transformer question
I'm using a Radio Shack 120 to 12 volt AC transformer. I've connected the
center tap on the secondary to one of the leads on the secondary in order to
halve the output voltage to 6v. The transformer casing is getting quite
warm, even hot. I have a 3k load attached to it, so I figure I'm drawing
around 2mA, which isn't too much current.
Is it normal for a transformer to get hot?
--Craig
center tap on the secondary to one of the leads on the secondary in order to
halve the output voltage to 6v. The transformer casing is getting quite
warm, even hot. I have a 3k load attached to it, so I figure I'm drawing
around 2mA, which isn't too much current.
Is it normal for a transformer to get hot?
--Craig
Comments
It's getting hot because you are shorting half the output windings. Just
use the center tap and *either* of the secondary connections.
Ray McArthur
Original Message
From: Craig Lefkowitz <craig.lefkowitz@m...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, April 23, 2001 1:06 AM
Subject: [noparse][[/noparse]basicstamps] transformer question
> I'm using a Radio Shack 120 to 12 volt AC transformer. I've connected the
> center tap on the secondary to one of the leads on the secondary in order
to
> halve the output voltage to 6v. The transformer casing is getting quite
> warm, even hot. I have a 3k load attached to it, so I figure I'm drawing
> around 2mA, which isn't too much current.
>
> Is it normal for a transformer to get hot?
The spec sheet for the transformer suggests to connect it in the way I had
it (short half the secondary). But it seems that is not a good thing. Is
there any merit in connecting it in that configuration, or is this just a
Radio Scrap blunder?
Here is the spec from Radio Shack:
12VAC CT UL Transformer
(273-1365) Hints and Tips Faxback Doc. # 34679
Q: What is the function of the three wires?
A: The secondary of this unit has two common colors and another color in
the middle. The two outside carry the combined voltage output of
12V. By connecting the middle wire with one of the other wires, the
voltage is then split in half.
--Craig
Original Message
From: Ray McArthur [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=bax_BOmNPXdUpwal7TiWT0xUtqFgW0i-N-eWtJraKoS3Y_D7Xw6r7HFfLA9shgBZs8X96DKVKUCH7A]rjmca@u...[/url
Sent: Monday, April 23, 2001 1:19 AM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] transformer question
Craig:
It's getting hot because you are shorting half the output windings. Just
use the center tap and *either* of the secondary connections.
Ray McArthur
Original Message
From: Craig Lefkowitz <craig.lefkowitz@m...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, April 23, 2001 1:06 AM
Subject: [noparse][[/noparse]basicstamps] transformer question
> I'm using a Radio Shack 120 to 12 volt AC transformer. I've connected the
> center tap on the secondary to one of the leads on the secondary in order
to
> halve the output voltage to 6v. The transformer casing is getting quite
> warm, even hot. I have a 3k load attached to it, so I figure I'm drawing
> around 2mA, which isn't too much current.
>
> Is it normal for a transformer to get hot?
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
I think what the phrase "By connecting the middle wire with one of the other
wires" means is
You'll connect two wires to two points in your circuit (often a rectifier).
If the two wires you use are the end wires, the transformer will provide
12V. If the two wires you use are either end wire and the center wire, the
transformer will deliver 6V. In that case, one end wire will not be
connected to anything.
I don't think they meant to say connect the middle wire _to_ one of the end
wires.
I can tell you first hand, trying to be clear about something like this when
you know what you mean and the reader doesn't is a tough job.
If you are building a power supply with +/- supplies, you might ground the
center tap and use the transformer for +/- 6V.
Transformers deal with AC which can be tricky. For example, if you plan to
put connect transformers together, you must observe the phasing or the
transformers will not have the desired boost (or buck) effect. When reading
schematics where this matters you'll see black dots on either side of the
transformer symbol. If the dots are both near the top of the coil, the
output is in phase with the input. If the dot on the primary is at the top
and the secondary dot is at the bottom, then the output is out of phase.
Most of the time you don't care, but if you are connecting transformers
together, or depending on them for a phase shift (for example, in an
Armstrong oscillator) it will matter and the designer should know that and
specify it on the drawings.
Regards,
Al Williams
AWC
*NEW: Floating point A/D: http://www.al-williams.com/awce/pak9.htm
>
Original Message
> From: Craig Lefkowitz [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=W989dKKjMyef56qWDEf9UPOrJt6YMsaSBPrhzs83jsXxhMkbmslsu8uBs7NMgW7kli5b_9BbSmCQixxDfys-cxodKuc2W6_c]craig.lefkowitz@m...[/url
> Sent: Saturday, April 28, 2001 3:53 PM
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] transformer question
>
>
> Thanks. That did the trick!
>
> The spec sheet for the transformer suggests to connect it in the way I had
> it (short half the secondary). But it seems that is not a good thing. Is
> there any merit in connecting it in that configuration, or is this just a
> Radio Scrap blunder?
>
> Here is the spec from Radio Shack:
>
> 12VAC CT UL Transformer
> (273-1365) Hints and Tips Faxback Doc. # 34679
>
>
> Q: What is the function of the three wires?
>
> A: The secondary of this unit has two common colors and another color in
> the middle. The two outside carry the combined voltage output of
> 12V. By connecting the middle wire with one of the other wires, the
> voltage is then split in half.
>
>
> --Craig
>
>
>
Original Message
> From: Ray McArthur [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=csUdirKEAAq7lO8BIc3pmIWlUjiDkVJiCoElD_w9UEFSPXxXYnKASalrdfqymJloaIQbUaqMBWefmQo]rjmca@u...[/url
> Sent: Monday, April 23, 2001 1:19 AM
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] transformer question
>
>
> Craig:
> It's getting hot because you are shorting half the output windings. Just
> use the center tap and *either* of the secondary connections.
>
> Ray McArthur
>
>
Original Message
> From: Craig Lefkowitz <craig.lefkowitz@m...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, April 23, 2001 1:06 AM
> Subject: [noparse][[/noparse]basicstamps] transformer question
>
>
> > I'm using a Radio Shack 120 to 12 volt AC transformer. I've
> connected the
> > center tap on the secondary to one of the leads on the
> secondary in order
> to
> > halve the output voltage to 6v. The transformer casing is getting quite
> > warm, even hot. I have a 3k load attached to it, so I figure
> I'm drawing
> > around 2mA, which isn't too much current.
> >
> > Is it normal for a transformer to get hot?
>
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>