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power supply 2
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Tue Jul 18, 2006 7:51 pm    Post subject: Re: power supply 2 Reply with quote

"John Popelish" <jpopelish@rica.net> wrote in message
news:k_udnXpcEMLyjiDZnZ2dnUVZ_rmdnZ2d@adelphia.com...
Quote:
Ken O wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:MtCdndlDEb9qqSHZnZ2dnUVZ_v6dnZ2d@adelphia.com...

Normally, the coil resistance drops only a few percent of the total
voltage when the transformer is operated within its ratings. Do you have
an amp meter that reads over 2 amps that you could put in series with the
battery being charges, to see what current is charging it? You also
probably don't need that big capacitor between the rectifier and the
battery, and having it makes the transformer hotter and raises the
charging current a bit. I suspect you do need some resistance in series
with the battery (or in series with the primary of the transformer) to
set the charge current to below what the transformer is rated to supply.


hi I replaced the capacitor with a 680uf 200v. I did not need 200v but
that was the only one over 50v I could find.

Okay.

The transistor is acting normal now, not too hoe, The transformer is not
getting as hot as before but I still find it too hot.

Have you tried with no capacitor? No particular need to have smoothed DC
to charge a battery. After you get the transformer temperature down, we
can get into what you have to do to power the 555 from the same rectifier.

I cant measure the current. I am using the impulses from the 555 timer to
charge it. Unless there is another way beside using an amp meter, please
let me know

If you can find a very low ohm resistor, like .1 ohm, you could put that
in series with the battery, and read the average DC voltage across it.
The average current is 1/R times the voltage you read.

But I think you need something like an automotive head lamp in series with
the battery, to act as a current limit (with a visual indication of high
current).

I removed the capacitor:
-The battery is charging a bit slower then before
- The transistor is cool
- The transformer is getting warm just like the small capacitor used before.

the transformer is a 115v to 25.2 v rated 2.0 A
So this some out to putting a 12.6 Ohm resistor @50 watt. But this is AC not
DC.

beside adding a fan next to the transformer , I do not know what to do. and
why it is getting that warm.

Ken
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John Popelish
electronics forum Guru


Joined: 29 Apr 2005
Posts: 1601

PostPosted: Tue Jul 18, 2006 10:04 pm    Post subject: Re: power supply 2 Reply with quote

Ken O wrote:
Quote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:k_udnXpcEMLyjiDZnZ2dnUVZ_rmdnZ2d@adelphia.com...

Ken O wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:MtCdndlDEb9qqSHZnZ2dnUVZ_v6dnZ2d@adelphia.com...

Normally, the coil resistance drops only a few percent of the total
voltage when the transformer is operated within its ratings. Do you have
an amp meter that reads over 2 amps that you could put in series with the
battery being charges, to see what current is charging it? You also
probably don't need that big capacitor between the rectifier and the
battery, and having it makes the transformer hotter and raises the
charging current a bit. I suspect you do need some resistance in series
with the battery (or in series with the primary of the transformer) to
set the charge current to below what the transformer is rated to supply.


hi I replaced the capacitor with a 680uf 200v. I did not need 200v but
that was the only one over 50v I could find.

Okay.


The transistor is acting normal now, not too hoe, The transformer is not
getting as hot as before but I still find it too hot.

Have you tried with no capacitor? No particular need to have smoothed DC
to charge a battery. After you get the transformer temperature down, we
can get into what you have to do to power the 555 from the same rectifier.


I cant measure the current. I am using the impulses from the 555 timer to
charge it. Unless there is another way beside using an amp meter, please
let me know

If you can find a very low ohm resistor, like .1 ohm, you could put that
in series with the battery, and read the average DC voltage across it.
The average current is 1/R times the voltage you read.

But I think you need something like an automotive head lamp in series with
the battery, to act as a current limit (with a visual indication of high
current).


I removed the capacitor:
-The battery is charging a bit slower then before
- The transistor is cool
- The transformer is getting warm just like the small capacitor used before.

the transformer is a 115v to 25.2 v rated 2.0 A
So this some out to putting a 12.6 Ohm resistor @50 watt. But this is AC not
DC.

beside adding a fan next to the transformer , I do not know what to do. and
why it is getting that warm.

