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Wednesday, May 14, 2008
TV remote control Blocker
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555 timer as the bases of the touch switch
Control electrical appliances using PC
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Generating -5VDC from +5VDC
The circuit is set up to oscillate at about 45kHz, with a duty cycle pretty close to 50%. None of the values of any of the parts are terribly critical, so if the capacitors or resistors are "in the ballpark", it should still work okay
Generating -5VDC from +5VDC
The circuit is set up to oscillate at about 45kHz, with a duty cycle pretty close to 50%. None of the values of any of the parts are terribly critical, so if the capacitors or resistors are "in the ballpark", it should still work okay
FM Oscillator
As with all VHF circuits, pay particular attention to construction technique. I recommend cutting little square islands on one side of a two-sided copper-clad board. Use the remainder of that side as the ground plane, and leave the bottom side to serve as a shield. If you keep all lead lengths short, the circuit is quite stable.
With the parts listed here, effective frequency range extends well beyond the FM broadcast band in both directions. If a 6V zener is substituted for CR2, the circuit will run from a 9V battery, with a slightly smaller tuning range. The output is hot enough that the signal can easily travel a city block using just a clip lead for an antenna.
Headlight Reminder Circuit
Peltier coolers/heaters
A typical peltier device consists of a number of series-connected N- and P-type semiconductors sandwiched between two ceramic plates, such that the flow of majority carriers (electrons or holes) in each semiconductor occurs in a single direction.
The device works by depleting the cold side of thermally-generated carriers and moving them to the hot side; in essence, the device is a heat pump. When a fixed potential is placed across the device's terminals, a fixed temperature difference will be maintained between the hot and cold sides. If the hot side has a sufficiently "beefy" heat sink, this temperature difference can be several tens of degrees C.
The process is reversible -- placing a temperature difference across the device will cause a voltage to develop across its terminals.
SIMPLE SECONDS FLASHER
The preset resistor VR1 is used here to adjust the led flash at a frequency of 1KHZ.
Although CMOS chips can work off supply voltages between 3 and 15 volts, a stable and regulated power supply should be used to mainta
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A simple Remote control Tester
Tech. Editor’s note: In fact, the complete gadget ca
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Concept and visual structure
The seven segments are arranged as a rectangle of two vertical segments on each side with one horizontal segment on the top and bottom. Additionally, the seventh segment bisects the rectangle horizontally. There are also fourteen-segment displays and sixteen-segment displays (for full alphanumeric); however, these have mostly been replaced by dot-matrix displays.
Often the seven segments are arranged in an oblique, or italic, arrangement, which aids readability.
A mechanical seven segment display for displaying petrol prices.
Most separate 7-segment displays use an array of light-emitting diodes (LEDs), though other types exist using alternative technologies such as cold cathode gas discharge, vacuum fluorescent, incandescent filament, liquid crystal display (LCD), etc. For gas price totems and other large signs, electromagnetically flipped light-reflecting segments (sometimes called "vanes") are still commonly used. An alternative to the 7-segment display in the 1950s through the 1970s was the vacuum tube-like nixie tube.
In a simple LED package, each LED is typically connected with one terminal to its own pin on the outside of the package and the other LED terminal connected in common with all other LEDs in the device and brought out to a shared pin. This shared pin will then make up all of the cathodes (negative terminals) OR all of the anodes (positive terminals) of the LEDs in the device; and so will be either a "Common Cathode" or "Common Anode" device depending how it is constructed. Hence a 7 segment plus DP package will only require nine pins to be present and connected.Integrated displays also exist, with single or multiple digits. Some of these integrated displays incorporate their own internal decoder, though most do not – each individual LED is brought out to a connecting pin as described
Seven segment displays can be found in patents as early as 1908 (in U.S. Patent 974,943, F W Wood invented an 8-segment display, which displayed the number 4 using a diagonal bar), but did not achieve widespread use until the advent of LEDs in the 1970s. They are sometimes even used in unsophisticated displays like cardboard "For sale" signs, where the user either applies color to pre-printed segments, or (spray)paints color through a seven-segment digit template, to compose figures such as product prices or telephone numbers.For many applications, dot-matrix LCDs have largely superseded LED displays, though even in LCDs 7-segment displays are very common. Unlike LEDs, the shapes of elements in an LCD panel are arbitrary since they are formed on the display by a kind of printing process. In contrast, the shapes of LED segments tend to be simple rectangles, reflecting the fact that they have to be physically moulded to shape, which makes it difficult to form more complex shapes than the segments of 7-segment displays. However, the high common recognition factor of 7-segment displays, and the comparatively high visual contrast obtained by such displays relative to dot-matrix digits, makes seven-segment multiple-digit LCD screens very common on basic calculators
Basic UPS Power Supply
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(VP5 - 0.6 ) / R1where VP5 is the unregulated DC power supply voltage.D