__Identifying Resistors – Resistor Colour Chart.__** **10/08/19

**Holding the resistor with the “GAP” to the right**.

__4
band – top.__

**1 ^{st}
band = the first digit.**

**2 ^{nd}
band = the second digit.**

**3 ^{rd}
band = the “multiplier” – **how many “0s” to add to the
first two digits.

**4 ^{th}
band = the tolerance in %.**

The
example is a “**yellow” for 4**, “**purple” for 7**, “**orange”
for 3 “0s”** and **red for 2%**
bands equals 4,7,000 a 47,000 ohm 2% tolerance
resistor, commonly called a 47K resistor.

** **

__5 band – bottom.__

**1 ^{st}
band = the first digit.**

**2 ^{nd}
band = the second digit.**

**3 ^{rd}
band = the third digit.**

**4 ^{th}
band = the “multiplier”** – how many “0s” to add to the 3 digits.

**5 ^{th}
band = the tolerance in %**

The
lower example “**green” for 5**, **Blue for 6, Black for 0, Red
for 2 “0s” Brown for 1% **bands
equals a 5,6,0,00 a 56,000 ohm 1% tolerance resistor, commonly called a 56K.

Resistors
are manufactured in a range of values and wattages (power).

** Resistance
values**:
the two common ranges are:

·
E12 series
that comes in twelve values per decade - 10, 12, 15, 18, 22, 27, 33, 39, 47,
56, 68 and 82. The above two 47K and 56K resistors fall in this range.

·
E24 series
comes in twenty four values per decade - 10, 11, 12, 13, 15, 16, 18, 20, 22,
24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 72, 82, and 91.

__Wattage:__

__ __

·
1/4, 1/2 and
1 watt carbon or metal film resistors

·
5, 10 25 etc
watt wire wound resistors (high power types).

Wattage
is the rating of the resistor. When current flows through a resistor like in
our LED and Incandescent headlight examples, the voltage that has to be dropped
will be converted into heat. The higher the current, the more heat generated.

Power,
therefore heat, that has to be dissipated by the resistor equals Amps x Amps x ohms.

When
using 1,000 Ohm resistor with 14 volts DC at the Function Output Common, there
will be at maximum .0125 Amps or 12.5 mAs to flow
through the LED. While this is less than the desired specified current for the
LED, it will give plenty of light and the brilliance is only marginally
affected. You won’t notice the difference. Operating at the lower current,
allows for a higher voltage at the track that some DCC systems have, mainly the
Entry Level systems.

Using
1,000 Ohm resistors with your LEDs, as I do, the heat dissipated is .0125 x
.0125 x 1,000 = .156

For
Incandescent 10 to 20 mAs 1.5 volt lamps use a 1 watt
resistor.

For
40 to 60 mAs 1.5 volt lamps,
use two resistors, twice the required value connected in PARALLEL would be MUCH
better. Two similar value resistors connected in parallel, make a resistor HALF
the value of each resistor with TWICE the wattage. E.G.
Two 1,000 ohm 1 Watt resistors in “parallel” makes a
500 Ohm 2 Watt resistor.

For
hobbyist and the like (us model railroaders), the E12 values are close enough
and because of the greater tolerance, makes them really cheap. Most electronic
stores carry this range.

The
later surface mount resistor like the ones used on our decoders etc, have
markings like 473 (47,000 ohms), 272 (2,700 ohms) etc that are converted using
4 band resistor colour code markings.