Elenco Solder Practice Kit w/ Iron &amp - Manual (Page 4)

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Types of Soldering Devices
A number of different types of soldering devices: irons, guns and stations
are available today. Irons are used for light to medium work and guns are
for medium to heavy-duty work. The station type can range from light to
heavy-duty. When working on PC boards, a soldering iron is ideal. Iron
sizes vary from 15 to over 500 watts. For working on PC boards, irons
ranging from 15 to 40 watts is suitable. If you use an iron with a higher
wattage rating than 40 watt, you may damage the copper tracks on the
PC board.
The higher wattage irons are best suited for heavy-duty
electrical jobs.
Solder Tips
The material that the tip is made from is an important factor. Most tips are
made of copper coated with some other material. The molten solder on
the tip will wear it down. To increase their lifetime, tip can be coated with
iron, but this decreases the heat transfer rate. The tip should be tinned
by lightly coating it with solder. This will prevent it from oxidating. The tip
becomes pitted (black spots) from normal use. You can remove these
spots by scraping them with a knife or filing item. After removing the
spots, you should re-tin the tip. It is important to clean the tip by wiping it
with a wet rag or sponge. A good clean solder tip makes soldering much
easier.
Today, tips are manufactured in a variety of different shapes (see figure
below). The chisel shape is one of the most common. Having a choice
of tip styles allows you to choose the one best suited for your soldering
needs. Due to the high heat, removable tips can bond themselves to the
heating element if left in place for extended periods of time. Periodic
removal of the tip is therefore advisable.
Theory of Operation
The solder practice kit produces the sound of the European siren. It
consists of two oscillators, a one hertz (one cycle per second) and a
1500Hz. The one hertz oscillator consists of two transistors Q1 and Q2,
and resistors R1, R2, R6 and R7 capacitors C1 and C2.
This
configuration is known as a multivibrator circuit.
When voltage is first applied to this multivibrator circuit, one transistor
(possibly Q1) will conduct faster, causing transistor Q2 to stay off. Q1 will
continue to conduct until it saturates. At this point, Q2 will start to conduct,
causing Q1 to rapidly cutoff. This process continues alternately causing Q1
or Q2 to conduct. The output will be a square wave. The frequency is
determined by the time constants of resistor R6 and capacitor C1, also R4
and C2. Two LED diodes are placed in the collectors of the transistors and
will light when current is passing through them. Resistors R2, R1 and R7
determine the current passing through the LEDs.
Integrated circuit IC1 is the heart of the second oscillator. A 555 timer IC
is used in the circuit. This IC contains many transistors and resistors on
a silicon chip and thus eliminates many external parts. The frequency of
this oscillator is determined by resistors R5, R9 and capacitor C4.
Capacitor C3 couples the output of operations of IC1 via resistor R8. This
changes the operations of IC1 during one half cycle of the multivibrator
causing the frequency to change from 1500Hz to 2200Hz. This results in
a speaker output that varies constantly in pitch. The multivibrator circuit
not only causes the LED to flash, but also varies the pitch at the speaker
output.
Troubleshooting
If you are experiencing a problem, first read the theory of operations to
familiarize yourself with the operation.
Remember, there are two
oscillators. If no sound comes out of the speaker, but the LED flashes
alternately, then the 555 timer is not working. Be sure that the volume
control is at maximum. Check the components IC1, R5, R8, R9, C3, C4
and C5. Be sure that the IC is in properly.
If a steady sound (not wobbling) comes out of the speaker, then the
multivibrator is not working.
Check the components associated with
transistor Q1 and Q2. Check the LED by shorting the transistor collector
to the emitter. The LED should light. If not, then the LED is either open
or backwards.
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Soldering Iron Soldering Gun Soldering Station