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Step 4Partly Assembled
The picture shows almost all components soldered in position, except the inductor and the connecting pins. The green wire connects the shutdown input of the ic to a pull up resistor placed upright against the positive lead of the input capacitor.
A large area is left for connecting the inductor because the efficiency of the circuit under load is determined to a large extent by the losses in the inductor. It should have low resistance and an inductance greater than 33 microhenrys. Several could be tried in position or one could be wound on ferrite core.
The input current passes through the MOSFET and its "on" resistance determines loss within it. The output current is carried by the freewheeling diode while the MOSFET is off and so the voltage drop across it contributes to the losses. Schottky diodes have lower voltage drop than ordinary diodes and so are preferred in this position.
Thus it is possible to assemble and test circuits using modern integrated circuits with little effort since very few external components are needed to make them work.
The manufacturer has very compelling reasons to put everything on one board, because additional boards increase the manufacturing and handling and testing costs.
The amateur constructor, on the other hand, is well advised to go to the other extreme and assemble his project using a large number of circuit modules which can be tested independently.
A large area is left for connecting the inductor because the efficiency of the circuit under load is determined to a large extent by the losses in the inductor. It should have low resistance and an inductance greater than 33 microhenrys. Several could be tried in position or one could be wound on ferrite core.
The input current passes through the MOSFET and its "on" resistance determines loss within it. The output current is carried by the freewheeling diode while the MOSFET is off and so the voltage drop across it contributes to the losses. Schottky diodes have lower voltage drop than ordinary diodes and so are preferred in this position.
Thus it is possible to assemble and test circuits using modern integrated circuits with little effort since very few external components are needed to make them work.
The manufacturer has very compelling reasons to put everything on one board, because additional boards increase the manufacturing and handling and testing costs.
The amateur constructor, on the other hand, is well advised to go to the other extreme and assemble his project using a large number of circuit modules which can be tested independently.
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