Page 178 - Making PIC Microcontroller Instruments and Controllers

CONDITIONING THE OUTPUT SIGNAL

General

The microcontroller we use will eithcr be a TTL- or CMOS level inpui/output device
Its signals can be jntroduced to other similar devices, almost alvr'ays, without altering
them. However. the real world is not full oiTTLand CMOS devices, and we will have
to connect to motors and relays, Silicon Controlled Rectifier (SCRS) and TRIode for
Alternating Cunent (TRIACS), lights and pumps, and a host of other equipment on our
bench tops and in our laboratories. This chapter shows us how to take the TTL signal
as il comes out of the microcontroller and prepare it to inform and control the real
world.
The types of devices we will be sending information to can b,3 broken down into the
following:

Computers
I Serial interfaces
r COM1
I COM2
r Parallel ports are more complicated to use and will not be discussed in detail
(Today, they are not often used for interaction wilh MCUS.)
Inductive loads
I Motors
I Relays
I Solenoids
Resistive loads
I Lighr butbs
I Heaters