Benchtop Power Supply Options

[Jurd]

Hello again,

It is time for me to acquire a better bench top power solution. Most of
the time I will use it to power a breadboard for experimentation. I
used a wall wart for awhile until it got super noisy, and batteries are
a hassle. I was about to go for something like this:
http://tinyurl.com/qexphfy

And then attach something like this: http://tinyurl.com/qc5e9ma to the
leads internally. (and maybe add a power switch, mount it and the
breadboard all to a piece of melamine board, etc). I would of course
verify output with the DVOM before I trusted the display.

For someone still in the larval stage, do you suppose this would be
adequate? Will 15V be enough for future growth? So far I've done mostly
5V logic, 9V guitar stompboxery and small radio. Occasionally I've done
some 18V and 24V stuff, though. I see that a lot of other power supply
kits say they go up to 30V, but they cost upwards of 4x as much.

Am I being too cheap? I was going to just buy/dumpsterdive the parts
and use an online schematic, but I might not know enough to verify a
schematic before I fry myself and burn the house down. Therefore I
think a kit is the way to go- should be correct, comes with all the
right parts, and (hopefully) has instructions that'll teach me a thing
or two.

I've looked at a bunch of kits and this Elenco one seems pretty idiot
proof, but is there anything else you folks might suggest otherwise?

Thanks.

-J

 

[Maynard A. Philbrook Jr.]

In article <lkeb1e$7kf$1@news.albasani.net>,
guitardorkspamspameggsandham74@gmail.com says...

Hello again,

It is time for me to acquire a better bench top power solution. Most of
the time I will use it to power a breadboard for experimentation. I
used a wall wart for awhile until it got super noisy, and batteries are
a hassle. I was about to go for something like this:
http://tinyurl.com/qexphfy

And then attach something like this: http://tinyurl.com/qc5e9ma to the
leads internally. (and maybe add a power switch, mount it and the
breadboard all to a piece of melamine board, etc). I would of course
verify output with the DVOM before I trusted the display.

For someone still in the larval stage, do you suppose this would be
adequate? Will 15V be enough for future growth? So far I've done mostly
5V logic, 9V guitar stompboxery and small radio. Occasionally I've done
some 18V and 24V stuff, though. I see that a lot of other power supply
kits say they go up to 30V, but they cost upwards of 4x as much.

Am I being too cheap? I was going to just buy/dumpsterdive the parts
and use an online schematic, but I might not know enough to verify a
schematic before I fry myself and burn the house down. Therefore I
think a kit is the way to go- should be correct, comes with all the
right parts, and (hopefully) has instructions that'll teach me a thing
or two.

I've looked at a bunch of kits and this Elenco one seems pretty idiot
proof, but is there anything else you folks might suggest otherwise?

Thanks.

-J

0-30V @ 3 AMps, digital display with current limiting controls
for 49 bucks. get two if you can so you can generate dual rails,
or look at that site and get a dual supply.

I always send people here when low cost is in their plan!

http://www.circuitspecialists.com/csi3003sm.html

Jamie

 

[Tim Wescott]

On Wed, 07 May 2014 17:11:00 -0500, Jurd wrote:

Hello again,

It is time for me to acquire a better bench top power solution. Most of
the time I will use it to power a breadboard for experimentation. I
used a wall wart for awhile until it got super noisy, and batteries are
a hassle. I was about to go for something like this:
http://tinyurl.com/qexphfy

And then attach something like this: http://tinyurl.com/qc5e9ma to the
leads internally. (and maybe add a power switch, mount it and the
breadboard all to a piece of melamine board, etc). I would of course
verify output with the DVOM before I trusted the display.

For someone still in the larval stage, do you suppose this would be
adequate? Will 15V be enough for future growth? So far I've done mostly
5V logic, 9V guitar stompboxery and small radio. Occasionally I've done
some 18V and 24V stuff, though. I see that a lot of other power supply
kits say they go up to 30V, but they cost upwards of 4x as much.

