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'[EE] Will phone charger work as a 5v DC power supp'
2005\05\11@160925 by Lindy Mayfield

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face
I found today lying around (and scavenged) a phone charger that reads on it:  Output 5.0v DC 1.7A.

Can I use this as a power supply to my breadboards for simple projects, Pics and other testing, etc?




2005\05\11@161506 by Paul James E.

picon face

Yes you can, but the filtering on the output may not be very good,
and it may not be regulated to 5 volts.   It probably is, but no
guarantee.   I would build up a dummy load out of some resistors
and check it out that way.  Or you could try powering something
that takes 5 volts, but that would be risky.

                                           Regards,

                                             Jim



> I found today lying around (and scavenged) a phone charger that reads
> on it:  Output 5.0v DC 1.7A.
>
> Can I use this as a power supply to my breadboards for simple projects,
> Pics and other testing, etc?
>
>
>
>
> --

2005\05\11@161921 by Kenneth Lumia

picon face
Probably not.  Unless it is regulated, the output voltage will
be well above 5.0 volts unless it is loaded close to its
maximum output current.  A quick measurement with a
voltmeter and no load should show whether or not it is regulated.

ken
spam_OUTklumiaTakeThisOuTspamadelphia.net

{Original Message removed}

2005\05\11@163129 by Lindy Mayfield

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face
Do you mean it might not be exactly 5 volts, or that it might fluctuate?  Can I check it with my multimeter?  

Would it be ok if I used a 5v voltage regulator?

Is this along the same lines as to why those small 220v to 110v converters say that you cannot use them with electronics?  

{Original Message removed}

2005\05\11@163219 by Richard Prosser

picon face
Lindy,
Yes - but you will probably still need a regulator to get a smooth 5V
out of it. Some plugpacks include a regulator, most do not.
Those that don't will provide something like 5V at the rated current
but the output voltage is likely to be significantly higher under
lower load conditions.
Protection against overload is likely to be minimal - possibly a
thermal fuse - so an inadvertant short could break it.
If it does not include a regulator, then it is likely to have
significant ripple under loaded conditions.

I'd measure the output voltage under no load, likely maximum load
(100mA ?) and full load conditions & work out what sort of regulator
is needed - e.g. at 100mA if the volts exceed ~7V then you can
probably just fit a 7805, rather than a LDO type.
If you can view the output on a scope then use the minimum trough
voltage for the determination. Otherwise add a good sized electrolytic
to the input of the regulator.

Richard P

On 5/12/05, Lindy Mayfield <.....Lindy.MayfieldKILLspamspam@spam@eur.sas.com> wrote:
> I found today lying around (and scavenged) a phone charger that reads on it:  Output 5.0v DC 1.7A.
>
> Can I use this as a power supply to my breadboards for simple projects, Pics and other testing, etc?
>
> -

2005\05\11@163804 by Lindy Mayfield

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face
I checked it with the multimeter and it shows 5.1 volts DC.

-----Original Message-----
From: piclist-bouncesspamKILLspammit.edu [.....piclist-bouncesKILLspamspam.....mit.edu] On Behalf Of Kenneth Lumia
Sent: Wednesday, May 11, 2005 22:19
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Will phone charger work as a 5v DC power supply?

Probably not.  Unless it is regulated, the output voltage will
be well above 5.0 volts unless it is loaded close to its
maximum output current.  A quick measurement with a
voltmeter and no load should show whether or not it is regulated.

ken
EraseMEklumiaspam_OUTspamTakeThisOuTadelphia.net

----- Original Message -----
From: "Lindy Mayfield" <Lindy.Mayfieldspamspam_OUTeur.sas.com>
To: "Microcontroller discussion list - Public." <@spam@piclistKILLspamspammit.edu>
Sent: Wednesday, May 11, 2005 4:08 PM
Subject: [EE] Will phone charger work as a 5v DC power supply?


>I found today lying around (and scavenged) a phone charger that reads on
>it:  Output 5.0v DC 1.7A.
>
> Can I use this as a power supply to my breadboards for simple projects,
> Pics and other testing, etc?
>
>
>
>
> --

2005\05\11@163931 by Carlos Marcano

picon face
You could probably add a 7805 (if the output meets the specs) and use
it. Not very efficient but quick and dirty.

Regards,
*Carlos Marcano*
-Guri, Venezuela-

On 5/11/05, Kenneth Lumia <KILLspamklumiaKILLspamspamadelphia.net> wrote:
> Probably not.  Unless it is regulated, the output voltage will
> be well above 5.0 volts unless it is loaded close to its
> maximum output current.  A quick measurement with a
> voltmeter and no load should show whether or not it is regulated.
>
> ken
> RemoveMEklumiaTakeThisOuTspamadelphia.net

2005\05\11@164028 by Eric Jorgensen

picon face
It will work if it is a regulated 5V. Most wall warts
that are regulated say so on the enclosure. If it
doesn't say so, it probably isn't.

Eric
KE6US

--- Lindy Mayfield <spamBeGoneLindy.MayfieldspamBeGonespameur.sas.com> wrote:
> I found today lying around (and scavenged) a phone
> charger that reads on it:  Output 5.0v DC 1.7A.
>
> Can I use this as a power supply to my breadboards
> for simple projects, Pics and other testing, etc?
>
>
>
>
> --

2005\05\11@165056 by Lindy Mayfield

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face
When I connect it directly to my voltmeter, am I measuring it with no load?  How would I use my voltmeter to measure it under load?

I assume by load, I would do some Ohms law math and pick a resistor that would give me some amps, no?  I'm trying to think how to measure that with the multimeter.  (It does do current.  Or did I just answer my own question:  A Resistor tied to the charger and using ohms law somehow...?)

I can check it with the scope and I look then for smoothness, no?  Also with a resistor between?

By good sized electrolytic, do you mean like this?


      + -----|+-------  +
Charger    Cap(
      - -----|--------  -



{Original Message removed}

2005\05\11@165134 by Paul James E.

