Regulated 9 Volt DC Power Supply

[Dave.H]

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

 

[Chris]

On Dec 28, 4:38 am, "Dave.H" <the19...@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

Hi, Dave. The easiest and safest way is to buy a wall wart.
Hobbyists and other newbies probably shouldn't be experimenting with
line voltage.

Mouser supplies a 9V 5 watt regulated DC output wall wart with a
variety of snap-on outlet plugs which will operate with all
international line voltages and frequencies for $12.82 ea. in single
quantities. It's their part number 552-PSA-05R-090-R

http://www.mouser.com/index.cfm?handler=home

Cheers
Chris

 

[John Fields]

On Fri, 28 Dec 2007 02:38:02 -0800 (PST), "Dave.H"
<the1930s@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

---
How much current?


--
JF

 

[Dave.H]

On Dec 28, 10:32 pm, Chris <cfoley1...@yahoo.com> wrote:

On Dec 28, 4:38 am, "Dave.H" <the19...@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

Hi, Dave. The easiest and safest way is to buy a wall wart.
Hobbyists and other newbies probably shouldn't be experimenting with
line voltage.

Mouser supplies a 9V 5 watt regulated DC output wall wart with a
variety of snap-on outlet plugs which will operate with all
international line voltages and frequencies for $12.82 ea. in single
quantities. It's their part number 552-PSA-05R-090-R

http://www.mouser.com/index.cfm?handler=home

Cheers
Chris

I can buy a 9 v regulated wall wart, rated at 800 mA, but as I'm on a
tight budget, I can't pay the $AU30 for it. I ALWAYS use extreme
caution around high voltage. I've worked around high voltage in old
valve radios, and learned to keep my hands away from energized
equipment, I'm pretty comfortable working around mains voltage. If I
build this PSU it will be in a plastic box.

 

[amdx]

"Dave.H" <the1930s@googlemail.com> wrote in message
news:c9bc7c5d-9f59-415f-b19c-a724b60cfe13@x29g2000prg.googlegroups.com...

On Dec 28, 11:09 pm, Chris <cfoley1...@yahoo.com> wrote:
On Dec 28, 5:48 am, "Dave.H" <the19...@googlemail.com> wrote:



On Dec 28, 10:32 pm, Chris <cfoley1...@yahoo.com> wrote:

On Dec 28, 4:38 am, "Dave.H" <the19...@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

Hi, Dave. The easiest and safest way is to buy a wall wart.
Hobbyists and other newbies probably shouldn't be experimenting with
line voltage.

Mouser supplies a 9V 5 watt regulated DC output wall wart with a
variety of snap-on outlet plugs which will operate with all
international line voltages and frequencies for $12.82 ea. in single
quantities. It's their part number 552-PSA-05R-090-R

http://www.mouser.com/index.cfm?handler=home

Cheers
Chris

I can buy a 9 v regulated wall wart, rated at 800 mA, but as I'm on a
tight budget, I can't pay the $AU30 for it. I ALWAYS use extreme
caution around high voltage. I've worked around high voltage in old
valve radios, and learned to keep my hands away from energized
equipment, I'm pretty comfortable working around mains voltage. If I
build this PSU it will be in a plastic box.- Hide quoted text -

- Show quoted text -

OK, Dave. But if you're on a tight budget, you probably want to stay
away from home brew power supplies, unless you've got most of the
parts in your junkbox -- it'll still be more expensive to make it
yourself.

Dick Smith Electronics has a new regulated 9VDC@600mA output wall wart
for A$7.98 as their P/N M9560. I'm sure you could scrounge something
at a local surplus outlet for less.

http://www.dse.com.au/

But if you're somewhat versed in electrical safety, and you've got
enclosure, line cord with strain relief, fuse and fuseholder, DPST
line voltage-capable switch, 12VAC secondary transformer that's good
for at least an amp and a half, 6 amp bridge rectifier, 2200uF 25WV
electrolytic cap and 10uF 16WV cap, you can buy an LM7809 from DSE for
A$1.20 as their P/N Z6550 to make your regulated 9VDC supply. Oh, yes
-- you'll also need a 6 to 10 watt heat sink for the TO-220 package,
as well as a bit of perfboard to mount the components. And mounting
hardware. And bumper feet for your enclosure. And some kind of light
to display that it's on.

Are you sure you want to go there?

Cheers
Chris

Didn't think it would be that complicated. I'll have a look around to
find the cheapest wall wart. Thanks for your help.

