28128 Parallax Inc, 28128 Datasheet - Page 149

• 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

Chapter 7: Digital to Analog the Easy Way using PWM· Page 139
Why did I learn it?
Using a simple RC circuit with a buffer is an inexpensive and easy way to get 8-bit DAC.
It's also really easy to program, and the accuracy is much closer to that of a D/A
converter integrated circuit than it is to the accuracy of the resistive ladder network with
10% resistors.
There are many instances in which analog quantities will change the resistance of a
device. The voltage divider can be an effective way to track these changes in resistance.
The measured voltage at the output of a voltage divider can give us information, not only
about the resistance value, but about the analog quantity that causes the resistance value
to change.
How can I apply this?
The optics industry has many applications where the levels of light are controlled and
sensed. In the communications industry, fiber optic cables are used to send your phone
conversation across long distances. In the robotics industry, sensing light is an important
aspect of controlling the movement of the mechanical parts of the robot.
The application you're probably most familiar with is the remote control on your
television set. When you point the remote control at your television and press a button to
change the channel, that information is sent using light, which is received by a sensor on
the front of your TV.
Many industrial processes need to use feedback to sense the level of light and adjust it to
keep it in a particular range. In photography, many cameras depend on analog
measurements taken by a light meter. These measurements can in turn be used to control
the aperture of the shutter when taking a photograph. The aperture is how far the shutter
opens to let light into the camera. In the next chapter, we'll build a light meter.