28122 Parallax Inc, 28122 Datasheet - Page 151

• Manufacturer Part Number: 28122
• Description: KIT WHAT'S A MICRO:PARTS ONLY
• Manufacturer: Parallax Inc

Specifications of 28122

• Accessory Type: Parts Kit
• Product: Microcontroller Accessories
• Core Processor: PIC16C57c
• Flash: 128 Bytes
• Operating Supply Voltage: 9 V
• Board Size: 31 mm x 16 mm
• For Use With/related Products: Board of Education Full Kit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

turn the potentiometer’s input shaft, the resistance between the A and W terminals
changes. This in turn changes the current flow through the LED circuit.
ACTIVITY #2: MEASURING RESISTANCE BY MEASURING TIME
This activity introduces a new part called a capacitor. A capacitor behaves like a
rechargeable battery that only holds its charge for short durations of time. This activity
also introduces RC-time, which is an abbreviation for resistor-capacitor time. RC-time is
a measurement of how long it takes for a capacitor to lose a certain amount of its stored
charge as it supplies current to a resistor. By measuring the time it takes for the capacitor
to discharge with different size resistors and capacitors, you will become more familiar
with RC-time. In this activity, you will program the BASIC Stamp to charge a capacitor
and then measure the time it takes the capacitor to discharge through a resistor.
Introducing the Capacitor
Figure 5-7 shows the schematic symbol and part drawing for the type of capacitor used in
this activity. Capacitance value is measured in microfarads (µF), and the measurement is
typically printed on the capacitors. The cylindrical case of the capacitor is called a
canister.
This capacitor has a positive (+) and a negative (-) terminal. The negative terminal is
the lead that comes out of the metal canister closest to the stripe with a negative (–) sign.
Always make sure to connect these terminals as shown in the circuit diagrams. Connecting
one of these capacitors incorrectly can damage it. In some circuits, connecting this type of
capacitor incorrectly and then connecting power can cause it to rupture or even explode.
3300 µF
+
-
3300 µF Capacitor
Schematic Symbol
and Part Drawing
Pay careful attention
to the leads and how
they connect to the
Positive and
Negative Terminals.
Figure 5-7