What is a Microcontroller (Paralax, v2.2, student guide, 2004)

PULSOUT 14, time

LOOP

P2. The key is to add IF…THEN blocks; an example is shown below.

'What's a Microcontroller - Ch5Prj02_ControlServoWithPot.bs2

'Read potentiometer in RC-time circuit using RCTIME command.

'The time variable ranges from 126 to 713, and an offset of 330 is

'needed.

'Modify so the servo only rotates from 650 to 850.

'{$STAMP BS2}

'{$PBASIC 2.5}

DEBUG "Program Running!"

PULSOUT 14, time

LOOP

Page 164 · What’s a Microcontroller?

Further Investigation

Several different electronic components, concepts and techniques were incorporated in this chapter. Some of the more notable examples are:

•Using a potentiometer as an input device

•Measuring the resistance/capacitance of a device using RCTIME

•Performing math on an input value and recycling it into an output

•Controlling a motor based on a measured value

“Advanced Robotics: with the Toddler”, Student Workbook, Version 1.2, Parallax Inc., 2003

“Robotics with the Boe-Bot”, Student Workbook, Version 2.0, Parallax Inc., 2003 “SumoBot”, Student Workbook, Version 1.1, Parallax Inc., 2002

Every Stamps in Class robotics text uses RCTIME to measure resistive sensors to detect a variety of conditions. Each condition leads to math and decisions, and the end result is robot movement.

“Basic Analog and Digital”, Student Guide, Version 2.0, Parallax Inc., 2003

Basic Analog and Digital uses the potentiometer to create a variable voltage, called a voltage divider, which is analyzed by an analog to digital converter. A potentiometer is also used as an input device to set the frequency of a 555 timer. This text takes a closer look at the math involved in RC voltage decay.

“Applied Sensors”, Student Guide, Version 1.3, Parallax Inc., 2003

RCTIME is used extensively in this book to collect data from a variety of sensors.

“Industrial Control”, Student Guide, Version 2.0, Parallax Inc., 2002

This book introduces techniques used extensively in industry for controlling machines based on sensor input. The techniques fall under the general category of control systems.

Chapter #6: Digital Display · Page 165

Chapter #6: Digital Display

THE EVERY-DAY DIGITAL DISPLAY

Figure 6-1 shows a display on the front of an oven door. When the oven is not in use, it displays the time. When the oven is in use, it displays the oven’s timer, cooking settings, and it flashes on and off at the same time an alarm sounds to let you know the food is done. A microcontroller inside the oven door monitors the pushbuttons and updates the display. It also monitors sensors inside the oven and switches devices that turn the heating elements on and off.

Figure 6-1

Digital Clock 7-Segment

Display on Oven Door

Each of the three digits in Figure 6-1 is called a 7-segment display. In this chapter, you will program the BASIC Stamp to display numbers and letters on a 7-segment display.

WHAT’S A 7-SEGMENT DISPLAY?

A 7-segment display is rectangular block of 7 lines of equal length that can be lit selectively to display digits and some letters. A very common form is the 7-segment LED display, a package with a rectangular block of 7 LEDs. Figure 6-2 shows a part drawing of the 7-segment LED display you will use in this chapter’s activities. It has one additional LED, a dot that can be used as a decimal point. Each of the segments (A through G) and the dot contains a separate LED, which can be controlled individually. Most of the pins have a number along with a label that corresponds with one of the LED segments. Pin 5 is labeled DP, which stands for decimal point. Pins 3 and 8 are labeled “common cathode”, and they will be explained when the schematic for this part is introduced.

Chapter #6: Digital Display · Page 171

ACTIVITY #2: CONTROLLING THE 7-SEGMENT LED DISPLAY

In this activity, you will connect the 7-segment LED display to the BASIC Stamp, and then run a simple program to test and make sure each LED is properly connected.

7-Segment LED Display Parts

(1) 7-segment LED display

(8) Resistors – 1 kΩ (brown-black-red)

(5) Jumper wires

Connecting the 7-Segment LED Display to the BASIC Stamp

Figure 6-10 shows the schematic and Figure 6-11 shows the wiring diagram for this BASIC Stamp controlled 7-segment LED display example.

√Build the circuit shown in Figure 6-10 and Figure 6-11.

Schematic and pin map: If you are trying to build the circuit from the schematic in Figure 6- 10 without relying on Figure 6-11, make sure to consult the 7-segment LED display’s pin map (Figure 6-2, page 166).

Be careful with the resistors connected to P13 and P14. Look carefully at the resistors connected to P13 and P14 in Figure 6-11. There is gap between these two resistors. The gap is shown because pin 8 on the 7-segment LED display is left unconnected. A resistor connects I/O pin P13 to 7-segment LED display pin 9. Another resistor connects P14 to 7- segment LED display pin 7.