Am I being too cheap? I was going to just buy/dumpsterdive the parts
and use an online schematic, but I might not know enough to verify a
schematic before I fry myself and burn the house down. Therefore I
think a kit is the way to go- should be correct, comes with all the
right parts, and (hopefully) has instructions that'll teach me a thing
or two.

I've looked at a bunch of kits and this Elenco one seems pretty idiot
proof, but is there anything else you folks might suggest otherwise?

Thanks.

-J

Your plan is sound, except that you'll find that the case is much too
small for the meter.

Look here if you want complete solutions: http://www.mpja.com/Benchtop-
Power-Supplies/products/2/.

I've found that regardless of whether you're doing a 1-off or production,
the box you put the electronics in almost always costs more than the
electronics. So you're tossing quite a bit of value along with the box.

You can also just use the power supply as-is, and check the voltage with
a meter when you need to. That works well for me.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[John Larkin]

On Wed, 7 May 2014 18:28:24 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <lkeb1e$7kf$1@news.albasani.net>,
guitardorkspamspameggsandham74@gmail.com says...

Hello again,

It is time for me to acquire a better bench top power solution. Most of
the time I will use it to power a breadboard for experimentation. I
used a wall wart for awhile until it got super noisy, and batteries are
a hassle. I was about to go for something like this:
http://tinyurl.com/qexphfy

And then attach something like this: http://tinyurl.com/qc5e9ma to the
leads internally. (and maybe add a power switch, mount it and the
breadboard all to a piece of melamine board, etc). I would of course
verify output with the DVOM before I trusted the display.

For someone still in the larval stage, do you suppose this would be
adequate? Will 15V be enough for future growth? So far I've done mostly
5V logic, 9V guitar stompboxery and small radio. Occasionally I've done
some 18V and 24V stuff, though. I see that a lot of other power supply
kits say they go up to 30V, but they cost upwards of 4x as much.

Am I being too cheap? I was going to just buy/dumpsterdive the parts
and use an online schematic, but I might not know enough to verify a
schematic before I fry myself and burn the house down. Therefore I
think a kit is the way to go- should be correct, comes with all the
right parts, and (hopefully) has instructions that'll teach me a thing
or two.

I've looked at a bunch of kits and this Elenco one seems pretty idiot
proof, but is there anything else you folks might suggest otherwise?

Thanks.

-J
0-30V @ 3 AMps, digital display with current limiting controls
for 49 bucks. get two if you can so you can generate dual rails,
or look at that site and get a dual supply.

I always send people here when low cost is in their plan!

http://www.circuitspecialists.com/csi3003sm.html

Jamie

This costs a little more, but it's a linear, so will be less noisy.

http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/mastech-regulated-variable-dc-power-supply-hy3003d-30v-3a/prod_2.html

I use one. It's very stable.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

John Larkin <jjlarkin@highnotlandthistechnologypart.com> wrote:

On Wed, 7 May 2014 18:28:24 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:
In article <lkeb1e$7kf$1@news.albasani.net>,
guitardorkspamspameggsandham74@gmail.com says...

And then attach something like this: http://tinyurl.com/qc5e9ma to
the leads internally.

Some of these little LCD and LED meters can measure their own power
supply voltage and some can't. In other words, some of them *require*
a 9 V battery to work. It usually says somewhere in the description.

I would of course verify output with the DVOM before I trusted the
display.

Good idea.

So far I've done mostly 5V logic, 9V guitar stompboxery and small
radio.

If you have any plans to do audio stuff that requires both positive and
negative supplies, it might pay to buy a dual-output supply. You can
interconnect the two supplies (either with built-in switches or by
applying wires to the outputs) and get both positive and negative. On
the fancy ones you can just turn one knob to vary both outputs.

Don't forget that a "power supply" adjustable in 1.5 V increments is as
close as all the AA batteries (and holders) you can scrounge. This is
not the right thing for 5 V at 10 A but if you need an odd voltage at
low current for a little while, it's hard to get anything simpler.