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Lindy,

Plug the phone charger into an outlet (AC) and using a voltmeter measure
the open circuit voltage at the phone connector end.   If it is 5 volts,
or thereabout, you're okay as far as voltage goes.  If you have a scope,
connect the scope to the phone connector end and look at the ripple
voltage.  If it is higher than say a few millivolts, you'll need to filter
it out.   A high value electrolytic capacitor across the output in
parallel with a low value should do it.  There is a formula for
calculating the needed capacitance to achieve a give ripple voltage, but I
don't recall what it is off hand.  But in the past as a starting point, I
have used 2500 uF / amp and it has worked well.  In your case with the
output current rated at 1.7 amp, I'd use a mininum of 5000 uF on the
output.  And I'd put a .047 uF to .1 uF in parallel with this to improve
the high speed transient performance.   This will remove most of the
ripple.  If there is still too much ripple voltage, go to a higher
capacitance on the output.

If the open circuit voltage is higher than 5 volts or so, you'll need an
external regulator to take care of it.   I'd probably just install a 7805
regulator to the output, along with a good heat sink to be able to handle
the current at full load, if you ever get there.

Of course, by adding all these things to the output, if needed, sort of
ruins the portability of the unit.  But you could build all of these
external things into the breadboard, along with a bridge rectifier, then
you could use virtually any wall wart as a power supply regardless of
voltage rating, current rating, polarity, or whether it is AC or DC.

Hope this helps you out.   Have fun.


                                            Regards,

                                              Jim



> Do you mean it might not be exactly 5 volts, or that it might
> fluctuate?  Can I check it with my multimeter?  
>
> Would it be ok if I used a 5v voltage regulator?
>
> Is this along the same lines as to why those small 220v to 110v
> converters say that you cannot use them with electronics?  
>
> {Original Message removed}

2005\05\11@165558 by Lindy Mayfield

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face
May I ask what "regulated" means?  I'm getting a feeling from this thread that it means that it stays steady at a certain voltage.  But I'm thinking, if it is 5 volts, then how would it change?  I'm seeing it has something to do with load, but I'm not quite getting it yet.

Sorry if this is a dumb question, but is a battery regulated? (I realized that the battery goes down slowly over time.  But we are talking seconds here I think, no?)

Is this a similar problem to why those small wallwart sized 220 to 110v converters say that they cannot be used with electronic things?  

{Original Message removed}

2005\05\11@165943 by John J. McDonough

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----- Original Message -----
From: "Lindy Mayfield" <TakeThisOuTLindy.MayfieldEraseMEspamspam_OUTeur.sas.com>
Subject: RE: [EE] Will phone charger work as a 5v DC power supply?


> Do you mean it might not be exactly 5 volts, or that it might fluctuate?
Can I check it with my multimeter?

If you put your meter on it, most likely it will be way above 5 volts.  At
least, that is typical of wall warts.  As you add load, the voltage will
drop, and in all liklihood, it will be somewhere in the neighborhood of 5
volts at 1.7A.

> Would it be ok if I used a 5v voltage regulator?

The answer to any question always seems to be, "it depends".

A 5 volt regulator typically needs a couple of volts overhead, so depending
on how much voltage the wall wart puts out, and how fast it drops, that
might not be such a bad plan.  If the thing puts out, say, 9 volts unloaded,
and drops to 7 at, say, 900 mils, then a 7805 and a couple of caps, and
you're in business for a few hundred mils ... probably plenty for most small
projects.

--McD



2005\05\11@170327 by John J. McDonough

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----- Original Message -----
From: "Lindy Mayfield" <RemoveMELindy.MayfieldspamTakeThisOuTeur.sas.com>
Subject: RE: [EE] Will phone charger work as a 5v DC power supply?


> I checked it with the multimeter and it shows 5.1 volts DC.

Wow.  If it's 5.1 volts unloaded, then maybe it is regulated.  Do you have a
scope to see what kind of ripple you have?  I think you said that it was
rated for 1.7A.  That's a pretty hefty wall wart.  You might try loading it
with a resistor and see whether the voltage stays in the 5 volt
neighborhood.  Keep in mind the power ... it's pretty easy to make those
1/8th watters light up.

--McD


2005\05\11@171243 by John J. McDonough

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face
----- Original Message -----
From: "Lindy Mayfield" <Lindy.MayfieldEraseMEspam.....eur.sas.com>
Subject: RE: [EE] Will phone charger work as a 5v DC power supply?


> May I ask what "regulated" means?  I'm getting a feeling from this thread
that it means that it stays steady at a certain voltage.  But I'm thinking,
if it is 5 volts, then how would it change?  I'm seeing it has something to
do with load, but I'm not quite getting it yet.

Typical wall warts put out a LOT more than their rated voltage under no
load.  It wouldn't surprise me to see a "5 volt" wall wart put out 10 or
even 15 volts with no load.  Many of them will drop close to their rated
voltage with relatively little load, but some take quite a lot of load to
get into the neighborhood.  Since they are intended to work with a
particular piece of equipment, you might well know the load will be
relatively constant, so why pay for more regulation than you need.

> Sorry if this is a dumb question, but is a battery regulated? (I realized
that the battery goes down slowly over time.  But we are talking seconds
here I think, no?)

A battery acts a lot more "regulated" than the typical wall wart.  A
battery's voltage will drop with load, too, but the drop is quite small.

> Is this a similar problem to why those small wallwart sized 220 to 110v
converters say that they cannot be used with electronic things?

More likely it is the noise.  A lot of equipment expects the power to look
something like an AC power line, which is a pretty good sine wave.  A
converter likely will have a square wave output, and it may well have an
asymmetrical square wave.  A motor, for example, won't really care if the
peaks are way too high as long as the average is in the ballpark.

