Embedded Systems Design with the Atmel AVR Microcontroller Part II

from
micro
10K
Vcc = 5 VDC
220
buzzer, 3850 Hz
5 VDC, 3-14 mA
2N2222
a) 5 VDC buzzer interface
Figure 7.25: Sonalert, beepers, buzzers.
7.8 SUMMARY
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7.8. SUMMARY 231
Vcc = 12 VDC
220
annunciator
12 VDC, 8 mA
2N2222
a) 12 VDC annunciator
In this chapter, we discussed the voltage and current operating parameters for the Atmel HC CMOS
type microcontroller. We discussed how this information may be applied to properly design an
interface for common input and output circuits. It must be emphasized, a properly designed interface
allows the microcontroller to operate properly within its parameter envelope.If due to a poor interface
design, a microcontroller is used outside its prescribed operating parameter values, spurious and
incorrect logic values will result. We provided interface information for a wide range of input and
output devices. We also discussed the concept of interfacing a motor to a microcontroller using
PWM techniques coupled with high power MOSFET or SSR switching devices.
7.9 CHAPTER PROBLEMS
7.1. What will happen if a microcontroller is used outside of its prescribed operating envelope?
7.2. Discuss the difference between the terms “sink” and “source” as related to current loading
of a microcontroller.
7.3. Can an LED with a series limiting resistor be directly driven by the Atmel microcontroller?
Explain.
7.4. In your own words, provide a brief description of each of the microcontroller electrical
parameters.