Basic Electronics: Passive Device
Basic Electronics: Passive Device
Basic Electronics: Passive Device
these next few sections we will help you to identify some of the simple
components and their schematical symbol. Then you should be able to call
or Active devices.
Inductors
control current and voltage within the circuit. You can identify a simple
resistor by its simple cigar shape with a wire lead coming out of each end. It
uses a system of color coded bands to identify the value of the component
size but performs the same function as its bigger brother, the simple
with a dial or sliding control in order to alter current or voltage on the fly.
1k = 1000 1M = 1000000 .
270K.
The standard colour code cannot show values of less than 10 . To show
these small values two special colours are used for the third
band:gold which means × 0.1 and silver which means × 0.01. The first
For example:
have a value within 10% of 390 , between 390 - 39 = 351 and 390 +
Condensors/Capacitors:
Capacitors, or "caps", vary in size and shape - from a small surface mount model
up to a huge electric motor cap the size of a paint can. It storages electrical
determines how much charge it can store. A small surface mount or ceramic cap
will only hold a minuscule charge. A cylindrical electrolytic cap will store a much
larger charge. Some of the large electrolytic caps can store enough charge to kill
Capacitor values can be very difficult to find because there are many
There are many types of capacitor but they can be split into two
groups, polarised and unpolarised. Each group has its own circuit symbol.
Electrolytic Capacitors
There are two designs of electrolytic capacitors; axial where the leads
are attached to each end (220µF in picture) and radial where both leads
clearly printed with their capacitance and voltage rating. The voltage
rating can be quite low (6V for example) and it should always be
Tantalum bead capacitors are polarised and have low voltage ratings
like electrolytic capacitors. They are expensive but very small, so they
Modern tantalum bead capacitors are printed with their capacitance and
voltage in full. However older ones use a colour-code system which has
two stripes (for the two digits) and a spot of colour for the number of
zeros to give the value in µF. The standard colour code is used, but for
the spot, grey is used to mean × 0.01 and white means × 0.1 so that
values of less than 10µF can be shown. A third colour stripe near the
leads shows the voltage (yellow 6.3V, black 10V, green 16V, blue 20V,
way round. They are not damaged by heat when soldering, except for
least 50V, usually 250V or so. It can be difficult to find the values of
these small capacitors because there are many types of them and
Many small value capacitors have their value printed but without a
multiplier, so you need to use experience to work out what the multiplier
should be!
difficult:
the 1st number is the 1st digit,
the 2nd number is the 2nd digit,
the 3rd number is the number of zeros to give the capacitance in pF.
Ignore any letters - they just indicate tolerance and voltage rating.
Diodes:
Diodes are basically a one-way valve for electrical current. They let it flow in one
direction (from positive to negative) and not in the other direction. This is used to
portion of a AC waveform. The diode terminals are cathode and anode and the
arrow inside the diode symbol points towards the cathode, indicating current flow
in that direction when the diode is forward biased and conducting current. Most
diodes are similar in appearance to a resistor and will have a painted line on one
end showing the direction or flow (white side is negative). If the negative side is
on the negative end of the circuit, current will flow. If the negative is on the ositive
Function
for cathode!). The cathode is the short lead and there may be a slight flat
on the body of round LEDs. If you can see inside the LED the cathode is
LEDs can be damaged by heat when soldering, but the risk is small
unless you are very slow. No special precautions are needed for
Testing an LED
Never connect an LED directly to a battery or power supply!
It will be destroyed almost instantly because too much current will pass
LEDs must have a resistor in series to limit the current to a safe value,
for quick testing purposes a 1k resistor is suitable for most LEDs if your
LEDs are available in red, orange, amber, yellow, green, blue and white. Blue and
white LEDs are much more expensive than the other colours.
Switch :
This is a mechanical part which when pressed makes the current to flow through
it. If the switch is released the current stops flowing through it. This helps to
control a circuit.
Transistors:
The transistor performs two basic functions. 1) It acts as a switch turning current
magnified version of the input signal. Transistors come in several sizes depending
Circuit.
current between the collector and emitter leads. Bipolar junction refers to
placed between two wedges of "N" material. In this NPN construction a small
base current controls the larger current flowing from collector to emitter (the lead
PNP Transistor:
Similar to NPN transistors, PNP's have a wedge of "N" material
between two wedges of "P" material. In this design, a base current regulates the
larger current flowing from emitter to collector, as indicated by the direction of the
arrow on the emitter lead. In CED players, PNP transistors are used less
Batteries:
Symbol of batteries shows +ve terminal by a longer line than the –ve terminal.
Speakers:
These convert electrical signals to accoustic viberations. It comprises a
permanent
magnet and a moving coil (through which electrical signal is passed). This moving
coil is
and metals are used to simulate resistors, capacitors, transistors, etc. It is a space
saving miracle. These components come in a wide variety of packages and sizes.
You can tell them by their "monolithic shape" that has a ton of "pins" coming out
SOLDERING INSTRUCTIONS
grease.
2. Use isopropyl alcohol with the help of non-static bristol brush for
cleaning.
3. Use lint-free muslin cloth for wiping or alternatively use mild soap
joints and for CMOS IC’s, FETS and ASIC’S use temprature controlled
3. Before using a new tip, ensure that it is tinned and before applying
5. Ensure that while applying the tip to the job, the tip of the soldering
iron is held at an angle such that the tip grazes the surface to
be heated and ensure that it does not transfer heat to other joints/
joint equally.
6. Heat the joint for just the.right amount of time, during which a
very short length of solder flows over the joint and then smoothly
8. Do not heat the electronic parts for more than 2-4 seconds since
9. Apply one to three mm solder which is neither too less nor too
10. Do not move the components until the molten solder, at the joint
has cooled.
_
1.3 Tips for de-soldering:
2. Use a de-soldering pump which is first cocked and then the joint
3. Repeat the above operation 2-3 times until the soldered component
pliers.
cables etc. and then press a short length of the wick using
the tip of the hot iron against the joint to be desoldered so that
the iron melts the solder which is drawn into the braid.
6. Do not allow the solder to cool while the braid is still adhering to
the joint.
1.4 Precautions:
circuit.
4. Position the board so that gravity tends to keep the solder where
5. Do not over heat the components at the board. Excess heat may
7. Do not put the kit under or over voltage source. Be sure about the
short circuit with the other components. To prevent this use sleeves
9. Do not use old dark colour solder. It may give dry joint. Be sure
dreadful stuff for developing PCBs. Apart from its causticity, it is very sensitive to
both temperature and concentration, and made-up solution doesn’t last long