Driving Transformer Help

[Athosworld]

I made a small transformer with 30 turns on primary and around 250 turns on the secondary and I want to know how to drive it. I thought I could drive it with a 2N2222 oscillator like this one

Could I just replace the LED with the primary of my transformer? What effect would this have on the circuit?
Here is my transformer

 

[ZipZapOuch]

Could I just replace the LED with the primary of my transformer? What effect would this have on the circuit?

First, try it. What damage could it do. With the 1k ohm in series, I don't see a possible problem of trying it. Other than the shock you may get out of the secondary.

 

[Diver300]

You will get some leakage inductance so you will probably need some supresion to stop the inductance destroying the transistor.

 

[crutschow]

Driving a transformer with a DC average component is not desirable, since it tends to saturate the core.
Better to drive it with a push-pull output buffer stage through a large capacitor to block the DC.

 

[schmitt trigger]

Why is the base open?
Why is the emitter of an NPN transistor connected to the positive supply?

In other words, why are you attempting to drive a transformer with the EC reverse breakdown current?

Lastly, what are the transformer’s electrical characteristics?

 

[rjenkinsgb]

Why is the base open?
Why is the emitter of an NPN transistor connected to the positive supply?

In other words, why are you attempting to drive a transformer with the EC reverse breakdown current?

It's a very crude type of relaxation oscillator, that has be posted online numerous times.

When the reverse base-emitter breakdown occurs, the transistor can "trigger" like a UJT, with the forward biased base-collector junction acting in place of the normal base-emitter junction.

 

[schmitt trigger]

Thanks for the explanation.

 

[crutschow]

I made a small transformer with 30 turns on primary and around 250 turns on the secondary and I want to know how to drive it. I thought I could drive it with a 2N2222 oscillator like this one

What output from the transformer are you expecting?

 

[Nigel Goodwin]

Driving a transformer with a DC average component is not desirable, since it tends to saturate the core.

You mean exactly as car ignition coils work

This 'circuit' works more like an ignition system than an actual oscillator.

 

[ZipZapOuch]

I was playing with a similar circuit recently. I had a nice polycarbonate sheet as a shield to protect my face from the possible spatter of copper wire used as an electrode - unfortunately, I spattered the window on my fluke meter.

 

[crutschow]

You mean exactly as car ignition coils work

Well, not exactly.
I don't think it's designed to saturate, just go to near saturation.
Anything beyond saturation would not add to the output.

 

[ZipZapOuch]

Well, not exactly.
I don't think it's designed to saturate, just go to near saturation.
Anything beyond saturation would not add to the output.

I think an old-school car ignition has to saturate at low rpm or it won't be close to saturation at high RPM where it needs the strongest spark.

 

[Diver300]

I think an old-school car ignition has to saturate at low rpm or it won't be close to saturation at high RPM where it needs the strongest spark.

I don't think that the ignition coil saturates on a car. The current is limited by the resistance of the coil, but that doesn't mean that the magnetic field is saturated.

Modern cars limit the time that the coil is turned on for, and with the coil inductance that stops the current getting too large.

 

[shortbus=]

Modern cars limit the time that the coil is turned on for, and with the coil inductance that stops the current getting too large.

they also have a gaped core, to give a slightly longer spark time.

 

[Athosworld]

Why is the base open?
Why is the emitter of an NPN transistor connected to the positive supply?

In other words, why are you attempting to drive a transformer with the EC reverse breakdown current?

Lastly, what are the transformer’s electrical characteristics?

the transformer has a ferrite core
30 turns on primary 250 on secondary (new version has 20 turns on pri and 400 on sec
The primary is 1 mm wire and the sec is 0.1 mm