Page 165 - Making PIC Microcontroller Instruments and Controllers

ustNc sENsoRs (TRANSDUCERSI

General

Before you can make a decision about modifying an existing condition, you have to sense
what the curent condition is. An awful lot can be done with the five senses we all have,
but for many other things that arc important in our everyday lives we need help. We get
this help from electronic sensors. These senso$ convert the informatiol in the syslem into
infomation we can absorb using our five senses. The preferred sensory input in humans
is visual and auditory, but we often also use touch. smell and taste are used less often afld
are usually reserved for organic inputs, sometimes those indicating a hazard or danger.
The following are some unusual examples ofhow we use our five senses.

I Sight Aulomobile traffic is conlrolled basically by drree colored lights.
I Hearitrg The ele\ ator beckon. us wrth a ping.
I Touch The cell phone vibrates (if set to do so).
: Sm€ll Gasoline contains an additive to help us detect its dangerous presence.
I Tast€ The DEA agent can recognize cocaine by its taste (at least on TV).

When we think about sensing something our human senses cannot detect, we are usu-
ally thinKng about signals that, to us, are weak or hard to difierentiate in the ambient
noise. These a.re signals that need to be filtered and amplified and then convefted to sig-
nals we cdr recognize. As you read this, a few hundred television and radio broadcasts
arc zipping past your brain that you are completely oblivious to. If you know what fre
quencies to look for, how to filter out the signal you want from them, and then how to
present it to the human eye and ear, you could watch and hear the data being broadcast.
Cable network subscriptions seem to indicate this is wo h a lot of money every month|
Thus, there are four main aspects of sensing.

of
I We musl have a knowledge and understanding the existence oithe signal.
I We must find a filter that will isolate and identifv the sienal.

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