HF Transformers

[Oldcodger]

Apologies if someone has posted useful info on this, but I can't find anything.

Years ago ,I got fed up with the limitations of car ignition timing using a cold cathode tube and twilight and built myself a HR lashup using a xenon tube driven by a TL494 ,via a pair of 2n3055 and a standard transformer .( Purists titter ye not, but this was in my younger days of ignorance, and lack of info on ferrite transformers). Works reasonably well ( always amazing how this sort of thrown together in ignorance ,stuff works) , but I've now got a SIL who's into bikes etc, and it could be useful to him, with it running at a reasonable percentage of efficiency.
So , can anyone point me in the direction of design parameters etc to replace the transformer with something a bit more efficient, and getable. I once had design parameters for a ferrite, but these days I can't find the type on the net.

What is a SIL?

[Hartley118]

Son In Law?

Martin

[Ed_Dinning]

Hi OC, if you use the transformer design equation N = V/ 4.44.B.F.Ae it is still valid for ferrites, but the frequency will be higher than 50Hz, and the flux density B is usually taken as about 200mT.
With a square wave signal the 4.44 becomes 4.

HTH, Ed

SIL, now I see, not being of the breeding type this acronym has passed us by.

[Herald1360]

I thought Single In Line to start with, but the "who's into" suggested some sort of wetware.

[M0FYA Andy]

SIL is the TLA for 'Software Integrity Level'.

(TLA? Three Letter Acronym)

Andy

[Skywave]

The inclusion of the acronym 'SIL' - if it is indeed an acronym - is bordering on an infringement of forum rules B5 and B7, q.v., in my opinion.
'SIL' is an abbreviation (or whatever) that I have never met before and, moreover, reading the above posts, it seems I am not alone in that ignorance. Having said that, I've never met the term 'wetware' (post #6) either!

Al.

[Refugee]

I have done some work on home brew chopper circuits.
The most important thing is to use fast transistors and diodes even if upgrading a pull from something old.
The most recent one was getting 500V DC from a small battery pack. This I did by taking the PCB from an old tow truck beacon that had failed to a short circuit 2N3055 and burned wiring. The pulse transformer was wound to about the correct ratio so I had a good start.
I first replaced the 2N3055 with a much faster BUT11 as used in many first generation SMPSUs and replaced the IN4005 with the faster UF4005.
This got the efficiency much better and cut down on the amount of space it took up with the smaller heat-sink.
I then just added NiMh batteries until I got the correct output voltage and ended up with 7.2 volts.
I can now use my old Megger that did not have its own generator with a simple clip on power pack.
The same thing can be done with the transformer from a dumped flat screen TV or other bit of modern gear. You may even get one that is fully regulated.
The push pull types with 50hz transformers and 2N3055s were generally unregulated.
For a new design I would go for fast FETs as these are cheap and easy to get hold of.

There are three types.
First there is unregulated with an uninsulated primary.
Then there is loosely regulated where the regulation is from the isolated primary.
Then finally there is the type with the most important secondary fully regulated with an opto isolated circuit.
It is down to how complex you are willing to make it.

[Station X]

Now we know what SIL means in this context, can we stay on topic please.

[Oldcodger]

Apologies, Station X, I thought most folks would know from SIL & bikes .( AND yes, it does mean Son in law ).
Thanks for the equation, ED, and likewise Refugee for the info. Idea of using the TL494( IC NUMBER , so as not to cause confusion) was that at the time I had both a good few of them ,and the components needed to make this circuit and still have a good few TL494.

[Refugee]

It is all down to the type of coil fitted to the bike.
Coils I have used most recently have had 12 volt primaries and in my case are driven to produce a string of about 10 or so 700hz pulses about once a second. This being used as a guard rail over seedlings in the garden in order to prevent them from being dug up by a random stream of wild animals or badly tended domestic pets. It works well as it meters out its signal at the point of offense.
The chip is a 3842 SMPSU controller with only the start sequence activated and it works with either bipolar or FET drives without modification.

[G6Tanuki]

Fast switching transistors *and* fast-recovery diodes are necessary here (the 1N400x series are barely good enough for 50Hz let alone anything faster).

Transformer-wise, just repurpose something from an old laptop PSU: indeed you could probably just 'turn the transformer round' - feed the chopped 12V to the transformer's original secondary winding, and take the HT from what was originally the primary.

[Oldcodger]

GT6- I like the idea - just the idea as when firm last moved from old premises I found a lot of laptop PSU in the skip. Still got a few left .

[Refugee]

Laptop power supplies tend to have the coil cores stuck together with epoxy.
You will need to work out how to heat the joints without melting the coil former.

[Diabolical Artificer]

I have two big jars of ferrite cored tfmr's pulled from all sorts of devices, your welcome to a few if needed. Though of coarse the problem is knowing their specs.

Andy.

[HamishBoxer]

Surely SIL equals Single In Line as against DIL Dual In Line referring to ic,s.

[Oldcodger]

#17, I'd refer the Hon gent to #10.