I was going to just buy/dumpsterdive the parts and use an online
schematic, but I might not know enough to verify a schematic before
I fry myself and burn the house down.

Use the right size fuse in the AC input, be very meticulous with all
the AC (120 V) wiring, and unplug the thing from the wall when you're
not using it, and you are unlikely to burn the house down. If it
develops a bad fault when you're sitting in front of it, it will
usually heat up slowly enough that you can either shut it off and
investigate, or (in urgent cases) toss it out the window.

General advice: if you buy one, it will probably have a fuse in the AC
input. Find out what type and size it is and put a few on your next
Digi-Key or Mouser order. You shouldn't blow it too often, but it's a
bummer to be out of commission for a 25 cent fuse. (If it keeps blowing
and you don't know why, then there is a problem inside the supply. But
sometimes you know why, like you accidentally connected that 300 A
diesel starter motor to your 3 A supply.)

It may or may not have a fuse in the DC output; most don't. Usually,
if you try to draw too much current from the output, the voltage
automatically drops lower (as low as maybe 1.5 V) to reduce the
current.

This costs a little more, but it's a linear, so will be less noisy.

http://www.mastechpowersupply.com/dc-power-supply/linear-power-supply/mastech-regulated-variable-dc-power-supply-hy3003d-30v-3a/prod_2.html

That design (or a clone of it) seems very popular. The oval power
button and three binding posts are exactly the same on all of them;
older ones had LED meters but the newer ones are LCD. I see the same
thing sold (for more money) as an "HQ Power PS3003U", and Tektronix
even rebadged the older LED-meter version. There is a wider version
with dual variable outputs and a fixed 5 V output as well.

I have used the Tektronix LED-meter version, plus someone else's clone
of the LED-meter version, before, and they both worked well. The meters
on someone else's clone were slightly inaccurate, but those specific
units had also had several years of exposure to students.

Personally, I use an 0-12V/6A, 0-24V/3A supply that I assembled from a
kit about 25 years ago. It has served for almost all of the trouble I
get into. It was designed by Western Electric engineers and I expect
it to outlive me.

Matt Roberds

 

[George Herold]

On Wednesday, May 7, 2014 6:11:00 PM UTC-4, Jurd wrote:

Hello again,


It is time for me to acquire a better bench top power solution. Most of
the time I will use it to power a breadboard for experimentation. I
used a wall wart for awhile until it got super noisy, and batteries are
a hassle. I was about to go for something like this:
http://tinyurl.com/qexphfy

And then attach something like this: http://tinyurl.com/qc5e9ma to the
leads internally. (and maybe add a power switch, mount it and the
breadboard all to a piece of melamine board, etc). I would of course
verify output with the DVOM before I trusted the display.

For someone still in the larval stage, do you suppose this would be
adequate? Will 15V be enough for future growth? So far I've done mostly
5V logic, 9V guitar stompboxery and small radio. Occasionally I've done
some 18V and 24V stuff, though. I see that a lot of other power supply
kits say they go up to 30V, but they cost upwards of 4x as much.

Am I being too cheap? I was going to just buy/dumpsterdive the parts
and use an online schematic, but I might not know enough to verify a
schematic before I fry myself and burn the house down. Therefore I
think a kit is the way to go- should be correct, comes with all the
right parts, and (hopefully) has instructions that'll teach me a thing
or two.


I've looked at a bunch of kits and this Elenco one seems pretty idiot
proof, but is there anything else you folks might suggest otherwise?

If you've got more time than money, then I like the idea of building your own power supply. Either from a kit... or better yet (more learning potential) building it yourself from pieces/parts. There are lots of places that will show you how to make a linear supply. ("Art of Electronics", for one.)

And hey you can draw up a schematic and post it here for comments.

If not, I also like the mastech linear supplies that John L. linked to.

George H.

Thanks.



