Name(s):
Must be typed:
In this lab experiment you become familiar with the following topics:

Relay
 Photoresistors

Voltage Dividers

Drawing the circuit

Schematic capture: http://phet.colorado.edu/simulations/sims.php?sim=Circuit_Construction_Kit_AC
DC

Circuit Simulator http://www.falstad.com/circuit/
Experiment A1 - Photoresistors
Carefully read http://www.acroname.com/howto/photoresistor/photoresistor.html
Measure the resistance of your Photoresistor

Measure the resistance of the device in the following conditions and record them in a table:

Completely dark room (cover the device with your hand)

Room light

Flashlight located far away from the device
 Flashlight shining very close to the device
Light Condition
Completely Dark
Room light
Flashlight far away
Flashlight very close
Resistance Measured

Experiment A2 - Use http://phet.colorado.edu/simulations/sims.php?sim=Circuit_Construction_Kit_ACDC and create the circuit below and complete the table below.
R2
R1 SW
5V
The voltage that voltmeter reads is V and can be calculated as follow: (make sure you set
Vcc = 5V. Assume R1= 10 ohm
R1
10
R2
20
V simulated Calculated
10
10
30
40
10 50
Using Excel plot both V simulated and V calculated on the same figure. You can do this at home.

Experiment B - Build a voltage divider

Build the circuit below

Set Vcc to 5 Volt

Set R1 = resistance that you measured for the photoresistor at room light
(about 2.5 Kohm).
 Use the potentiometer on the board (the POT) instead of the resistor.
Connect to
LED!
Complete the table below:
Light
Condition
Voltage measured (V)
Voltage
Simulated
(V) **
Voltage
Calculated
(V) ***
Is LED on or Off?
Completely
Dark
Room light
Flashlight far away
Flashlight very close
** use http://www.falstad.com/circuit/
***

Explain how you can change the circuit operate opposite of what it is doing.

Explain the importance of the potentiometer and how it impacts the operation of the circuit.

Experiment C - Learn About Relays
Setup the circuit as shown below:
R

Draw the circuit and show how these components are connected to each other.
Make sure you include the PIN number of the relay.

Explain how this relay operates.

Draw the internal schematic of this mechanical relay. You can use the figure below:

Pin 1 to LED
Pin 2 to + Pin 3 to 1
Pin 4 to LED