sponge and place it in the base of your soldering iron stand or in a dish close by. Lay down a piece of cardboard in case you drip solder (you probably will) and make sure you have room to work comfortably. Step 3: Thoroughly Coat The Tip In Solder Thoroughly coat the soldering tip in solder. It is very important to cover the entire tip. You will use a considerable amount of solder during this process and it will drip, so be ready. If you leave any part of the tip uncovered it will tend to collect flux residue and will not conduct heat very well, so run the solder up and down the tip and completely around it to totally cover it in molten solder. Step 4: Clean The Soldering Tip After you are certain that the tip is totally coated in solder, wipe the tip off on the wet sponge to remove all the flux residue. Do this immediately so there is no time for the flux to dry out and solidify.

The Etiology of Autism Essay -- Psychology Neurology Disorders autisti

The Etiology of Autism Autism is a syndrome that is characterized by the impairment of social interaction skills, verbal and nonverbal communication, and a decreased interest in participating in a variety of activities. In 1943, Kanner, the man who is attributed with the identification of this disease, hypothesized that autism might be a biological disorder as opposed to a psychological one. Numerous studies have been conducted supporting Kanner’s hypothesis. These studies have ranged from examining the effects of rubella to investigating certain purine metabolic disorders as possible etiological agents. Recently, the areas of neuroanatomy, neurochemistry, and genetics have played a crucial role in developing a clearer picture into the etiology of this disease. Upon exploring the biological aspects of autism, the fields of neuroanatomy, neurochemistry, and genetics have offered new insights concerning their association with the onset of this disease. Neuroanatomy is one of the latest fields involved in uncovering the possible causes of autism. Many past studies conducted in this area found that autistic patients had enlarged lateral ventricles, however, this abnormality didn’t reveal any damage to a specific anatomical site. The most recent studies conducted on the cerebella of autistic patients showed much more dramatic results. In one specific experiment conducted by Dr. Courchesne, the cerebellar lobules of eighteen autistic patients were compared with the lobules of twelve subjects within a normal control group. The eighteen autistic patients were chosen on the basis that their autistic state was "... not complicated by severe mental retardation, cerebral palsy, epilepsy, genetic abnormality, other neurologic dise... ... R. S. and B. H. Herman. A Novel Biochemical Model Linking Dysfunctions in Brain Melatonin, Proopiomelanocortin Peptides, and Serotonin in Autism. Biological Psychiatry, 28:773-793, 1991. Courchesne, E. et. al. Hypoplasia of Cerebellar Vermal Lobules VI and VII in Autism. New England Journal of Medicine, 318:1349-1354, May 26, 1988. Gillberg, C. et. al. Monozygotic Female Twins With Autism and the Fragile X Syndrome (AFRAX). J. Child Psychol. Psychiat., 29(4); 447-451, 1988. Herman, B. H. and Panksepp, J. Effects of Morphine and Naloxone on Social Attachment in Infant Guinea Pigs. Pharmacol. Biochem. Behaviour, 9;213-220, 1978. Lowenstein, P. R. et. al. Effects of Naloxone on the Nocturnal Rise of Rat Pineal Melatonin Content. Eur. J. Pharmacol., 98;26 Reiss, A. L. et. al. Autism and Genetic Disorders. Schizophrenic Bulletin.12(4); 724-38, 1986.

The Campbell Company

The Campbell Company is evaluating a proposal to buy a new milling machine. The base price is $108,000, and shipping and installation costs would add another $12,500. The machine falls into the MACRS 3-year class, and it would be sold after 3 years for $65,000. The machine would require a $5,500 increase in working capital (increased inventory less increased accounts payable). There would be no effect on revenues, but pre-tax labor costs would decline by $44,000 per year. The marginal tax rate is 35 percent. 1. What is the net cost of the machine for capital budgeting purposes, that is, the Year 0 project cash flow? Net Cost of the machine = $108,000 + $12,500 + $5,500 = $126,000 2. What are the net operating cash flows during Years 1, 2 and 3? Â   | Year | |Â   |0 |1 |2 |3 | |After-Tax Savings |Â   |$28,600 |$28,600 |$28,600 | |Depreciation Tax Savings |Â   |$13,918 |$18,979 |$6,326 | |Net Cash Flow |Â   |$42,518 |$47,579 |$34,926 | . What is the terminal year cash flow? |Salvage Value |$65,000 | |Tax on Salvage Value |$19,798 | |NWC Recovery |$5,500 | |Terminal Cash Flow |$50,702 | 4. If the project’s cost of capital (WACC) is 12 percent, should the machine be purchased? Yes, the machine should be purchased as the investment has a positive NPV of $10,840 as per the following table. |NPV Analysis | |Year |Cash Flow |PV Factor @ 12% |PV | |0 |($126,000) |1 |($126,000) | |1 |$42,518 |0. 929 |$37,962 | |2 |$47,579 |0. 7972 |$37,929 | |3 |$85,629 |0. 7118 |$60,949 | |NPV |Â   |Â   |$10,840 |

Managing Individuals Performance in the Workplace

Managing Individual Performance Introduction The purpose of this paper is to identify the criteria needed for making team selections along with the factors to manage a team effectively. Once I have defined the criteria for team making and management, I will elaborate on how an individual s personality affects the workplace. Criteria for selecting team members Many organizations have difficulty forming effective working teams and that is because labor and management lack shared values. Another reason is because of the structure and function of problem solving teams was not established according to behavior science concepts and techniques. Additionally, it is important to consider that it is not always necessary for supervisors†¦show more content†¦David Sharp stated that the manager has the responsibility of giving employees latitude to decide how to do their job, thus, if the employee enjoys what he or she does, the employee will perform the task better. Don t put your introverted loner into customer service, thus, a person that is extroverted would be the best candidate. Sharp also stated that, Some people may not enjoy their jobs and they may only be performing the job for prestige. Thus, some employees may not have the ability to perform their job due to lack of training and skills needed. To remedy problems as such, the manager will need to be sensitive to the skills and interests employees to assure that employees are assigned to the right position (Sharp 2005). P vs. J- Perceptive or Judgmental- A person with a perceptive type of attitude is known to be curious, spontaneous, flexible, adaptable and tolerant. Usually, this person focuses on starting a task and postpones decisions because they want to find out about the task before starting it. On the other hand, judgmental types are decisive, good planners and exacting. These individuals are known for focusing on completing a task and making decisions quickly, mostly, they focus on only necessary information to get the job done. The ideal team should consist of a mixture of individuals who have different behavioral styles. In addition to the mixture, managers should also take theShow MoreRelatedMotivation, Stress, and Communication1713 Words   |  7 Pagesï » ¿Motivation, Stress and Communication: As part of analyzing motivation, stress, and communication in the workplace, I have selected the position of human service manager in United Way of Central Indiana. The company is located in Indianapolis and focuses on helping to sustain significant services for people in need of help and preventing the occurrence of such needs for future generations. 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