"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in
message news:4vrmk3lrracpttm5bo5vo06vohf4is43ku@4ax.com...
> On Mon, 26 Nov 2007 19:41:09 -0500, the renowned "robb"
> <some@where.on.net> wrote:
> >"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in
> >message news:cinmk3dr3oielksfcurunlbmb5o28dm49a@4ax.com...
> >> On Mon, 26 Nov 2007 13:48:51 -0500, the renowned "robb"
> >> <some@where.on.net> wrote:
> >> >
> >> > "robb" <some@where.on.net> wrote in message
> >> > news:13k7a00pc8c8870@corp.supernews.com...
> >> > is there a problem with the universal psu schematic (page
2)
> >> > shown in the following document ?
> >> > more specifically with the selectable voltage part of the
> >> > schematic
> >> >
> >> >
http://www.qsl.net/lu3mgp/electronica/U ... Supply.pdf
> >>
> >> Yeah, there's an error. The connection between the (-)
> >> output and R1 should not be there.
> >
> > well i can not figure which connection you are talking about
iis
> > it the same as the one i described ?
> >
>
> http://server2.hostingplex.com/~zstoretr/fix.gif
>

not the wire i was thinking, but i was close
thanks for the correction
robb

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote
in message news:bMI2j.55$rp7.39@newsfe07.lga...
>
> Some 78xx regulators oscillate a bit especially with out
> the proper load on them.
> even then, you may need to place some by pass caps on it
> as you did.
>
so the oscillation that probably contributed to frying my first
7805
and is it typical that the oscillation shows up on the bridge out
?

thanks for reply,
robb

robb wrote:

> "Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote
> in message news:bMI2j.55$rp7.39@newsfe07.lga...
>
>> Some 78xx regulators oscillate a bit especially with out
>> the proper load on them.
>> even then, you may need to place some by pass caps on it
>> as you did.
>>
>
> so the oscillation that probably contributed to frying my first
> 7805
> and is it typical that the oscillation shows up on the bridge out
> ?
>
> thanks for reply,
> robb
>
>
board lay and lead run lengths plays a roll in that.

I assume you had a electrolytic cap on the bridge +/- outputs?

in any case, that does not stop the high freq you saw in there, you
don't always see this problem in all 78xx, I've seen it in some
depending on who made the component where is others, they work fine
with out any compensation. Also, if you constructed the bridge your
self instead of using a ready made unit, it's smart to put some small
bypass caps across the diodes..

Other issues is when voltages on the output side exceed the voltage
on the input side.. the internals of the regulator have an issue with
this how ever, like I said before, it depends on who made the component.
I've seen some that included the bleeder diode.
In a case like that, a bleeder diode from the output to the
input is a desirable component to use. For a + type, the anode would
be on the output, cathode on the input. Basically, that simply causes
a by pass of the regulator if the output voltage happens to be higher
than the input voltage by 0.7V or more.


Hope that did something for you.


--
"I'd rather have a bottle in front of me than a frontal lobotomy"
http://webpages.charter.net/jamie_5

robb wrote:
>>"robb" <some@where.on.net> wrote in message
>>news:13k7a00pc8c8870@corp.supernews.com...
>>
>>> yes i googled and found lots of different mods to the basic
>
> 5v
>
>>> *7805* regulator power supply
>>> that is {AC in, bridge, 7805, 5v out}
>
>
> (images on a.b.s.e)
>
> i built and experimenting with the 5v DC psu

The images do not show a filter cap after the bridge and
before the 7805. Add a large cap (4700uF shown) across
the brideg output:

--------
| +|-----+------in[7805]out---
| Bridge | | + |
| | [4700uF] |
| | | |
| -|-----+-----------+
--------