-J

 

[Michael Black]

On Thu, 8 May 2014, mroberds@att.net wrote:

John Larkin <jjlarkin@highnotlandthistechnologypart.com> wrote:
On Wed, 7 May 2014 18:28:24 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:
In article <lkeb1e$7kf$1@news.albasani.net>,
guitardorkspamspameggsandham74@gmail.com says...

And then attach something like this: http://tinyurl.com/qc5e9ma to
the leads internally.

Some of these little LCD and LED meters can measure their own power
supply voltage and some can't. In other words, some of them *require*
a 9 V battery to work. It usually says somewhere in the description.

If not, grab a small transformer out of a clock radio or something and
make a little linear power supply for it. The meter won't require much
power. I suppose at this point, there are plenty of switching type AC
adapters that could be put in a box without taking much space.

Michael

 

[Ian Field]

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1405081039270.10885@darkstar.example.org...

On Thu, 8 May 2014, mroberds@att.net wrote:

John Larkin <jjlarkin@highnotlandthistechnologypart.com> wrote:
On Wed, 7 May 2014 18:28:24 -0400, "Maynard A. Philbrook Jr."
jamie_ka1lpa@charter.net> wrote:
In article <lkeb1e$7kf$1@news.albasani.net>,
guitardorkspamspameggsandham74@gmail.com says...

And then attach something like this: http://tinyurl.com/qc5e9ma to
the leads internally.

Some of these little LCD and LED meters can measure their own power
supply voltage and some can't. In other words, some of them *require*
a 9 V battery to work. It usually says somewhere in the description.

If not, grab a small transformer out of a clock radio or something and
make a little linear power supply for it. The meter won't require much
power. I suppose at this point, there are plenty of switching type AC
adapters that could be put in a box without taking much space.

IIRC - old ethernet cards have a handy switcher transformer, presumably
dimensioned for a 5V supply, I think the secondary is about right for 9V or
so - that would suit probably most of the commercially available digital
display modules.

 

[whit3rd]

On Wednesday, May 7, 2014 3:11:00 PM UTC-7, Jurd wrote:

Hello again,



It is time for me to acquire a better bench top power solution. ...

I've looked at a bunch of kits and this Elenco one seems pretty idiot
proof, but is there anything else you folks might suggest otherwise?

For fiddling about, you'll want one or more adjustable supplies.
If you are comfortable doing the low-voltage parts, it's often
suitable to pick up a carcass of some disused appliance, and
adapt its supply to your bench (like, get an old PC power
supply for gobs of +12 and +5V, or a newer one for those
and +3.3).

Add indicator lights, at least one for each independent section,
or you'll not notice an overload/short circuit and shutdown or
fuse-blowing response.

Variable voltage is nice, and variable current limit is very useful
(like, for charging batteries); consider a time switch, as well
(to prevent overcharging batteries).

Both voltage-variable and current-limit-variable supplies benefit from
a built-in (ALWAYS CONNECTED) meter. Whenever you adjust the knob,
you'll want to watch the voltmeter, or (for current limit) you'll
want to short the output while watching the ammeter.
Watch for sales on inexpensive multimeters... like at HarborFreight.

If AC power is important in your experimentation, get a GCFI
module, an isolation transformer, and a variac (variable autotransformer).

 

[Michael Black]

On Fri, 9 May 2014, Jasen Betts wrote:

On 2014-05-08, Ian Field <gangprobing.alien@ntlworld.com> wrote:

IIRC - old ethernet cards have a handy switcher transformer, presumably
dimensioned for a 5V supply, I think the secondary is about right for 9V or
so - that would suit probably most of the commercially available digital
display modules.

yeah it's a dc-dc converter producing an isolated 9VDC from a 5VDC supply
This is used to power the thinnet tranceiver. so look for cards with BNC
connectors.

That old? I think I cleared those out, maybe keeping a sample or two.

There was a time when I had all kinds of neat boards, and no computer to
put them in. Then at one point, I finally leaped ahead, so I'm not sure I
have a computer with an ISA bus anymore.