--McD


2005\05\11@171340 by olin_piclist

face picon face
Lindy Mayfield wrote:
> I found today lying around (and scavenged) a phone charger that reads
> on it:  Output 5.0v DC 1.7A.
>
> Can I use this as a power supply to my breadboards for simple
> projects, Pics and other testing, etc?

Maybe.  A charger is not the same thing as a power supply, and the meaning
of the ratings can be different.  In the case of the charger, the votage
rating may apply only when a battery is connected.  If it's a "smart"
charger, it may do all manner of strange things depending on load and over
time.  In your case, dumber is better.  Test it and see.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\05\11@171717 by Spehro Pefhany

picon face
At 10:08 PM 5/11/2005 +0200, you wrote:
>I found today lying around (and scavenged) a phone charger that reads on
>it:  Output 5.0v DC 1.7A.
>
>Can I use this as a power supply to my breadboards for simple projects,
>Pics and other testing, etc?

Most modern cell phone chargers (especially ones that put out >5W) are
small regulated switching power supplies in a wall-wart form factor.
It should be fine for that purpose, however if you're into analog you may
have problems with noise on the 5V line.

If it's a switching supply it will often (but not always) have a universal
input range (eg. 85-250VAC) and will be quite light compared to typical
wall-warts supplied with cheap prouducts.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
EraseMEspeffspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Inexpensive test equipment & parts    http://search.ebay.com/_W0QQsassZspeff




2005\05\11@172018 by Lindy Mayfield

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Really?  It's just a normal sized mobile phone charger that I found in a colleague's desk that I rifled through after he had left the company.  (-:

And that was quite a while after he left, like some months!  This is in Europe, in Germany.  I know in the US, you have to get to the guys desk first thing the next morning, early, and even then you're only lucky to find some paper clips. (-:

{Original Message removed}

2005\05\11@183754 by Kenasw

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face

> May I ask what "regulated" means?  I'm getting a feeling from this thread
that it means that it stays steady at a certain voltage.  But I'm thinking,
if it is 5 volts, then how would it change?  I'm seeing it has something to
do with load, but I'm not quite getting it yet.

Linsey,
Regulated mean that the voltage will be what was written on the box
and the ripple is reduced to something insignificant, so you might get
5.000V with no load and 5.001V with load.
Why would a voltage change, because the resistance of electronic
equipment is variable.

>
> Sorry if this is a dumb question, but is a battery regulated? (I realized
that the battery goes down slowly over time.  But we are talking seconds
here I think, no?)

A battery will not qualify as "regulated" because
over time the voltage will become less and less. However, a battery will not
have
ripple.


2005\05\11@191615 by Glenn Jones

picon face
Many phone charger's I've seen are fancier than standard unregulated
transformer wall warts. They usually seem to be a regulated switchmode
supply in a tiny package. Since it is rated for 1.7A I would guess
this is what he has.


On 5/11/05, John J. McDonough <RemoveMEmcdEraseMEspamEraseMEis-sixsigma.com> wrote:
> {Original Message removed}

2005\05\11@192736 by David P Harris

picon face
Glenn Jones wrote:

>Many phone charger's I've seen are fancier than standard unregulated
>transformer wall warts. They usually seem to be a regulated switchmode
>supply in a tiny package. Since it is rated for 1.7A I would guess
>this is what he has.
>
>  
>
Yes, probably.  Chetan picked some up for an incredibly inexpensive
price, and I have used them as a 5V supply.

The light weight is a real plus, too.

David


2005\05\11@192759 by olin_piclist

face picon face
kenasw@btinternet.com wrote:
> Regulated mean that the voltage will be what was written on the box
> and the ripple is reduced to something insignificant, so you might get
> 5.000V with no load and 5.001V with load.

You might, but that would be very impressive even for a regulated power
supply!

Also, regulated doesn't necessarily mean no ripple.  Regulated only means
that there is something that is actively trying to maintain (regulate) the
output voltage despite variations in input voltage and load current draw.
Many switching power supplies are well regulated, but have significant
ripple too.  There are many parameters for measuring power supply
performance, and "regulated" only tells you a little about the
implementation.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\05\11@193739 by Lindy Mayfield

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face
When does ripple cause problems?  Will a rippled (rippling?) input cause a problem with PICS?  More specifically, let's say I'm using a PIC to blink LED's or control a small stepper motor.  Would this be a problem?

{Original Message removed}

2005\05\11@201120 by Jinx

face picon face

> When does ripple cause problems?  Will a rippled (rippling?) input
> cause a problem with PICS?  More specifically, let's say I'm using
> a PIC to blink LED's or control a small stepper motor.  Would this
> be a problem?

Well, you wouldn't want to use a rippling supply as Vref, and you'd
need to be sure that ripple doesn't exceed Vdd max. If you're unsure
about the charger (if it were me I'd put it on the scope with various
loads to see what the o/p really looks like), buffer it with a reservoir
cap, perhaps with a series resistor and/or diode. Or even a zener to
clip anything over 5V1

LEDs shouldn't present too much of a problem but a stepper will
probably put noise on Vdd, which can upset logic/reset pins. That's
where the R-C-ZD above can help to isolate the PIC's Vdd from
the raw charger V the stepper is using

BTW, I had a PIC board come back to me for repairs the other day.
It normally runs on an automotive 12V battery but had been hooked
up to a car battery charger (basically a transformer and diode). The
average DC o/p was in spec but regulator and PIC were toasted, so
don't under-estimate ripple

2005\05\11@201930 by Kenasw

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face


> When does ripple cause problems?  Will a rippled (rippling?) input cause a
problem with PICS?  More specifically, let's say I'm using a PIC to blink
LED's or control a small stepper motor.  Would this be a problem?

The datasheet tells you to use regulated, if you don't then expect strange
results.
Are you just trying to be difficult?

2005\05\11@201956 by Dwayne Reid

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face
At 02:08 PM 5/11/2005, Lindy Mayfield wrote:
>I found today lying around (and scavenged) a phone charger that reads on
>it:  Output 5.0v DC 1.7A.
>
>Can I use this as a power supply to my breadboards for simple projects,
>Pics and other testing, etc?