Ed

In article <cinmk3dr3oielksfcurunlbmb5o28dm49a@4ax.com>,
speffSNIP@interlogDOTyou.knowwhat says...
> On Mon, 26 Nov 2007 13:48:51 -0500, the renowned "robb"
> <some@where.on.net> wrote:
>
> >
> >"robb" <some@where.on.net> wrote in message
> >news:13k7a00pc8c8870@corp.supernews.com...
> >> yes i googled and found lots of different mods to the basic 5v
> >> *7805* regulator power supply
> >> \that is {AC in, bridge, 7805, 5v out}
> >>
> >
> >I came across this universal psu design while searching for 5V
> >psu info ...
> >is there a problem with the universal psu schematic (page 2)
> >shown in the following document ?
> >more specifically with the selectable voltage part of the
> >schematic
> >
> >http://www.qsl.net/lu3mgp/electronica/UniversalPowerSupply.pdf
> >
> >
> >also
> >i am trying to understand how that PSU can produce higher voltage
> >than 5V while using a 7805 5V regulator and no path for the
> >bridge rectifier (+) voltage to bypass the 5V regulator ?
> >
> >thanks for any help
> >robb
>
> Yeah, there's an error. The connection between the (-) output and R1
> should not be there.
>
>
> Best regards,
> Spehro Pefhany
>

I noticed that when I looked at the schematic. I'm planning on building
this one since it's a variable power supply, hell I might just build two
of them because I've got a couple products in mind that use 5V for logic
and 12V to drive things like steppers, etc.

In article <13kmpqe31s4p45@corp.supernews.com>, some@where.on.net
says...
>
> "Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in
> message news:cinmk3dr3oielksfcurunlbmb5o28dm49a@4ax.com...
> > On Mon, 26 Nov 2007 13:48:51 -0500, the renowned "robb"
> > <some@where.on.net> wrote:
> >
> > >
> > >"robb" <some@where.on.net> wrote in message
> > >news:13k7a00pc8c8870@corp.supernews.com...
> > >> yes i googled and found lots of different mods to the basic
> 5v
> > >> *7805* regulator power supply
> > >> \that is {AC in, bridge, 7805, 5v out}
> > >>
> > >
> > >I came across this universal psu design while searching for 5V
> > >psu info ...
> > >is there a problem with the universal psu schematic (page 2)
> > >shown in the following document ?
> > >more specifically with the selectable voltage part of the
> > >schematic
> > >
> > >http://www.qsl.net/lu3mgp/electronica/UniversalPowerSupply.pdf
> > >
> > >
> >
> > Yeah, there's an error. The connection between the (-) output
> and R1
> > should not be there.
>
> hi, thanks Sphero,
>
> wait a minute are you toying with me ?
>
> well i can not figure which connection you are talking about iis
> it the same as the one i described ?
>
> thanks for help,
> robb
>
>
>
>
>
>

If you look at the schematic the connection between the lower end of R1
and the other end of C3 should not exist.

In article <4vrmk3lrracpttm5bo5vo06vohf4is43ku@4ax.com>,
speffSNIP@interlogDOTyou.knowwhat says...
> On Mon, 26 Nov 2007 19:41:09 -0500, the renowned "robb"
> <some@where.on.net> wrote:
>
> >
> >"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in
> >message news:cinmk3dr3oielksfcurunlbmb5o28dm49a@4ax.com...
> >> On Mon, 26 Nov 2007 13:48:51 -0500, the renowned "robb"
> >> <some@where.on.net> wrote:
> >>
> >> >
> >> >"robb" <some@where.on.net> wrote in message
> >> >news:13k7a00pc8c8870@corp.supernews.com...
> >> >> yes i googled and found lots of different mods to the basic
> >5v
> >> >> *7805* regulator power supply
> >> >> \that is {AC in, bridge, 7805, 5v out}
> >> >>
> >> >
> >> >I came across this universal psu design while searching for 5V
> >> >psu info ...
> >> >is there a problem with the universal psu schematic (page 2)
> >> >shown in the following document ?
> >> >more specifically with the selectable voltage part of the
> >> >schematic
> >> >
> >> >http://www.qsl.net/lu3mgp/electronica/UniversalPowerSupply.pdf
> >> >
> >> >
> >>
> >> Yeah, there's an error. The connection between the (-) output
> >and R1
> >> should not be there.
> >
> >hi, thanks Sphero,
> >
> >wait a minute are you toying with me ?
> >
> >well i can not figure which connection you are talking about iis
> >it the same as the one i described ?
> >
> >thanks for help,
> >robb
>
> http://server2.hostingplex.com/~zstoretr/fix.gif
>
>
>
> Best regards,
> Spehro Pefhany
>

Nice graphic! Thanks for that, I used a plain black pen to cross out the
connection on my schematic.

