Mtazamowetu
Invention and Development of ICT and Telecommunication Technology
Wednesday, February 26, 2014
Jinsi
ya kuongeza frequeny kwenye azam tv iliuweze kuongeza chanel ambazo
utaweza kuangalia mechi za UEFA na EPL.zinazokubari ni za mbc 1 & 2
wakati wa soka 2 inakuwa 3 #11192h3210,/recodmozambiq #10963h3255./ zile zimbotv #12728h30000./hii mpya test #11144h5714 mnirudishie majibu kama mmepata au la #12646h30000. nilijaribu zote zenye majibu nilizojaza.Ila kwa wale ambao mnaona ina wasumbua tafadhari
muoneni fundi ili waingizie hizo frequency kwani kwa mara ya kwanza
lazima ua add satelite kwanza na uipe name kisha ndio uingize frequency
tatizo lipo kwenye kuaadd satelite kwani lazima kuna vitu vya kuseti
kama LNB Freq 9750- 10600.Disceqc - 1.2,LNB Power - auto, 22k - auto,
switch port - port 1, Toneburst - 1, Location - west, Longitude - 0.0
Monday, January 20, 2014
Monday, December 2, 2013
Advance
Photocopier Engineering Course
|
|||||||||
|
|||||||||
Course Code :
|
APEC
|
||||||||
Course Name :
|
Advance Photocopier Engineering
Course
|
||||||||
Course Duration :
|
Three Months
|
||||||||
|
|||||||||
|
Friday, November 15, 2013
How to remove Notepad file which loads every time I boot: [.ShellClassInfo] LocalizedResourceName=@%SystemRoot%\system32\shell32.dll,-21787
Hi,This happens if the Hidden attribute for the desktop.ini file is somehow removed. Follow these steps to resolve the problem:
Open an elevated Command Prompt window. To do so, click Start, click All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator.
Type the following commands below and press ENTER after typing each command.
(You may copy the text below and paste it in the Command Prompt window.)
attrib +s +h "%appdata%\Microsoft\Windows\Start Menu\Programs\Startup\desktop.ini"
And then run the following command:
attrib +s +h "%programdata%\Microsoft\Windows\Start Menu\Programs\Startup\desktop.ini"
Type EXIT and then press enter to close the Command Prompt window.
Hope this information is helpful. Please let us know if you require further help.
Thursday, November 14, 2013
How to Solder Electronic Components
What is soldering and when should you use it?
- Soldering is a process in which two or more metal items are joined together by melting and then flowing a filler metal into the joint—the filler metal having a relatively low melting point.
- Soldering is used to form a permanent connection between electronic components.
- The metal to be soldered is heated with a soldering iron and then solder is melted into the connection.
- Only the solder melts, not the parts that are being soldered.
- Solder is a metallic "glue" that holds the parts together and forms a connection that allows electrical current to flow.
- You can use a solderless breadboard to make test circuits, but if you want your circuit to last for more than a few days, you will want to solder the components together.
Materials and Equipment
- A soldering iron
- A soldering iron is used to heat the connections to be soldered.
- For electronic circuits, you should use a 25- to 40-watt (W) soldering iron.
- Higher wattage soldering irons are not necessarily hotter; they are just able to heat larger components. A 40-W soldering iron makes joints faster than a 25-W soldering iron does.
- A soldering iron can be purchased at hardware stores and at most large department stores.
- Rosin core solder
- Solder has a lower melting point than the metals that are being connected do. The solder melts when it is heated by the soldering iron, but the metals being joined will not melt.
- The rosin core acts as a flux. It prevents oxidation of the metals that are being connected, and enhances the ability of the solder to "wet" the surfaces that are being joined.
- Solder that is used to join copper pipes has an acid core, which is appropriate for pipes, but will corrode electronic connections. Use solder that has a rosin core.
- For most electronics work, a solder with a diameter of 0.75 millimeters (mm) to 1.0 mm is best. Thicker solder might make soldering small joints difficult and also increases the chances of creating solder bridges between copper pads that are not meant to be connected.
- An alloy of 60/40 (60% tin, 40% lead) is used for most electronics work, but lead-free solders are available as well.
- Stand on which to hold the hot soldering iron
- There are a variety of stands available. It is important to always keep the hot iron in its stand when not in use.
- Sponge
- The damp sponge is used to clean the tip of the iron.
