Cannot manage to wire up a transistor :@

Other Hardware General Electronics
1

So I followed this diagram and I have no idea why it's not working...

 3V --+--------+
      |        |
      /      __|__   .
      \ 1k   \   /  /.  blue
      /      _\_/_  /   LED
      |        |
      |        | collector
      |        |/
      +-------|
          base |\  emitter
               |
              ---
               -

I know it's hard to see in the photo but I followed the diagram exactly. The only thing in not 100% sure of is whether the the emitter goes tk ground (which is where I put it). This is so frustrating. I have tried to put transistors in a circuit so many times and it never works, why!!?

image.jpg
image.jpg2448×3264 3.07 MB

2

What is Vf for the LED?

3

What's the transistor? it might be a PNP which would account for this issue.

But with 3v, take a 100-300 ohm resistor and find out if the LED is even working!

4

cjdelphi:
What's the transistor? it might be a PNP which would account for this issue.

But with 3v, take a 100-300 ohm resistor and find out if the LED is even working!

Yes the LED is working and the transistor is a PNP (S8550), so it is the right way, I looked at the data sheet. But I have tried it the opposite way and it still doesnt work.

5

Noahsdev:
I know it's hard to see in the photo but I followed the diagram exactly.

  • no you didn't : I see 2 resistors in you wiring :wink:
  • I'm not sure of the colours from your photo, could you tell us the resistors values ?
  • last, but not least .... if it is a pnp, it will never work if you follow this diagram : for a PNP to switch on, its base must be at least 0,6V less than emitter voltage !!

edit : look at this page SECARS Homepage - SECARS

6

Noahsdev:

cjdelphi:
What's the transistor? it might be a PNP which would account for this issue.

But with 3v, take a 100-300 ohm resistor and find out if the LED is even working!

Yes the LED is working and the transistor is a PNP (S8550), so it is the right way, I looked at the data sheet. But I have tried it the opposite way and it still doesnt work.

By the looks of it, youhave the base pin hooked up to the positive voltage rail (NPN's do this) PNP needs to be connected to gnd/0v.

PNP and NPN are wired up completely differently.

7

The way you have the circuit wired up is correct for an NPN transistor, but not for a PNP transistor.