Electronics > Beginners

Transistor Switching

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Oslaw:
Hello all, I was testing switching with a 2n2222 NPN transistor and every time I connect the base directly to data source( or set my potentiometer to zero), the LED on the collector side turns off or goes dull Please what might be wrong.

Zero999:
A schematic would help.

The transistor must have a base resistor and the LED a current limiting resistor.

Oslaw:
This is the schematic I used. It switches well until I remove 1k resistor connected to the base, then the LED goes dim or dies.

hamster_nz:
What are you using as a power source?

Without either a base resistor, or a current limiting resistor for the LED everything should burn out (that is unless you are using a current limited power supply).

Do you want to:

a) see a design that will work

or

b) to understand why the existing design doesn't work, allowing you to design something that will.

Oslaw:
Both. I did just that and still same result. I am using a 9v battery. Below are pictures of the potentiometer tuned to both ends. At level 0 Ohm LED is dull and at 10k Ohms bright(at any resistance level above 0 ).

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