Probably.  Given that it says "5.0v DC 1.7A", it is most likely a SMPS
unit.  It is most likely both well regulated and well filtered.

Grab your trusty mulit-meter and measure the output with both the AC and DC
functions.  DC should show very close to 5V, AC should show very close to 0V.

Now grab any small 12V lamp (dashboard lamps work well).  Connect it to the
output of the supply while the meter is reading the DC voltage.  The
voltage should remain the same, whether the lamp is connected or not.

If all the above are true, I'd say that the unit is ideal for your uses.

dwayne

--
Dwayne Reid   <RemoveMEdwaynerspam_OUTspamKILLspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

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2005\05\11@204651 by Chetan Bhargava

picon face
Thanks David,

Good thing I liked about those is the folding mains plug, 100v-220v
operating range and light weight indeed!

I'll flock around the store sometime this month, will see if I can get
some more of those.

Regards,

--
Chetan Bhargava
Web: http://www.bhargavaz.net
Blog: http://microz.blogspot.com


On 5/11/05, David P Harris <RemoveMEdpharrisTakeThisOuTspamspamtelus.net> wrote:
>
> Yes, probably.  Chetan picked some up for an incredibly inexpensive
> price, and I have used them as a 5V supply.
>
> The light weight is a real plus, too.
>
> David

2005\05\11@205322 by Josh Koffman

face picon face
I don't think the original poster is trying to be difficult. To me,
the question seemed more of a "what is ripple and what will it do"
rather than a "I know what ripple is, what happens if I ignore
instructions".

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On 5/11/05, EraseMEkenaswspamspamspamBeGonebtinternet.com <RemoveMEkenaswKILLspamspambtinternet.com> wrote:
> > When does ripple cause problems?  Will a rippled (rippling?) input cause a
> problem with PICS?  More specifically, let's say I'm using a PIC to blink
> LED's or control a small stepper motor.  Would this be a problem?
>
> The datasheet tells you to use regulated, if you don't then expect strange
> results.
> Are you just trying to be difficult?

2005\05\11@210631 by Bob Ammerman

picon face
>From what I have seen it is reasonably usual for the actual charging control
circuit to be in the phone, and the 'charger' to be nothing more than a raw
(often regulated) supply.

Bob Ammerman
RAm Systems

2005\05\12@062838 by Alan B. Pearce

face picon face
>Good thing I liked about those is the folding mains plug,
>100v-220v operating range and light weight indeed!

I like the one that came with my Palm for this reason. When the US plug is
folded in they have a slide on converter for foreign (from US that is)
connectors.

2005\05\12@071435 by olin_piclist

face picon face
Lindy Mayfield wrote:
> When does ripple cause problems?  Will a rippled (rippling?) input
> cause a problem with PICS?

Ripple means the supply bounces around hopefully between two known limits.
First and foremost those limits must not exceed the PICs Vdd limits for its
operating mode.  As long at that is true, the PIC should continue to work.
However, the external circuit may not be so happy with that.  If you're
trying to make analog measurement, supply ripple can be a problem.  The same
is true if the PIC is trying to produce an output voltage for uses not
relative to the supply voltage.  For example, if the PIC is producing PWM
that will be low pass filtered and driven into a speaker with respect to
ground, then you will hear the ripple to the extent it is in the range of
frequencies passed by the filter and the speaker.

High frequency ripple is also bad due to its dV/dt, but that is usually not
an issue for 120Hz power line ripple.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\05\12@072316 by olin_piclist

face picon face
kenasw@btinternet.com wrote:
> The datasheet tells you to use regulated, if you don't then expect
> strange results.

Oh?  What data sheet?  Where?  I have never seen such statement in a PIC
data sheet.

The relevant specs that I know of are the min/max Vdd limits during
operation.  I don't recall the data sheet telling me (nor should it) how to
produce this voltage, only what it needs to be.

> Are you just trying to be difficult?

I thought it was a legitimate question that deserved a straight answer.  If
you're going to be uppity, you need to be right first.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\05\12@073710 by Spehro Pefhany

picon face
At 07:23 AM 5/12/2005 -0400, you wrote:
>kenaswSTOPspamspamspam_OUTbtinternet.com wrote:
>>The datasheet tells you to use regulated, if you don't then expect
>>strange results.
>
>Oh?  What data sheet?  Where?  I have never seen such statement in a PIC
>data sheet.
>
>The relevant specs that I know of are the min/max Vdd limits during
>operation.  I don't recall the data sheet telling me (nor should it) how to
>produce this voltage, only what it needs to be.

Presumably there may be some upper limit to the dv/dt of Vdd, but I've never
seen that specified, only the lower limit for proper reset (along with the
oh-so-stupid specification that it must start from a *maximum* of exactly
zero volts to guarantee reset, but I digress).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spamBeGonespeffSTOPspamspamEraseMEinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\05\12@074350 by Lindy Mayfield

flavicon
face
Sorry, I wasn't trying to be difficult.  I just honestly haven't noticed the term ripple in anything I've studied so far about PICS and electronics, and I was legitimately curious to understand more about what it was.  (Besides being a song by the Grateful Dead.)



> {Original Message removed}

2005\05\12@085202 by Steve Halla - LEAP

flavicon
face
Generally, most phone chargers will need 5.5V to successfully and completely
charge its battery, expecting the battery is either a 3 cell Ni or 1 cell
Li.

I agree that ripple is a greater concern with ADC measurements and other
components in the design, and less of a concern for most micros as long as
the supply voltage does not drop below or rise above specs.

{Original Message removed}

2005\05\12@092505 by jrem

picon face
I think it's a troll.  The folks that post here don't "rifle through"
ex-workers desks looking for wall warts to power their projects, lord
knows they come our way without having to look for them.  And my guess
is there are more lurkers than posters.  Good thing the April Fools
post was just  a joke . . .

On to Hamvention in Dayton ! ! !


