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Connecting base to high state from MCU

Transistor: BD239C

Collector-emitter is powered by 12 V 2 A and resistance is 660 Ω, 12 V / 660 Ω = 0.018 A

Base is powered from MCU output by 5 V 0.2 A and resistance is 330 Ω 5 V / 330 Ω = 0.015 A

When base is connected to high state (as on image 2) then collector-emitter voltage is 12 V, but LED no. 1 on image 2 shines slightly.

What is wrong, why doesn't the LED light?

schematic

simulate this circuit – Schematic created using CircuitLab

Jakub Kutrzeba
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    Please show a schematic for your circuit. There is a schematic editing tool available when you edit your question. – Math Keeps Me Busy Aug 28 '23 at 14:35
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    Looks like you've got the transistor and LED resistor the wrong way round. But add a schematic so we can tell for sure. – Finbarr Aug 28 '23 at 14:41
  • What that mean? – Jakub Kutrzeba Aug 28 '23 at 14:45
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    Please crop your images to the relevant portion. – JYelton Aug 28 '23 at 14:50
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    "What's a schematic?" Please see https://electronics.stackexchange.com/q/105136/2028 – JYelton Aug 28 '23 at 14:53
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    I've put a small schematic in your question, which may represent part of what I can guess from your words, nothing can be guessed from your pictures. Please edit the schematic to correct and complete it. You'll notice how it tells us exactly what's in the circuit, no guesswork required. – Neil_UK Aug 28 '23 at 15:00

2 Answers2

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fritzing should be easily able to give you a schematic instead of a breadboard emulation. You put the LED into the emitter path, meaning that the base voltage needs to exceed the forward voltages of both LED and transistor (at nominal current, about 2.2V and 0.7V, respectively). A high-level output is defined to be above 2.2V. That does not leave enough voltage reserves to yield enough base current for turning the LED fully on. Putting the LED in the collector path should yield much saner results.

user107063
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I fixed the very, very, very simple circuit: LED circuit

Audioguru
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