It's not hard to find wall warts that are being thrown away or sold
for 50 cents or $1 at yard sales. I have about 25 in a box ranging from 3v
to 24v, ac and dc.
If you really want to build one on the cheap, start picking up discarded
stereos, tv and microwaves, they have much of the hardware you need.
Mike

 

[Chris]

On Dec 28, 5:48 am, "Dave.H" <the19...@googlemail.com> wrote:

On Dec 28, 10:32 pm, Chris <cfoley1...@yahoo.com> wrote:





On Dec 28, 4:38 am, "Dave.H" <the19...@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

Hi, Dave.  The easiest and safest way is to buy a wall wart.
Hobbyists and other newbies probably shouldn't be experimenting with
line voltage.

Mouser supplies a 9V 5 watt regulated DC output wall wart with a
variety of snap-on outlet plugs which will operate with all
international line voltages and frequencies for $12.82 ea. in single
quantities.  It's their part number 552-PSA-05R-090-R

http://www.mouser.com/index.cfm?handler=home

Cheers
Chris

I can buy a 9 v regulated wall wart, rated at 800 mA, but as I'm on a
tight budget, I can't pay the $AU30 for it. I ALWAYS use extreme
caution around high voltage. I've worked around high voltage in old
valve radios, and learned to keep my hands away from energized
equipment, I'm pretty comfortable working around mains voltage. If I
build this PSU it will be in a plastic box.- Hide quoted text -

- Show quoted text -

OK, Dave. But if you're on a tight budget, you probably want to stay
away from home brew power supplies, unless you've got most of the
parts in your junkbox -- it'll still be more expensive to make it
yourself.

Dick Smith Electronics has a new regulated 9VDC@600mA output wall wart
for A$7.98 as their P/N M9560. I'm sure you could scrounge something
at a local surplus outlet for less.

http://www.dse.com.au/

But if you're somewhat versed in electrical safety, and you've got
enclosure, line cord with strain relief, fuse and fuseholder, DPST
line voltage-capable switch, 12VAC secondary transformer that's good
for at least an amp and a half, 6 amp bridge rectifier, 2200uF 25WV
electrolytic cap and 10uF 16WV cap, you can buy an LM7809 from DSE for
A$1.20 as their P/N Z6550 to make your regulated 9VDC supply. Oh, yes
-- you'll also need a 6 to 10 watt heat sink for the TO-220 package,
as well as a bit of perfboard to mount the components. And mounting
hardware. And bumper feet for your enclosure. And some kind of light
to display that it's on.

Are you sure you want to go there?

Cheers
Chris

 

[Dave.H]

On Dec 28, 11:09 pm, Chris <cfoley1...@yahoo.com> wrote:

On Dec 28, 5:48 am, "Dave.H" <the19...@googlemail.com> wrote:



On Dec 28, 10:32 pm, Chris <cfoley1...@yahoo.com> wrote:

On Dec 28, 4:38 am, "Dave.H" <the19...@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

Hi, Dave. The easiest and safest way is to buy a wall wart.
Hobbyists and other newbies probably shouldn't be experimenting with
line voltage.

Mouser supplies a 9V 5 watt regulated DC output wall wart with a
variety of snap-on outlet plugs which will operate with all
international line voltages and frequencies for $12.82 ea. in single
quantities. It's their part number 552-PSA-05R-090-R

http://www.mouser.com/index.cfm?handler=home

Cheers
Chris

I can buy a 9 v regulated wall wart, rated at 800 mA, but as I'm on a
tight budget, I can't pay the $AU30 for it. I ALWAYS use extreme
caution around high voltage. I've worked around high voltage in old
valve radios, and learned to keep my hands away from energized
equipment, I'm pretty comfortable working around mains voltage. If I
build this PSU it will be in a plastic box.- Hide quoted text -

- Show quoted text -

OK, Dave. But if you're on a tight budget, you probably want to stay
away from home brew power supplies, unless you've got most of the
parts in your junkbox -- it'll still be more expensive to make it
yourself.

Dick Smith Electronics has a new regulated 9VDC@600mA output wall wart
for A$7.98 as their P/N M9560. I'm sure you could scrounge something
at a local surplus outlet for less.

http://www.dse.com.au/

But if you're somewhat versed in electrical safety, and you've got
enclosure, line cord with strain relief, fuse and fuseholder, DPST
line voltage-capable switch, 12VAC secondary transformer that's good
for at least an amp and a half, 6 amp bridge rectifier, 2200uF 25WV
electrolytic cap and 10uF 16WV cap, you can buy an LM7809 from DSE for
A$1.20 as their P/N Z6550 to make your regulated 9VDC supply. Oh, yes
-- you'll also need a 6 to 10 watt heat sink for the TO-220 package,
as well as a bit of perfboard to mount the components. And mounting
hardware. And bumper feet for your enclosure. And some kind of light
to display that it's on.

Are you sure you want to go there?

Cheers
Chris

Didn't think it would be that complicated. I'll have a look around to
find the cheapest wall wart. Thanks for your help.