--- Josh Koffman <KILLspamjoshybearspamBeGonespamgmail.com> wrote:
{Quote hidden}

> --

2005\05\12@093743 by Spehro Pefhany

picon face
At 06:25 AM 5/12/2005 -0700, you wrote:
>I think it's a troll.  The folks that post here don't "rifle through"
>ex-workers desks looking for wall warts to power their projects, lord
>knows they come our way without having to look for them.

I've got an old filing cabinet drawer full of them, not counting
a thousand or so new ones. ;-)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spamBeGonespeffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\05\12@095603 by Kenasw

flavicon
face
Linsey,
If you want to know what ripple is, why don't you open an electronics
general purpose text book, they normally have whole chapters on
power supplies?

----- Original Message -----
From: "Lindy Mayfield" <.....Lindy.Mayfieldspam_OUTspameur.sas.com>
To: "Microcontroller discussion list - Public." <TakeThisOuTpiclist.....spamTakeThisOuTmit.edu>
Sent: Thursday, May 12, 2005 12:42 PM
Subject: RE: [EE] Will phone charger work as a 5v DC power supply?


> Sorry, I wasn't trying to be difficult.  I just honestly haven't noticed
the term ripple in anything I've studied so far about PICS and electronics,
and I was legitimately curious to understand more about what it was.
(Besides being a song by the Grateful Dead.)
>
>
>
> > {Original Message removed}

2005\05\12@104630 by Lindy Mayfield

flavicon
face
Thanks, I have the Art of Electronics at home and I'll look it up tonight.  



{Quote hidden}

2005\05\12@114103 by peiserma

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face
piclist-bounces@mit.edu wrote:
> At 06:25 AM 5/12/2005 -0700, you wrote:
>> I think it's a troll.  The folks that post here don't "rifle through"
>> ex-workers desks looking for wall warts to power their projects, lord
>> knows they come our way without having to look for them.
>
> I've got an old filing cabinet drawer full of them, not counting
> a thousand or so new ones. ;-)

trolls? :-)

2005\05\12@141044 by Lindy Mayfield

flavicon
face
Thanks to the kind and patient help of people in this list, plus RTFM-ing and sacrifices to the Google Gods, I now have the answer for you.  So be ye not afraid.

A diode blocks AC and allows DC to pass.  By using the correct combination of diodes you can convert an AC current into a DC current.  (Pages 45-46 of The Art of Electronics, 2nd Ed., Page 47 of Forrest Mimms' Getting Started in Electronics.)  This diode circuit is called a full-wave rectifier.  The output of this looks like a bunch of speed bumps next to each other.  Forrest calls this a "pulsating voltage" (page 36) while Horowitz & Hill call it a "ripple" (Page 46).  

How to fix this?  This gets confusing.  Forrest Mimms shows on page 36 that a capacitor connected to + and - will smooth out (filter) the output voltage.  But on page 45 of The Art, Figure 1.72, they show a resistor on the + side with the capacitor crossing + and -.  However on page 37, Mimms calls this particular RC circuit an Integrator which would turn a square wave into a sawtooth wave.

Hope this helps!  (-:


-----Original Message-----
From: spamBeGonepiclist-bounces@spam@spamspam_OUTmit.edu [TakeThisOuTpiclist-bouncesspamspammit.edu] On Behalf Of kenaswEraseMEspambtinternet.com
Sent: Thursday, May 12, 2005 15:56
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Will phone charger work as a 5v DC power supply?

Linsey,
If you want to know what ripple is, why don't you open an electronics
general purpose text book, they normally have whole chapters on
power supplies?



2005\05\12@152557 by James Newton, Host

face picon face
> A diode blocks AC and allows DC to pass.  By using the
> correct combination of diodes you can convert an AC current
> into a DC current.  (Pages 45-46 of The Art of Electronics,
> 2nd Ed., Page 47 of Forrest Mimms' Getting Started in
> Electronics.)  This diode circuit is called a full-wave
> rectifier.  The output of this looks like a bunch of speed
> bumps next to each other.  Forrest calls this a "pulsating
> voltage" (page 36) while Horowitz & Hill call it a "ripple"
> (Page 46).  

Each is correct from the authors point of view. Ripple is the word most
often used when people are talking about power supplies or other
applications where the desired voltage does not change. Pulsating is just a
general (and pretty accurate) description of that wave.


> How to fix this?  This gets confusing.  Forrest Mimms shows
> on page 36 that a capacitor connected to + and - will smooth
> out (filter) the output voltage.  But on page 45 of The Art,
> Figure 1.72, they show a resistor on the + side with the
> capacitor crossing + and -.  However on page 37, Mimms calls
> this particular RC circuit an Integrator which would turn a
> square wave into a sawtooth wave.

The resistor helps to "disconnect" the capacitor, and therefore the output
of the circuit, from the input. It allows the capacitor to have more effect
with a smaller farad rating.

Again, the terms are correct from the authors point of view. A ripple filter
is an integrator. Hopefully, the output is integrated so much that it
approaches DC. With the right components, the sawtooth will be almost flat.
With other components, the sawtooth will reach almost the full range of the
square wave.

In each case, the VALUES of the components in the circuit probably mean as
much as the connections of the components. An integrator will have a larger
resistor and a smaller capacitor for less integration. A ripple filter will
have a much smaller resistor (probably none aka a resistor of 0 ohms) and a
larger capacitor for more integration.

Hope that helps.

---
James Newton: PICList webmaster/Admin
RemoveMEjamesnewtonEraseMEspamspam_OUTpiclist.com  1-619-652-0593 phone
http://www.piclist.com/member/JMN-EFP-786
PIC/PICList FAQ: http://www.piclist.com



2005\05\12@163728 by Lindy Mayfield

flavicon
face
Is it safe to say then that a ripple or an uneven DC output from an AC to DC converter is due to the omission of some very cheap and simple passive components?  And if so, where they left out just to keep costs down because they aren't necessary when charging a battery or providing the input DC supply like a wall-wart does? And as a hobby electronics person, I can just understand that and add them myself if I really need a more filtered DC output?

