Tuesday, November 25, 2008

Hmo Insurance Dermatologist

Repair a welder

I recently had the opportunity to work for the first time on an electronic welder. I must say that it 'was very interesting, especially for the satisfaction in having seen "live" the things I studied at the University. I do not happen every day to see a circuit capable of delivering fifty times with nearly two hundred amperes of current!
Here is a picture of the "patient" before the repair:


After a rather intense period of operation, the welder has simply stopped working. And not 'more heated, I' the light on the panel has more 'showed signs of life, even the fan is stopped.

Open the welder.
Needless to say, I opened suddenly poor welding, chasing a failure!
The first step when you examine the inside of an electronic device and 'identify the basic components, imagining a possible block diagram.
first assumptions are often wrong, but careful observation and 'essential to decide what to do.

The interior side of the Fan:


From this perspective one can 'follow the path of the power cord, passing through the switch, the gate voltage to the first small board. in all probability 'is the filter feeding, omnipresent in the circuit-switched, looking closely you can ' guess the structure of the filter formed by capacitors, polyester and double inductance clearly visible in the center. The block diagram of a filter of this type, 'this:


Capacitors help filter out high frequency disturbances, especially those made by the welder, while the inductance helps filter out the component of common mode current, always in high frequency.
One disadvantage of circuit switching consists in the generation of several harmonics of the disorder.
A filter, even if rudimentary as the one in question, it is essential to not overly stress the components of the electricity grid.

On the right side of the board, mounted at the rear, and 'guess the placement of the large bridge rectifier, from where the red and black wires to the main board.

protection system against overheating and 'very elementary. The resistance wire inductance can see next provides power to a secondary circuit present on the main board. By processing the signal from the thermocouple mounted on the heatsink, does energize the relay 'in case of overheating . Typically this is an amplifier followed by a comparator to trigger of Schmitt .

cables for power and control signals are contained in the pocket, sterling black, best seen in this photo together with the thermocouple (mounted on the aluminum plate in the rear):

click to enlarge

always show the same picture can be seen on the filter capacitors (red).
Let us look at the main board:


We note immediately rather intuitive layout of the components. The mains voltage is rectified previously leveled electrolytic capacitors in the picture above, and the DC voltage of about 320V so 'obtained is sent to the stage (and here' mounted behind the printed, covered by heavy cooling fins).
The finish seems to be of dual - forward, given the presence of an isolating transformer windings for simple (a single primary winding and a secondary recirculation diodes , no center tap), but I found more information in merit. It matters little, since the problem was somewhere else.
fact, is derived from previously obtained immediately 320V power supply for the control stage. Looking at the top of the tab, you can 'see a governor in a container TO 220 (in this case a LM 7815), and several other capacitors leveling, as well as two large wire resistance, which have been aroused my suspicion.
The first thing I did after having opened, reviewed and cleaned up the welder and 'the measure was "hot" stress more' important.

WARNING: The test 'was carried out with fully open and welding voltage mode. How 'reported on the carcass of any electronic device, any measure should never be done in this way, but respecting the minimum precautions I decided to take a chance.
It goes without saying 'that's inexperience, haste and lack of knowledge of the internal electronics are factors that require immediate closing and that the delivery to the repairer as' trusted.

I started the measure starting from the filter capacitors, and verifying the actual presence of continuous 320V. It must be said that the bridge rectifiers and are always slightly oversized and rarely undergo failure.
I then shifted the focus on nutrition monitoring, starting from the controller.
E 'soon became clear that the 7815 does not pay any tension between the central terminal and the output terminal (easily identifiable by datasheet ). Not even the upstream voltage regulator showed signs of life. Evidently the problem was before, and indeed the two-wire resistance revealed the secret.
To the leaders of most resistance 'to the regulator fell near zero volts, while the other heads I measured the famous 320V!
At this point it was quite desirable that the resistance was broken, and in fact the measure has proved me right.
you look closely you can see the photo already cut the legs of the resistance (cutting and 'need to get a reliable measure of resistance, do not forget watch out!). One was still healthy, the other, as expected, lost.

repair.
I immediately searched the resistance wire identical to the originals, but in addition to having experienced significant difficulties to find it, I was not totally happy with your purchase, simply say that I bought four replacement heaters at a shopkeeper who was fortunately provided, and one of them (certainly not the fault of poor seller!) Was already 'lost. .. Quality 'zero.
Here is a picture of the original strength, open to verify the fault, and that "new," interrupted


The original strength and 'up, its a full compromise does not need words.
acquired resistance, below, presents the filament slightly loose in the center, a sure sign of a break. Even with a measure clarifying the meter gave an interesting result: from one end and sliding one of the two leads to the other, the measured resistance rose linearly to about 1.5 Kohm , only to meet the ' interruption.

