TAMIZAJE FITOQUIMICO

coil consisting of a 4′foot long 6′′inch diameter PVC pipe, the coil consists of about 3000 turns of insulated wire on it. You will find that just a straight whip antenna works fine, so it was found that the large coil is not mandatory. The original thought for using the coil at the antenna was to have a lot of signal at low frequencies with a high Q inductor, to give more signal while trying to reduce the overall gain of the circuit, to minimize 60 cycle hum. On that note, long whips or especially long wires are not very desirable here, so stay with a 5′to 6′vertical whip antenna.

The input signal is amplified with a JFET input op-amp at U1, with selectable input range through a small value capacitor to allow high gain to be achieved with minimum 60 cycle hum. A LM741 op-amp gives gain to provide audio signal and then another LM741 is used to drive a 500µA single ended meter for a reading of RF levels. You may find it easier to make the series resistance control for the meter to be a front mounted control as well as the gain control for the meter driver, i.e. the 741 op-amp, as it give much more flexibility under differing weather conditions. This meter is very helpful in determining the number of lightning strokes per unit time in severe weather.

The audio output from the Spheric monitor section is derived form an LM380 IC circuit; you will notice interaction between controls if you build it as shown. A buffer and mixer circuit might be helpful here, but in the original design we decided to keep the parts count low. Also, an equalizer circuit for the signal out is a very good addition, so you can tailor the output response and reduce unwanted signals such as line power noise. A signal output is provided so the output can be fed to a digital multi-meter with PC interface, if desired to log readings of the Lightning Monitor over time.

Building the lightning

monitor

Prior to constructing the Lightning Monitor, you will want to locate a well lit and well ventilated work area. A large clean work bench or work table would be suitable for building the project. Grab a 27 to 33 watt

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pencil tipped soldering iron, a roll of 22 gauge 60/40 tin/lead rosin core solder. You should also have a small jar of “Tip Tinner,” a soldering iron tip dresser which is available from your local Radio Shack store. You’ll probably want to gather a few tools, such as a pair of end-cutters, a small pair of needle-nose pliers, a pair of tweezers, a magnifying glass, a small Phillips screwdriver as well as a small flat-blade screwdriver. Place your schematic diagram along with your circuit layout diagram and various charts and tables in front of you on your work table. Place your project components and circuit board in front of you and we can begin constructing the Lightning Monitor. A printed circuit is highly recommended for building this project rather than trying to use perf-board construction to permit more reliable operation from your circuit. Warm up your soldering iron and we will begin construction!

Let’s begin building the monitor by first identifying the project resistors. Locate the resistors from the parts pile. Refer to the chart in Table 16-1, which illustrates the resistor color codes and their values. Resistor R1, for example, is a 47k ohm 1_⁄

4watt 5% resistor. Try and

locate it from the parts pile. The first color band at one edge of the resistor body should be yellow, which is the number (4). The second color band should be violet or number (7) on the chart. The third color band is the multiplier and should be orange in color and

represents a multiplier value of 1000, so 47 times 1000 is 47,000 ohms or 47k ohms. The fourth color band on resistors represents the resistor’s tolerance. A silver band denotes a 10% tolerance, a gold band represents a 5% tolerance resistor and no color band denotes a 20% tolerance resistor. Once you have found R1, you can try and locate resistor R2 and so on. You can place the resistors on the circuit board in groups of four or so in their respective locations on the circuit board. Once you have the first four resistors placed on the PC board, you can go ahead and solder them in place on the board. After the resistors have been soldered onto the circuit board, you can cut the excess component leads flush to the edge of the circuit board using your end-cutters. Now, you can locate the next batch of four resistors and place them in their respective locations on the circuit board, then go ahead and solder them in place. Remember to trim the excess component leads. Finish up installing the resistors and then we will move on to installing the two silicon diodes.

There are two silicon diodes in this project, and they are located in the meter range and display circuit. Diodes have two leads, a cathode lead and an anode lead. Take a look at the resistors and you will notice that there will be either a black or white color band at one edge of the diode’s body. The color band denotes the cathode lead of the diode. It is important that you install

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Lightning Storm Monitor

Table 16-1

Resistor color code chart

Color Band 1st Digit 2nd Digit Multiplier Tolerance

Black 0 0 1 Brown 1 1 10 1% Red 2 2 100 2% Orange 3 3 1,000 (K) 3% Yellow 4 4 10,000 4% Green 5 5 100,000 Blue 6 6 1,000,000(M) Violet 7 7 10,000,000 Gray 8 8 100,000,000 White 9 9 1,000,000,000 Gold 0.1 5% Silver 0.01 10% No color 20%

the diode correctly with respect to this polarity. One you have installed the two diodes in their proper place, you can solder them in place on the circuit board. Don’t forget to cut the extra component lead lengths.

