28128 Parallax Inc, 28128 Datasheet - Page 135

• 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

All that's left is to plug in the numbers to solve for t
resistance and capacitance values shown in Figure 7-1, and V
V
Then, the same calculation can be done for t
An oscilloscope could be used to monitor the output voltage of the RC circuit from
Figure 7-1. The response when a single, very wide pulse (a voltage step) is applied would
resemble that shown in Figure 7-3. As you can see, it takes just a fraction of a second for
the capacitor to charge up to 5 volts. Nonetheless, it is a gradual change when compared
to pulses sent by the BASIC Stamp, which can be as narrow as 2 microseconds
Output
is 2.5 volts.
ln
t
t
2
. 4
5 .




95
1
Volts
−
Volts
V
V
=
Output
Input
=
−
−
R
R
×




×
C
=
C
×
ln
×
ln




ln
e




1




R
−
1
×
−
t
C
−
V




V
V
Output
V
Input
Output
Input
⇒








=
R
=
−
−
×
−
(
t
10
C
(
10
×
=
×
10
ln
4.95 Volts
10
3




1
)
3
×
)
−
×
1 (
V
1 (
V
×
Output
Input
.
×
10
10
−
2.5 volts
6
−




)
6
×
)
×
ln
⇒
ln



1



and t
−
1
t
−
2
5
=
5 .
0 .
. 4
5
−
Input
4.95 volts
95
0 .
R



=
×



. 6
C
=
= 5 volts. The first
93
×
46
ln
×
. R and C are the
1 .
10




1
×
−
−
10
3
V
sec
−
V
3
Output
Input
sec
onds
onds




.
.