I wanted to test out making a circuit with a transistor. The way I understood transistors from online videos:

The transistor (using BC327, see below) needs a closed circuit from the positive terminal through a resistor (first I used a 200 ohm resistor, but I then feared it would burn the transistor, so I used a 4.7 kohm resistor) through the base → emitter of the transistor all the way to the negative terminal.

That should allow the current to pass from +Terminal+ → 200 ohm resistor → LED → transistor collector → transistor emitter → -Terminal-

I enclose the schematics I made beforehand and a few angles of the actual breadboard project. Do I understand the working of transistors wrong, or did I just connect something in a wrong way?

What are some additional tips to make my breadboarding look "better" or closer to any standards that there might be?

BC327 pinout picture

MS Paint circuit design

View from above 1

View from above 2


  • 1
    \$\begingroup\$ 1) The schematic is correct and should work but realize that it doesn't do anything more than make the LED light up. 2) If it works on the breadbord, you're done, it works. Congratulations. There are no rules / standards / ways to make it better (better how?). \$\endgroup\$ Commented Dec 8, 2021 at 13:24
  • \$\begingroup\$ The LED doesn't light up, and I cannot figure out what I did wrong, so I guess the question is: Can anyone see why this doesn't work? \$\endgroup\$ Commented Dec 8, 2021 at 13:27
  • 2
    \$\begingroup\$ The LED doesn't light up OK, then retrace every connection and make sure it is exactly the same is shown in the schematic. Disconnect the 5 V and use a multimeter on continuity check to confirn each connection. Pay attention to the polarity of the LED, LEDs work only in one direction. No, I'm not going to check your breadboard connections from the photos, that will be your task. \$\endgroup\$ Commented Dec 8, 2021 at 13:29
  • 1
    \$\begingroup\$ Schematics and datasheets are your best friends here, as is your attention to detail. Pay close attention to the location and direction of the arrows in those two diagrams and ask yourself what looks different. Electronics is a discipline of details and all of them matter. \$\endgroup\$
    – J...
    Commented Dec 9, 2021 at 13:03

1 Answer 1


BC327 is a PNP transistor. The circuit in your schematic requires a NPN transistor (BC337 for example).

  • 4
    \$\begingroup\$ It worked! Thank you so much, it seems I have more studying to do with transistors! \$\endgroup\$ Commented Dec 8, 2021 at 13:40
  • 5
    \$\begingroup\$ Or you can make it work with the PNP transistor by changing the battery polarity and the LED polarity. \$\endgroup\$ Commented Dec 9, 2021 at 9:31

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