The simplistic Salas low voltage shunt regulator

[50AE]

Hi, I have a question about the current. I have built a v1.1 5V shunt ment for low current (10mA) but I decided to give it to a person who wants to use it for currents like 500mA and a little more (say 600-700). For how much current can the v1.1 work?

 

[Salas]

For as much as the safe operation area of the Mosfets used, the sinking, and the ambient temperature allow. Its about dissipated power so voltage is as much important as current.
An example of a 5V reg biased at 1A would need 1.5C/W common sink for both Mosfets.

 

[orelli]

Hi Salas, I want purchase some R-core txs from Selectronic, but by the photos they are all
center tapped (they have 3 output wires).Can I divide phisically the secondary to get two
indipendent ones? ... desoldering the two wires that form the central tap?
Ciao, Orazio

 

[merlin el mago]

Selectronic R-Core aren't center taped, input are phase, neutral & 3rd wire gnd is electrostatic shield, outputs are almost all transformers dual secondary with 4 wires.

Ciao
Felipe

 

[orelli]

Muchas gracias Felipe, I'm confused by the photo of 50VA, there are 3 big wires(white,yellow and black),I thinked they are the secondary ones, and 4 little ones
that I thinked the primary ones.
Ciao, Orazio

 

[AndrewT]

to be absolutely sure ask the retailer what the wires colours are and how to connect up.

As a back up safety measure, use a bulb tester for mains power up. Then you can check voltages without damaging the transformer.

BUT !!!!!! if you wire it back to front, then the secondary voltages will be enormous, maybe way over 1kVac. So sort out the wires colours first.

 

[merlin el mago]

Muchas gracias Felipe, I'm confused by the photo of 50VA, there are 3 big wires(white,yellow and black),I thinked they are the secondary ones, and 4 little ones
that I thinked the primary ones.
Ciao, Orazio

Prego, yes 3 big wires are the primaries for AC & the 4 small wires are secondaries
Buon lavoro, Felipe

 

[merlin el mago]

to be absolutely sure ask the retailer what the wires colours are and how to connect up.

As a back up safety measure, use a bulb tester for mains power up. Then you can check voltages without damaging the transformer.

BUT !!!!!! if you wire it back to front, then the secondary voltages will be enormous, maybe way over 1kVac. So sort out the wires colours first.

Selectronic R-Cores transformers have writed the color codes in each transformer so don't need to do nothing.

 

[AndrewT]

.......... I want purchase some R-core txs from Selectronic, but by the photos they are all
center tapped (they have 3 output wires).Can I divide phisically the secondary to get two
indipendent ones? ... desoldering the two wires that form the central tap?.................

............... I'm confused by the photo of 50VA, there are 3 big wires(white,yellow and black),I thinked they are the secondary ones, and 4 little ones
that I thinked the primary ones.
...........

Selectronic R-Cores transformers have writed the color codes in each transformer so don't need to do nothing.

then why does he need to ask the questions?
Is he a danger to him/herself?
Should we be helping this person to kill themselves?

 

[merlin el mago]

Thick 3 wires primary, thin 4 wires secondary.

 

[orelli]

thanks to Felipe and Andrew.

 

[AndrewT]

Thick 3 wires primary, thin 4 wires secondary.

thick insulation and small copper area is likely to be high voltage winding tappings.
Thin insulation and big copper area is likely to be low voltage winding tappings.

Merlin:
Your advice/comment is very misleading in that it uses the wrong information to chance upon the correct conclusion.
Better to keep quiet than to make up the science you don't understand.

 

[orelli]

thick insulation and small copper area is likely to be high voltage winding tappings.
Thin insulation and big copper area is likely to be low voltage winding tappings.

You are correct Andrew, this si the point!

ps. don't be afraid, I don't kill myself with a transformer.

Arios, Orazio

 

[Salas]

A picture settles it better.

 

[orelli]

Have you connected the yellow wire to chassis?

 

[AndrewT]

That pic clearly tells me that this Rcore has a single primary marked Black/White (Blanc/Noir) for 230Vac duty
AND
it also tells me it is NOT a 3 wire primary !!!!!!!!!!
(I can't read French upside down), but I'll guess the yellow wire is an electrostatic screen that should be connected to Chassis.
AND
finally it tells me it has dual primaries marked Violet/Green and Blue/Red, they are insulated as pairs.

 

[Salas]

The yellow primary side wire is ''Ecran electro-statique'' i.e. electrostatic screen to be grounded. I connect that to the mains earth IEC prong and from there I run a wire to chassis ground. You may see a white one bolted to the trafo's bottom right corner.

 

[orelli]

I understood, thanks Nick.

 

[loek]

That pic clearly tells me that this Rcore has a single primary marked Black/White (Blanc/Noir) for 230Vac duty
AND
it also tells me it is NOT a 3 wire primary !!!!!!!!!!
(I can't read French upside down), but I'll guess the yellow wire is an electrostatic screen that should be connected to Chassis.
AND
finally it tells me it has dual primaries marked Violet/Green and Blue/Red, they are insulated as pairs.

You ment Dual Secundairies AndrewT.......

 

[AndrewT]

Yes, That's three times in as many days. I going to book myself in!