 

[Dave.H]

On Dec 28, 11:39 pm, John Fields <jfie...@austininstruments.com>
wrote:

On Fri, 28 Dec 2007 02:38:02 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

---
How much current?

--
JF

I'm not exactly sure. The radio uses 6 "D" cells. I'm not sure of the
current rating of "D" cells.

 

[robb]

"Dave.H" <the1930s@googlemail.com> wrote in message
news:08eeda33-c772-4464-a8ba-6afd4feb83af@d21g2000prf.googlegroups.com...

Can anyone help me with information on building a 9 volt
regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

when i need stuff like this... cheap ! there are several sources.

borrow one from stuff i have allready have, go to local
salvage/second hand shop and buy it (usually small fraction of
new cost), yard sales, flea markets any used stuff sale.

the electronics may be useless but you get the part you are
wanting.

the second hand shops here usually have a 5 gallon (20 liter)
(BIN/basket) full of wallwarts for 50 cents a piece and they get
so many they dump the lot when the bin is full,
hth
robb

 

[Michael Black]

Chris (cfoley1064@yahoo.com) writes:

OK, Dave. But if you're on a tight budget, you probably want to stay
away from home brew power supplies, unless you've got most of the
parts in your junkbox -- it'll still be more expensive to make it
yourself.

You pull a suitable transformer out of a piece of junked electronic

equipment. Take a "computer power supply", they are certainly plentiful
in North America, and strip it down, using the box for building the
power supply. That first piece of equipment is likely to supply a suitable
bridge rectifier, and electrolytic capacitors.

All that will really be needed is a 9volt regulator. An LM317 variable
regulator may be easier to come by.

Michael

 

[Jonathan Kirwan]

On Fri, 28 Dec 2007 07:02:35 -0600, "amdx" <amdx@knology.net> wrote:

snip
It's not hard to find wall warts that are being thrown away or sold
for 50 cents or $1 at yard sales. I have about 25 in a box ranging from 3v
to 24v, ac and dc.

That's the way I go, but I just keep an eye out for them -- when I
actually need something I don't have and need it now, it's not so easy
to just find the right yard sale or junk bin, quickly.

For example, I found our local store "dumping" 18VAC@1.5A transformers
at $1.50 each. I bought six, knowing that I'd use them for students
wanting to learn, later on, where I'd give them away. Also, got a
largish-looking (bigger than other wall warts I'd ever seen, frankly)
+5V@1A, -5V@1A, +15V@250mA, -15V@250mA wall wart power supply (bought
5) that cost me just a couple dollars each, in an electronics surplus
outlet store. But if I needed something fast, I'm not sure I'd know
where to go, right away.

Also, keep in mind the cost of gas, these days! One can "burn up"
one's power supply budget just driving, looking around. UPS and FedEX
have been recently raising their rates, as well.

If you really want to build one on the cheap, start picking up discarded
stereos, tv and microwaves, they have much of the hardware you need.

If it weren't the case that so many things carry specialized ICs and
parts, making junking them out for personal use less valuable than it
once was, I'd begin to wonder if there might be a return to a practice
of junking out TVs, radios, and so on.

I definitely used to do a lot of that, in my youth -- I lived poor,
without access to medical care and in houses without walls for some
time as a child and worked the berry and vegetable fields for money as
soon as I could (age 11, I think), so what electronics I did I had to
do without any cost to speak of. Which reminds me... used to be, kids
were allowed to work the fields for money and I definitely needed to
do that to survive -- I suppose this is a reason why welfare [which
didn't exist for me] is needed, since there are laws preventing
children from working the fields, now. By the way, when a bowling
alley was demonlished by a freak tornado in our area, as a kid I
actually got up the gumption to call up the owner and asked him for
permission to rummage through it for parts... and got it! I got lots
of good, long wire and relays from that. Boxes of stuff.

But things are different, today, in ways. I still do a cursory "go
through" on TVs and so on before throwing them away, perhaps more out
of old habit than anything. I make enough money today that I don't
need to worry, but it still carries some fun for me so I do it and
tuck away the parts in small drawers. Microwave units definitely get
their power transformers pulled -- my daughter is profoundly autistic
and has burned up perhaps 5 or 6 of them in the last few years, so I
have a few sitting aside for some future use. Old habits die hard, I
suppose.

But it would not be easy to set up a nice looking 9V power supply from
that stuff. Modifying the transformers is often doable, of course,
but would take some dedication to eventually get right for someone who
hasn't done it before. And that is only one step along the way.

Jon

 

[Michael Black]

Jonathan Kirwan (jkirwan@easystreet.com) writes:

But it would not be easy to set up a nice looking 9V power supply from
that stuff. Modifying the transformers is often doable, of course,
but would take some dedication to eventually get right for someone who
hasn't done it before. And that is only one step along the way.