Next, we will try and locate the capacitors for the Lightning Monitor project. This project uses two types of capacitors, small ceramic disk types and the larger electrolytic types which have polarity. The small capacitors come in many different styles and shapes and sometimes they are so small that there is not enough room to print their actual value on the component, so a three-digit code is used. Refer to the chart shown in Table 16-2 when installing the small capacitors. For example, a .1µF capacitor would have a code value of (104). The Lightning Monitor also utilizes larger value electrolytic capacitors, these capacitors are usually large and have polarity marking on them, such as a black or white color band or a plus (+) or minus (−) marking on them. These polarity markings must be observed when installing the capacitors on the circuit board. Failure to observe the correct polarity could result in either a damaged component or a damaged circuit when first power-up.

Look through your component parts pile and let’s try and identify some capacitors. Let’s begin with some of the small types such as C1 and C2. Capacitor C1 may be marked 2.2 or 2n2, while Capacitor C2 will most likely be labeled 181. Try and locate the lower value capacitor from the parts stock and place about four components at a time on the PC board in their respective locations. After placing four or so of the first lot of capacitors, you can go ahead and solder them in place. Remember to trim the excess component leads from the board. Take the next grouping of four capacitors and install them on the PC board while referring to the schematic and parts layout diagrams. Go ahead and solder the next group of four capacitors and trim the excess lead lengths. Install the remaining smaller capacitors and then we will move on to installing the larger value electrolytic capacitors. As mentioned, electrolytic capacitors will have polarity markings on them and they must be installed correctly in order for the circuit to work properly. Take your time when identifying the electrolytic capacitors. Observe their polarity marking and then make sure you orient them correctly and in their proper location on the PC board. Refer to the schematic and parts layout diagram. Install a few electrolytic capacitors at one time, and them

solder them in place, follow up by removing the excess lead lengths. Install the remaining electrolytic capacitors and solder them in place. Use your end-cutters to remove the extra lead lengths by cutting them flush to the edge of the circuit board.

The Lightning Monitor uses a single FET transistor at Q1, which is connected to antenna-2. The P channel J-FET at Q1 is a J176 FET, which must be handled with care using an anti-static wrist band to avoid damage. This component is very sensitive to static electricity and can be easily damaged in handling. The three leads of the transistor Q1 are all in a single row with the Drain lead at one end and the Gate lead in the center and the Source lead at the opposite end of the plastic case of the transistor. Refer to Figure 16-3, which illustrates the semiconductor pin-outs.

Before we install the integrated circuits in this project, we would highly recommend using IC sockets. Integrated circuit sockets are good insurance in the event of a possible circuit failure at some possible distant point in time. It is much easier to simply unplug a defective IC, rather than trying to un-solder a 14-pin IC from the circuit board. Integrated circuit sockets are inexpensive and easy to locate. There a number of integrated circuits in this project, from 8-pin to 14-pin dual in-line types. In order to install the integrated circuits correctly, you must observe the correct orientation. Failure to install the integrated circuits correctly can cause serious damage to the IC and to the circuit itself, so you must get it right the first time! Each plastic IC package will have either a cut-out, a notch or small indented circle at one end of the plastic package. Looking just to the left of the notch or cut-out you will find pin 1 of the IC. You must align pin 1 of the IC to pin 1 of the IC socket when installing the chip on the PC board. Take a look at U1, this is an 8-pin dual in-line IC. Since we will not be using pin 1 on this IC, you will have to make sure that pin 2 or the minus (−) input is connected or aligns with C1 and R2, while pin 3 of U1 is connected to resistor R1 and so on. Now, go ahead and insert the integrated circuit into their respective sockets.

There are a number of potentiometers in this project, some of which are chassis mounted controls, while other potentiometers will be circuit board mounted types. Refer to the parts list below and Table 16-3. You can locate the circuit board trimmer type potentiometer and install them at their respective locations on the

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