FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Electronix » Basics
power supply 2
Post new topic   Reply to topic Page 3 of 3 [41 Posts] View previous topic :: View next topic
Goto page:  Previous  1, 2, 3
Author Message
James Thompson
electronics forum Guru Wannabe


Joined: 08 Mar 2006
Posts: 120

PostPosted: Wed Jul 19, 2006 3:10 pm    Post subject: Re: power supply 2 Reply with quote

"Ken O" <lera@yahoo.com> wrote in message news:e9lfvs$jhl$1@nntp.aioe.org...
Quote:

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




Look here for the circuit on desulfating:
http://www.shaka.com/~kalepa/desulf.htm
Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 3:14 pm    Post subject: Re: power supply 2 Reply with quote

"James Thompson" <Jamesthompson2002@hotmail.com> wrote in message
news:ba6bf$44be4b56$471cd6e3$2394@ALLTEL.NET...
Quote:

"Ken O" <lera@yahoo.com> wrote in message
news:e9lfvs$jhl$1@nntp.aioe.org...

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




Look here for the circuit on desulfating:
http://www.shaka.com/~kalepa/desulf.htm

i want to charge at the same time. I did his circuit, the battery discharge
very quickly, even more with a badly sulfated battery. the idea of using a
pulse charger is a bit better I think.
k
Back to top
<tapwater@roomtemperat
electronics forum addict


Joined: 06 May 2006
Posts: 82

PostPosted: Wed Jul 19, 2006 4:03 pm    Post subject: Re: power supply 2 Reply with quote

http://www.aaroncake.net/circuits/dimmer.htm

This was the first of many triac light dimmer circuits that I found.
I would substitute the transformer primary for the lamp, and hope the change
from a resistive load to an inductive load didn't make too much difference.
Other possibilities would be to use an SCR instead of your transistor. SCRs
can control huge currents.

"Ken O" <lera@yahoo.com> wrote in message news:e9lgno$hm8$1@nntp.aioe.org...
Quote:

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

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

Back to top
<tapwater@roomtemperat
electronics forum addict


Joined: 06 May 2006
Posts: 82

PostPosted: Wed Jul 19, 2006 4:30 pm    Post subject: Re: power supply 2 Reply with quote

Now that I'm starting to think about it I am starting to wonder if the lamp
dimmer wouldn't just cut the voltage to the point where your charger wasn't
charging! May be you will have to control it with some feedback from the
output? Well at least I am bringing up the subject of Triacs and SCRs
(Silicon Controlled Rectifiers).

"Ken O" <lera@yahoo.com> wrote in message news:e9lgno$hm8$1@nntp.aioe.org...
Quote:

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

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

Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 7:31 pm    Post subject: Re: power supply 2 Reply with quote

"John Fields" <jfields@austininstruments.com> wrote in message
news:vjfob2lm4pg0v0rto3ciaounu2cl2gkgds@4ax.com...
Quote:
On Mon, 17 Jul 2006 19:18:39 -0400, "Ken O" <lera@yahoo.com> 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.??

---
So far, who knows?
---


I use a 120v to 25v AC transformer, to a Bridge rectifier, then to a
2000uF
110 v capacitor .

---
So the output of the supply, after the filter, will be about 35VDC
---

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 ?

---
Post the circuit.


yes I did, in my first post. Just add a rectifier and a transformer to the
capacitor like I mentionned
Its that simple of a circuit, nothing more.

ken
Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Wed Jul 19, 2006 10:33 pm    Post subject: Re: power supply 2 Reply with quote

I just got a huge transformer, Its about three times the size from the
previous.
The rating is not mentionend but I get the right voltage
I try it out tonight

ken
Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Thu Jul 20, 2006 12:18 am    Post subject: Re: power supply 2 Reply with quote