A 25.2 VAC winding puts out 1.414 times that much voltage at its
peaks. So the rectifier puts out about 27.6 volts after the .12 volt
rectifier drop.

What is the nominal voltage of the battery being charged?
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Eeyore
electronics forum Guru


Joined: 22 Jun 2006
Posts: 642

PostPosted: Tue Jul 18, 2006 10:15 pm    Post subject: Re: power supply 2 Reply with quote

Ken O wrote:

Quote:
HI,

I am working on a power supply. The transformer is getting hot after 30
minutes of use. I can touch it , but not more then a few seconds in a row. I
guess this is because of too much current.??

Transformers got warm / hot on account of I^2R heating mostly.

That indeed suggests the load current is greater than the transformer was
designed to deliver.

Graham
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Tue Jul 18, 2006 11:40 pm    Post subject: Re: power supply 2 Reply with quote

"John Popelish" <jpopelish@rica.net> wrote in message
news:LtqdnX03IsZxxCDZnZ2dnUVZ_s2dnZ2d@adelphia.com...
Quote:
Ken O wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:k_udnXpcEMLyjiDZnZ2dnUVZ_rmdnZ2d@adelphia.com...

Ken O wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:MtCdndlDEb9qqSHZnZ2dnUVZ_v6dnZ2d@adelphia.com...

Normally, the coil resistance drops only a few percent of the total
voltage when the transformer is operated within its ratings. Do you
have an amp meter that reads over 2 amps that you could put in series
with the battery being charges, to see what current is charging it? You
also probably don't need that big capacitor between the rectifier and
the battery, and having it makes the transformer hotter and raises the
charging current a bit. I suspect you do need some resistance in
series with the battery (or in series with the primary of the
transformer) to set the charge current to below what the transformer is
rated to supply.


hi I replaced the capacitor with a 680uf 200v. I did not need 200v but
that was the only one over 50v I could find.

Okay.


The transistor is acting normal now, not too hoe, The transformer is not
getting as hot as before but I still find it too hot.

Have you tried with no capacitor? No particular need to have smoothed DC
to charge a battery. After you get the transformer temperature down, we
can get into what you have to do to power the 555 from the same
rectifier.


I cant measure the current. I am using the impulses from the 555 timer
to charge it. Unless there is another way beside using an amp meter,
please let me know

If you can find a very low ohm resistor, like .1 ohm, you could put that
in series with the battery, and read the average DC voltage across it.
The average current is 1/R times the voltage you read.

But I think you need something like an automotive head lamp in series
with the battery, to act as a current limit (with a visual indication of
high current).


I removed the capacitor:
-The battery is charging a bit slower then before
- The transistor is cool
- The transformer is getting warm just like the small capacitor used
before.

the transformer is a 115v to 25.2 v rated 2.0 A
So this some out to putting a 12.6 Ohm resistor @50 watt. But this is AC
not DC.

beside adding a fan next to the transformer , I do not know what to do.
and why it is getting that warm.

A 25.2 VAC winding puts out 1.414 times that much voltage at its peaks.
So the rectifier puts out about 27.6 volts after the .12 volt rectifier
drop.

What is the nominal voltage of the battery being charged?

I have to turn off the charger , the transforme was getting very hot. The
transistor is still cool. But the last design charges a lot slower without
th capacitor.
The battery being charged is a deep cycle marine battery with 650 cranking
amps.
Not sure what you mean by nominal voltage

ken
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Tue Jul 18, 2006 11:41 pm    Post subject: Re: power supply 2 Reply with quote

"Eeyore" <rabbitsfriendsandrelations@REMOVETHIS.hotmail.com> wrote in
message news:44BD5D82.464AC352@REMOVETHIS.hotmail.com...
Quote:


Ken O wrote:

HI,

I am working on a power supply. The transformer is getting hot after 30
minutes of use. I can touch it , but not more then a few seconds in a
row. I
guess this is because of too much current.??

Transformers got warm / hot on account of I^2R heating mostly.

That indeed suggests the load current is greater than the transformer was
designed to deliver.

