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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
NOTE: A SCR is very
sensitive to a lot of
electrical energy, we use
a 1000 ohm resistor to
protect the SCR from
burning out.
Use this schematic to construct the experiment.
Be sure to label your schematic!
anode
220 Ohms
1K Ohms
9 volts
cathode
+
gate
-
Beveled Edge front
Gate
Anode
Cathode
Quick Check:
Your circuit should like this one.
But remember you should use the schematic to
build your circuit, not the photo!
1.
2.
3.
4.
5.
6.
Connect the 9 volt battery.
Observe the brightness of the LED.
Briefly touch the “loose” wire to the gate side of the SCR.
Observe the brightness of the LED.
Briefly touch the “loose” wire to the gate again.
Does anything change?
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”?
1. The SCR conducts electricity under what conditions? Is it always
conducting electricity (is the light always lit?) When you touch the
wire to the gate, does the light go on or off? Once the light is on, does
touching the gate again change anything?
2. How many of the 3 leads need to be connected for the light to be lit?
Try disconnecting different leads, is it possible to keep the light lit with
only one of the SCR leads connected to something in the circuit?
Light the LED and try different combinations.
3. Which leads can you disconnect after the light is lit that allow the light
to stay lit? The anode, the gate or the cathode?
4. What does an SCR do?
5. Where could you use an SCR with its unique
abilities?