(I would like to say I've really learned a lot from this thread and I do really appreciate the time people took to explain things.)



{Original Message removed}

2005\05\12@172632 by Dave VanHorn

flavicon
face
At 03:36 PM 5/12/2005, Lindy Mayfield wrote:
>Is it safe to say then that a ripple or an uneven DC output from an
>AC to DC converter is due to the omission of some very cheap and
>simple passive components?  And if so, where they left out just to
>keep costs down because they aren't necessary when charging a
>battery or providing the input DC supply like a wall-wart does? And
>as a hobby electronics person, I can just understand that and add
>them myself if I really need a more filtered DC output?
>
>(I would like to say I've really learned a lot from this thread and
>I do really appreciate the time people took to explain things.)

Cheap is all in your definition.
I like to use AC wall warts, because they are significantly less
expensive than DC output, or filtered/regulated ones.
Plus, I really distrust putting the regulation on the wrong side of a
long transmission line.

On pretty much anything I've designed, the wall wart will be as
simple as possible, and the smarts will be in the product.

2005\05\12@174853 by Mark Rages

face picon face
On 5/12/05, Lindy Mayfield <@spam@Lindy.MayfieldRemoveMEspamEraseMEeur.sas.com> wrote:
> Is it safe to say then that a ripple or an uneven DC output from an AC to DC converter is due to the omission of some very cheap and simple passive components?  And if so, where they left out just to keep costs down because they aren't necessary when charging a battery or providing the input DC supply like a wall-wart does? And as a hobby electronics person, I can just understand that and add them myself if I really need a more filtered DC output?
>
> (I would like to say I've really learned a lot from this thread and I do really appreciate the time people took to explain things.)
>

I think you're catching on.  What makes this discussion kind of
confusing is there are generally two kinds of plug-in adapters:

1)  Old-fashioned "wall-wart".  AC input->Transformer->diode
bridge->big capacitor.  These are not very well regulated.  Due to
resistance in the transformer, the output voltage goes down as you
draw more current. At no load they generate a voltage about 40% above
rated. At the rated current, should output the rated voltage.  If it
is made for charging only, the capacitor may be omitted or skimpy.
You can compensate with a bigger capacitor in your circuit.

2) New-fangled "brick".  AC input->rectifier->high-DC
voltage->switchmode regulator->output.  These are useally pretty well
regulated to the rated voltage and ripple should be pretty small too.

It sounds like you've got the second type.

If you don't have a scope, you can measure ripple by setting your
voltmeter on AC volts with a capacitor in series to block DC. (most
multimeters have the capacitor built-in for their AC range, but some
analog ones don't)   Ripple will go up as the load increases, so
measure under the load of your circuit.    Note, the ripple is not
exactly sinusoidal, so RMS readings will be slightly inaccurate with
this method and a typical cheap meter.  Still, it's in the ballpark to
tell you if ripple will be a problem with your supply or not.

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.
 - fortune cookie

2005\05\12@182310 by olin_piclist

face picon face
Lindy Mayfield wrote:
> Is it safe to say then that a ripple or an uneven DC output from an
> AC to DC converter is due to the omission of some very cheap and
> simple passive components?

No.  Depending on the voltages, currents, frequencies, size, weight, power
dissipation, etc, throwing more passive components at the problem is not a
feasible fix.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\05\12@185805 by Kenasw

flavicon
face
> I think you're catching on.  What makes this discussion kind of
> confusing is there are generally two kinds of plug-in adapters:

And what is even more confusing is that battery chargers are not
power supplies, they are what they are - battery chargers. This
means that using them for anything else other than what they are
designed for will lead to strange things happening. They usually
do not have a smoothing capacitor, why? because the batteries
are the capacitor, think about it, a 1.2v nicad battery will
immediately soak up all the ripple, so you don't need a
capacitor. On the other hand, connect to a pic, and expect
a burning smell to tickle your nose.

{Quote hidden}

> --

2005\05\12@193221 by Jinx

face picon face
> Cheap is all in your definition

> On pretty much anything I've designed, the wall wart will be as
> simple as possible, and the smarts will be in the product.

I'm truly disappointed for a customer who accidentally and easily
blew up a $300 Cry Baby Wah pedal. Dunlop supply a wall wart
with a -ve tip, all of his other effects pedals use the more common
+ve tip. You can guess what happened. Sure, ultimately his fault
but for the sake of a 1c diode........

2005\05\12@193841 by Dave VanHorn

flavicon
face
At 06:32 PM 5/12/2005, Jinx wrote:
> > Cheap is all in your definition
>
> > On pretty much anything I've designed, the wall wart will be as
> > simple as possible, and the smarts will be in the product.
>
>I'm truly disappointed for a customer who accidentally and easily
>blew up a $300 Cry Baby Wah pedal. Dunlop supply a wall wart
>with a -ve tip, all of his other effects pedals use the more common
>+ve tip. You can guess what happened. Sure, ultimately his fault
>but for the sake of a 1c diode........

So I should burden my product design, for a few million devices, to
prevent someone from having an accident when they plug in my power
pack to a different device that it wasn't designed for?

Also, a 1C diode would leave the power pack in a state that I
couldn't use it in.

What else should I add in to all five million of my power packs, to
assure that I have the right voltage output for his pedal?


I'm a great believer in "if it fits, it works, or at least it does no
harm", but in the world of power packs, the damage was done when I
was in grade school, by manufacturers who failed to see the need for
and to establish a standard.


2005\05\12@200932 by Jinx

face picon face
> >+ve tip. You can guess what happened. Sure, ultimately his fault
> >but for the sake of a 1c diode........
>
> So I should burden my product design, for a few million devices,
> to prevent someone from having an accident when they plug in my
> power pack to a different device that it wasn't designed for?

