me_guitarist
Full Member level 6
can I use some transistor to make a simple circuit to turn on a led indication when the switch is opened? How? normally the led turned on when the swicth is close, how to do in oppasite?
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I follow this circuit but it doesn't work...base voltage 12V also,I put 220K coz don't know how to calculate transistor, my component:Q1=BC556B,
with 12 V on R2, the LED can't on, you have to use lower than 12 V for R2my input for R2 is 12V DC
Hi,me_guitarist said:Dear Budhy,
Is it a NPN transistor?
Added after 3 minutes:
I follow this circuit but it doesn't work...base voltage 12V also,I put 220K coz don't know how to calculate transistor,
my component:Q1=BC556B,
h**p://www.mayothi.com/images/transistor6.GIF[img]
[size=2][color=#999999]Added after 1 minutes:[/color][/size]
[img]h**p://www.mayothi.com/images/transistor6.GIF