Gate

Anode

Cathode

You will need the following parts from your kit:1. Breadboard

2. 220 ohms resistor (red, red, brown, gold)

3. 1000 ohms resistor (brown, black, red, gold)

4. SCR

5. LED (light emitting diode)

6. 9 volt battery lead

7. 3 wires

8. 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.

an

od

eca

tho

de

220 Ohms

+

-9 volts

Quick Check:

Your circuit should like this one.But remember you should use the schematic to

build your circuit, not the photo!

1K Ohms

gate

Gate

Anode

Cathode

Beveled Edge front

Be sure to label your schematic!

1. Connect the 9 volt battery.2. Observe the brightness of the LED.3. Briefly touch the “loose” wire to the gate side of the SCR.4. Observe the brightness of the LED.5. Briefly touch the “loose” wire to the gate again.6. 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”?

4. What does an SCR do?

5. Where could you use an SCR with its unique abilities?

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?