blinking L.E.D.s using a single transistor

[rajaram04]

Hello sir,
would you please tell me if there is any possiblity of a circuit using a single transistor as a major past to make an l.e.d. blinking continue or say can we make an simple oscillator using a single transistor ? if there is any option then please tell let me have the proper circuit diagram of that
thanks

 

[godfreyl]

The Joule thief is a simple oscillator: https://en.wikipedia.org/wiki/Joule_thief

 

[rajaram04]

thank you so much sir but can we replace this coil with capacitor ? how will the circuit then ?

 

[godfreyl]

can we replace this coil with capacitor ?

No. It must have the transformer.

But with 2 transistors you can make a circuit like this:

 

[rajaram04]

ok sir thanks a lot i got it ! thank you very much sir

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Sir what is the formula we basically use to get the timings for the astable multivibrator circuit u gave me here ? how can we decide diffrent timing parameters for the either outputs of this circuit ?

 

[BradtheRad]

Some other coilless 1-transistor oscillators are:

* phase-shift
* twin-T
* Wien bridge

The above types each use 3 or more capacitors.

The common astable (per post #4) is easier to work with than the above types, in the sense that it is easier to get oscillating. A certain amount of asymmetry may be needed to help achieve this.

Also, the common astable yields squarish waves, whereas the above three generate sine waves.

The values shown in post #4 will result in 1-2 Hz per complete cycle.

 

[tpetar]

Hello sir,
would you please tell me if there is any possiblity of a circuit using a single transistor as a major past to make an l.e.d. blinking continue or say can we make an simple oscillator using a single transistor ? if there is any option then please tell let me have the proper circuit diagram of that
thanks

My friend of course this is possible, see this:

http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html

**broken link removed**

**broken link removed**

 

[FvM]

My friend of course this is possible, see this

I guess we all know, that this is not what the original post is asking for. A blinking LED is already blinking on it's own, without a transistor. If you don't have this special part, an unijunction transistor oscillator would be the second best option in terms of part count. But it's not a a single BJT, strictly speaking.

 

[godfreyl]

Apparently the first circuit shown by tpetar will actually flash a normal LED. The principle of operation is so far from normal transistor action that it's more likely to confuse than enlighten anyone trying to learn about transistors. The explanation in the link does make for interesting reading though.

 

[FvM]

The principle of operation is so far from normal transistor action that it's more likely to confuse than enlighten anyone trying to learn about transistors.

Yes, you are right, I didn't refer to the link. I would classify the operation principle as inverse mode avalanche breakdown. Long time reliability may be critical, I would prefer a more reliable UJT or thyristor-tetrode circuit.