"pom" <pom@free.fr>
>>>
> Hello
> nobody mentioned it but the schematic is faulty!
> Negative output should not be connected to the "mass" leg of the
> regulator. Else, output voltage cannot be different from 5V - other
> effects neglected

http://www.qsl.net/lu3mgp/electronica/U ... Supply.pdf

** The design is purest crap.

Output regulation wil be poor, as will hum rejection - since Iq is a highly
variable quantity.

Bound to be HF unstable at some settings and loads too.

That ain't no way to treat a 7805.

Just sub in a LM317 and nearly all the troubles go.



.......... Phil

On Tue, 27 Nov 2007 17:50:08 +1100, the renowned "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>"pom" <pom@free.fr>
>>>>
>> Hello
>> nobody mentioned it but the schematic is faulty!
>> Negative output should not be connected to the "mass" leg of the
>> regulator. Else, output voltage cannot be different from 5V - other
>> effects neglected
>
>http://www.qsl.net/lu3mgp/electronica/UniversalPowerSupply.pdf
>
>** The design is purest crap.
>
>Output regulation wil be poor, as will hum rejection - since Iq is a highly
>variable quantity.

It's actually fairly stable with output current, less so with input
voltage and temperature. Probably better than most switchable AC
adapters wot consist primarily of a badly made multi-tap transformer
and a crappy slide switch with PCB contacts. But it could be <1%
rather than <10%, as you point out.

>Bound to be HF unstable at some settings and loads too.

I have yet to see a 7805 oscillate under any reasonable conditions.

>That ain't no way to treat a 7805.

It should probably have a larger output cap and a diode eg. 1N5403
across the 7805 and probably across the output too since we don't know
what will get hooked up to it.

>Just sub in a LM317 and nearly all the troubles go.
>
>
>
>......... Phil
>

Yup. Of course you have to recalculate the resistor values, taking
into account that you should draw a minimum of 5mA from the '317 to
keep it in regulation. Eg. 237R and 715R for 5V.

Another potential problem with the original circuit is that the output
voltage will spike as high as Vin - 1.xV during the switch transitions
unless it's a shorting type rotary switch.

That's typically considered an undesirable characteristic in a power
supply.



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

On Nov 23, 11:34 am, "Clubsprint" <spamspamspams...@nospam.com> wrote:
> I have a device requiring 9v AC 2.5 Amp.
>
> So do I get a 240v-9v transformer from the electronics shop and put it in a
> case, attach the correct leads and I'm done.
>
> I suppose an inline fuse might be a safety precaution.
>
> Is this all that's required or is there some sort of regualting curcuit that
> I should add?
>
> Tranformer I was thinking of using
>
> http://www.rsaustralia.com/cgi-bin/bv/r ... n.do?N=0...

Just buy a proper one, they are available
Try here for a 9.6V 2.5A one for example:
http://www.accesscomms.com.au/Products/Adaptors.htm
Or parallel a couple of 1A ones, everyone stocks those.

Dave.

"Spehro Pefhany"
"Phil Allison"
>>"pom" <pom@free.fr>
>>>
>>> Hello
>>> nobody mentioned it but the schematic is faulty!
>>> Negative output should not be connected to the "mass" leg of the
>>> regulator. Else, output voltage cannot be different from 5V - other
>>> effects neglected
>>
>> http://www.qsl.net/lu3mgp/electronica/U ... Supply.pdf
>
>>
>>** The design is purest crap.
>>
>>Output regulation will be poor, as will hum rejection - since Iq is a
>>highly
>>variable quantity.
>
>
> It's actually fairly stable with output current, less so with input
> voltage and temperature.


** Natsemi data shows Iq may change by up to 0.5 mA in the range of normal
output currents up to 1 amp,
by up to 1mA over the nominal input voltage range & by 1 mA over the
allowed temp range.

Adds up to 2.5 mA.

2.5 mA flowing in 1.5 kohms = 3.75 volts.

That IS craaaaap !!



>>Bound to be HF unstable at some settings and loads too.
>
> I have yet to see a 7805 oscillate under any reasonable conditions.


** A comment about you and other circuits.

Waste of type.


>>That ain't no way to treat a 7805.
>
> It should probably have a larger output cap....


** There is effectively no output stability cap.

That 0.01uF hanging off the + output finds it way back to the 7805's ground
terminal via a crippling amount of series resistance.


>>Just sub in a LM317 and nearly all the troubles go.
>>
>
> Yup.