But you're suggesting that people only throw away recent stuff, when

in reality there's still lots of older things that have yet to be
discarded.

Yes, recent VCRs have switching supplies, which aren't too useful
in themselves and certainly aren't a source of power transformers. But
lots of VCRs have been sold over the decades, and they traditionally did
have fancy transformers (full of multiple windings with a wide variety
of voltages).

A lot of consumer electronics is out there waiting to donate a transformer.
Admittedly in this case the transformer current rating may be higher than
a lot of equipment will supply, but transformers (and casing) are often
one of the biggest cost items when building things, and if you can pull
that relatively low power transformer out of that clock radio, it will
power that little project without costing you anything (or forcing you
to use batteries).

And the older the equipment, the more likely you will find parts that
can be reused. Those VCRs I keep bringing home are full of low power
transistors that are fine for a lot of general purpose use.

If you're starting out, the lack of parts is often a liability, since
you have to buy every single part and aren't likely to experiment
as a result. But again, those VCRs (and other equipment) are a great
source to build up a supply of ceramic capacitors and even resistors.
Forget the cost of the parts, with the local electronic store often
a thing of the past in many locations, being able to get that needed
capacitor to finish a project can mean the difference between finishing
it now, and having to order lots of other parts to fill an order and
waiting.

Dot matrix printers can be a source of transformers too, though their
time is enough in the past that the peak time for seeing them waiting
for the garbage truck is mostly in the past.

Inkjets are what you see a lot of nowadays, and they can be a supply
of many power transistors. They also tend to have switching supplies
in standalone modules (if they don't use an external supply), which
make them easy to extract. And unlike "computer power supplies" their
current capacity is more appropriate for the experimenter, and even
usually provide a higher voltage (ie up to around 24vdc).

I grab "computer power supplies" any time I see them, and I see them
just lying by themselves often (no computer in sight). Like I said,
the boxes are pretty useful for building things in.

I think it's a far better time to find scrap electronics than when I
was a kid. 35 years ago, the average household had a tv set or two
and a few radios, and not much else. Electronics was something you
bought and kept and had repaired. If it was tossed, it was old
tube stuff grungy with dust attracted by the heat and high voltage.
Now there's a lot more variety of stuff, and even if you have to
buy it at garage sales than wait for the garbage, it will cost next
to nothing.

I think salvaging parts is as important for educational reasons than
it is for saving money. Having parts around forces you to make a leap,
instead of copying that project part by part and not understanding much,
it requires you to know what the parts are doing and how tolerant
each part is to variation. I also think it helps to demistify things;
once you've taken things apart it's less of a mystery.

It's often worth just keeping a basic set of tools with you, so when
you see some old junk, you can extract just the things you want, without
having to haul the whole unit home. A little bit of knowledge helps. So
if you see a radio, and are interested in radio projects, you know to
grab the variable capacitor and loopstick if you see a radio, and maybe
the whole circuit board. If you've got the tools, you can easily unscrew
it and cut the wires to get the board out. Or just pull the power
transformer, like I said those often cost more than the parts for a small
project.

Michael

 

[gearhead]

On Dec 28, 4:51 am, "Dave.H" <the19...@googlemail.com> wrote:

On Dec 28, 11:39 pm, John Fields <jfie...@austininstruments.com
wrote:

On Fri, 28 Dec 2007 02:38:02 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

---
How much current?

--
JF

I'm not exactly sure.  The radio uses 6 "D" cells. I'm not sure of the
current rating of "D" cells.

Maximum battery power doesn't come into play. It matters how much the
RADIO draws. The power supply needs enough grunt to meet the radio's
maximum current draw while still putting out 9 volts.

Now, old-fashioned wall warts, the kind with line frequency
transformers in them, seldom have any sort of regulation circuitry.
They come rated with a current. They will supply that current while
still providing the nominal voltage. Heavier loads will drag the
voltage down, and with lighter loads you will get a somewhat higher
voltage. With such power supplies, voltage depends on how much power
the device consumes, so you need to match the size of the power supply
with the size of the device.
An ordinary 9 volt wall wart, if it has enough heft, will run your
radio. How big a wall wart you need depends on the size of the
radio. A pocket transistor radio would run off the real small wall
warts, like about one inch cube. A bigger radio would require bigger
power supply.
So grab a wall wart at a flea market or even out of the rubbish. See
if it says 9 volts dc, weigh it in your hand, and take a guess at
whether you think it has enough heft to run your radio. Then plug it
in.

