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Foundations of Technology
SCR
(Silicon-Controlled Rectifier)
Teacher Resource Unit 4 Lesson 4
© 2013 International Technology and Engineering Educators Association,
STEMCenter for Teaching and Learning™
Foundations of Technology
Objectives:
1.
2.
You will build a simple circuit to show
that an SCR conducts only after a
positive pulse is applied to its gate.
You will be able to observe an LED will
light until the power is removed from the
anode or cathode of the SCR.
Gate
Anode
Cathode
You will need the following parts from your kit:
1.
2.
3.
4.
5.
6.
7.
8.
Breadboard
220 ohms resistor (red, red, brown, gold)
1000 ohms resistor (brown, black, red, gold)
SCR
LED (light emitting diode)
9 volt battery lead
3 wires
9 volt battery
Use this schematic to construct the experiment.
anode
220 Ohms
1K Ohms
9 volts
cathode
+
gate
-
Beveled Edge front
Gate
Anode
Cathode
Quick Check:
Your circuit should like this one.
This circuit will light the LED after a pulse to the gate.
1. The SCR acts like a switch.
2. When a positive pulse is applied to the gate, it
allows current to flow through the rest of the circuit.
3. An SCR is very sensitive to a lot of electrical
energy, we use a 1000 ohm resistor to protect the
SCR from burning out.
4. An SCR is used in computers and an alarm
systems.
1.
2.
3.
4.
Connect the 9 volt battery.
Observe the brightness of the LED.
Briefly touch the “loose” wire to the gate.
Observe the brightness of the LED.
Troubleshooting:
1. If the LED does not light up, check to make sure it is in correctly.
2. Check the battery. Does it have voltage?
3. Are there any breaks in the circuit?
4. Are you touching the “gate”?
By completing this experiment, you should have
noticed that current will flow through the SCR only
after you put a positive pulse to the gate.
In complete sentences, write what you learned about
an SCR in a circuit.