Electronics > Beginners
Transistor Switching
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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