** Just follow the data sheet for the LM317 for the needed R values.


The only way that horribly crude idea of converting a LM7805 into a variable
reg can be even half satisfactory is * IF * the input voltage is itself
regulated and the load current fixed.



....... Phil

"David L. Jones"

>
> Just buy a proper one, they are available
> Try here for a 9.6V 2.5A one for example:
> http://www.accesscomms.com.au/Products/Adaptors.htm
>
> Or parallel a couple of 1A ones, everyone stocks those.


** That is an EXTRAORDINARILY dangerous suggestion !!

AC adaptors must NEVER be wired in parallel - or one will power the other
making the exposed pins live at 240 volts.

Shame, shame, shame on you DLJ.





....... Phil

On Tue, 27 Nov 2007 23:33:37 +1100, the renowned "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>The only way that horribly crude idea of converting a LM7805 into a variable
>reg can be even half satisfactory is * IF * the input voltage is itself
>regulated and the load current fixed.

It's more than okay to put a zener or LED on the GND lead.

It's also okay if you don't mind blowing all kinds of current in the
resistor network (the Fairchild data sheet recommends > 25mA rather
than the 5mA the Poptronics circuit has), which would reduce the
effect of Iq variations by about 3:1.

They also show an op-amp, but that has potential stability issues that
might actually exist in the real world.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

On Tue, 27 Nov 2007 23:47:40 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>"David L. Jones"
>
>>
>> Just buy a proper one, they are available
>> Try here for a 9.6V 2.5A one for example:
>> http://www.accesscomms.com.au/Products/Adaptors.htm
>>
>> Or parallel a couple of 1A ones, everyone stocks those.
>
>
>** That is an EXTRAORDINARILY dangerous suggestion !!
>
>AC adaptors must NEVER be wired in parallel - or one will power the other
>making the exposed pins live at 240 volts.

---
If their mains plugs are used to plug in to mains receptacles and
they're phased correctly, how so?


--
JF

"John Fields"
"Phil Allison"
>"David L. Jones"
>>
>>>
>>> Just buy a proper one, they are available
>>> Try here for a 9.6V 2.5A one for example:
>>> http://www.accesscomms.com.au/Products/Adaptors.htm
>>>
>>> Or parallel a couple of 1A ones, everyone stocks those.
>>
>>
>>** That is an EXTRAORDINARILY dangerous suggestion !!
>>
>>AC adaptors must NEVER be wired in parallel - or one will power the
>>other
>>making the exposed pins live at 240 volts.
>
> ---
> If their mains plugs are used to plug in to mains receptacles and
> they're phased correctly, how so?


** Whaaaaaattttttt ??????????????

Serious lack of imagination and the basic principle of Murphy's Law noted.


BTW

A 9 volt 1 amp adaptor is a " wall wart" - so no plugs.



...... Phil

"Spehro Pefhany"
"Phil Allison"

>>
>>The only way that horribly crude idea of converting a LM7805 into a
>>variable
>>reg can be even half satisfactory is * IF * the input voltage is itself
>>regulated and the load current fixed.
>
> It's more than okay to put a zener or LED on the GND lead.


** Completely different matter.

Remaining within context is a real trial for you.



> It's also okay if you don't mind blowing all kinds of current in the
> resistor network (the Fairchild data sheet recommends > 25mA rather
> than the 5mA the Poptronics circuit has),


** The Poptronics abortion runs at circa 11mA.

5 / 470 = ???



.......... Phil

Spehro Pefhany wrote:
> On Mon, 26 Nov 2007 13:48:51 -0500, the renowned "robb"
> <some@where.on.net> wrote:
>
>
>>"robb" <some@where.on.net> wrote in message
>>news:13k7a00pc8c8870@corp.supernews.com...
>>
>>> yes i googled and found lots of different mods to the basic 5v
>>> *7805* regulator power supply
>>> \that is {AC in, bridge, 7805, 5v out}
>>>
>>
>>I came across this universal psu design while searching for 5V
>>psu info ...
>>is there a problem with the universal psu schematic (page 2)
>>shown in the following document ?
>>more specifically with the selectable voltage part of the
>>schematic
>>
>>http://www.qsl.net/lu3mgp/electronica/UniversalPowerSupply.pdf
>>
>>
>>also
>>i am trying to understand how that PSU can produce higher voltage
>>than 5V while using a 7805 5V regulator and no path for the
>>bridge rectifier (+) voltage to bypass the 5V regulator ?
>>
>>thanks for any help
>>robb
>
>
> Yeah, there's an error. The connection between the (-) output and R1
> should not be there.
>
>
> Best regards,
> Spehro Pefhany

And the circuit description is demented, the output topology is not a
'voltage divider', he's putting some ridiculous amount of current
through that LED, the whole thing is bad. No wonder that generation of
kids just threw their hands up and quit electronics.

