Hi, I built this circuit and it doesn't oscillate, so no outputs.
I can't see how the circuit can start oscillating.
Went to trouble of winding quality inductor with core and it measures 270uH.

 

What type of core, steel, ferrite? Does it have an airgap?

Otherwise the core will saturate with the DC bias and the inductance will drop to near zero.
You can alleviate this with powder-iron toroids, which have distributed air gaps.
Unless you are using an expensive LCR meter, the inductance they measure is with zero bias.

Show a picture of the inductor.

 

What type of core, steel, ferrite? Does it have an airgap?

Otherwise the core will saturate with the DC bias and the inductance will drop to near zero.
You can alleviate this with powder-iron toroids, which have distributed air gaps.
Unless you are using an expensive LCR meter, the inductance they measure is with zero bias.

Show a picture of the inductor.

Hi, I built this circuit and it doesn't oscillate, so no outputs.
I can't see how the circuit can start oscillating.
Went to trouble of winding quality inductor with core and it measures 270uH.
View attachment 348696View attachment 348697

The ferrite E core was in my scrap box with a winding from a SMPS. There was a gap but I removed the spacer. My LCR meter is an eBay LCD module type.
With spacer I needed many more turns to get inductance given in circuit. I still have the spacer in the mess on the table. About 0.5 mm.

 

Please post a link to the source of the article.

ak

 

Don't have link as made screenshot. The website is in the overlay credit. homemade-circuits.com

 

With spacer I needed many more turns to get inductance given in circuit. I still have the spacer in the mess on the table. About 0.5 mm.

Why did you think you could remove the spacer?
It's there to prevent the core from saturating at a low current level, causing the inductance to drop to near zero
You likely need to reinstall the spacer and add more turns to prevent this saturation.

 

Exactly, as you removed the spacer there is no longer an airgap. And ferrite core’s inductance drops like a rock with a minimal amount of DC bias.

 

Ok thanks. Found the spacer and will re-install it.

 

For your info, the spacer allows inductive energy to be stored in the air gap, with a lower core magnetic flux.
This occurs because the inductive energy is proportional to 1/2LI² so, for example, if the inductance and core flux were reduced by 1/2 from the air gap, the current (or NI) could then be doubled for the same flux, with a result of doubling of the stored energy.

 

Yeah, ok. Now, how do I get the I part off the E part that I stuck with super glue. The ferrite is very brittle. Nail varnish remover hadn't done the job.

 

Yeah, ok. Now, how do I get the I part off the E part that I stuck with super glue. The ferrite is very brittle. Nail varnish remover hadn't done the job.

Try pure acetone or isopropyl alcohol .

 

After I put the spacer back, do I rewind using the LCR module to give inductance reading of 270uH?

 

After I put the spacer back, do I rewind using the LCR module to give inductance reading of 270uH?

Yes.

 

But before you start rewinding, measure the inductance drop with the air gaps.

 

Inductance with original air gap using original plastic spacer.
So I need to wind on twice as many turns, to achieve four times this inductance. As measured on my meter?

 

Yep, can you get by with thinner wire?

 

Got another 30 turns on with existing wire. LCR measurement now 270uH with gap.
No voltage output with 1.2v nicad/nimh.
The circuit flickered into action for a moment with a 1.5v alkaline, got 2.3v on positive rail and something about - 2v on negative.
Apart from that moment, no activity.
When connecting battery, slight voltage on negative rail but it decays as smoothing capacitor discharges.

 

Apply a small load, say 1k resistor to each the positive and negative outputs.

 

Ok, thanks. Will try that.
I thought for that brief moment I could at least scope out the issues.
It would be great to have a working circuit for anyone that would replace the now very expensive PP3 batteries.

 

Do you have a scope to at least be able to capture what is happening during the start up sequence?