Monday, December 27, 2010
【 Weak current College 】 PCB wire design techniques】
Microcomputer peripheral electric baseboard road conductor design
A.LED current conductor design
LED components widely used in computer peripherals, but most of the led package location, quite far away from the computer itself. LED brightness as long as you maintain the right to, in some cases require a bright environment can easily distinguish the luminance LED 's, yet even IF the same driving current, LED by the luminance with the glow color variance. As shown in Figure 1 LED for currents up to 10 mA, with the led current wire length and path extension of the LED's ON/OFF often become peripheral circuit switching noise occurs (switchingnoise) incentives.
LED luminous color and luminance relations
Typical LED driver circuit
This package when the driver transistors required as close as possible to the reduced LED LED current IC flow path. The brilliance and LED drive current is proportional, generally designed to green LED for benchmarks, in accordance with table 1 of the set value changes the color of the current value. LED circuit substrate pattern may, in accordance with Figure 2 of the matrix (matrix) arrangement, appearance is very simple, driver transistor is deemed digital transistor (digitaltransistor), series resistance in General is located in the back of the circuit board.
Typical led driver circuit board designs (double-sided printed circuit boards)
B. hours LED by common terminal design
Is the use of microprocessor-controlled dynamic driven anode opendrain Terminal (anode) commontype7 periods (segment) LED circuit, from the power supply to the 7 hours LEDcommon Terminal wire, when based on full time light currents up to 40 ~ 100mA, therefore designed as far as possible, bold circuit substrate pattern (pattern) wire width. Use double-sided circuit substrate and disclead, components required in the monitor, so you can avoid affecting 7 hours LED packaging operations. Chip (chip) component if it is located in the back ofthe substrate, as shown in Figure 4 you can eliminate the monitor around the component, if coupled with connectors (connector), cn1, encapsulation of LED modules can be directly fixed to the microcomputer.
Is the use of circuit board designs CADEAGLE software automatic routing, the software has the automatic Layout feature, and you can design an unlimited number of changes, in addition to automatic routing through the trial calculation error for various paths (route), but the author recommends that initial set of plates on the back of the wiring-direct personally, relatively easy to modify, especially like the circuit, if no specific wiring direction success rate is very low.
Chip components of 7 hours LED circuit pattern (double-sided printed circuit boards)
C. high humidity atmospheres of substrate wiring
Photo 1 is built-in peripheral circuit of humidity sensor CHS-GSS actual appearance, as shown in the relative humidity of 100% CHS-GSS humidity sensor only 1V, so can be used as a digital voltmeter directly read the humidity. If the microprocessor's A-Dconverter connection is necessary for the conversion into a 5v grades (range).
Humidity sensor CHS-GSS appearance relative-humidity sensor output voltage characteristic
The circuit uses a single power supply, which is an increase by railtorailOP, for consisting of humidity sensor 1V to 5V, besides using the VR1 gain spinner, you can make a gain (1 + 480/120) = 5.
Wiring design in order to reduce the high humidity environment of leakage (leak) phenomenon, it is necessary to avoid an increase in the OP for Earth (ground) set pattern, while trying to increase the interval between the pattern cut pattern conductor width. R1, R2 uses 1/4W ± 1% resistor metal coating; is drawn in a double-sided circuit autorouter substrate pattern, the welding surface to ground (fullground), the circuit board Assembly and test on resin-coated after moisture-proof.
Expand the humidity sensor outputrange of circuit
Humidity sensors around the circuit pattern
(Double-sided printed circuit boards, not shown on the back ground)
The first two set describes computer peripherals, mock circuit substrate, broadband and high-frequency circuit board, power supply and power circuit substrate, and digital circuit substrate conductor design, this will be followed by a description of the Video application circuit substrate conductor design.
Broadband growth in circuit pattern MHzvideo dozens of design skills
Analog signal especially similar 0 ~ dozens MHzvideo signal broadband circuit, circuit diagrams, flow path marking signal and component placement is very important. Current return-type video increases with the OP for the increase of image HA-5020 circuit (videoamplifier). Traditional voltage reversion type OP increase circuit, gain once larger bandwidth decreases when, in comparison with current return circuit, due to the increase in OP theoretical bandwidth depends on reversion resistance values agreed, is not affected by the gain of impact can be greater bandwidth. From the left input video signal, using a (HA-5020) increases with increase OP 2 times after the output to the right.
Is tens of MHz bandwidth increase circuit substrate of image patterns, frequency once inside the image bandwidth range, circuit board design has a direct impact on circuit performance, especially in the distance, while the path along the circuit diagram of mobile substrate pattern is very important. According to the above point of comparison, you can determine signal flow paths and component settings, almost entirely consistent
If the image using chip-increase circuit components, generally easier to getExpected operating characteristic, if you use the traditional wire components, wire inductance ingredients may affect circuit characteristics.
Provide IC power and grounding plug between bypass capacitor (bypasscondenser), in addition to the tripod insert 47 respectively around μ F electrolytic capacitors, and in parallel than 0 μ F, 0.01 μ F ceramic capacitors, followed by rough short pictorial connection, since limited component encapsulates the space, and other components are encapsulated in the back of the circuit board.
Power supply source and insert a bypass capacitor to ground, if you insert from the right side of the IC, you cannot play a bypass capacitor.