How do I turn down the voltage on the secondary?
Should I just put a resistor between the capacitor and the battery being
charged?

ken
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John Popelish
electronics forum Guru


Joined: 29 Apr 2005
Posts: 1601

PostPosted: Wed Jul 19, 2006 12:53 am    Post subject: Re: power supply 2 Reply with quote

Ken O wrote:
Quote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:LtqdnX03IsZxxCDZnZ2dnUVZ_s2dnZ2d@adelphia.com...
(snip)
A 25.2 VAC winding puts out 1.414 times that much voltage at its peaks.
So the rectifier puts out about 27.6 volts after the .12 volt rectifier
drop.

What is the nominal voltage of the battery being charged?


I have to turn off the charger , the transforme was getting very hot. The
transistor is still cool. But the last design charges a lot slower without
th capacitor.
The battery being charged is a deep cycle marine battery with 650 cranking
amps.
Not sure what you mean by nominal voltage

If you measure the battery voltage with a meter, when it is charged,
what do you measure?
Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 6:56 am    Post subject: Re: power supply 2 Reply with quote

"John Popelish" <jpopelish@rica.net> wrote in message
news:ucadnU5_yYivHyDZnZ2dnUVZ_rWdnZ2d@adelphia.com...
Quote:
Ken O wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:LtqdnX03IsZxxCDZnZ2dnUVZ_s2dnZ2d@adelphia.com...
(snip)
A 25.2 VAC winding puts out 1.414 times that much voltage at its peaks.
So the rectifier puts out about 27.6 volts after the .12 volt rectifier
drop.

What is the nominal voltage of the battery being charged?


I have to turn off the charger , the transforme was getting very hot. The
transistor is still cool. But the last design charges a lot slower
without th capacitor.
The battery being charged is a deep cycle marine battery with 650
cranking amps.
Not sure what you mean by nominal voltage

If you measure the battery voltage with a meter, when it is charged, what
do you measure?

somewhere around 12.9v

k
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John Popelish
electronics forum Guru


Joined: 29 Apr 2005
Posts: 1601

PostPosted: Wed Jul 19, 2006 11:53 am    Post subject: Re: power supply 2 Reply with quote

Ken O wrote:
Quote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:ucadnU5_yYivHyDZnZ2dnUVZ_rWdnZ2d@adelphia.com...

If you measure the battery voltage with a meter, when it is charged, what
do you measure?

somewhere around 12.9v

It is kinda rough on a 25 volt transformer to slap a 12 volt load
across it. You need to big resistor in series (or do something more
like a switching step down regulator) if you expect5 the on state
current to be reasonable. Or you could start looking for another
transformer that was better suited to this task. The cheapest might
be one from a battery charger.
Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 12:57 pm    Post subject: Re: power supply 2 Reply with quote

"John Popelish" <jpopelish@rica.net> wrote in message
news:yZOdnUqFDNn2gSPZnZ2dnUVZ_qSdnZ2d@adelphia.com...
Quote:
Ken O wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:ucadnU5_yYivHyDZnZ2dnUVZ_rWdnZ2d@adelphia.com...

If you measure the battery voltage with a meter, when it is charged, what
do you measure?

somewhere around 12.9v

It is kinda rough on a 25 volt transformer to slap a 12 volt load across
it. You need to big resistor in series (or do something more like a
switching step down regulator) if you expect5 the on state current to be
reasonable. Or you could start looking for another transformer that was
better suited to this task. The cheapest might be one from a battery
charger.

I basically used a similar circuit to antoon:
http://www.uoguelph.ca/~antoon/circ/vps.htm
without the Lm317, I just dump the DC voltage to the battery.
How is it so much differnt then what i am doing ?
So I should be charging a 24v battery with this apparatus and it will not
get hot?

ken
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John Popelish
electronics forum Guru


Joined: 29 Apr 2005
Posts: 1601

PostPosted: Wed Jul 19, 2006 1:26 pm    Post subject: Re: power supply 2 Reply with quote

Ken O wrote:
Quote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:yZOdnUqFDNn2gSPZnZ2dnUVZ_qSdnZ2d@adelphia.com...

Ken O wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:ucadnU5_yYivHyDZnZ2dnUVZ_rWdnZ2d@adelphia.com...

