In this paper, practical application, combined with the welding machine control system power embedded system design and debugging process encountered some problems, analyzed and discussed the power embedded system design and debugging methods.

1 system hardware architecture

Embedded systems based Welding Electrode Manufacturer control system design, to AT91RM9200 as the system core microprocessor control system requirements based on expansion of SDRAM, SRAM, Flash, keyboard, LCD display circuit parameters can be adjusted in real time, display and error alarm, RS485 serial interface for data transfer communications, infrared remote control can be. System hardware structure shown in Figure 1.

2 System Power Supply Design

2.1 System Power Works

AT91RM9200 is a complete system built around the ARM920T processor chip. It has a wealth of system and application peripherals and standard interfaces, making low-power, low-cost embedded industrial products. AT91RM9200 offers a full-function power management controller (PMC), to optimize the overall system power consumption, and to support normal, idle, slow clock and Standby mode, to provide different power levels and incident response delay time [1]. In idle mode, ARM processor clock and wait for the next interrupt is disabled (or master reset); slow clock mode is selected after reset mode, in this mode the main oscillator

Oscillator circuit is the basis for sending and receiving equipment, its role is to produce a certain frequency of the AC signal, an energy conversion device - the DC can be converted to a certain frequency AC power. Off to reduce power consumption and PLL; Standby mode is the slow clock mode and idle mode of combination, which enables the processor to quickly respond to wake events, and maintains a low power consumption. When the system outside normal working hours from the DC power supply and battery charging, disconnect the external power supply automatically switches to the internal backup battery.

2.2 Power Circuit Design

AT91RM9200 has five types of power supply pins: VDDCORE pin for power supply to the core, typically 1.8 V; VDDPLL, VDDOSC respectively, to the PLL or oscillator power supply, typically 1.8 V; VDDIOP, VDDIOM were used to the outside set I / O port cable, USB transceiver and the external bus interface I / O port line power supply, usually 3.3 V. In addition, the system's keyboard, display circuit supply voltage of +5 V power supply needs. Therefore, the control system needs to use three groups of power. Through control of the whole control system requirements and performance analysis to determine the system load current is about 3 A. Therefore, the system power supply voltage regulator chips use a series of ON's LM2576 voltage regulator, the external DC power supply voltage regulator into the system needs to +3.3 V and +5 V power supply. As the power supply requirements of the system kernel 1.8 V, so the system should be used two power conversion circuit. This selection of TI's micro-power, low dropout voltage PMOS regulator (LDO chip) TPS72518 chip as the core power conversion, the +3.3 V regulator to +1.8 V, supplies power for the processor core. System power supply circuit shown in Figure 2. Figure 2 shows the power supply decoupling and other embedded systems, PCB design. C3, C6 is the voltage regulator chip electrolytic bypass capacitor in the circuit which enables the circuit to stabilize access to work; C2, C5, C8 and stability for the output capacitor, for reducing the output ripple, noise and output load current change impact good results, according to the regulator's own work requirements, were selected capacitance 10 μF, 100 μF electrolytic capacitor

Electrolytic capacitor is made of two parallel metal plates and the electrolyte is placed between two metal plates that form the capacitor. Capacitors used in accordance with the electrode material. Paid to the type of electrolyte capacitor name. Coated with electrolyte media have polarity, positive and negative points can not be connected correctly.

32-bit microprocessor-based embedded system performance depends largely on the stability and reliability of the clock circuit, the clock circuit depends on the stability of the system phase-locked loop (PLL) stability. Therefore, the analog part of the PLL power supply filter circuit should be used to ensure the stability of power supply [2]. Microprocessor internal clock, power and reset control key components of various modes of operation parameters on the system plays an important or even decisive role. Therefore, in order to ensure that the various modes of operation under the same set of parameters, usually in the embedded system design to provide back-up battery power supply circuit. Shown in Figure 2, using TI BQ24200 battery charger as a back-up power system battery, external power supply when the system is working properly charge it, the external power supply is cut off after the system power by it, in order to save important system parameters.

3 debug system power

3.1 Debugging the content and procedures

A large embedded system hardware circuit, should be sub-module for welding, testing, to avoid the problems encountered can not start checking. Because the system requires access to each circuit block input power, if power input properly, then the output will not correct or even burn IC

IC is the use of semiconductor production process, in a small silicon chip production, many transistors and resistors, capacitors and other components, and multi-layer wiring in accordance with the method or tunnel routing components into a complete electronic circuit . It is in the circuit by the letter "IC" (also useful for text symbol "N", etc.) said. So should the first installation, commissioning and system power supply module. The success of the system power supply circuit debugging module is the hardware circuit debug key to success.