Michael

 

[Jasen Betts]

On 2014-05-08, Ian Field <gangprobing.alien@ntlworld.com> wrote:

IIRC - old ethernet cards have a handy switcher transformer, presumably
dimensioned for a 5V supply, I think the secondary is about right for 9V or
so - that would suit probably most of the commercially available digital
display modules.

yeah it's a dc-dc converter producing an isolated 9VDC from a 5VDC supply
This is used to power the thinnet tranceiver. so look for cards with BNC
connectors.




--
umop apisdn


--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Ian Field]

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1405090208470.12233@darkstar.example.org...

On Fri, 9 May 2014, Jasen Betts wrote:

On 2014-05-08, Ian Field <gangprobing.alien@ntlworld.com> wrote:

IIRC - old ethernet cards have a handy switcher transformer, presumably
dimensioned for a 5V supply, I think the secondary is about right for 9V
or
so - that would suit probably most of the commercially available digital
display modules.

yeah it's a dc-dc converter producing an isolated 9VDC from a 5VDC
supply
This is used to power the thinnet tranceiver. so look for cards with BNC
connectors.

That old? I think I cleared those out, maybe keeping a sample or two.

There's bound to be PSU manufacturers that can supply something suitable off
the shelf - but waiting for the order to arrive is less convenient than
raiding the junk box, and I'm really not keen on the paying for it bit!

 

[Cydrome Leader]

Michael Black <et472@ncf.ca> wrote:

On Fri, 9 May 2014, Jasen Betts wrote:

On 2014-05-08, Ian Field <gangprobing.alien@ntlworld.com> wrote:

IIRC - old ethernet cards have a handy switcher transformer, presumably
dimensioned for a 5V supply, I think the secondary is about right for 9V or
so - that would suit probably most of the commercially available digital
display modules.

yeah it's a dc-dc converter producing an isolated 9VDC from a 5VDC supply
This is used to power the thinnet tranceiver. so look for cards with BNC
connectors.

That old? I think I cleared those out, maybe keeping a sample or two.

There was a time when I had all kinds of neat boards, and no computer to
put them in. Then at one point, I finally leaped ahead, so I'm not sure I
have a computer with an ISA bus anymore.

Speaking of ISA cards, I saw a "new" 16 bit ISA card at the "Design 2
Part" show last week just outside Chicago.

I had to ask the PCB assembler who was showing this board off if this was
really the best thing they had to ooh and aaah customers with.

A couple other shoddy-ish board assemblers had rejected garbage with
defective wave soldering on display. I have no idea why these companies
even bother to bring anything if that's all they can come up with.

The other fun stuff at the show was lots of springs (really it should be
called the Spring Show), hand grenades (obviousy not primed and full of
explosives but still fun) and lots of molded rubber parts that didn't
stink.

 

Jurd <guitardorkspamspameggsandham74@gmail.com> wrote:

I'm not above dumpster diving and salvaging parts, but I'll suspect
most transformers in consumer electronics are going to be for 9V-12V
output. A ~36V or whatever might be rare.

Look for (solid-state) stereo amplifiers, or tuners with built-in
amplifiers. These usually have a big transformer with a center-tapped
winding that originally was used to generate +/- 30 to 60 V DC for the
main audio output transistors. The transformer may also have another
winding in the neighborhood of 12 V that originally ran the tuner, dial
lights, etc. Look at the AC line input rating (watts) printed on the
back panel to estimate the transformer capacity. Usually these die
because the audio output transistors give up, or possibly because the
diodes or capacitors in the power supply give up; the transformer is
often OK.

As a bonus, you get a nice case, usually with lots of venting. It has
an AC cord and possibly a switch you can re-use. You also may get a
decent-sized heat sink, and you might be able to re-use the diodes and
filter capacitors. The speaker terminals can get re-used as output
connectors, although you might prefer "real" binding posts. Replace
the existing front panel with a piece of aluminum with meters, knobs,
etc to taste.

