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Detector ConstructionFrom SPCoast
[edit] Detector Parts List
[edit] Assembly InstructionsAssembly order is not important but you might want to follow the order below, which starts with the smaller parts and works up to the bigger ones. Check off each item on the parts list as it is completed. Insert the part, solder it in then inspect the solder joint to make sure it shines (a dull color indicates a cold joint, which is not good - simply reheating it and letting it cool without moving the part will fix a cold joint). Once it is complete, cut off the excess component lead. [edit] ResistorsThe resistors are the cylindrical shaped parts with leads on each end and colored bands around them. The bands are indications of the resistance of the part. If you have good eyesight you can use the bands to identify the resistors. If not, use an ohm meter to measure their resistance. Since resistors are not polarity sensitive, they can be installed in either orientation. For ease of identification when checking things later, I like to keep them consistent, with the gold band (which indicates a "5%" manufacturing tolerance) to the right or bottom. [edit] DiodesThe diodes are the cylindrical shaped parts with leads on each end and a black band around one end. A part number may be printed on the part in very small letters. Diodes are polarity sensitive - the lead with a band should go into the square pad on the circuit board. LEDs are a half-round plastic dome with two leads coming out of the flat end. They come in many colors; I use Yellow for the Detection indications, though you can use whatever color you wish. LEDs are polarity sensitive as well, with the SHORT lead going to the square pad. [edit] CapacitorsThere are two kinds of capacitor used in this circuit - electrolytic and bypass. The Power Supply uses a large cylindrical shaped electrolytic capacitor; the remote sensors use a smaller one. Electrolytics are polarized, and have their shorter "-" lead marked on the component, along with their value and voltage rating. For these electrolytic capacitors, the "+" lead is the longer one, and it should go into the square pad on the circuit board. The other caacitors are all small, flat bypass capacitor with 2 leads coming out of the same side; it may be marked ".1" or "104". These bypass caps are not polarity sensitive. In general, one is used across the power supply pins of every IC. [edit] TransistorsThe NPN transistors are "D" shaped black plastic components with 3 leads in a row out of the same end. If you slightly bend the middle lead away from the plane of the other two leads (towards the round side of the "D"), you will be able to easily insert it into the circuit board. Orientation is important, so double check things to make sure. The "D" shape of the transistor should match the "D" shape of the three holes. One transistor is used on each remote sensor, and another is used on the base unit as part of the LocoNet interface. [edit] Sockets, terminals and stuffThe IC sockets have a notch on one end to indicate "pin 1". They should be oriented to match the square pad and the marking for "pin 1". Start by soldering only one pin of a socket, pressing down on a different part of the socket (so you don't burn your finger!) to make sure it is seated tightly. Double check the orientation, and then solder the rest of the pins. Watch for unwanted solder bridges between adjacent pins. The LocoNet interface, the ICSP and the connections to the remote sensors all are 6-position RJ12 telephone-style jacks. Guide the 6 pins of each jack into the circuit board holes before snapping the larger mounting studs into place. In order to remind me to not connect LocoNet cables to the ICSP programming jack, I use a "top loading" RJ12 jack for the ICSP and "right angle loading" jacks for the others. If you don't have a Microchip compatible ICD programmer, you can leave out the ICSP jack. You will need to find a way to program the PICs - Hans Deloof sells preprogrammed LocoIO PICs on his web store. [edit] Pulse TransformerThis is a flat, "D"-shaped device about the size of a $US quarter, with a hole in the middle and 2 leads on the flat side. It is about 1"x1"x1/4" in size. The pulse transformers have a "polarity" (actually a phase relationship), but since the DCC waveform is symetrical, it doesn't matter which way they are inserted. (For consistancy, if there is an arrow on the transformer, I try to have it point towards the diode on the sensor board) |