Spehro Pefhany wrote:
> On Tue, 27 Nov 2007 23:33:37 +1100, the renowned "Phil Allison"
> <philallison@tpg.com.au> wrote:
>
>
>>The only way that horribly crude idea of converting a LM7805 into a variable
>>reg can be even half satisfactory is * IF * the input voltage is itself
>>regulated and the load current fixed.
>
>
> It's more than okay to put a zener or LED on the GND lead.
>
> It's also okay if you don't mind blowing all kinds of current in the
> resistor network (the Fairchild data sheet recommends > 25mA rather
> than the 5mA the Poptronics circuit has), which would reduce the
> effect of Iq variations by about 3:1.
>
> They also show an op-amp, but that has potential stability issues that
> might actually exist in the real world.
>
>
> Best regards,
> Spehro Pefhany

The pos is intractable as shown. Note that S2 is more likely a
break-before-make, opening the 7805 return for even a few hundred usecs
is not a good idea, output heads for the upper limits, then filtering
the output with a reasonable value of capacitance is also problematic
with that dammed switch too.

On Wed, 28 Nov 2007 00:34:16 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>"Spehro Pefhany"
> "Phil Allison"
>
>>>
>>>The only way that horribly crude idea of converting a LM7805 into a
>>>variable
>>>reg can be even half satisfactory is * IF * the input voltage is itself
>>>regulated and the load current fixed.
>>
>> It's more than okay to put a zener or LED on the GND lead.
>
>
>** Completely different matter.
>
> Remaining within context is a real trial for you.

My context (in this thread)is hobby-level power supply circuits.
Switching zeners rather than resistors is not an unreasonable
approach, but we're still left with the spiking-during-switching
issue.

>> It's also okay if you don't mind blowing all kinds of current in the
>> resistor network (the Fairchild data sheet recommends > 25mA rather
>> than the 5mA the Poptronics circuit has),
>
>
>** The Poptronics abortion runs at circa 11mA.
>
> 5 / 470 = ???

Right, okay, bad memory, more like a 2:1 difference.

>......... Phil
>

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Spehro Pefhany wrote:

> Another potential problem with the original circuit is that the output
> voltage will spike as high as Vin - 1.xV during the switch transitions
> unless it's a shorting type rotary switch.

If it was done the sensible way by adding resistors in parallel that problem
could at least be minimised.

Graham

On Wed, 28 Nov 2007 00:30:41 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

>
>"John Fields"
> "Phil Allison"
>>"David L. Jones"
>>>
>>>>
>>>> Just buy a proper one, they are available
>>>> Try here for a 9.6V 2.5A one for example:
>>>> http://www.accesscomms.com.au/Products/Adaptors.htm
>>>>
>>>> Or parallel a couple of 1A ones, everyone stocks those.
>>>
>>>
>>>** That is an EXTRAORDINARILY dangerous suggestion !!
>>>
>>>AC adaptors must NEVER be wired in parallel - or one will power the
>>>other
>>>making the exposed pins live at 240 volts.
>>
>> ---
>> If their mains plugs are used to plug in to mains receptacles and
>> they're phased correctly, how so?
>
>
> ** Whaaaaaattttttt ??????????????
>
>Serious lack of imagination and the basic principle of Murphy's Law noted.
>
>
>BTW
>
>A 9 volt 1 amp adaptor is a " wall wart" - so no plugs.

How does it connect to the mains, then?


--
JF

On Nov 27, 11:47 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:
> "David L. Jones"
>
>
>
> > Just buy a proper one, they are available
> > Try here for a 9.6V 2.5A one for example:
> >http://www.accesscomms.com.au/Products/Adaptors.htm
>
> > Or parallel a couple of 1A ones, everyone stocks those.
>
> ** That is an EXTRAORDINARILY dangerous suggestion !!
>
> AC adaptors must NEVER be wired in parallel - or one will power the other
> making the exposed pins live at 240 volts.
>
> Shame, shame, shame on you DLJ.
>
> ...... Phil

Simply put them in an ABS box, along with a nice big warning sticker
and Phil's Toaster Repairs contact number in case of emergency or
service.