Matt Roberds

 

[Michael Black]

On Mon, 12 May 2014, Jurd wrote:

On 5/8/2014 8:35 PM, whit3rd wrote:

For fiddling about, you'll want one or more adjustable supplies.
If you are comfortable doing the low-voltage parts, it's often
suitable to pick up a carcass of some disused appliance, and
adapt its supply to your bench (like, get an old PC power
supply for gobs of +12 and +5V, or a newer one for those
and +3.3).

Add indicator lights, at least one for each independent section,
or you'll not notice an overload/short circuit and shutdown or
fuse-blowing response.

Variable voltage is nice, and variable current limit is very useful
(like, for charging batteries); consider a time switch, as well
(to prevent overcharging batteries).

Both voltage-variable and current-limit-variable supplies benefit from
a built-in (ALWAYS CONNECTED) meter. Whenever you adjust the knob,
you'll want to watch the voltmeter, or (for current limit) you'll
want to short the output while watching the ammeter.
Watch for sales on inexpensive multimeters... like at HarborFreight.

If AC power is important in your experimentation, get a GCFI
module, an isolation transformer, and a variac (variable autotransformer).


Thanks a bunch for the tips and suggestions, everyone. I too like the idea
of building my own supply from scratch. I've avoided the easy and obvious
computer power supply because they tend to be noisy, and (I thought at least)
the voltage outputs were biased off each other. I.e., the +12V will only
give +12V with a proper load across the +5V section and vice versa. I don't
foresee the need for an AC supply, and if someday I need one I'll make that
its own project.

I'm not above dumpster diving and salvaging parts, but I'll suspect most
transformers in consumer electronics are going to be for 9V-12V output. A
~36V or whatever might be rare. This is what drove me to start looking at
kits. If the Mastech unit that John Larkin posted was available in kit form
I'd be all over it.

I don't see that many transformers these days.

But, inkjet printers are plentiful in the garbage, and they seem to always
have higher voltage power supplies, either internal or external. I once
brought home a Powerbook 1400CS, and needed some higher voltage to run it,
I seem to recall 24V, and I immediately thought of an inkjet printer, and
the first one I opened, had the right voltage on a board by itself.

Dot matrix tended to need higher voltages too, though I'm not seeing many
of those these days. Though back then, they tended to have linear
transformers.

I've also found AC adapters giving off about 30VDC, I think those were for
lighting.

LCD monitors are become more common in the garbage. Though those
generally just need some new electrolytics in the power supply, if that
doesn't fix them but does get the power supply going, those power supplies
tend to be on their own board, and have reasonable specs for a lot of
experimenting. Beats having to hack the switching supply off a single VCR
board, or some cable box.

If you can find AC adapters of the right current, they'll be inefficient
again if you use a regulator to drop the voltage, but cheaper than looking
for transformers.

One thing about the switching supply AC adapters, they tend to not need a
load to provide the proper voltage, and certainly since most offer only
one voltage, only need a load on the one output. That makes things
simpler.

I once bought some surplus switching supplies, and they actually had load
resistors built in, which seems wasteful but if the design has power to
waste, it's a way of ensuring the supply works properly.

IN the old days, it was often useful to grab the transformers out of
electronics found ont the sidewalk, even if not taking more of the parts.
They often did have transformers of the right voltage, with a big run it
was better to have transformers wound and thus have multiple windings for
all the needed voltages than to regulate one output voltage down to size.
VCRs, before they moved to switching supplies, tended to have endless
windings to cover all the needed voltages.


Michael

 

[Jurd]

On 5/8/2014 8:35 PM, whit3rd wrote:

For fiddling about, you'll want one or more adjustable supplies.
If you are comfortable doing the low-voltage parts, it's often
suitable to pick up a carcass of some disused appliance, and
adapt its supply to your bench (like, get an old PC power
supply for gobs of +12 and +5V, or a newer one for those
and +3.3).

Add indicator lights, at least one for each independent section,
or you'll not notice an overload/short circuit and shutdown or
fuse-blowing response.

