Physics 120/220 Lab Equipment, Hints & Tips

Transcription

1 Physics 120/220 Lab Equipment, Hints & Tips Solderless Breadboard... 2 Power supply... 4 Multimeters... 5 Function generator... 5 Oscilloscope X probe... 7 Resistor color code... 7 Components... 8 Polarized capacitor

2 Solderless Breadboard All of the analog labs and most of the digital labs will be built on solderless breadboards (or protoboard, PB, type 103A or 203A). These provide 3 solderless breadboard strips to insert components and jumpers for building circuits. The +5, +15 and -15 volt power supplied built into the breadboard are adequate to power most of these labs. The PB-203A has the power supply built in, while the power should be supplied to the PB-103. To provide power to the PB-103 connect your benchtop PS to the binding posts using banana connectors, then use wires to power the PB strips. Remember to turn-off/power off the breadboard when building or making changes to your circuits. We strongly urge you to adopt a color code when wiring your lab projects. It may take few extra minutes to find the correct color/length hookup wire but it will save you much more time when debugging your circuits (and make life infinitely easier to your instructor). Use the following colors only for power: Red: +5 volts Black: ground (GND) Yellow: +15 volts Blue: -15 volts Consider using separate colors for inputs, outputs and internal signal, for example: Brown: inputs Purple: outputs Green: internal signal lines PS: If you are color blind, make sure to talk to your instructor. 2

3 For the PB-203A, if you find a supply voltage low, it is probably because your circuit is drawing excessive current. The breadboard has strip of metal underneath the board and connect the holes on the top of the board. The metal strips are laid out as shown below. Note that the top and bottom rows of holes are connected horizontally and split in the middle while the remaining holes are connected vertically. Note how all holes in the selected row are connected together, so the holes in the selected column. The set of connected holes can be called a node. Typically the outer sections of the breadboard are used for power. A B To interconnect the selected row (node A) and column (node B) a cable going from any hole in the row to any hole in the column is needed: If you never used a breadboard, you may want to take a look at this link before coming to lab-1: Tips: Add partially stripped black hookup wire to the ground bus to provide a place to connect test equipment ground clips to. Use jumpers (small wire) to connect two sets of horizontal strips. Bend the components leads away from the body of the components rather than right at the component, to avoid stress that can cause the leads to break (especially on resistors, diodes, tubular capacitors). Place integrated circuits (ICs) over the trench so that you can access the ICs pins via the column of contacts. Use needle-nose pliers to insert components and hookup wires. 3

4 When you disassemble a circuit, remove integrated circuits carefully using a chip puller or a thin screwdriver to avoid bending any of the leads. See the video on the Hints and Tips page of the course web site. Please do not remove ICs by hand, you will bend the leads! Avoid daisy-chaining multiple short lengths of hookup wire to reach between components. Each contact introduces a point of failure. If you cannot find a long enough jumper of the correct color, there are spools of wire at the back of the lab. For complicated circuits (or maybe even simple one) consider building a portion of the circuit and testing it before building the next section. You ll find it easier to debug small portions of a design than on big mess and you will be less likely to disturb a working section while debugging a nonworking section. When building a circuit from schematic in your notes, use a highlighter pen to mark the components and wires completed. This help catch missing portions of the circuits and is easier than debugging a non-working circuit only to find you left out a jumper. Be very careful of polarity when inserting components such as diodes or electrolytic capacitor (these can explode by a large bang and you can be hit by flying shrapnel s). Even if you don t blowup your circuit, a reversed or incorrectly inserted component can lead to odd circuit behavior that is difficult to diagnose. It s better to take time building a circuit than to waste time debugging it. Common mistakes: Open circuits or circuit not plugged correctly Forgetting to replace a resistor going from one experiment to another Words of wisdom: If you do not understand why changing something appears to fix the problem, you probably have not fixed the problem. Manuals of the following equipment can be found at the back of the lab. Power supply 4

5 Multimeters We use a variety of multimeters makes in the lab. They are all very similar. Some are auto- ranging and others require you to guess what the amplitude range of your signal will be. It is better to start on a higher range and decrease it than to subject the input to a much higher signal than it is expecting. All the multimeters use separate inputs from current and voltage. Be very careful not to apply voltage to a current input to avoid blowing the internal fuse. All of our multimeters can read resistance and most of them can read capacitance and/or inductance. This is very useful for double-checking that a component is the value you think it is, particularly on hard-to-read metal film resistors and secrethandshake encoded capacitors. Some multimeters can check semiconductor components such as diodes and transistors as well. To measure voltage press: DC V Use the RH-side HI and the ground To measure current press: shift + DC V Use I and GND Check position of the font/rear button Function generator There are two types of function generator in the lab. Both are straight forward to use. 5

6 Agilent 33120A To enter a value, press the desire function (eg Freq), press Enter number, enter your value + Enter. Agilent 33210A Instruction manual: Don t forget to press output to send the wave function out. Oscilloscope Online version of the user manual. Typically, your channel should be set on DC coupling, to get both the AC and DC component of the input. AC coupling blocks the DC part of the input. 6

7 10X probe Resistor color code The first and second band represents the numerical value of the resistor, and the color of the third band specifies the power-of-ten multiplier. The color bands are always read from left to right starting with the side that has a band closer to the edge. 7

8 Components Components datasheets: Polarized capacitor 8