 

[Jonathan Kirwan]

On 28 Dec 2007 21:34:06 GMT, et472@FreeNet.Carleton.CA (Michael Black)
wrote:

Jonathan Kirwan (jkirwan@easystreet.com) writes:

But it would not be easy to set up a nice looking 9V power supply from
that stuff. Modifying the transformers is often doable, of course,
but would take some dedication to eventually get right for someone who
hasn't done it before. And that is only one step along the way.

But you're suggesting that people only throw away recent stuff, when
in reality there's still lots of older things that have yet to be
discarded.

Yes, I suppose that is the case. However, just looking at me (and
I've got a 1200 sq ft shed with "stuff" in it dating back a ways) and
what I throw out these days, I can certainly see a lot less of easy
use for a new hobbyist who is nearer the beginning than the end of
their hobby.

Yes, recent VCRs have switching supplies, which aren't too useful
in themselves and certainly aren't a source of power transformers. But
lots of VCRs have been sold over the decades, and they traditionally did
have fancy transformers (full of multiple windings with a wide variety
of voltages).

I tend to "part out" the easy stuff in everything electronic we throw
away -- which deeply bugs my wife, since she can't just get rid of
things when she is busy and doesn't want to wait for my convenience.
And of late, I am speaking of the recent 10 year period and comparing
it with the decade of my early hobby years from '65 to '75. I have to
say that I'm pulling out less and less I can later use for hobby
things... by quite a stretch... and I know how to use a wider variety
today than I could back then.

A lot of consumer electronics is out there waiting to donate a transformer.
Admittedly in this case the transformer current rating may be higher than
a lot of equipment will supply, but transformers (and casing) are often
one of the biggest cost items when building things, and if you can pull
that relatively low power transformer out of that clock radio, it will
power that little project without costing you anything (or forcing you
to use batteries).

And the older the equipment, the more likely you will find parts that
can be reused. Those VCRs I keep bringing home are full of low power
transistors that are fine for a lot of general purpose use.

If you are talking about older, used VCRs, I don't have access to
"VCRs I keep bringing home." Do you work somewhere in proximity to
these things? I ask, because for the OP it may be nice to actually
know where to go to get things with good stuff in them to extract. I
was thinking about where to recommend, as a ready supply, and I'm not
sure I have a good recommendation. Goodwill, perhaps. Or some place
that scraps computers -- though I've actually volunteered at such a
place a few months ago and helped out there and didn't find nearly as
much as I'd imagined beforehand. Good motors in printers, yes. Heat
sinks, yes. Some EEPROMs and FLASH memories, yes. I suppose the
power supplies might have a few items. But nothing like the old
Kaypro 286i, for example, which pre-dated the "chipset days" and had a
board FULL of 7400 series SSI chips on them. And I'm not sure how
easy it is to get them to let you rummage stuff -- the folks I worked
with separated out the gold for extraction and sold other stuff, once
sorted a bit, by the pound. But if I were to have asked to take
stuff, I'd have had to "ask the boss" and I'm not sure how much they
would have wanted to bother or worry about someone hauling out goodies
while interfering with the sorting process.

I agree, conceptually, with you. The problem is in the details of
actually knowing where to go for setting hands on good stuff to gut at
low/zero cost.

If you're starting out, the lack of parts is often a liability, since
you have to buy every single part and aren't likely to experiment
as a result. But again, those VCRs (and other equipment) are a great
source to build up a supply of ceramic capacitors and even resistors.
Forget the cost of the parts, with the local electronic store often
a thing of the past in many locations, being able to get that needed
capacitor to finish a project can mean the difference between finishing
it now, and having to order lots of other parts to fill an order and
waiting.

Dot matrix printers can be a source of transformers too, though their
time is enough in the past that the peak time for seeing them waiting
for the garbage truck is mostly in the past.

This last one interests me. Where in the world can you hope to get a
dot matrix printer, these days??? I just had someone ask me if I had
any ideas at all where to get one. They wanted something that used a
ribbon for the ink and supported _impact_ printing. I didn't have
anything to offer, though I admit I assumed that he'd already searched
on the web a bit before asking me. I could be wrong about that. But
if you know of a source, I'll pass it on to him.

Inkjets are what you see a lot of nowadays, and they can be a supply
of many power transistors. They also tend to have switching supplies
in standalone modules (if they don't use an external supply), which
make them easy to extract. And unlike "computer power supplies" their
current capacity is more appropriate for the experimenter, and even
usually provide a higher voltage (ie up to around 24vdc).

I grab "computer power supplies" any time I see them, and I see them
just lying by themselves often (no computer in sight). Like I said,
the boxes are pretty useful for building things in.

I haven't gutted a recent PC power supply. But they seem to be much
smaller, from seeing them on the outside. Which makes me think they
are line-powered, chopping and using high frequency inductors with
opto feedback to operate them -- and if that is right, there won't be
a nice transformer there for handy hobby use. But I admit not
looking, yet. Can you say more about the recent supplies?