If you chose the right size box and a power board, the OP wouldn't
have to touch any mains wiring at all, and the lid could close down on
the plugpacks holding them securely in place. Of course, it's much
easier and less fuss to simply buy the right adapter as I mentioned.

Dave.

ehsjr wrote:

> robb wrote:
>
>>> "robb" <some@where.on.net> wrote in message
>>> news:13k7a00pc8c8870@corp.supernews.com...
>>>
>>>> yes i googled and found lots of different mods to the basic
>>
>>
>> 5v
>>
>>>> *7805* regulator power supply
>>>> that is {AC in, bridge, 7805, 5v out}
>>
>>
>>
>> (images on a.b.s.e)
>>
>> i built and experimenting with the 5v DC psu
>
>
> The images do not show a filter cap after the bridge and
> before the 7805. Add a large cap (4700uF shown) across
> the brideg output:
>
> --------
> | +|-----+------in[7805]out---
> | Bridge | | + |
> | | [4700uF] |
> | | | |
> | -|-----+-----------+
> --------
>
> Ed
You know, that's a good catch. Power supplies to many of us
are like car's. We assume to much..

You get in your car to drive it, you shouldn't have to
question if you have an engine in it! You just naturally assume
that. But then again, that analogy maybe flawed if you live in a
shady neighborhood




--
"I'd rather have a bottle in front of me than a frontal lobotomy"
http://webpages.charter.net/jamie_5

"David L. Jerkoff "
>
>>
>> > Just buy a proper one, they are available
>> > Try here for a 9.6V 2.5A one for example:
>> >http://www.accesscomms.com.au/Products/Adaptors.htm
>>
>> > Or parallel a couple of 1A ones, everyone stocks those.
>>
>> ** That is an EXTRAORDINARILY dangerous suggestion !!
>>
>> AC adaptors must NEVER be wired in parallel - or one will power the
>> other
>> making the exposed pins live at 240 volts.
>>
>> Shame, shame, shame on you DLJ.
>>
>
>
> Simply put them in an ABS box, along with a nice big warning sticker
> and Phil's Toaster Repairs contact number in case of emergency or
> service.

** Pathetic, really.


> If you chose the right size box and a power board, the OP wouldn't
> have to touch any mains wiring at all, and the lid could close down on
> the plugpacks holding them securely in place.


** How idiotic.

The OP could just buy a step down tranny and use the adaptor he has.

Only problem being - that he is an UTTER FUCKING MORON.




........ Phil

PinkFloyd43 wrote:

> robb wrote:
>
>> "robb" <some@where.on.net> wrote in message
>> news:13k7a00pc8c8870@corp.supernews.com...
>>
>>> yes i googled and found lots of different mods to the basic 5v
>>> *7805* regulator power supply
>>> \that is {AC in, bridge, 7805, 5v out}
>>>
>>
>> I came across this universal psu design while searching for 5V
>> psu info ...
>> is there a problem with the universal psu schematic (page 2)
>> shown in the following document ?
>> more specifically with the selectable voltage part of the
>> schematic
>>
>> http://www.qsl.net/lu3mgp/electronica/U ... Supply.pdf
>>
>>
>> also
>> i am trying to understand how that PSU can produce higher voltage
>> than 5V while using a 7805 5V regulator and no path for the
>> bridge rectifier (+) voltage to bypass the 5V regulator ?
>>
>> thanks for any help
>> robb
>>
>>
>>
>>
>>
> Everyone seems to agree the schematic is a POS, any links to
> what more than one person believes to be a decent 5V PS?

In my opinion, you would be better off with fixed post regulators of
every voltage you need all branching off from the same bridge and filter
cap..

If you want a variable out, you can create one from one of the higher
voltage fixed post regulators with 2 Resistors and a pot.

Some Links.

http://www.tkk.fi/Misc/Electronics/circuits/psu_5v.html
http://www.paia.com/KRUKits/K4/K4.pdf
http://www.aaroncake.net/circuits/supply6.asp
http://members.tripod.com/michaelgellis/power2.html
http://www.educypedia.be/electronics/ci ... pplies.htm



--
"I'd rather have a bottle in front of me than a frontal lobotomy"
http://webpages.charter.net/jamie_5