Figure 1. Soldering equipment and materials. The solder in this picture is coiled inside a plastic tube; it is pulled through the top as needed. The spring on the stand holds the hot soldering iron. The damp sponge is used to clean the tip of the iron. Solder braid is used to remove solder; solder is "soaked up" into the braid when it is heated by the soldering iron. The wire strippers can be adjusted to strip the plastic covering off of various thicknesses of wire. The prototype board is used to connect electronic components in a circuit. |
- Solder braid
- This is used to remove solder.
- To use the braid, place it over the solder to be removed and heat it from above with the iron. The solder will flow into the braid.
- Solder braid is used to extract an electronic component that is soldered onto a board.
- It is also used to reduce the amount of solder on a connection.
- Prototype board
- A prototype board is used to assemble the circuit. The board shown is from www.protostack.com, but www.radioshack.com also supplies prototype boards.
- Prototype boards have copper tracks or pads for connecting components.
- Steel wool or fine sandpaper
- This is used to clean connections prior to soldering.
- Solder will not flow over a dirty connection.
- Crocodile clips
- These can be used as heat sinks, if needed.
Safety Precautions
- Caution: A soldering iron can heat to around 400°C, which can burn you or start a fire, so use it carefully.
- Unplug the iron when it is not in use.
- Keep the power cord away from spots where it can be tripped over.
- Take great care to avoid touching the tip of the soldering iron on a power line. If a power cord is touched by a hot iron, there is a serious risk of burns and electric shock.
- Always return the soldering iron to its stand when it is not in use.
- Never put the soldering iron down on your work bench, even for a moment!
- Work in a well-ventilated area.
- The smoke that will form as you melt solder is mostly from the flux and can be quite irritating. Avoid breathing it by keeping your head to the side of, not above, your work.
- Solder contains lead, which is a poisonous metal. Wash your hands after using solder.
Tips
Reliable operation of a circuit with soldered connections depends on good soldering practices. Here are some tips for successful soldering.- Plan before you start to solder. Identify all the parts that you will be using.
- It is helpful to attach each part to a piece of paper and write what it is and its value (for example, resistor #1: 100 ohms).
- Some components, such as LED's, must be placed the correct way around in order to function.
- The following is a suggested order for the installation of various components:
- Integrated circuit (IC) holders (note the orientation). The IC will be added later.
- Resistors
- Capacitors, less than 1 micro farad
- Large capacitors, 1 micro farad or greater, note the orientation.
- Diodes, note the orientation.
- LED's, note the orientation.
- Transistors, note the orientation.
- Solid wire connections between components on the board
- Solid wire is fairly rigid, so it will stay in place once attached.
- Stranded wire to parts that are connected by wire to the circuit
- Stranded wire is more flexible than solid wire.
- Integrated circuits
- Connect them the correct way around.
- Many IC's are static sensitive.
- Leave IC's in their antistatic packaging until you need them, then ground your hands by touching a metal water pipe or window frame before touching the IC's.
- Carefully insert IC's in their holders. Make sure all the pins are lined up with the socket, then push down firmly with your thumb.
Preparing the Soldering Iron: Tinning the Tip
- Place the soldering iron in its stand and plug it in.
- Wait for the soldering iron to heat up.
- Moisten the sponge.
- 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 flow from the iron's tip to the joint.
- The solder should flow onto the tip, producing a bright shiny surface.
- If the solder will not flow onto the tip, clean it by wiping it on the wet sponge.
- When tinned, wipe excess solder off on the wet sponge.
- You do not need to tin the tip before every joint, but you should re-tin it if it has gone dull when the soldering iron has not been used for a few minutes.
- Check the manufacturer's instructions related to tinning the tip.
- The tip of the soldering iron should be a shiny silver color. If it is black and pitted, replace it with a new one.
Soldering
- Solder needs a clean surface on which to adhere.
- Buff the copper foil of a PC board with steel wool before soldering.
- Remove any oil, paint, wax, etc. with a solvent, steel wool, or fine sandpaper.
- To solder, heat the connection with the tip of the soldering iron for a few seconds, then apply the solder.
- Heat the connection, not the solder.
- Hold the soldering iron like a pen, near the base of the handle.
- Both parts that are being soldered have to be hot to form a good connection.
Figure 2. The tip of the soldering iron heats both the copper pad and the lead from the electronic component. Solder melts when placed in contact with the hot metals to be joined. |
- Keep the soldering tip on the connection as the solder is applied.
- Solder will flow into and around well-heated connections.
- Use just enough solder to form a strong connection.
- Remove the tip from the connection as soon as the solder has flowed where you want it to be. Remove the solder, then the iron.
- Don't move the connection while the solder is cooling.
- Don't overheat the connection, as this might damage the electrical component you are soldering.
