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Thursday, August 13, 2009

Auto Car 04 - Input Infra Red 02

In this part, we shall look into analog and digital and how to change our infra red signal into digital form.


Figure of example of Analog.

Analog is something that has a continuous value like height of a human, weight, where the value if placed in a range. Some of the stuff the stuff that uses analog is the cassette and film camera. Our Infra Red Signal Output too is an analog value.


Figure of example of discrete.

Discrete which is different from Analog, is a system which has values that is fixed like Number of Member in a Family, Blood Type, Number of Rooms in a House. This is not a digital value but it can be used to transform from Analog to Digital in Z-Transform which involves Digital Control.


Figure of example of Digital.

While Digital is a system where it can only posses 0 and 1. 0 means NO, or LOW, or OFF while 1 means YES, or HIGH, or ON.

Next, we shall move on to the Infra Red.


Figure of When facing the Black Surface.

This figure shows the ray when hitting Black surface, which is our line in the field. When it hit black line, it will be absorbed and leave less ray back to the receiver.


Figure of When facing the White Surface.

While in this figure, then ray hits a white surface and it could reflect almost all of the ray. Therefore the receiver will receive maximum ray.


Figure of Signal Voltage versus Ray Brightness.

This is the graph of signal voltage produced when hitting different surfaces. In 'a', the surface is black thus it will produce Higher Voltage. In 'b', the surface is white, thus producing Lower Voltage. This Graph is only applicable for this type of connection. If the 4.7kOhm resistor and IR Receiver is switched place, it will produce different graph.


Figure of the analogy of Operational Amplifier as a Comparator.

So to produce a '1' on black surface and '0' on white surface, we need an Operational Amplifier as a Comparator. In this mode, we shall take the input as Digital. So we need to convert Black into '1' and White into '0' although the Signal Voltage is an Analog Value.

In the figure, when Operational Amplifier act as a Comparator (and only comparator, the diagram is applicable). When 'a' voltage is higher than 'b' voltage, the hand will turn on the upper part switch thus letting the voltage at the upper part to flow to the output. On the contrary, when 'b' voltage is higher than 'a' voltage, the hand will turn down to switch on the lower part switch thus making the voltage at the lower part flow to the output.


Figure of the Comparator.

Therefore, the Digital is actually coming from 0 Volt and 5 volts in the Operational Amplifier. Anything from Black to 50% Gray will produce 5 volts at the output (HIGH) and anything from 50% Gray to White will produce 0 volt at the output (LOW). the gray value is 50% because we are using 2.5Volts comparing value.

This shall not be confused to Analog to Digital where for example 10 Volts will be converted to 1010 Binary Volts where an Analog to Digital Converter is needed. In our case, it is more like converting a Range to '0' and another range to '1'.

To view previous posts about the Auto Car Project, you could click on the 'Project' Label at the right sidebar.

1 comment:

Anonymous said...

if i reflect the IR signal by using a mirror, will the signal been effected by the reflection?

What is the result if i use diffent mirror? visible?
please reply me at eric_yeoh88@hotmail.com