The issue of the abbreviation.
Looking carefully at the picture, there is an apparent inconsistency between the symbols of resistance. Look at them closely:


resistance originally stated the letters J 3K3, namely 3.3 Kohm 5%, 9W power.
The new one shows just the initials 3R3 K. Now, until proven otherwise, identifies 3R3 a resistance of 3.3 ohms, and 3.3 Kohm .
According to the seller, the "K" would identify the multiplication by 1000, but we all know that the letter after the code identifies the tolerance. Otherwise how to identify this parameter? Let
also the standard code (borrowed from another site):


We note that the "K" indicates a tolerance of 10%, while the "J", found on the original strength, indicates a 5% .
Not only does the resistance have a new acronym ambiguous and one in four and 'bad, but also have a high tolerance more!
In my opinion it is a gross lack of production.
It remains an open question on the code, I invite readers to give their opinion!

However, given the reduced critical component in this specific application, and given the difficulty of finding them, I decided to also finish the repair.

I then proceeded with the cleaning of the weld with flux solid and desoldering braid. The welding of new resistances took much time because of the need 'to heat the large mass of track on which he insisted one of the leads.
warming estimate (made by simply taking the 50W soldering iron for about twenty seconds on the card, moving it from time to time) and it 'was necessary to ensure a reliable weld. Otherwise we would have obtained the most welding classic "cold", and the adhesion of the pond would have been very very weak.
I took advantage to also to brush the welds of the capacitors.

assembly and testing.
Here is a detailed picture of the area after the repair:


I considered appropriate rebadged resistance in case of future repairs. Not having anything better, I used a permanent marker fine tip, hoping it will not discolor. It would be rather sad if, in the distant future, a repairman had to make my own operation, and replace the burned resistors with resistance of 3.3 Ohm ...

is worth a look also to the first "heavy" of the circuit:


Fascinating, right? I must say the quality general assembly and 'definitely above average, and the precision of puncture and alignments, and' very high. The eye
note several important measures in the printed circuit board, such as the ground plane and the bolting of busbars flanked to the riveting, in order to ensure optimal electrical contact.

exception, I have decided not to clean up the welding with the solvent, because the flux solid use often and 'high quality , and still leaves a protective film on the weld itself. If you work with signal circuits I worry more and remove all traces of flux , working carefully with a brush and paint thinner, but in this case I also withdrew because of the protective coating deposited on the PCB.
fact that I noticed and 'usual practice of covering the printed circuit board manufacturers of varnish after finishing the welds. In and thus 'provided additional protection for critical working conditions like those of a welder and' very important.

And finally a photo on your mobile electronics re:


All images can be viewed at full resolution on PICASA .

Wednesday, November 19, 2008

Tooth Extracting Inpregnant






Debut Opening Invocations




Party This Saturday the skipper course, dedicated to all those who are tired of being "carried" by boat and want to lead the 'boat in complete autonomy. The boats used are sailing cruisers from 11 to 12 meters and the program includes: motor maneuvers in port, maneuvering in restricted waters, berths, moorings, spinnaker cruising, engine maintenance, aircraft instrumentation.

Whats Cheaper Smirnoff Or Jack Dainals

CRUISE SKIPPER COURSE IN FINE FALL Flotilla


RIVIERA
Three days to enjoy the charming towns of the coast of France. Possible Destinations: Villefranche, Nice, Antibes. Embarking and disembarking in San Remo.

SARDINIA
Forget the cold! On board the new Delphia 37 discover the coast North Sardinia: Asinara, Isola Rossa, Castel Sardo ... .. Embarking and disembarking in Porto Torres

Life After Calcaneal Fracture



Veladoc Sailing School is one of the oldest schools in Italy and stay ahead. Nini Sanna and his team for over thirty years to the sail approach people of all ages, bringing them the early edge in the cruise on the autonomy and international regattas. The characteristic of the sailing school is divided into didactic courses that allows everyone to familiarize themselves with the boat and the sea highlighting the potential of each student. The boats used are modern cruisers owned by the school offering brilliant racing performance and comfort cruise. Veladoc team consists of professionals who have made skipper of the sail their profession. The courses are held throughout the year. The mild climate in Sanremo allows pleasant trips out to sea in all seasons and the nearby Riviera cruises lets in just the weekend. From September to June, a full calendar of races is the gym for those who want to keep training.

Thursday, November 13, 2008

Sitting Bouncing On Stomach

use a graphical display

Many of you surely know the 2 x 16 alphanumeric display, also known as "two rows sixteen characters," or simply "HD44780" in the name of the controller typically adopted.


On the web there is plenty of material about the piloting of these displays, which is actually quite simple.
In a few words and 'just send the data line codes corresponding to characters to be displayed, using the appropriate control signals specifying the position of the characters, the blinking cursor, scrolling text etc. possible.
Clearly, a display of this type is suitable for display exclusive of letters and numbers, and even when they have a pretty good choice of symbols (bar, special characters, etc.). Any attempt to display "graphics", such as a slider bar or a diagram, it becomes a compromise between visual quality and the choice of the symbol more intuitive. And 'in fact can not display an image.