- Transistors and some other components can be damaged by heat when soldering. A crocodile clip can be used as a heat sink to protect these components.
Figure 3. By absorbing heat, the crocodile clip will reduce the heat that flows to the component, helping to prevent damage. |
- Soldering a connection should take just a few seconds.
- If it is taking longer, see the troubleshooting section below.
- Inspect the joint closely. It should look shiny.
- If you are soldering a wire (called the lead) onto a PC board (on the track), it should have a volcano shape. See Figure 3.
- If the connection looks bad, reheat it and try again.
Figure 4. The solder in a good join will be shaped like a cone, with solid contact between the solder and all surfaces to be joined. Bad joins (also called dry joins) should be melted and remade. |
- Wipe the tip of the iron on a damp sponge to clean it. The tip should now be shiny.
- Unplug the soldering iron when it is not in use.
Common Problems and Troubleshooting
- Solder will not flow.
- The parts to be joined may be dirty. Remove the solder and clean the parts.
- The connection looks grainy or crystalline.
- Parts were moved before the solder was allowed to cool.
- Reheat to form a good joint. You may need a larger soldering iron to heat connections adequately.
- The tip is oxidized.
- Soldering is much easier with a shiny, clean tip.
- Clean the tip with a damp synthetic sponge while the iron is hot.
- To avoid oxidizing the tip, do not leave the iron plugged in when not in use.
- Do not use the iron at a higher temperature than is necessary to melt solder.
- Clean the tip of the iron on a damp synthetic sponge as soon as it starts to change from a silver color.
- There is too much or too little solder.
- Using too much solder can cause a solder bridge, which means that two adjacent joints are accidentally connected.
- Using too little solder might result in poor electrical continuity between the board and component. The connection should be smooth, shiny, and rigid.
Laser printer and photocopier operation
Copiers and laser printers have a lot in common. The major difference is in how the image is formed on a photosensitive drum:- A copier uses a bright light and lens to focus an image of the original (actually, a strip at a time which is scanned in most modern low to medium performance copiers) onto the drum. Adjusting the lens-to-original and lens-to-drum distance is used to vary the reduction or magnification.
- A laser printer uses a low power sharply focused laser beam to scan one
line at a time on the drum. Modern laser printers use infra-red solid
state laserdiodes similar to those used in CD players and optical disk
drives while older ones used helium neon lasers.
The digital image is generated from a bit map stored in the printer's
memory and modulates the laser beam. Scanning is mechanical - a high
speed motor spins a multifaceted deflection mirror to get the X-axis
and the paper moves to get the Y axis.
LED printers use a large array of LEDs as the image source but are otherwise similar to laser printers.
Plain paper fax machines use similar techniques in their printing mechanism.
The most sophisticated machines are now actually scanner-laser printer combinations with buffer memory so that multiple copies can be made without rescanning the original, sorting and collating is more flexible, scaling and rotation can be done digitally, and other features not possible with simple copiers.
(Portions from: Copenhagen Cowboy (cowboy@fastlane.net).)
The photosensitive drum is the heart of the laser printer or copier. In larger machines, it may be a separately replaceable unit. In most laser printers and smaller copiers, it is part of the 'toner cartridge' and is a throw-away (or may be recycled).
The drum is coated with a photosensitive material which has an extremely high resistance when in darkness. It's resistance drops to a low value when illuminated.
All of the following takes place as a continuous process as the drum rotates. Note that the actual photosensitive drum in most copiers and laser printers has a circumference that is much smaller than the length of the printed page. Therefore, only a portion fits at any given time and the charging, exposure, transfer to the paper, cleaning, and erasing is a continuous process:
- The drum's surface is charged to a high positive voltage (typically 5 to 6 kV) by a set of charging corona wires in close proximity to the drum.
- The exposure process differs for copiers and laser printers:
- For copiers, a swath of the original is focused onto the drum. As the drum turns, a quartz lamp and strip mirror moves along the original and second strip turning mirror moves at half this speed. The result is that the entire original's image is kind of 'peeled' onto the rotating drum. (Look through the glass platform that supports the original of a copier as it is copying and you will see what I mean.)
- For laser printers, the negative image of the page stored in the printer's buffer memory (the laser is turned on where the print is to be black) is read out and scanned onto the drum one line (i.e., 1/300th or 1/600th of an inch) at a time.
At this point, a swath of the image of your ultimate copied or printed page resides as areas of electrostatic charge on the drum. This is a 'latent' image and must be 'developed'.
- As the drum continues to turn, the latent image rotates past the 'developer
unit' which contains a mixture of developer and toner. For the most part,
developer is not really used up during the printing process but some is lost
and may need to be replenished from time-to-time (depends on design).
