[General] How to attach the center tap wire in a 230V to 15V-0-15V step down transformer ?

[Shanks Sharma]

I have a 230V to 15V-0-15V step down transformer without the center tap wire. Is it okay to just insert the wire in the hole (middle one) to make it work ? I have to use the 0V connection in the circuit from the transformer.
Any suggestion ?

 

[betwixt]

Without knowing what the hole is nobody can tell you. However, it would be extremely unlikely that this 'hole' had any electrical connection to it. I can't understand how you claim the transformer is 15V-0-15V but doesn't already have a center tap, the '0' is the center on that kind of transformer.

Brian.

 

[FvM]

If you don't have a "center" wire, it's not a 15-0-15 winding configuration. You need a different transformer if you require the centertap, e.g. for a dual power supply.

 

[paulfjujo]

Hello

Without voltage applied on primary of tranformer!
with a multimeter used as ohmmeter ,Check resitance value between your 0 point and the 2 other pins 15V

 

[kripacharya]

Better if you put that wire into that hole in your head.
LoL .. just kiddin' !!!

I think the best thing for you is to post a picture of this supposed "center-tap" transformer of yours. Then this forum will be able to give proper advice.

 

[Shanks Sharma]

Better if you put that wire into that hole in your head.
LoL .. just kiddin' !!!

I think the best thing for you is to post a picture of this supposed "center-tap" transformer of yours. Then this forum will be able to give proper advice.

Hey, sorry I forgot to post the picture with the post earlier. Here it is.

- - - Updated - - -

Yes, I was thinking about the same thing. So, maybe I got the wrong component !!

 

[betwixt]

That is NOT a 15V-0-15V transformer - in fact if the red wires are connected like that it may not be a transformer at all by now!

You cannot add a center tap but if the reason you needed it was to use a two diode full wave rectifier, you can still use it with four diodes wired in a bridge configuration.

If you absolutely need a center tap, the only way to to make one would be to remove the secondary winding and wire two windngs in it's place, each of thinner wire so you have space for them. I would not recommend you try, the transformer core probably won't come apart easily and threading the wire around the plastic bobbin with a needle would take a long time and test a Saint's patience. It would be much easier to just buy a new one.

Brian.

 

[Shanks Sharma]

That is NOT a 15V-0-15V transformer - in fact if the red wires are connected like that it may not be a transformer at all by now!

You cannot add a center tap but if the reason you needed it was to use a two diode full wave rectifier, you can still use it with four diodes wired in a bridge configuration.

If you absolutely need a center tap, the only way to to make one would be to remove the secondary winding and wire two windngs in it's place, each of thinner wire so you have space for them. I would not recommend you try, the transformer core probably won't come apart easily and threading the wire around the plastic bobbin with a needle would take a long time and test a Saint's patience. It would be much easier to just buy a new one.

Brian.

Hey Brian, thanks for the reply !

I have got this power supply circuit (in the picture) on my PCB, that's why I need a 15V-0-15V transformer.

 

[betwixt]

For that schematic is HAS to be a center tapped transformer so I would strongly advise you buy a new one. Being perfectly honest, it would not be feasible to modify the one you have. It would take many hours of work and the result would be the correct voltage but with less current rating anyway.

If you have a second transformer of the same type and it has a single 15V secondary, in theory you can connect the primary windings in parallel and the secondaries in series to make it 15V-0-0-15V but the cost would be about the same as starting with a center tapped one.

Brian.

 

[Shanks Sharma]

For that schematic is HAS to be a center tapped transformer so I would strongly advise you buy a new one. Being perfectly honest, it would not be feasible to modify the one you have. It would take many hours of work and the result would be the correct voltage but with less current rating anyway.

If you have a second transformer of the same type and it has a single 15V secondary, in theory you can connect the primary windings in parallel and the secondaries in series to make it 15V-0-0-15V but the cost would be about the same as starting with a center tapped one.

Brian.

Thanks Brian, That's what I needed to confirm. I will surely buy a new one. But there is one more thing that I have to ask. I have already put this transformer to work in my PCB and switched on the Power Supply. I need to know if all the components in the PCB will still work ?

 

[FvM]

The answer depends on the transformer's open circuit voltage, if it's too high, it might damage a voltage regulator. Because the transformer output is rather 15 than 30 VAC, I guess it won't.