After the welding circuit components based on a good, carefully check whether the Tungsten Welding Electrode is wrong components, circuit boards or welding slag existence Weld short circuit phenomenon, check and correct the power to debug. By the DC power supply

For the load to provide a stable DC power electronic devices. DC power supply power supply mostly AC power, when the AC power supply voltage or load resistance changes, the regulator of the DC output voltage will remain stable. DC power supply with electronic equipment to high precision, high stability and high reliability in the direction of the power supply for electronic equipment put forward higher requirements.

Generator output power access system power module input port (POW1), input power Vin adjusted to +6 V, with an oscilloscope check the system power supply 1.8 V, 3.3 V, 5 V output port, there is no voltage output. Power to re-check the circuit and found that electrolytic capacitor C6 has been burned black, because the C6 positive and negative polarity reversed. A new capacitor for correct welding power debugging, 1.8 V, 5 V output voltage is normal, while the output voltage of 3.3 V voltage less than 3 V. View LM2576 voltage regulator chip data sheet, the regulator input power Vin, simultaneous detection of three groups of system power supply voltage, power output is correct when the three groups, the input voltage Vin is 6.7 V or so. As the load current control system is about 3 A, so by adding the load current in the circuit load resistance of 3 A in order to test the stability of the system power supply. After debugging, capacitors, inductors and other components, the normal heat output voltage value is correct. At this point, the system power supply module debugging success.

Next, step by step installation, commissioning other module circuits. Each installation of a power-detection module, the main power supply voltage detection system and the module's input voltage, the output is correct. When the entire system installed after the hardware power-on circuit debugging and found that the system power supply instability, which often power-down DC input power, resulting in the system power supply is not working properly. Because the system circuits are more difficult to check, has not been resolved. In many power testing, debugging, and found a circuit voltage (boost) converter smoke - the chip was burned. Carefully inspect the chip's data sheet, found that the chip model wrong, positive and negative feedback voltage pin is reversed. After the removal of the chip, the system power supply is working properly.

3.2 Analysis of Debugging

Commissioning of the system power supply circuit and the entire system hardware installation and commissioning process analysis, combined with the installation, the problems encountered during commissioning, the following conclusions:

â‘  chip resistors

Chip fixed resistor, from Chip Fixed Resistor directly translated, commonly known as chip resistors (SMD Resistor), uranium glass, metal resistors in one. Is the uranium metal powder and glass powder mixture, using the screen printing method on a substrate made of printed resistors. Resistant to moisture, high temperature, the temperature coefficient.

Capacitors are mostly used by the collision of the substrate, cracking of the ceramic material, and SMD IC pin quantity, spacing narrow, low hardness, very likely lead solder shorts, cold solder joint, such as failure, so the demolition, temperature control should be mastered welding, preheating, touch and other techniques.

â‘¡ the power module during debugging, you must carefully check the components installed is wrong with a voltmeter the presence Weld detection circuit or short circuit welding slag and so on, to ensure the correctness of the circuit, to avoid burn out components.

â‘¢ If there is not much on the power to grasp, consider using an adjustable band-limiting function of power supply, the power supply's voltage to rise slowly, testing the input current (voltage) and output voltage until the output voltage to meet the requirements.

â‘£ When debugging a relatively large system circuit should be installed and debugging the system power, and then gradually debugging a successful installation, commissioning and other modules. Each module is installed on a power-on tests to ensure correct and then debug the other modules.

Conclusion

In this paper, based on the AT91RM9200 embedded control systems, for example, the focus of the system power supply circuit design ideas, methods, and system power installation and commissioning process, combined with the problems encountered during commissioning, debugging of embedded systems approach and attention to the circuit items were analyzed. With the extensive use of embedded systems, power supply circuit design and debugging is particularly important in this paper the design and debugging ideas worth learning.

Drug by the welding electrode core and skin of two parts. The metal core Welding Electrodes are outside the paint (drug skin) evenly to carefully pressure

applied to the welding core. Different types of Tungsten Electrodes, welding core is different. Welding electrode metal core that is the core, in order to ensure the weld

quality and performance, the core butt in the content of the metal elements have strict rules, especially for harmful impurities (such as sulfur, phosphorus,

etc.) the content, there should be strict restrictions, better than the base metal. Direct impact on the core components of welding the weld metal

composition and performance, so the harmful elements in the core welding to as little as possible.

Welding carbon and low alloy steel welding core, low-carbon steel is generally used as a welding cell, and fill up the manganese, silicon, chromium, nickel

and other elements (see the national standard GB1300 a wire 77). The reason the one hand, low-carbon low carbon steel wire plastic, wire drawing easier, on

the other hand can reduce the CO content of reducing gas to reduce splashing or pores, and higher weld metal solidification temperature, beneficial to the

overhead position welding. Adding other alloying elements mainly to ensure the weld mechanical properties, while the welding process performance and to

remove impurities, also have a role.

High alloy steel and aluminum, copper, iron and other metal materials, the core component of its welding and the welded metal in addition to

requirements similar to, but also have control of impurities, according to process requirements often by adding certain alloying elements.