- Developer is a material which includes powdered iron or other powder which is attracted by a magnet.
- Toner is the actual 'ink' and consists of very finely powdered thermo plastic particles. These are 'fixed' in the fuser by literally melting the image onto the paper.
A magnet in the developer unit which is as long as the page is wide causes the developer along with trapped toner to stand out following its lines of force off of its long N-S pole pieces. This forms a kind of brush of toner and developer material which is in contact with the drum as it rotates with its latent image. Normally, the developer material brush is C-shaped, and toner particles are carried in the C-shape (the back of the 'C' is against the drum).
Here is where the developing processes of copiers and laser printers differ:
- For copiers, the relative charges of the drum and toner are set up so that toner is drawn to the unexposed (dark parts of the original) portions of the drum resulting in a positive image on the paper.
- For laser printers, the relative charges of the drum and toner are set up so that toner is drawn to the exposed (where the laser beam was turned on) portions of the drum resulting in a negative image on the paper.
- The drum continues to rotate around and comes in contact with the paper.
Below the paper is another corona, the 'transfer corona'. Another high
voltage is applied to the back of the paper (once again, around 7 or 8
kV DC) to draw the toner from the drum to the paper. (Remember, all this
is going on in a continual cycle and it is all in motion).
- Depending on the manufacturer of the machine, you may or may not have a third corona, the 'separation corona'. This is needed to separate the paper from the drum, but not disturb the toner on the paper (the separation corona is usually 4 or 5 kV AC (if it was DC, you would separate the paper, but have VERY smeared toner all over the page as to make it unreadable). The separation corona usually has guides over it to keep the paper from 'dipping' down too far into the corona shell.
- Paper is then transported to the fuser which 'fixes' the toner to the paper via heat (to soften the toner particles) and pressure (to embed them in the paper fiber). There are parts in the fuser which also keep the paper from sticking to the hot rollers. A thermostatically controlled quartz tube lamp provides the heat inside the anti-stick (Teflon coated) fuser roller.
- Finally, your copy or printed page is ready!
- However, we are not done as there is still some toner on the drum - it is not possible to get it all off electrically) so there is usually a rubber or plastic blade which rubs in direct contact with the drum. This 'drum blade' scrapes the toner off the drum, and the 'recovery blade' catches it to keep it from falling back into the machine. A 'used toner auger' transports the used toner (which is now changed both physically and electrically and is also contaminated with paper dust (don't reuse your used toner) because it can eventually damage the developer unit, cleaning blades, fuser sections and other parts of the mechanism.
- Now that all the toner has been scraped off the drum, there is still some residual charge on the drum from the previous exposure process. You can't scrape the static charge off the drum, so the cleaned drum is now fully exposed to a bright light to discharge the drum surface and prepare it again for a new charge, which comes right after the discharge lamps.
There is also some photocopier information at:
Laser printer operation summary
(Portions from: Zaki (zg@ix.netcom.com).) In general the principle of electrostatic laser printing is as follows:- Charging a photoconductive selenium (or other) coated drum.
- Discharging the drum with the laser steering engine in accordance with the input image rasterized pattern. (the laser is modulated to generate a predefined pixel pattern on the face of the drum - the focal plane).
- The rotating drum attracts toner to the charged pattern (latent image) generated by the laser.
- The toner is transfered from the drum to the moving papaer to generate a full image.
- The paper carrying the toner moves through the heater to fuse the toner to a fine non-erasable image.
- Infra-red diode laser, 3 to 4 mW in basic units, up to 30 mW or more for high performance printers.
- Beam expander to form the required size of the collimated input beam which generates the beam spot size in the focal plan.
- Cylindrical lens to reshape the laser elliptical beam to a round one.
- Spinning polygonal mirror to deflect the laser over the focal plan.
- F-Theta lens to flatten the inherent circular plan of a rotating mirror. This lens is a very special lens which only few in the optical community know how to design and fabricate. The one that you own is particularly special because it is a Sectioned F-Theta lens which are typicaly more expensive (most of them are spherical). If you need to scan or to print in high resolution 500 dpi or higher, you end up using a glass F-Theta lens.