No, I was alluding to what you said here -

"On pretty much anything I've designed, the wall wart will be as
simple as possible, and the smarts will be in the product"

If the product had a 1c blocking diode, not the wall wart

An SMT diode is probably 0.1c, if that, but working back
through all the mark-ups, it's still around 1/50,000th (in my
estimation) of the production cost. Hardly over-engineering

I won't be hypocritical - accidents do happen, through inattention
or ignorance (eg my customer who used a 12V charger instead of
a 12V battery - my boards have a blocking diode but a virtually
AC supply is just too brutal) and I have killed my own circuits.
Although I routinely add a diode to everything now. In some cases,
when the customer has to supply their own wall wart, a full bridge

2005\05\12@200933 by phil B

picon face
Actually, yes, you should.  How many times have you
"lost" the original wall wart that came with a
product?  Or put a bunch of gear into a box and when
unpacking, go "hmm, which WW is which?".  In fact,
most WWs don't have an easy way of associating it with
the equipment it came with. Some devices don't even
say what the polarity requirement is.  Its completely
unreasonable to expect the customer to get it right
all the time.

Personally, I always check the polarity requirements
on the product but I'm definitely not the average
consumer.

The guy that blew up his pedal should be totally
p*ssed at the dunlop.  it was their fault for sloppy
engineering (selecting an uncommmon polarity and not
protecting).

--- Dave VanHorn <EraseMEdvanhornspam@spam@dvanhorn.org> wrote:
{Quote hidden}

> --

2005\05\12@201647 by Dave VanHorn

flavicon
face
At 07:09 PM 5/12/2005, Jinx wrote:
> > >+ve tip. You can guess what happened. Sure, ultimately his fault
> > >but for the sake of a 1c diode........
> >
> > So I should burden my product design, for a few million devices,
> > to prevent someone from having an accident when they plug in my
> > power pack to a different device that it wasn't designed for?
>
>No, I was alluding to what you said here -
>
>"On pretty much anything I've designed, the wall wart will be as
>simple as possible, and the smarts will be in the product"
>
>If the product had a 1c blocking diode, not the wall wart

Ah.. My designs will either survive, or work on wrong polarity DC or AC.

2005\05\12@202955 by Jinx

face picon face

> >If the product had a 1c blocking diode, not the wall wart
>
> Ah.. My designs will either survive, or work on wrong polarity DC
> or AC.

Yes, I like the consumer-friendly approach too. However I take
your point about standards. If I make my product indestructable,
would that lead a customer to take liberties with other products ?
It never ceases to amaze me how reckless people can be when
they don't know what they're doing. "Wonder if it'll work ?"
"Wonder if it'll blow up ?". Then they do it anyway and pfffft

2005\05\12@203419 by Jinx

face picon face
> So I should burden my product design, for a few million devices

I'm not in the position of having to let someone go if I add a diode
to millions of units. Chances are I would have a different attitude,
but hopefully I'd not be that ruthless

Cry Baby is a long-established "name" product (like Fender or
Marshall - sought after) and I expected a little better

2005\05\12@204311 by Dave VanHorn

flavicon
face
At 07:34 PM 5/12/2005, Jinx wrote:
> > So I should burden my product design, for a few million devices
>
>I'm not in the position of having to let someone go if I add a diode
>to millions of units. Chances are I would have a different attitude,
>but hopefully I'd not be that ruthless
>
>Cry Baby is a long-established "name" product (like Fender or
>Marshall - sought after) and I expected a little better

Given the average technical capabilities of musicians, I would have
expected a more bulletproof front end.


2005\05\12@205823 by Spehro Pefhany

picon face
At 12:34 PM 5/13/2005 +1200, you wrote:
> > So I should burden my product design, for a few million devices
>
>I'm not in the position of having to let someone go if I add a diode
>to millions of units. Chances are I would have a different attitude,
>but hopefully I'd not be that ruthless
>
>Cry Baby is a long-established "name" product (like Fender or
>Marshall - sought after) and I expected a little better

On a pure economic basis, you can balance off the cost of unhappy
customers and warranty repairs against the fractional-cent cost of a
series diode (or a reverse-voltage tolerant regulator). Sure you can
argue the warranty repairs, but it's hard to even break even on repairs
these days, and the customer is still left unhappy.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
@spam@speffspam_OUTspam.....interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\05\12@210318 by Dave VanHorn

flavicon
face

I am going through the docs now on a radio repeater by daniels electronics.
Superb design, but it's the sort of thing you pay top dollar for,
then helicopter out to the south pole, and expect to drop it off and
have it work for 6 months without a glitch.

VERY VERY nice.  VERY pricey to build.
Ever seen a receiver that uses four helical filters on the input, and
two on the first local oscillator?

2005\05\12@210442 by Jinx

face picon face
> indestructable

Tut-tut. That was unexcusible

2005\05\13@024044 by Wouter van Ooijen

face picon face
> Yes, I like the consumer-friendly approach too. However I take
> your point about standards. If I make my product indestructable,
> would that lead a customer to take liberties with other products ?

It would probably lead to the customer buying the other product, which
is $.01 cheaper.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\05\13@071645 by olin_piclist

face picon face
Jinx wrote:
> No, I was alluding to what you said here -
>
> "On pretty much anything I've designed, the wall wart will be as
> simple as possible, and the smarts will be in the product"

I agree with that philosophy in general.  Somewhere you're going to have a
full wave bridge, some caps, and some form of regulator.  You're going to
pay for these one way or the other.  And even though wall warts are mass
produced, it's surprising how much more those with regulated outputs cost
over just bare transformers.  It's usually more than the power supply in the
product.

Of course none of this should be a rule.  There are always unique tradeoffs
for every product.  A good case for a wall wart with a switcher is when you
need enough power so that a transformer directly from the AC line would be
too large, or universal input power is important.  I think I'd still want to
put a diode in there unless it's a high volume design.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\05\13@091239 by Gerhard Fiedler

picon face
Wouter van Ooijen wrote:

>> Yes, I like the consumer-friendly approach too. However I take
>> your point about standards. If I make my product indestructable,
>> would that lead a customer to take liberties with other products ?
>
> It would probably lead to the customer buying the other product, which
> is $.01 cheaper.

