Hi Everyone

I am trying to connect a NPN Bipolar Transistor to a led light.(experimenting)(trying to understand)

Here is what I am using.


1) 10v power supply for collector
2) 5v power supply for base.
3) green led light
4) NPN transistor.

I connect 5v positive to base of transistor.
I connect 10v positive to positive led light and negative to collector.
I connect 10v and 5v negative to emitter.

The result is the led does not light up.
Please help. What am I doing wrong


Thank you
Gasant

 

The Completed Projects Forum is for Completed Projects only. It is meant to allow members to show plans for projects they built so other members can duplicate them if desired. New threads are also automatically moderated per Moderator review for this reason. Your thread does not belong in this forum, and was moved here.

 

...take a look at this...and this...

 

...without using an resistors for current limiting as shown in the links listed above, you likely would have smoked the transistor by connecting 5V between the base and collector.

 

From one Noob to another

Here are some of the "rules" I've learned.

1. EVERY LED needs to have an appropriately calculated resistor connected to it to limit the current to the level recommended by the datasheet and or adjusted slightly for a light output that works for you.

2. Read the datasheet for the transistor, looking at maximal collector-emitter current (this will tell you if the transistor can "drive" what you want to drive).

3. Learn how to calculate a base resistor/current - this is very instructive particularly about how the transistor works in general.

4. For a "transistor as a switch" the base current needs to put the transistor into the "saturation" zone.

As soon as you pick a couple of resistors, you'll see it work nicely.
Think about using some pots to "play" with your system.


I went through the same thing a few months ago, and I've learned a lot from this forum since then.
There's a little transistor project I'll post on the projects forum for comments over the next week.

 

+5V on the base and 0V on the emitter without a current-limiting resistor causes a very high current which blows up the base-emitter.

Why use an emitter-follower transistor anyway?

 

Just to give you an idea connection wise-heres 2 simple circuits using an npn transistor in one and a pnp in the other.....

 

HI

Just need to thank everyone whom tried to help me.

Bit late. Nevertheless.

Thank you
Gasant