Cleaning and Handling of Photosensitive Drums
Where the drum is located inside a replaceable toner cartridge, there is no need for special handling. However, where the drum is a separate unit, the following applies. Or, if for some reason, you need to disassemble (gasp!) a cartridge: (From: David Kuhajda (dkuhajda@locl.net).)Whatever you do, do NOT use alcohol on an organically based drum, it will ruin it. The alcohol causes the material to crystalize. I use to do copier service and this was stressed a lot by the manufacture as they switched from the old selenium drums to the new opc drums. Direct sunlight will immediately destroy the drum. A couple of minutes under normal lighting is no problem, just place it in a dark area and put a black cloth over the top of the drum while it is out. If you are replacing the drum cleaning blade or cleaning the crud off the blade, make sure you powder up the drum completely and the blade before reapplying power. The toner actually is a slight lubricant and the rubber cleaning blade directly on the drum will also ruin it. Just print a few low text copies after reassembling to allow the blade to reseat properly.
(From: hapticz@email.msn.com.)
Short periods (less than 5 min) under fluorescent lighting is safe.
Direct sunlight kills them immediately.
Just have a clean brown paper bag to shove it into while it sits on the table outside the machine.
Often more damage is done to them physically during insertion/removal. just be careful.
Xerox used to clean the 10" diameter drums with 90% isopropyl alcohol and some kind of "Kim Wipes" in our office, that was years ago though.
Book on laser printer maintenance and rapair
(From: Michael (ncacaver@aol.com).) Get the book: "Easy Laser Printer Maintenance and Repair by Stephen J. Bigelow".Your local library should have it or be able to get it. Stephen J. Bigelow has several other books on printer repair, both laser and non laser types. All are very good.
Discussion on laser diodes in laser printers
"I just acquired the optics from a dead laser printer and have been trying to understand it. There are two functions I have yet to grasp. One is something which it has but for which I see no need. There seems to be a heater (Contains mica) and a thermometer, with PCB markings like "T1" and H2" or something similar. If these the laser is temperature controlled, why? There seems to be a control photodetector to monitor the laser diode so temperature control appears like overkill unless the photodiode itself has too much temperature dependence and the drum exposure is very critical."(From: Jonathan M. Elson (jmelson@artsci.wustl.edu).)
There is a heater inside the fuser roller. This is what melts the toner into the paper. It is thermostatically controlled, and then has a safety thermostat in case the control fails.
There are two photodetectors for the laser. One compensates for dimming of the laser over years of use, the other picks up the beam at a particular angle of the polygon mirror, and synchronizes the raster electronics to the polygon rotation.
"The other thing is something I cannot find, the aperture defining the nice well-formed pixel. So far I must admit the study has been a bit superficial but the aperture ought to be pretty obvious if there is one!"The laser is the aperture. With an optical path of 0.5 m or so, the laser is a pretty good approximation of a true point source. A simple lens makes it look like a very good point source.
"Finally, how are the correction lens made? They look like slices out of the middle of some fair sized lenses, but that would be a very wasteful way to make them. Can they be diamond formed to nearly the final shape and with such good finish so only a simple polish completes them. Grinding the old-fashioned way on a sliver of glass looks doomed to generating all sorts of defective approximations to a sphere. (As far as I can tell they are glass, or some wonderfully hard plastic I would like to know more about!) Can they be molded to sufficient precision? (The sides are ground or sawn.) Thanks to anyone who can bring me up to date on lens fabrication technique."I think they mold these lenses to near correct shape, then grind and polish to the desired aspheric shape with specialty machines for that purpose. (Note that almost all eyeglasses are aspheric for astigmatism correction.) Yes, these lenses are glass, I've had a few printers apart myself.
Types of toner
(From: Lionel Wagner (ck508@FreeNet.Carleton.CA).) There are two basic kinds of toner: magnetic and non-magnetic. If your laser printer has a Cannon 'engine' it most likely uses magnetic. NEVER use the wrong type. The imaging process is extremely delicate and specific toners are important. Use of toner that is slightly different could result in all black or all white copies.So you put in the wrong type of toner?
"I have a 3M Model 6312 copier. I believe it is a re-badged Lanier. I didn't pay much for it but it worked well. When the toner warning light came on, I made the mistake of adding the wrong kind of toner. I removed the wrong toner as much as I could by vacuum. Is there anything I should do before adding the right type of toner? Did I do serious damage to the system? What to do if the warning light remained on even with the right type of toner added? Any suggestion will be greatly appreciated."(From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)
If your copier uses non-magnetic toner, it is mixed with iron powder, called the Developer. Both have to be removed and all residue vacuumed out. If the copier uses magnetic toner, less of it will remain in the machine. Try to get as much as possible out. Do not scratch the roller on which the toner sits.
WARNING: See the section: Warnings about vacuuming laser printer toner before using a household vacuum cleaner to do this!
Subscribe to:
Posts (Atom)