I think it's a far better time to find scrap electronics than when I
was a kid. 35 years ago, the average household had a tv set or two
and a few radios, and not much else. Electronics was something you
bought and kept and had repaired. If it was tossed, it was old
tube stuff grungy with dust attracted by the heat and high voltage.
Now there's a lot more variety of stuff, and even if you have to
buy it at garage sales than wait for the garbage, it will cost next
to nothing.

Well, I think there is a lot more "scrap electronics" around now --
admitted. But I'm thinking also of 35-40 years back, when I was
needing these things and I feel this is all a bit of a mixed bag --
some good, some bad.

I used to find quite a few ready supplies of parts in the area. We
had at least 4 or 5 BIG warehouse-style stores in the area -- Allied
Elec, for example, operated a huge facility here that was open to the
public. But there were four others here in the area and they competed
heavily with each other. I used to take several days and walk through
these places, over the flat tables of hand-bagged items or loose parts
these places had collected up and offered for sale. NONE of these
retail facilities exist, today. Not one. And I've lived here my
entire life and watched the change. Radio Shack (and I remember the
Tandy leathercraft stores here, too, before and after the merger) used
to be, by and large, a parts store. No more.

On the other hand, I am greatly gratified by places like Mouser and
Digikey, of course. And, except perhaps for Allied, I didn't have
something like that as a kid -- though I probably couldn't have
afforded it, either. But I did also have access to perhaps 20 or so
suppliers of hobbyist quantities of glass of various types (a good two
dozen types, at least, for lenses) and got copies of the five
periodicals that used to exist for building your own telescopes -- all
gone, now. Sky and Telescope still exists, but doesn't cater as it
used to, of course, to that market. Of course, Heathkit is gone.

It's a mixed bag. I LOVE much of the change. I have ready access to
microcontrollers of every ilk and because of that I can do things that
would have been simply impossible, back then. I can buy demo boards
for almost nothing (in today's terms) and, instead of having to wire
wrap like a madman, I can get a nice FPGA board and program in VHDL to
wire up all that logic for me. I don't even need to do the floor
planning of it, if I am just experimenting around for play. I can't
tell you how much of a boon that is. For example, I've designed a few
CPUs of my own and was able to test out my own code, too. And it
didn't take long, nor was it hard work. So, there are some big pluses
today. For some of us.

But if I were starting out... well, ... okay, maybe you are right.
Hard to say. But I do miss some things.

I think salvaging parts is as important for educational reasons than
it is for saving money. Having parts around forces you to make a leap,
instead of copying that project part by part and not understanding much,
it requires you to know what the parts are doing and how tolerant
each part is to variation. I also think it helps to demistify things;
once you've taken things apart it's less of a mystery.

yes.

It's often worth just keeping a basic set of tools with you, so when
you see some old junk, you can extract just the things you want, without
having to haul the whole unit home. A little bit of knowledge helps. So
if you see a radio, and are interested in radio projects, you know to
grab the variable capacitor and loopstick if you see a radio, and maybe
the whole circuit board. If you've got the tools, you can easily unscrew
it and cut the wires to get the board out. Or just pull the power
transformer, like I said those often cost more than the parts for a small
project.

I enjoyed reading this and perhaps you are right about the times, as
well. But I do wonder about someone starting out these days. There
is so much available, for so little money to buy, that the motives
needed to do the real digging are harder to come buy. "Back in the
day," you didn't really have a choice. You either built it, or did
without. When the Altair 8800 came out, I bought the kit and built
it. In fact, that was the only way I could have afforded my own
computer. I built my own telescopes, because back then there wasn't a
ready market for a wide variety of them and where they did exist
pre-made, they were WAY too expensive and there was a ready supply of
cheap materials for making your own. In fact, I'd add to what you
wrote above and say that you really cannot understand your telescopic
instrument well, if you haven't been through all the trouble of
actually constructing and testing your own to near perfection. The
process of actually seeing what light does is very important and no
"book learning" will quite do it for most of us. Setting up knife
edge or Ronchi gratings and going through various repeated steps of
correction and testing and trying out various light sources and so on
is as much an important part as anything. I'm not sure that an
amateur really can know what they are working with, if they have never
been through that process at least once or twice.

Thanks,
Jon

 

[Jonathan Kirwan]

On Fri, 28 Dec 2007 04:51:04 -0800 (PST), "Dave.H"
<the1930s@googlemail.com> wrote:

On Dec 28, 11:39 pm, John Fields <jfie...@austininstruments.com
wrote:
On Fri, 28 Dec 2007 02:38:02 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:
Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

---
How much current?

