28128 Parallax Inc, 28128 Datasheet - Page 117

• 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 6: Recording Frequency Data · Page 107
Chapter #6: Recording Frequency Data
In the previous chapter we used the BASIC Stamp to control a D/A converter to produce
audible tones. In this chapter, we'll use a 555 timer to generate frequencies in the audible
sound range, then we'll use the BASIC Stamp to sample and process the frequency data.
We'll start by viewing a pulse train generated by a 555 timer on a simplified version of
the Stamp-O-Scope. Two potentiometers will be used to control the frequency and duty
cycle of the pulse train. After viewing the pulse train's signal characteristics, the 555
timer's output will be directed to a piezoelectric speaker. The 555 timer's output will also
be connected to a BASIC Stamp I/O pin set to input. The BASIC Stamp will be
programmed to monitor and record the frequencies generated by the 555 timer.
Parts Required
This experiment requires the following parts:
(2) 100 k potentiometers
(1) Piezoelectric speaker
(1) 555 timer
(1) 10 µF electrolytic capacitor
(1) 0.1 µF capacitor
(2) 2 k resistor
Not all the parts will get used at once on the same circuit. Certain capacitors and resistors
are substituted in the second circuit to increase the 555 timer's output frequency.
The electrolytic capacitor shown in Figure 6-1 has a positive and negative terminal. The
wire that comes out of the metal canister closest to the black stripe is the negative
terminal. The arrows (>>) on the black stripe point to the negative terminal. The canister
also has the value printed on it. 1µF indicates 1 microfarad while 10 µF indicates a 10
microfarad capacitance value.