And you're feeding 2V into it?

A red LED generally has a voltage drop of 1.8V. Using a 2V supply and a 300 ohm resistor, that means that the current flowing through the LED is (2V-1.8V)/300 = 0.6mA. Something seems wrong there. If the LED is only seeing 0.6mA it would not be shining very brightly. So what dannyf said (besides "rectified static", which is total rubbish) is correct--it should only be lighting very faintly, even when the transistor is in saturation.

Actually I'm using 820 Ohm resistor for the LED and changed voltage to 3V. I'm starting to think that problem is in the breadboard.
Voltage after the LED is 1V so Mr. Ohm isn't lying.

 

Actually I'm using 820 Ohm resistor for the LED and changed voltage to 3V. I'm starting to think that problem is in the breadboard.

3V supply and 820R resistor gives you (3V-1.8V)/820 = 1.46mA. Still not very much, and shouldn't make your LED shine that brightly (even if it is high-efficiency, I would expect). What are you using for a power supply?

Your breadboard is not going to give your LED more current unless you have other connections you are not telling us about.

 

I'm guessing the resistor is positioned incorrectly on the breadboard and is being bypassed by an internal link.

 

3V supply and 820R resistor gives you (3V-1.8V)/820 = 1.46mA. Still not very much, and shouldn't make your LED shine that brightly (even if it is high-efficiency, I would expect). What are you using for a power supply?

Your breadboard is not going to give your LED more current unless you have other connections you are not telling us about.

PSU is linear regulated one based on LM317,I measured the voltage at output stays precisely 3V and doesn't fluctuate when its loaded.
Current drawn from the PSU measured at 60mA.

Uploaded the setup,red wire is "finger" wire.

 

Ancient diagnostic tool: Finger Hum. First invented for testing audio amplifiers.

I have also used "digital" temperature probes.

 

I'm starting to think that problem is in the breadboard.

You can think of your fingers as a signal source with very high output impedance. At moderate current levels, your transistor's b-e junction look to be a very low impedance load -> if you couple the two together, you don't get much on the b-e junction and you wouldn't turn on the led.

A mosfet, in comparison, can have input impedance in excess of 100s of MOhms -> would have been higher if it were not for the protection diodes. and it would easily work here.

Current drawn from the PSU measured at 60mA.

It would be a miracle if you could get 60ma through a 820ohm resistor + led under a 3v source. Something is seriously wrong here.

 

You can think of your fingers as a signal source with very high output impedance. At moderate current levels, your transistor's b-e junction look to be a very low impedance load -> if you couple the two together, you don't get much on the b-e junction and you wouldn't turn on the led.

A mosfet, in comparison, can have input impedance in excess of 100s of MOhms -> would have been higher if it were not for the protection diodes. and it would easily work here.



It would be a miracle if you could get 60ma through a 820ohm resistor + led under a 3v source. Something is seriously wrong here.

I'm pretty sure that problem is in the PSU. After plugging it in the USB the LED would just be barely lit,if i connect it to Arduino 5V it wouldn't even be on and batteries give a bit brighter light but not even close to the PSU.

 

If you look back at those cell phone ringing flashers, they consist of a coil + an led. When a call comes in, the led would lit up. Those phones radiate close to 1w.

So if an led will lit up when your finger touches it, your finger must be radiating as much energy, or you live in a very rough environment, radiation-wise.

 

Gonna grow third arm soon.No need for helper hands anymore.