If you measure the battery voltage with a meter, when it is charged, what
do you measure?

somewhere around 12.9v

It is kinda rough on a 25 volt transformer to slap a 12 volt load across
it. You need to big resistor in series (or do something more like a
switching step down regulator) if you expect5 the on state current to be
reasonable. Or you could start looking for another transformer that was
better suited to this task. The cheapest might be one from a battery
charger.


I basically used a similar circuit to antoon:
http://www.uoguelph.ca/~antoon/circ/vps.htm
without the Lm317, I just dump the DC voltage to the battery.
How is it so much differnt then what i am doing ?

The LM317 is a linear regulator, that drops all the extra voltage
(acts like a self adjusting variable resistor).

Quote:
So I should be charging a 24v battery with this apparatus and it will not
get hot?

It would be better. But the current still is uncontrolled in any
intentional way. If the battery developed a short, it would still
overheat the transformer. A good charger limits the current into the
battery, for an battery voltage below normal, and also cuts the
charging process off, if the battery voltage gets too high (above full
charge voltage). I don't know what your 555 circuit is supposed to
accomplish, but I don't see either of these features.
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<tapwater@roomtemperat
electronics forum addict


Joined: 06 May 2006
Posts: 82

PostPosted: Wed Jul 19, 2006 1:30 pm    Post subject: Re: power supply 2 Reply with quote

You have a real world problem that will require dealing with real world
currents and voltages that exceed the "twink limit" of 12V and 100mA. This
is a twinky forum but I will gladly risk blowing the twinkys fuses by
pointing out that a large marine battery can draw hundreds of amps when
charging. You should think about regulating the current on the input (mains
voltage) side of your charger where the current is lower, but the voltage is
higher with a lamp-dimmer type circuit using (for example) a triac.

"Ken O" <lera@yahoo.com> wrote in message news:e9h5rm$jh4$1@nntp.aioe.org...
Quote:
HI,

I am working on a power supply. The transformer is getting hot after 30
minutes of use. I can touch it , but not more then a few seconds in a row.
I
guess this is because of too much current.??
I use a 120v to 25v AC transformer, to a Bridge rectifier, then to a
2000uF
110 v capacitor . This capacitor is then discharge through a transistor,
with a timer at 2% duty cycle to its base. The transistor too get very
hot,
hotter then the tranformer.
The following is the rest of the circuit.
Should I be adding a resistor to decrease the current ?



|
o------o||o--------o
| | |
o |
.------------. | o
| | |/ ---
| Timer |-| ---
| | |> o
| | o |
'------------' | |
| |
| |
o---------o---------o
|
o
ground
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)


ken

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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 2:14 pm    Post subject: Re: power supply 2 Reply with quote

<tapwater@roomtemperature.deg> wrote in message
news:ytqvg.1931$157.450@newsread3.news.pas.earthlink.net...
Quote:
You have a real world problem that will require dealing with real world
currents and voltages that exceed the "twink limit" of 12V and 100mA. This
is a twinky forum but I will gladly risk blowing the twinkys fuses by
pointing out that a large marine battery can draw hundreds of amps when
charging. You should think about regulating the current on the input
(mains
voltage) side of your charger where the current is lower, but the voltage
is
higher with a lamp-dimmer type circuit using (for example) a triac.

A triac sounds good, I never work with them before. Will have to study it a
bit more before I can implement it. So from what I just read, I can change
the gate voltage of the triac using a voltage divider from the main, hum mm
is triac any good for Ac voltage ?? I,ll have to switch the gate voltage
too..

ken
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 2:36 pm    Post subject: Re: power supply 2 Reply with quote

"John Popelish" <jpopelish@rica.net> wrote in message
news:QsqdnU88O4yTrCPZnZ2dnUVZ_sidnZ2d@adelphia.com...
Quote:
Ken O wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:yZOdnUqFDNn2gSPZnZ2dnUVZ_qSdnZ2d@adelphia.com...

Ken O wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:ucadnU5_yYivHyDZnZ2dnUVZ_rWdnZ2d@adelphia.com...