--
JF

I'm not exactly sure. The radio uses 6 "D" cells. I'm not sure of the
current rating of "D" cells.

The Energizer E95 (D cell) datasheet uses 10 ohms as the load for a
radio example. Assuming that is correct, you are talking about
(6x1.5V/10) or almost an amp load. But I'm sure that volume affects
this, too. Anyway, using that as a reference I guess that a solid 1A
or 1.5A supply would probably cover the need. Of course, that could
indeed vary a lot from radio to radio, so of course more is better.

Problem is, you can expect transformers delivering much more than an
amp on their secondary, at voltages enough higher than 9V to be useful
in linear circuits, to be expensive/big. You may be able to measure
your current draw, with an ammeter if you have one. But my guess is
that a largish wall wart supply should be okay for your use. I think
you can get to around the 1A to 1.5A you are probably looking at.

By the way, D cells are rated to operate over a range of current
loads. They are usually selected over C or AA, not quite so much
because they last longer (they do) but more because they are capable
of larger current draws without serious loss of lifetime. This
suggests that your radio really does want access to something in the
100's of milliamps rather than something in the 10's. So you really
do need to figure on estimating about .5-1A or so, simply because it
uses D cells.

Jon

 

[Michael A. Terrell]

Jonathan Kirwan wrote:

This last one interests me. Where in the world can you hope to get a
dot matrix printer, these days??? I just had someone ask me if I had
any ideas at all where to get one. They wanted something that used a
ribbon for the ink and supported _impact_ printing. I didn't have
anything to offer, though I admit I assumed that he'd already searched
on the web a bit before asking me. I could be wrong about that. But
if you know of a source, I'll pass it on to him.

Thrift stores, yard sales, or even Ebay. 498 listings, right now:
<http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=dot+matrix+printer&category0=>

Google has 2 million hits for dot matrix printer:
<http://www.google.com/search?q=dot+matrix+printer&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GWYA>

I have two sitting in the shop right now to test. I have about a
dozen IEEE-488 Commodore 4032 printers in storage.

Banks and Credit Unions still use them to print multi-part forms. The
OKI MICROLINE 320 is still a popular, new printer used in bamks.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[HapticZ]

i use a standard euro voltage adapter to get 120vac, then use any number of
off-the shelf 9v ac/dc supplys


"Dave.H" <the1930s@googlemail.com> wrote in message
news:08eeda33-c772-4464-a8ba-6afd4feb83af@d21g2000prf.googlegroups.com...

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

 

[Jonathan Kirwan]

On Fri, 28 Dec 2007 22:39:57 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Jonathan Kirwan wrote:

This last one interests me. Where in the world can you hope to get a
dot matrix printer, these days??? I just had someone ask me if I had
any ideas at all where to get one. They wanted something that used a
ribbon for the ink and supported _impact_ printing. I didn't have
anything to offer, though I admit I assumed that he'd already searched
on the web a bit before asking me. I could be wrong about that. But
if you know of a source, I'll pass it on to him.

Thrift stores, yard sales, or even Ebay. 498 listings, right now:
http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=dot+matrix+printer&category0=

Thanks, I'll let him know that folks on ebay seem to be willing to
take money for them.

Google has 2 million hits for dot matrix printer:
http://www.google.com/search?q=dot+matrix+printer&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GWYA

Well, that might only be people _talking_ about them. I will not send
him towards some 2M listing on google.

I have two sitting in the shop right now to test. I have about a
dozen IEEE-488 Commodore 4032 printers in storage.

In fact, it was the Commodore printers that sprang to mind that I felt
people might have sitting on closet shelves. I'll assume for now that
you aren't offering, though.

Banks and Credit Unions still use them to print multi-part forms. The
OKI MICROLINE 320 is still a popular, new printer used in bamks.

hehe. Thanks. That's a pointer for him. I'll let him know.

Jon

 

[Ian Malcolm]

Dave.H wrote:

On Dec 28, 11:09 pm, Chris <cfoley1...@yahoo.com> wrote:

On Dec 28, 5:48 am, "Dave.H" <the19...@googlemail.com> wrote:




On Dec 28, 10:32 pm, Chris <cfoley1...@yahoo.com> wrote:

On Dec 28, 4:38 am, "Dave.H" <the19...@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

Thanks,
Dave

Hi, Dave. The easiest and safest way is to buy a wall wart.
Hobbyists and other newbies probably shouldn't be experimenting with
line voltage.

