28128 Parallax Inc, 28128 Datasheet - Page 148

• Manufacturer Part Number: 28128
• Description: KIT BASIC ANALOG/DIGI PARTS ONLY
• Manufacturer: Parallax Inc

Specifications of 28128

• Accessory Type: ADC, DAC
• Product: Microcontroller Accessories
• For Use With/related Products: BASIC Stamp® 2 and Board of Education
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Questions
Challenge!
1. Can changing the capacitor or resistor values improve the resolution of the PWM
2. Given the command:
3. Why does the capacitor loose its charge if you attach a resistive element to the
4. If you want a 2.5 volt output, what do you have to set the duty to? Assume you
5. If you want to do DAC using a 10 µF capacitor and a 47 k-
6. If the measured voltage in a voltage divider with a photoresistor as shown in
1. Write a program that controls the voltage on 2 separate D/A converters that
2. Design and build the circuit for the program in Challenge 1. You will need to
3. Program your dual output DAC to make the LED load on channel 1 get
4. Write a program that tells you the measured resistance value of the photoresistor
D/A converter? Explain your answer.
does the command take to execute? How many milliseconds is the pulse train
high?
output of the
are using the
should your
Figure 7-10 is 2.3 volts, what is the value of the photoresistor?
maintain different voltage values.
make use of the second op-amp in the LM358. Refer to Figure 1-5 for the
schematic.
gradually brighter as the LED on channel 2 gets gradually dimmer.
from Figure 7-8. Hint: Apply the voltage divider equation and use the existing
DVM program. You will need to modify the
subroutines.
cycles
PWM
PWM
D/A converter?
command in Program Listing 7.1. Explain your reasoning.
be?
PWM 14,51,50
, approximately how many milliseconds
Calc_Volts
and
resistor, what
Display