Not always. In some areas there exists something like brand recognition,
and some brands have a reputation for robustness that isn't earned
overnight or with one product (and not necessarily with actual robustness
either... :). And some people are even willing to pay a premium for that.

For a $300 consumer product, I imagine that distribution channel
distortions make much more of a difference than a $.01 supply protection
diode. In this particular case, the fault can even be predicted to happen,
because it is quite frequent for guitarists to have various effect pedals
from different manufacturers. Pair this with the lack of a standard for
power supply connectors, and I'd say the lack of that diode, overall, is
providing a serious contribution to the entropy level of the universe :)

Gerhard

2005\05\13@093401 by jrem

picon face

<snip>
> > your point about standards. If I make my product indestructable,
> > would that lead a customer to take liberties with other products ?
>
> It would probably lead to the customer buying the other product,
> which
> is $.01 cheaper.

or it might lead to $2.50 additional profit since the mfg'er now
doesn't have to design in the diode, purchase them, stock them, handle
them, get them on the board, and deal with the additional variable of
that component failing quality, trashing the entire assembly.  Instead
they just buy cases of wall warts and sell them as a$12.95 option with
a 50% profit margin for the mfg'er and the distribution chain.

And so what Dunlop lost another customer, there are fourty more in line
to buy the product.  And most of their stuff will never make it out of
some kid's beadroom.


               
Yahoo! Mail
Stay connected, organized, and protected. Take the tour:
http://tour.mail.yahoo.com/mailtour.html

2005\05\13@093416 by Spehro Pefhany

picon face
At 07:17 AM 5/13/2005 -0400, you wrote:

>Of course none of this should be a rule.  There are always unique tradeoffs
>for every product.  A good case for a wall wart with a switcher is when you
>need enough power so that a transformer directly from the AC line would be
>too large, or universal input power is important.

If the product is going to be shipped long distances by air, the weight
saving from using a SMPS adapter should be taken into account. The cost
savings can be in the dollars per kg range. Even if that's not important,
the packing and overall size (cost of sea shipments of electronic goods are
usually determined by the volume, not weight) can be much less if there isn't
a heavy battering ram packed in each box.

Presumably the combination of factors (including international approvals
and universal input) led Microchip to standardize on a 9VDC-out switching
adapter with separate cord and secondary regulation on the products.

I was a bit surprised that Nintendo supplies only a 120V SMPS adapter to
recharge their Gameboy Advance SP. I guess they thought the few pennies
they saved by optimizing the SMPS for a single input voltage was worth
it (it's quite small, and the US/Canada version has a folding AC plug).
I picked up a replacement universal supply for the kid's Gameboy
at the Blockbuster for US8.00 retail. (marked "100-240VAC
5V/1.2A set at 0.32A", whatever that means**!). If you need a tiny wall-plug
5V supply in a hurry at 10pm, there's a possibility (we were heading off
to China*** the next morning and the Gameboy is a vital accessory..
a bit like a sedative). It has a strange rectangular connector, a bit
like USB and Firewire connectors, not sure if mating connectors are
easily available (but it could be cut off).

5.36V no load
5.26V at 100mA

** the original adapter has a 320mA rating, so perhaps the 3rd party
adapter is approved for 1.2A but they've set the current limit at
320mA for this application to match the original.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spamBeGonespeffEraseMEspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
>>>Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff




2005\05\13@094917 by Dave VanHorn

flavicon
face
At 08:38 AM 5/13/2005, Spehro Pefhany wrote:
>At 07:17 AM 5/13/2005 -0400, you wrote:
>
>>Of course none of this should be a rule.  There are always unique tradeoffs
>>for every product.  A good case for a wall wart with a switcher is when you
>>need enough power so that a transformer directly from the AC line would be
>>too large, or universal input power is important.
>
>If the product is going to be shipped long distances by air, the weight
>saving from using a SMPS adapter should be taken into account. The cost
>savings can be in the dollars per kg range.

We are starting to see switchers in wall-warts at wal-mart, which
means that it's cheaper to design in a switcher than to ship the iron.


>  Even if that's not important,
>the packing and overall size (cost of sea shipments of electronic goods are
>usually determined by the volume, not weight) can be much less if there isn't
>a heavy battering ram packed in each box.

That is a factor too, and yes, the power pack can act as a hammer if
it breaks loose.
I have been known to check packing by tossing a packed box of product
off the third floor ledge, and then inspect every unit for damage and
effect on packing materials.


2005\05\13@100919 by J. Gromlich

flavicon
face
Many years ago I worked for a company which make a device
called a Lock-In Amplifier for laboratory measurements. We
had designed special shipping boxes with multiple folded cardboard
pieces which fit into the box around the unit and acted like springs
to absorb jolts.  This was before industry got into using foam-in-place
packing foam and the like.

These packages worked really well most of the time.  One day we
got a unit which was returned for calibration. It had fallen off of a
loading dock or something and landed directly on the end against
which was positioned the front panel. The springs did their job and
the panel would have been fine EXCEPT that the power transformer
mounted in the center rear panel tore loose from its bolts and flew
forward.  It went through 4 circuit boards and came out through the
big analog meter in the center of the front panel.

The unit was a write-off.
The transformer mounting was redesigned, as was the packaging..
Never happened again, AFAIK.

RJG
>
> {Original Message removed}

2005\05\15@054639 by Lindy Mayfield

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My bad.  On page 101 of Mr. Mimms' book where he talks about diode circuits he does use the term "ripple".  

And what is a ripple?  Funny how things move in full circle.  A ripple is simply an AC signal superimposed onto DC.  The VERY thing I was asking people for help understanding on this list in the past year.  (-:  

{Original Message removed}

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