Variable voltage is nice, and variable current limit is very useful
(like, for charging batteries); consider a time switch, as well
(to prevent overcharging batteries).

Both voltage-variable and current-limit-variable supplies benefit from
a built-in (ALWAYS CONNECTED) meter. Whenever you adjust the knob,
you'll want to watch the voltmeter, or (for current limit) you'll
want to short the output while watching the ammeter.
Watch for sales on inexpensive multimeters... like at HarborFreight.

If AC power is important in your experimentation, get a GCFI
module, an isolation transformer, and a variac (variable autotransformer).

Thanks a bunch for the tips and suggestions, everyone. I too like the
idea of building my own supply from scratch. I've avoided the easy and
obvious computer power supply because they tend to be noisy, and (I
thought at least) the voltage outputs were biased off each other. I.e.,
the +12V will only give +12V with a proper load across the +5V section
and vice versa. I don't foresee the need for an AC supply, and if
someday I need one I'll make that its own project.

I'm not above dumpster diving and salvaging parts, but I'll suspect most
transformers in consumer electronics are going to be for 9V-12V output.
A ~36V or whatever might be rare. This is what drove me to start
looking at kits. If the Mastech unit that John Larkin posted was
available in kit form I'd be all over it.

We have two bench top supplies where I work that look very similar to
that one. I don't recall the brand off the top of my head (might be
Tektronix or other badge engineering) but they get abused quite a bit by
the other folks and yet they're still accurate, reliable and holding
together when I go to use one.

Meanwhile, I'll look into AoE for linear psu designs. (I happen to have
a copy but it can be a little dense for my skill level at times).

Thanks again.

-J

 

[Ian Field]

<mroberds@att.net> wrote in message news:lks75r$rk9$1@dont-email.me...

Jurd <guitardorkspamspameggsandham74@gmail.com> wrote:
I'm not above dumpster diving and salvaging parts, but I'll suspect
most transformers in consumer electronics are going to be for 9V-12V
output. A ~36V or whatever might be rare.

Look for (solid-state) stereo amplifiers, or tuners with built-in
amplifiers. These usually have a big transformer with a center-tapped
winding that originally was used to generate +/- 30 to 60 V DC for the
main audio output

You beat me to it!

Salvage transformers are pretty much drying up - some end user disposals
houses still get the occasional antique computer with linear PSU, you can
get some really chunky transformers - but it could be a long wait.

Radio hams tend to stick with linear PSUs because switchers tend to be
RF-noisy, AFAIK - some ham magazines still advertise parts stockists.

 

[Michael Black]

On Tue, 13 May 2014, Ian Field wrote:

mroberds@att.net> wrote in message news:lks75r$rk9$1@dont-email.me...
Jurd <guitardorkspamspameggsandham74@gmail.com> wrote:
I'm not above dumpster diving and salvaging parts, but I'll suspect
most transformers in consumer electronics are going to be for 9V-12V
output. A ~36V or whatever might be rare.

Look for (solid-state) stereo amplifiers, or tuners with built-in
amplifiers. These usually have a big transformer with a center-tapped
winding that originally was used to generate +/- 30 to 60 V DC for the
main audio output

You beat me to it!

Salvage transformers are pretty much drying up - some end user disposals
houses still get the occasional antique computer with linear PSU, you can get
some really chunky transformers - but it could be a long wait.

I didn't mention them precisely because I'm not seeing them like I used
to.

I was thinking recently that some things are disappearing, and I never
stocked up. They seemed so plentiful, it seemed impossible that they'd
all stop.

I needed some UHF transistors for something, and realized I should have
stocked up when there were endless tv sets being tossed out. There are
fewer analog sets in the garbage, and the ones I keep noticing are
massive, too much trouble to handle to get parts out of.

There was a period when I'd grab variable capacitors out of any radio I
saw that had no more value (and wasn't worth bringing home for the rest of
the parts) and those are mostly gone. Certainly I'm not seeing them.

