Print transformers: what are they good for?

[roibm]

Saw some good auction on ebay, 10 pieces print transformers like pictured bellow:

They are rated 115-230V and 2x9 3.5A
Any ideas what could be achieved with these?
Any good for audio? Good for use in a PSU for opamps or a DAC?

thanks

 

[Bill Fitzpatrick]

What do you mean by "print transformer?"

 

[roadkill]

I guess he means "PCB mounting" transformer.

Yes, this would be quite useful to power a preamp, DAC or crossover board.

See this thread for a picture of a DSP board which uses similar transformers.

 

[peranders]

They are very pratical in general!

See here

 

[dhaen]

They should be used with caution on DIY kit, as their use puts mains on the PCB.
I always have mains voltages double insulated and separate from the low voltage electronics.

 

[analog_sa]

John

You always try to take the fun away from DIY A different approach

 

[dhaen]

That's very funny, in coincidental way.
Compare:

His estate or personal representative brought a §402 A product liability action,
...snip...

with:

Q: What on earth is a 402 error?

A: This error code is puzzling. According to the HTTP specification, this code is reserved for future use and means "Payment required"
...snip..

Ok, so I'm a crank...

 

[ARAD]

roibm,

the transformer in the picture is a very small transformer - it is rated at 2x9V and delivers 2x 3.5 VA (not A)... what translates to a little less then 400 milliAmps per secondary.

Regards,
Andreas

 

[Circlotron]

Hummmmmmm..

They should be used with caution on DIY kit, as their use puts mains on the PCB.
I always have mains voltages double insulated and separate from the low voltage electronics.

Not only for safety - you want to keep mains wiring as far away as possible from low level signal wiring.

 

[Thomas]

I use a small print transformer to drive the relays and LED's in a amplifier I'm building. Good thing about this, it keeps the "foreign" circuitry out of the signal path and got the correct voltage for the relays I'm using.

 

[roibm]

What do you mean by "print transformer?"

A transformer that looks like the one pictured above. What is the name I ishould have been used?(sorry I don't know it)

 

[roibm]

roibm,

the transformer in the picture is a very small transformer - it is rated at 2x9V and delivers 2x 3.5 VA (not A)... what translates to a little less then 400 milliAmps per secondary

Thank you for mentioning it, I already know what VA is

400mA should be enough for supplying some opamps I think... any other opinions?

 

[Hybrid fourdoor]

Sometimes those are referred to as encapsulated toroids



Digikey sells 'em.

 

[roibm]

Sometimes those are referred to as encapsulated toroids
Digikey sells 'em.

Thanks for the help. Now I know it...

BTW, Reichelt has them too
Reichelt Printtrafos

 

[peranders]

They should be used with caution on DIY kit, as their use puts mains on the PCB.

If you don't know anything about safety you should avoid pcb transformers. You must have knowledge about regulations but if you have it's no problems at all. You must mainly have control over which parts you can use and which distances you must have for certain parts.

 

[peranders]

Re: Hummmmmmm..

Not only for safety - you want to keep mains wiring as far away as possible from low level signal wiring.

Quite true but rather often it's less critical than you think. This amp has no problems with hum, what so ever.

 

[roadkill]

I believe Elektor publishes some info about this in any project of thiers which uses such a transformer. At least these conform to the European electrical standards.

On closer inspection, those transformers are clearly marked "INDIA"... strange that I've never seen any on the local market. Most of the locally available transformers are E-I, and the low-current ones tend to heat up quite a bit even with zero power drawn.

 

[Circlotron]

Weren't they first called "Print Transformers and Peace" ?

/Circlotron - ducks for cover after making a *terrible* joke...

 

[pinkmouse]

Weren't they first called "Print Transformers and Peace" ?

/Circlotron - ducks for cover after making a *terrible* joke...

Hmmm

/Al - Looks for the shortcut to the sinbin page...

 

[roibm]

Weren't they first called "Print Transformers and Peace" ?

/Circlotron - ducks for cover after making a *terrible* joke...

there is a difference between peace and the word I would like to say