Resistor colour codes

resistor

4 Band resistor colour coding

On a resistor which has four bands of color, the first and second bands represent a two digit number. This can be found by looking at which number value the colours represent. In the Figure below, the first band is brown and the second is black. This gives use 10 as our two digit number. Next, you look at the third colour, which represents the multiplier. You take this value and multiply it by the two digit number. In this case, it would be 10 x 100Ω. This would give us a resistor value of 1kΩ.

resistor-colour-coding

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Triangle wave generator

triangle wave gen sch

This triangle wave generator is comprised of an integrator and a threshold detector. The integrator acts as a ramp generator, slowly incrementing the voltage over time until it reaches its maximum voltage. However, unlike a ramp generator, when it reaches its maximum voltage, the threshold detector saturates low and causes the integrator to reverse the process and slowly decrement the voltage over time, until it reaches its minimum voltage. Upon reaching the minimum voltage, the threshold detector saturates high, hence begging the loop again.

Fibre optic cables

Optic fibre cables are comprised of four layers. Data is transferred using beams of light by utilising an effect known as total internal reflection.

optic

Light travels into the glass core, and so long as it is above the critical angle, total internal reflection will occur, causing light to reflect off of the inside of the glass core repeatedly until it reaches the other end.

glass

 

 

Coaxial cables

This type of cable is comprised of four layers. The innermost, is a copper wire which is the conductor, and carries the signal. This is then covered by a dielectric insulating layer, which has a copper braid wrapped around it, with a further outer protection and insulation layer on the outside of that. The copper braid acts as a screen, which greatly reduces leakage in and out of the cable.

coax

555 Astable

555555%

The amount of time that the signal is at 0v (Time Low), is calculated by the following equation:

TL

 

 

The amount of time that the signal is approximately 5v (Time High), is calculated by the following equation:

TH

 

 

The total period is calculated either by adding together the time high with the time low, or by using this condensed equation:

T

 

 

Finally, the frequency can be calculated using this formula:

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More information about 555 timers can be found here: ‘http://www.ti.com/lit/ds/symlink/ne555.pdf‘.

Wavelength & Frequency calculations

This equation allows you to calculate wavelength from frequency, and frequency from wavelength.

lambarda

 

 

freq

In this equation:

lambda

(lambda) represents wavelength (in metres).

 c         represents the velocity of light (which is approximately 3.00×108 m/s).

 f         represents frequency (in hertz).

 

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Wavelength is the distance between two peeks of the signal.

frequency is the number of oscillations in one second.

 

Resistors in series and parallel

Resistors in a series alignment

Calculating resistance in series is the easier of the two. You simply add them together to find the total resistance.
resis series

series resistors

Resistors in a parallel alignment

When calculating resistance in parallel, it’s a little more complicated. But so long as you follow the formula, it should be okay. In addition to this, you can double check your results, because it should always be lower than the value smallest resistor.resis paraparallel resistor

Capacitors in series and parallel

Capacitors in a parallel alignment

This is the easier of the two to calculate, the total capacitance is simply the sum of both of the capacitors.

cap seriesCapacitors in parallel

Capacitors in a series alignment

When calculating capacitance in series, it’s a little more complicated. But so long as you follow the formula, it should be okay. In addition to this, you can double check your results, because it should always be lower than the value smallest capacitor in the series.

para capCapacitors in series