In this regard, for some time made their pop-up graphic displays, or dot matrix, where the viewing area is evenly covered with pixels.
The resolutions are relatively high, ranging from 64 x 64 display of mobile phones, passing for 128 x 64, 128 x 256 etc.. up to VGA display with 640 x 480 pixels and above.

As is intuitive, can drive these displays is more complex than the text of the 44780 protocol, but the structure is basically the same: the string of alphanumeric characters of 44780 is simply replaced by a set of vector coordinates, to be managed properly by control signals. In most cases, just send the sequence to the display on and off of individual pixels, sweeping the entire surface. A little 'as you would fill an array box to box, in groups of eight bits at a time.

If the display is connected to a computer, the image preprocessing must be handled by the software of an aircraft, but the amount of programs already written for this specific function makes the task quite easy.
If you work with a microcontroller, the work is further simplified by the abundant presence of appropriate software packages and libraries, to paste directly into your code.

The display in question.
I was able to deal with this when I found a display PG12864A, recovering from a handheld PC industrial (recovered the old crap, and at no cost!) when I saw him taken a relentless curiosity that led me to a first approach based on the port by PC (in fact it is the easiest and fastest way to exploit the graphical display of some complexity like this).

Technically PG12864A and 'just another display of 128 x 64 pixels based on the KS0108 controller, widely used and tested.

Here is a picture of the display, before:


and behind:

You immediately notice the presence of a row of 20 contacts. From datasheet of the display and 'immediately guess the similarity with the classic pin-44780; in fact the only differences relate to some hardware control pins.

interface with your computer.
the most 'direct and easy way to display and use these' parallel interface (unidirectional, although SPP is fine) to a desktop computer, not only for the limited hardware needed, but for the most simplicity 'in the management and content management software. Assuming an implementation on a microcontroller in fact, must necessarily be out on a substantial amount of memory in which the frame and keep all the pictures!
PC connection also allows the display of the content more 'different, notes interfaces for winamp network status, the temperature inside the PC using the RAM, just to name a few.

Basically the scheme to be implemented follows this example:



WARNING: The diagram shows a generic way to pin the display, on completion, you should check the actual pin-out of its display, and provide any adjustments.

You notice the absolute simplicity of this solution, which provides an immediate and direct connection between the pins of parallel port and the corresponding pin of the display.
Obviously this is 'the best solution' rudimentary; I personally have made an interface using the very well known 74LS245, Octal bidirectional buffer, which for this application are in fact a little 'wasted.

Also note the presence of a pin labeled "Vout". Well, by that pin comes out a negative voltage of approximately-10V, which is generated internally by the electronics of the display, which is needed to power the LCD panel. Using a trimmer
10Kohm between this pin and ground, before returning to the pin "Vo" is obtained by adjusting the contrast.

to connect to the parallel port I used a 20-pin flat cable, and that 'proved particularly versatile and reusable for future projects.


Inside:



To display connection, I used 40-pin IDE interface, they use only half, but the practice 'of this solution is unrivaled.
to complete the work I added a 7805 regulator and trimmer for contrast on the same card. The 40-pin IDE interface I can be useful to make an interface for both alphanumeric and graphic displays, using just the two rows of contacts at a time.
will improve in the future 'interface for alphanumeric.

The interface card then so is' be:

Since the card
spacers, the rear and 'very popular in fact work more' long 'was the wiring to the various connectors:


The work will not be' clean but it 's very robust and versatile. This gives rise to the natural light on the choice of buffer. Some might ask: why not use the 74LS244 ? Looking at the datasheet, and in particular the effective provision of internal buffers, the answer is' obvious: '245 in the buffer are all aligned, and the adjacent 8-pin can be assigned to all input or output, while in the '244 you the alternation of an input with the output of the pin opposite.

I initially made an attempt (also works) for the use of 244, with this result:


Confusion reigns. I confess I had not expected such a tangle of connections, the use of a 74LS244 and 'practical benefit only in the case of PCBs specifically designed, or where it is used in a "cross", ie the inputs in the head and exits at the foot of the chip, in order to avoid too many overlaps.

The overall interface is so 'made:


software.
For the management of these displays are numerous software, more 'or less' homemade'. Personally I used LCDHype ( Home ), I found it quite intuitive and feature-rich pre-compiled for those (like me) did not really want to be there 'to plan! There are other programs
more 'specific, for example interfaces shown Winamp. Most

'Note:
LcdStudio, similar to LCDHype: Home
Microchipc, for libraries to download the PIC microcontroller series: Home
LCDSmartie, more' suitable for alphanumeric displays eg. 4 x 40: Home

An interesting article about the Ubuntu-known program jaLCDs: Article .

Examples of operation.

interface for Winamp:


bar interface, always for winamp:


Displaying an image:



A analog clock:




All images are visible in high resolution on PICASA .