"Ken O" <lera@yahoo.com> wrote in message news:e9mc1a$3bm$1@nntp.aioe.org...
Quote:
I just got a huge transformer, Its about three times the size from the
previous.
The rating is not mentionend but I get the right voltage
I try it out tonight

ken

yes that fixed it, just the transistor is getting a bit hot, but thats not a
big deal.

k
Back to top
<tapwater@roomtemperat
electronics forum addict


Joined: 06 May 2006
Posts: 82

PostPosted: Thu Jul 20, 2006 12:27 am    Post subject: Re: power supply 2 Reply with quote

You are on the right track with a bigger transformer, but, if I were doing
this job I wouldn't be happy until I found a circuit that could protect the
charger even if the output leads got shorted together. That happens
sometimes by accident.

"Ken O" <lera@yahoo.com> wrote in message news:e9mc1a$3bm$1@nntp.aioe.org...
Quote:
I just got a huge transformer, Its about three times the size from the
previous.
The rating is not mentionend but I get the right voltage
I try it out tonight

ken

Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Thu Jul 20, 2006 10:11 am    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).

John

You mentionned earlier that I would need a circuit to supply the timer. I
was going to use the LM317, but that has a maximum of 36 v. Now the
transformer is given me 44v, that do not matter, Should I be just using
resistors for a voltage divider and feed my timer directly with that? would
there be any problem ?

Ken
Back to top
Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Thu Jul 20, 2006 1:46 pm    Post subject: Re: power supply 2 Reply with quote

<tapwater@roomtemperature.deg> wrote in message
news:E5Avg.7083$vO.1186@newsread4.news.pas.earthlink.net...
Quote:
You are on the right track with a bigger transformer, but, if I were doing
this job I wouldn't be happy until I found a circuit that could protect
the
charger even if the output leads got shorted together. That happens
sometimes by accident.

^putting a zener diode on the positive end would work ?

k
Back to top
John Popelish
electronics forum Guru


Joined: 29 Apr 2005
Posts: 1601

PostPosted: Thu Jul 20, 2006 2:30 pm    Post subject: Re: power supply 2 Reply with quote

Ken O wrote:

Quote:
John

You mentionned earlier that I would need a circuit to supply the timer. I
was going to use the LM317, but that has a maximum of 36 v. Now the
transformer is given me 44v, that do not matter, Should I be just using
resistors for a voltage divider and feed my timer directly with that? would
there be any problem ?


This has to be designed, just like anything else.

Start with the voltage and current your 555 circuit requires. What
current is it supplying to the base of the power switch? You have to
get rid of all the extra voltage and still supply that total current.
I would be thinking of a several watt resistor and a 15 volt zener
to lower the voltage. The resistor would have to be sized to carry
the peak circuit load current, and the zener would have to burn that
additional current when the circuit was in the low current phase of
its operation. If you wanted more precise regulation than that, you
could add the LM317 downstream of that.
Back to top
Google

Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 3 of 3 [41 Posts] Goto page:  Previous  1, 2, 3
View previous topic :: View next topic
The time now is Wed Oct 18, 2017 1:18 pm | All times are GMT
Forum index » Electronix » Basics
Jump to:  

Similar Topics
Topic Author Forum Replies Last Post
No new posts Circuit inside PC power supply foxOnTheRun design 0 Tue Nov 01, 2011 10:07 am
No new posts Problem with output power-linear amplifier tzitzikas design 0 Thu May 20, 2010 3:32 pm
No new posts Converting GSM Signal to usable electrical power xiaoma design 0 Mon Dec 04, 2006 8:55 am
No new posts Researching maximum life span of the power supply of a sm... alphacentauri@doglover.co Basics 0 Fri Jul 21, 2006 12:08 pm
No new posts Researching maximum life span of the power supply of a sm... alphacentauri@doglover.co Misc 0 Fri Jul 21, 2006 12:06 pm

Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums |  Medicine forum |  Science forum  |  Send and track newsletters


Powered by phpBB © 2001, 2005 phpBB Group