If you measure the battery voltage with a meter, when it is charged,
what do you measure?

somewhere around 12.9v

It is kinda rough on a 25 volt transformer to slap a 12 volt load across
it. You need to big resistor in series (or do something more like a
switching step down regulator) if you expect5 the on state current to be
reasonable. Or you could start looking for another transformer that was
better suited to this task. The cheapest might be one from a battery
charger.


I basically used a similar circuit to antoon:
http://www.uoguelph.ca/~antoon/circ/vps.htm
without the Lm317, I just dump the DC voltage to the battery.
How is it so much differnt then what i am doing ?

The LM317 is a linear regulator, that drops all the extra voltage (acts
like a self adjusting variable resistor).

So I should be charging a 24v battery with this apparatus and it will not
get hot?

It would be better. But the current still is uncontrolled in any
intentional way. If the battery developed a short, it would still
overheat the transformer. A good charger limits the current into the
battery,

Ok How do I do that ???

for an battery voltage below normal, and also cuts the
Quote:
charging process off, if the battery voltage gets too high (above full
charge voltage).

yes I did a circuit that will do that, a comparator will evaluat the battery
voltage and when so, the output will a activate a MOsfet that will bypass
the charging. I saw a few version of this on the net, But I have not ssen a
version using Mosfet, they usually go with a transistor. I just did not show
this because I dont think it is relevant to the heating of the transformer.

I don't know what your 555 circuit is supposed to
Quote:
accomplish, but I don't see either of these features.
The 555 is used to pulse charge the battery. I read some things on the net

about desulfating batteries using pulses. I want to see if its true.

ken
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 2:48 pm    Post subject: Re: power supply 2 Reply with quote

"Ken O" <lera@yahoo.com> wrote in message news:e9lenf$5ch$1@nntp.aioe.org...
Quote:

tapwater@roomtemperature.deg> wrote in message
news:ytqvg.1931$157.450@newsread3.news.pas.earthlink.net...
You have a real world problem that will require dealing with real world
currents and voltages that exceed the "twink limit" of 12V and 100mA.
This
is a twinky forum but I will gladly risk blowing the twinkys fuses by
pointing out that a large marine battery can draw hundreds of amps when
charging. You should think about regulating the current on the input
(mains
voltage) side of your charger where the current is lower, but the voltage
is
higher with a lamp-dimmer type circuit using (for example) a triac.

How would I control the current, ... I would need a big ass resistor. I
think

k
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 3:07 pm    Post subject: Re: power supply 2 Reply with quote

"John Popelish" <jpopelish@rica.net> wrote in message
news:QsqdnU88O4yTrCPZnZ2dnUVZ_sidnZ2d@adelphia.com...
Quote:
Ken O wrote:
"John Popelish" <jpopelish@rica.net> wrote in message
news:yZOdnUqFDNn2gSPZnZ2dnUVZ_qSdnZ2d@adelphia.com...

Ken O wrote:

"John Popelish" <jpopelish@rica.net> wrote in message
news:ucadnU5_yYivHyDZnZ2dnUVZ_rWdnZ2d@adelphia.com...

If you measure the battery voltage with a meter, when it is charged,
what do you measure?

somewhere around 12.9v

It is kinda rough on a 25 volt transformer to slap a 12 volt load across
it. You need to big resistor in series (or do something more like a
switching step down regulator) if you expect5 the on state current to be
reasonable. Or you could start looking for another transformer that was
better suited to this task. The cheapest might be one from a battery
charger.


I basically used a similar circuit to antoon:
http://www.uoguelph.ca/~antoon/circ/vps.htm
without the Lm317, I just dump the DC voltage to the battery.
How is it so much differnt then what i am doing ?

The LM317 is a linear regulator, that drops all the extra voltage (acts
like a self adjusting variable resistor).

So I should be charging a 24v battery with this apparatus and it will not
get hot?

It would be better. But the current still is uncontrolled in any
intentional way. If the battery developed a short, it would still
overheat the transformer. A good charger limits the current into the
battery, for an battery voltage below normal, and also cuts the charging
process off, if the battery voltage gets too high (above full charge
voltage). I don't know what your 555 circuit is supposed to accomplish,
but I don't see either of these features.

I just saw that the chip L200C can reduce current. would that be an
approach??
The transformer I use is rated 2 Amp.
Should I be using a 1.0 amp transformer then ?

K
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