Revised 02/28/01 mjh
LAB 3
BASIC ELECTRONIC CIRCUITS LAB
LAB PROCEDURE
1.
LOCATE the following PIECES and PARTS in your ELECTRONIC PARTS KITS or on
the TABLE:
A power supply with wire leads, a Digital Multi-Meter (DMM), a switch, two 330
ohm resistors (orange/orange/brown color bands), a 2200 microfarad capacitor, a light
emitting diode (LED), a wire jumpers kit, and a prototyping board.
2.
UNPLUG the power supply from the outlet.
3.
On the prototyping board, CONNECT one LEAD of the SWITCH to a POWER (+5 Vdc)
hole. CONNECT the other LEAD to a hole in any one of the 5-hole terminal sets.
4.
CONNECT a 330 ohm resistor from that same set to another nearby set.
5.
CONNECT an LED from that nearby set to ground. Note that the LED must be oriented
properly for it to work. The lead with a spearhead shape to it inside the LED is the
positive lead.
6.
CONNECT LEADS from the POWER SUPPLY to the prototyping board. INSURE that
the POSITIVE LEAD goes to the GREEN POST while the NEGATIVE LEAD (ground)
goes to the BLACK POST. At the same time, CONNECT JUMPER WIRES from the
POSTS to the POWER BUS sets. The +5 (GREEN POST) should wire to the RED
STRIPED sets while the GROUND (BLACK POST) should go to the BLUE STRIPED
sets.
7.
PLUG IN the POWER SUPPLY to the 120 Vac ELECTRICAL OUTLET.
8.
PRESS SWITCH LEVER and the LED should EMIT LIGHT. RELEASE the LEVER and
the LED should STOP EMITTING LIGHT.
9.
SET the DMM to a 20 Vdc range (three ‘clicks’ counterclockwise from OFF position).
10.
LOCATE the points AA, BB, and CC on the SCHEMATIC DRAWING. Now LOCATE
the SAME ELECTRICAL POINTS on your prototyping board.
11.
PRESS and HOLD the SWITCH LEVER.
12.
PLACE BLACK DMM LEAD so it CONTACTS BLACK POST METAL (or equivalent
point CC). PLACE RED DMM LEAD so it CONTACTS POINT AA. RECORD the
READING of the DMM DISPLAY.
13.
PLACE BLACK DMM LEAD so it CONTACTS BLACK POST METAL (or equivalent
point CC). PLACE RED DMM LEAD so it CONTACTS POINT BB. RECORD the
READING of the DMM DISPLAY.
14.
RELEASE the SWITCH LEVER.
15.
CONNECT ANOTHER 330 OHM RESISTOR in PARALLEL with the EXISTING
RESISTOR.
Lab 3 Procedure
Revised 02/28/01 mjh
16.
REPEAT STEPS 11 THROUGH 14. Does the LED output seem different? If so, how is
it different?
17.
CONNECT a 2200 MICROFARAD CAPACITOR from the HOLE SET of the JUNCTION
OF THE SWITCH LEAD AND RESISTOR LEAD ( AA ), TO the SYSTEM GROUND
(SETS OF HOLES MARKED BLUE). INSURE THE CAPACITOR LEAD MARKED –
(negative) IS CONNECTED TO THE BLUE MARKED HOLES (ground).
18.
PRESS the SWITCH LEVER.
19.
NOTE and RECORD what happened to the LED OUTPUT.
20.
RELEASE THE SWITCH LEVER. NOTE and RECORD what happened to the LED
OUTPUT.
21.
PRESS the SWITCH LEVER, WAIT a moment, then RELEASE the SWITCH LEVER.
BEGIN TO COUNT when you release the SWITCH LEVER. HOW LONG does it take
for the LED to BE COMPLETELY OFF? TRY THIS A FEW TIMES AND RECORD AN
AVERAGE TIME in seconds.
22.
USE the DMM to MONITOR point AA (RED LEAD TO AA, BLACK LEAD TO CC). Now
REPEAT STEP 21 BUT COUNT the TIME it takes for the VOLTAGE LEVEL at AA to
DROP TO 1.7 Vdc after the SWITCH LEVER is RELEASED.
23.
REMOVE ONE of the 330 OHM REISITORS and REPEAT STEPS 21 and 22.
24.
YOU HAVE COMPLETED THE MEASUREMENT STEPS FOR THIS LAB !
Lab 3 Procedure
Revised 02/28/01 mjh
ENGINEERING 182 BASIC ELECTRONICS
MEASUREMENT RECORDING AND NOTATIONS:
STEP 12(one resistor):
_____________ Volts
STEP 13(one resistor): _____________ Volts
STEP 12(two resistors):
___________ Volts
STEP 13(two resistors): ___________ Volts
What can you conclude about the variation of voltage across the LED?
Is a diode (LED) a regulator (‘maintainer’) of voltage? Explain your answer.
Notes for Step 16:
_____________________________________________________________________________
Notes for STEP 19:
Notes for STEP 20:
_____________________________________________________________________________
Time for LED to completely turn off: ____________________ seconds (STEP 21, 2 resistors).
Time for voltage level to reach 1.7 Vdc: _________________ seconds (STEP 22, 2 resistors).
Time for LED to completely turn off: _____________________ seconds (STEP 21, 1 resistor).
Time for voltage level to reach 1.7 Vdc: __________________ seconds (STEP 22, 1 resistor).
Lab 3 Procedure
Revised 02/28/01 mjh
What can you conclude about the effect of resistance (along with capacitance) on the time
response of the circuit?
Lab 3 Procedure