Electrode is coated with a medicine for skin use welding arc melting electrode, which is welded by the drug skin and core composed of two parts. Drugs

in front of the skin with electrodes of about 45 ° chamfer, which is to facilitate the arc. In the rear there is a bare-core welding, electrode length about 1 /

16, easy to maintain and facilitate the welding clamp conductive. Electrode diameter of core Chung actually refers to the weld diameter) is usually 2,2. 5,3 2 or

4, 5 or 6mm and other types of specifications, used a small 3.2, small 4, 5 three small species, its length "L" is generally between 250 ^ -450 mm.

1 welding core

Medicine bag was covered electrode the metal core is called core welding. Welding cell is generally a certain length and diameter of the wire. Welding,

welding core has two effects: first, conduction welding current, arc to convert electrical energy into heat energy, and second, the core itself is melted as

welding filler metal and base metal fused to form the liquid weld.

Electrode welding, weld metal core part of the total weld metal. Therefore, the {welding core chemical composition directly affect weld quality.

Therefore, as the electrode wires are single-core potential with the unique requirements of its grade and composition. If used for submerged arc welding,

electroslag welding, gas welding, gas welding method for welding filler metal, then known as the wire. (1) in the core welding welding of alloy elements on

the

1) carbon (C) carbon is the main alloying elements in steel, when the carbon content increases, the steel {strength, hardness significantly increased,

while the plasticity decreased. In the welding process, the carbon oxygen play a role in the arc under high temperature and oxygen compounds, generating

carbon monoxide and carbon dioxide gas, the arc and weld pool ambient air exclusion zone to prevent air oxygen and nitrogen gases adverse impact on the

pool, reducing the weld metal oxygen and nitrogen content. If the carbon content is too high, to restore the role of severe, will cause a larger splash and

pores. Taking into account the carbon steel hardened to the crack and its increased sensitivity to the effects of low-carbon steel welding general carbon

content of the core cluster 0.1%.

2), manganese (Mn) of manganese in steel is a good alloying agent, as the manganese content increases, its strength and toughness will be increased.

In the welding process, the manganese is also a good deoxidizer, can reduce the oxygen content in the weld. Together with the formation of manganese

sulfide in the slag floating manganese sulfide, thereby reducing the weld hot cracking tendency. It is generally the core of carbon structural steel welding

manganese content of 0.30% ~ 0.55%, some special purpose welding wire, the manganese content up to 1.70% a 2.10%.

3) Silicon (Si) alloy of silicon is a good agent in the steel by adding an appropriate amount of silicon can improve steel yield strength, flexibility and acid

resistance; if the content is too high, then reduce the ductility and toughness. In the welding process, the silicon also has good oxygen capacity, and oxygen

to form silicon dioxide, but it will increase the viscosity of slag, easy to promote non-metallic inclusions generated.

4) Chromium (Cr) chromium steel to improve hardness, wear resistance and corrosion resistance. For low carbon steel, the chromium is a kind of

accidental impurities. The main features of Chrome is easy to rapid oxidation of metallurgy, the formation of refractory oxides of chromium oxide (Cr203),

thereby increasing the likelihood of weld metal inclusions. Transition to the chromium oxide slag, the slag viscosity can increase, decrease liquidity.

5) Ni (NO nickel on the toughness of the steel have more significant effects, generally require a higher temperature impact value, the appropriate

incorporation of some of the nickel.

6) Sulfur (S) S is a harmful impurity, with the sulfur content increases, will increase the tendency of hot cracking of weld, thus welding the core sulfur

content of no greater than 0.04%. Important in the soldering structure, the sulfur content of no greater than 0.03%.

7) P

(2) the classification of welding core

Welding core is based on national standards, "welding wire" (GB 1300-77) classification requirements for welding steel wire can be divided into carbon

steel, alloy steel, stainless steel categories.

2 drug skin

Pressure applied to the welding cell surface coating as drug skin. The drug electrode welding process in the skin plays an extremely important role. The

use of a drug-free light skin electrode welding, the welding process, the oxygen and nitrogen in the air will be a substantial intrusion of molten metal, the

metal iron and beneficial elements carbon, silicon, manganese oxide and nitride formation of various oxides and nitride, and left in the weld, causing the weld

slag or cracks. And melt into the molten pool in gas welding may produce a large number of pores, these factors can make the weld mechanical properties

(strength, impact value, etc.) greatly reduced, while the weld brittle. In addition, the use of optical electrode welding, the arc is very unstable, serious splash,

poor weld.

It found that in practice outside if the electrode coated with a layer of light mineral composed by a variety of drug skin, make the arc combustion

stability, improved weld quality, this is called electrode coated electrodes. With the continuous development of industrial technology, people created a now

widely used high-quality thick coated electrodes.