Mouser supplies a 9V 5 watt regulated DC output wall wart with a
variety of snap-on outlet plugs which will operate with all
international line voltages and frequencies for $12.82 ea. in single
quantities. It's their part number 552-PSA-05R-090-R

http://www.mouser.com/index.cfm?handler=home

Cheers
Chris

I can buy a 9 v regulated wall wart, rated at 800 mA, but as I'm on a
tight budget, I can't pay the $AU30 for it. I ALWAYS use extreme
caution around high voltage. I've worked around high voltage in old
valve radios, and learned to keep my hands away from energized
equipment, I'm pretty comfortable working around mains voltage. If I
build this PSU it will be in a plastic box.- Hide quoted text -

- Show quoted text -

OK, Dave. But if you're on a tight budget, you probably want to stay
away from home brew power supplies, unless you've got most of the
parts in your junkbox -- it'll still be more expensive to make it
yourself.

Dick Smith Electronics has a new regulated 9VDC@600mA output wall wart
for A$7.98 as their P/N M9560. I'm sure you could scrounge something
at a local surplus outlet for less.

http://www.dse.com.au/

But if you're somewhat versed in electrical safety, and you've got
enclosure, line cord with strain relief, fuse and fuseholder, DPST
line voltage-capable switch, 12VAC secondary transformer that's good
for at least an amp and a half, 6 amp bridge rectifier, 2200uF 25WV
electrolytic cap and 10uF 16WV cap, you can buy an LM7809 from DSE for
A$1.20 as their P/N Z6550 to make your regulated 9VDC supply. Oh, yes
-- you'll also need a 6 to 10 watt heat sink for the TO-220 package,
as well as a bit of perfboard to mount the components. And mounting
hardware. And bumper feet for your enclosure. And some kind of light
to display that it's on.

Are you sure you want to go there?

Cheers
Chris


Didn't think it would be that complicated. I'll have a look around to
find the cheapest wall wart. Thanks for your help.
Its *not* that complicated. If you've been fixing radios you probably

have a couple of chassis hanging around you can gut for a n enclosure,
mains lead switch etc. and a filament transformer good for 50% more than
you want output current. You need 12V so 2 6.3V windings in series
should do. If the current you want is under 1/2A use a 78M09. Should
be able to scrounge equivalent diodes and caps out of your junk box.
78xx series regulators have Ov on the tab so you can use the chassis as
a heatsink for moderate output currents. If you can find a 15-0-15
transformer build up a decent bench supply with 7805, 7809 and 7812
positive regulators and 7912 and 7909 negative regulators (not 0V on the
tab) Then its time to think about a fully floating adjustable supply
with variable current limit.

I hacked an old 8bit computer PSU to make a nice +5 & +/-12V psu (with
power LED and a 4 pole isolating switch for the outputs so I can solder
on my circuit board without blowing anything) many years ago and its
still in regular use. Dont use 9V much but a 7809 with its caps
soldered to its legs and wire leads with aterminal block all on an old
heatsink hooks up to an old CB supply if I need it.

*collect* old good quality wallwarts. Always usefull for projects ;-)
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL:

 

[Ian Malcolm]

gearhead wrote:

On Dec 28, 4:51 am, "Dave.H" <the19...@googlemail.com> wrote:

On Dec 28, 11:39 pm, John Fields <jfie...@austininstruments.com
wrote:


On Fri, 28 Dec 2007 02:38:02 -0800 (PST), "Dave.H"

the19...@googlemail.com> wrote:

Can anyone help me with information on building a 9 volt regulated
power supply that runs off 250 volts AC mains? Any help greatly
appreciated.

---
How much current?

--
JF

I'm not exactly sure. The radio uses 6 "D" cells. I'm not sure of the
current rating of "D" cells.

How many hours does it get out of a set of Alkalines?

Maximum battery power doesn't come into play. It matters how much the
RADIO draws. The power supply needs enough grunt to meet the radio's
maximum current draw while still putting out 9 volts.

Now, old-fashioned wall warts, the kind with line frequency
transformers in them, seldom have any sort of regulation circuitry.
They come rated with a current. They will supply that current while
still providing the nominal voltage. Heavier loads will drag the
voltage down, and with lighter loads you will get a somewhat higher
voltage. With such power supplies, voltage depends on how much power
the device consumes, so you need to match the size of the power supply
with the size of the device.
An ordinary 9 volt wall wart, if it has enough heft, will run your
radio. How big a wall wart you need depends on the size of the
radio. A pocket transistor radio would run off the real small wall
warts, like about one inch cube. A bigger radio would require bigger
power supply.

So grab a wall wart at a flea market or even out of the rubbish. See
if it says 9 volts dc, weigh it in your hand, and take a guess at
whether you think it has enough heft to run your radio. Then plug it
in.
Check the polarity first unless you *like* the smell of burning ICs. It

can also be worth hooking up a 5 watt car bulb and seeing if the
wallwart is good and can supply a bit over 300ma for an hour wihout
burning up.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL: