Autoformer Pot Core Design

On a sunny day (24 Feb 2007 08:07:04 -0800) it happened snipped-for-privacy@yahoo.com wrote in :

Use the cannon. Ultrasound has little effect on some dogs. If the cannon is illegal, email the Whitehouse Iranian nukes are there.

Without designing the transformer from the ground up, there is insufficient information in at this site to properly wind your own. The author talks of pot cores yet the picture of the Williamson Labs coil is not a pot core. Secondly the single ended output FET driver puts DC in the tansformer. This requires a gaped core design. The Williamson part is a open core providing a large "gap", not closed like a pot core or torroid and is therefore suited for the DC unbalance that this circuit gives. Unless you use a powdered metal core, stay away form torroids, they do not have gaps. A pot core can be used but must be gaped. The particular core, number of turns, and gap length are unknown but can be calculated. Unfortunately the aritcle does not provide sufficient information to simply wind a part. Digikey doesn't have very many magnet parts in any case. If it were me, I'd try to find the Williamson Labs part used in the circuit already wound and ready to go. Good Luck.

I think they've used the term potcore loosely. I'd be inclined to look at the tweeter maker's info.

From the website:

• What type of pot core and winding? -- Actually, I used several pot cores stacked, such that the primaries were driven in parallel and the secondaries were connected in series--all phased correctly. This was done as a quick & dirty way of achieving a "step up" and allow for enough power--before core saturation. The specific pot core specs are only important relative to optimum operating frequency: ~10 kHz to ~40 Khz, peaking at ~ 20 kHz. However, this is not critical due to the broadband nature of ferrite transformers. One could use alternate transformer technology: single large ferrite torrid.

Thanks for the info. I've already asked the guy who designed it to provide some more info, but no luck yet.

Any other ideas to get around this?

I would look for the tweeter you are going to use and look at the design specs. See if they have a suggested driver circuit. I would also look on Amidon's site for information on a suitable transformer.

Right. I mean wrong. It's not a pot core. It's a ferrite drum core.

John

Looks like a bobbin but I'm not sure how much is ferrite.

bobbin core = drum core

I, too, was going to point this out.

Interesting idea though, I'd been thinking about doing just that. Although a can of oven cleaner with the nozzle & tube from a can of CRC-556 is cheaper and easier (sort of a highly corrosive mace), albeit a lot less friendly.

I got the idea from the tech who installed my last burglar alarm. it sounds like a pretty good idea for women living alone. Im sure a shot of caustic soda in the face will be quite a deterrent to a would-be rapist.

Cheers Terry

Look at Amidon parts B-77-1111 and B-77-1011. One of those might match the transformer used.