28128 Parallax Inc, 28128 Datasheet - Page 120

• 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

After you've built the circuit, adjust the potentiometers until the piezoelectric speaker
makes a steady, slow tic-toc sound. A frequency of 1 Hz is desirable. You can make the
tic-toc stop any time you want by connecting pin-5 of the 555 Timer to ground (Vss).
In the previous experiment, the Stamp-O-Scope digitally sampled and displayed signal
data. Program Listing 6.1 is a greatly simplified version of the Stamp-O-Scope (the
Stamp-O-Scope 2), and it only displays variation in logic level (0 or 1). Since the 555
timer's output is a pulse train that varies between 0 and 5 volts, A/D conversion is not
required. The Stamp-O-Scope 2 is all that's needed.
' Basic Analog and Digital - PL6_1R0.bs2
' Stamp-O-Scope 2
' {$STAMP BS2}
' {$PBASIC 2.5}
DEBUG CLS
DO
LOOP
About the Code
The command
P0 to dictate how many spaces are printed. No variables are used. When the input is zero,
the asterisk gets printed without any spaces before it, indicating a 0 at the input. When the
value at P0 is 1, twenty spaces are printed before the asterisk, indicating a measured input
value of 1.
DEBUG REP " "\IN0*20, "*", CR
PAUSE 100
How to predict the 555 Timer's frequency?
More facts acquired from a data sheet, this one on the 555 family of timers. T
width, is given by:
0.69 x C x (R
where C, R
pot B as shown in Figure 6.3. T
given by:
0.69 x C x R
f = 1.45/[C*(R
DEBUG REP " "\IN0*20, "*", CR
A
B
A
and R
A
+R
+ 2R
B
),
B
'Start display
B
are the values of the capacitor and two resistance values of pot A and
)
L
, the duration of the low signal (the time between pulses) is
uses the input value measured at pin
H
, the pulse