There was a time when I was paying a few dollars a piece for clunky early
generation cellphones, becuase the parts were recognizable and full size.
But those are gone too, and you can't pull much out of a tiny pocket
cellphone, the parts are way too small, and the integration means you
don't find many parts that can be reused.

Michael

Radio hams tend to stick with linear PSUs because switchers tend to be
RF-noisy, AFAIK - some ham magazines still advertise parts stockists.

 

[Ian Field]

"Michael Black" <et472@ncf.ca> wrote in message
news:alpine.LNX.2.02.1405131946280.23300@darkstar.example.org...

On Tue, 13 May 2014, Ian Field wrote:



mroberds@att.net> wrote in message news:lks75r$rk9$1@dont-email.me...
Jurd <guitardorkspamspameggsandham74@gmail.com> wrote:
I'm not above dumpster diving and salvaging parts, but I'll suspect
most transformers in consumer electronics are going to be for 9V-12V
output. A ~36V or whatever might be rare.

Look for (solid-state) stereo amplifiers, or tuners with built-in
amplifiers. These usually have a big transformer with a center-tapped
winding that originally was used to generate +/- 30 to 60 V DC for the
main audio output

You beat me to it!

Salvage transformers are pretty much drying up - some end user disposals
houses still get the occasional antique computer with linear PSU, you can
get some really chunky transformers - but it could be a long wait.

I didn't mention them precisely because I'm not seeing them like I used
to.

I was thinking recently that some things are disappearing, and I never
stocked up. They seemed so plentiful, it seemed impossible that they'd
all stop.

I needed some UHF transistors for something, and realized I should have
stocked up when there were endless tv sets being tossed out. There are
fewer analog sets in the garbage, and the ones I keep noticing are
massive, too much trouble to handle to get parts out of.

Last night I found a WW power resistor with wire just right for rewinding
(expensive) E-cigarette cartomisers, I might get as many as 20 rewinds out
of that resistor. At one time I had a large box of resistors salvaged from
scrap CTVs, they became less common as TV designs became more energy
efficient so I binned loads of them - I wish I still had them now!

DVB tuners still use UHF transistors - they're just PITA SMD packages. The
old pill style transistors were easy to use but the leads were very fragile.

For prototyping with the SMD dual gate MOSFETs, I scribe a 2x2 bit of
Veroboard to make 4 lands, the pins just about straddle the lands. and if
you centre it neatly don't foul the holes so you can solder in 4 bits of TC
wire for connecting to the outside world.

 

[Ian Field]

"Jurd" <guitardorkspamspameggsandham74@gmail.com> wrote in message
news:ll0q90$hh9$1@news.albasani.net...

On 5/13/2014 1:52 PM, Ian Field wrote:


mroberds@att.net> wrote in message news:lks75r$rk9$1@dont-email.me...
Jurd <guitardorkspamspameggsandham74@gmail.com> wrote:
I'm not above dumpster diving and salvaging parts, but I'll suspect
most transformers in consumer electronics are going to be for 9V-12V
output. A ~36V or whatever might be rare.

Look for (solid-state) stereo amplifiers, or tuners with built-in
amplifiers. These usually have a big transformer with a center-tapped
winding that originally was used to generate +/- 30 to 60 V DC for the
main audio output

You beat me to it!

Salvage transformers are pretty much drying up - some end user disposals
houses still get the occasional antique computer with linear PSU, you
can get some really chunky transformers - but it could be a long wait.



My city has a pretty comprehensive electronics recycling system in place.
It's good for the big picture and all because it keeps recyclable
resources out of landfills, but for guys like me it means that 95% of
'broken' electronics go to a 24/7 monitored dropoff site instead of to the
curb.

However, it's the insult to injury that makes it the worst- As I
mentioned previously, I work for an electronics recycler so I get to see
(literally) hundreds of thousands of pounds of this stuff on any given
workday. The caveat: I can't have *any* of it. I can't even *buy* it at
all.

That would be too much for me to take - I'd be looking for a job where it
was out of sight out of mind.