Watson Power Supply
Alasdair
am surprised to see the second thing on the istruction manual is
"WARNING - This unit must not be used to charge lead acid batteries,
run light bulbs, or operate any equipment containing a motor".
Please, can someone tell me why there is this restriction? What harm
can these uses do to the power supply so long as the maximum current
is not exceeded?
--
Alasdair.
c...@nospam.netunix.com
Batteries can pull very heavy currents
Light bulbs often fail to a short circuit
Motors pull heavy starting current, especially when mechanically loaded.
Looks like their output overcurrent protection is not very good.
--
g4jci
METWO
news:0jteq5dtm2ngribdd...@4ax.com...
I use mine to: Charge Lead acid batteries, use for testing motors and lamps,
And never had a problem.
So please let us know what you find out
metwo
Brian Reay
"Alasdair" <ma...@bobaxter.coo.uk> wrote in message
news:0jteq5dtm2ngribdd...@4ax.com...
I suspect the reasons differ between the "loads".
Lead Acid batteries: A normal lead acid battery would be in a sorry state to
sink 25A when discharged, so I doubt it is the load current. Maybe the maker
is concerned what happens if the mains is turned off while the battery is
connected. If this is correct, a series diode would solve the problem. I've
certainly been asked to repair similar style PSUs in the past which were
used to "float charge" a battery and provide a UPS type supply.
Light bulbs: perhaps the cold filament resistance is the issue, allowing a
high peak current the designer is concerned will cause an issue.
Motors: Inductive loads with a low load impedance before they are spinning.
The Watsons are quite nice supplies for the money, I use one on my work
bench.
--
73
Brian G8OSN/W8OSN
www.g8osn.net
Steve
che...@nomail.afraid.org (Jim) wrote:
>
> ... and there's a cooling fan in the W25AM itself!
>
> --
Which on mine has taken to revving up and down like a chav in a Clio,
when I'm only rx'ing!
It wasn't always like that. Then again, it has been switched on
continuously for the last 10 years.
Maybe it was charging batteries, running motors and light bulbs that
porked it?
- Steve
news.virginmedia.com
less because they do not have a transformer in them and thats one of the
expensive parts in a linear power supply....Switch mode power supplies work
differently and do not like --->>>>Inductive loads<-----. This could be like
a electric motor or even a fluorescent lamp or fluorescent tube....Switch
mode power supplies are more energy efficient... cost less and weigh
less...I deal for many more purposes like mobile phone charging...... I
personally dont like them for running radio equipment.. I prefer linear
power supplies..
Comparison of a linear power supply and a switched-mode power supply
Linear power supply Switching power supply Notes
Size and weight If a transformer is used, large due to low operating
frequency (mains power frequency is at 50 or 60 Hz). Small if
transformerless. Smaller due to higher operating frequency (typically 50
kHz-1 MHz) A transformer's power handling capacity of given size and weight
increases with frequency provided that hysteresis losses can be kept down.
Therefore, higher operating frequency means either higher capacity or
smaller transformer.
Output voltage With transformer used, any voltages available; if
transformerless, not exceeding input. If unregulated, voltage varies
significantly with load. Any voltages available. Voltage varies little with
load. A SMPS can usually cope with wider variation of input before the
output voltage changes.
Efficiency, heat, and power dissipation If regulated, output voltage
is regulated by dissipating excess power as heat resulting in a typical
efficiency of 30-40%;[2] if unregulated, transformer iron and copper losses
significant. Output is regulated using duty cycle control, which draws only
the power required by the load. In all SMPS topologies, the transistors are
always switched fully on or fully off. The only heat generated is in the
non-ideal aspects of the components. Switching losses in the transistors,
on-resistance of the switching transistors, equivalent series resistance in
the inductor and capacitors, core losses in the inductor, and rectifier
voltage drop contribute to a typical efficiency of 60-70%. However, by
optimizing SMPS design, the amount of power loss and heat can be minimized;
a good design can have an efficiency of 95%.
Complexity Unregulated may be diode and capacitor; regulated has a
voltage regulating IC or discrete circuit and a noise filtering capacitor.
Consists of a controller IC, one or several power transistors and diodes as
well as a power transformer, inductors, and filter capacitors. Multiple
voltages can be generated by one transformer core. For this SMPSs have to
use duty cycle control. One of the outputs has to be chosen to feed the
voltage regulation feedback loop (Usually 3.3 V or 5 V loads are more fussy
about their supply voltages than the 12 V loads, so this drives the decision
as to which feeds the feedback loop. The other outputs usually track the
regulated one pretty well). Both need a careful selection of their
transformers. Due to the high operating frequencies in SMPSs, the stray
inductance and capacitance of the printed circuit board traces become
important.
Radio frequency interference Mild high-frequency interference may be
generated by AC rectifier diodes under heavy current loading, while most
other supply types produce no high-frequency interference. Some mains hum
induction into unshielded cables, problematical for low-signal audio.
EMI/RFI produced due to the current being switched on and off sharply.
Therefore, EMI filters and RF shielding are needed to reduce the disruptive
interference. Long wires between the components may reduce the high
frequency filter efficiency provided by the capacitors at the inlet and
outlet.
Electronic noise at the output terminals Unregulated PSUs may have a
little AC ripple superimposed upon the DC component at twice mains frequency
(100-120 Hz). Can cause audible mains hum in audio equipment or brightness
ripples or banded distortions in analog security cameras. Noisier due to the
switching frequency of the SMPS. An unfiltered output may cause glitches in
digital circuits or noise in audio circuits. This can be suppressed with
capacitors and other filtering circuitry in the output stage. With a
switched mode PSU the switching frequency can be chosen to keep the noise
out of the circuits working frequency band (e.g., for audio systems above
the range of human hearing)
Electronic noise at the input terminals Causes harmonic distortion to
the input AC, but relatively little or no high frequency noise. Very low
cost SMPS may couple electrical switching noise back onto the mains power
line, causing interference with A/V equipment connected to the same phase.
Non power-factor-corrected SMPSs also cause harmonic distortion. This can be
prevented if a (properly earthed) EMI/RFI filter is connected between the
input terminals and the bridge rectifier.
Acoustic noise Faint, usually inaudible mains hum, usually due to
vibration of windings in the transformer and/or magnetostriction. Inaudible
to humans, unless they have a fan or are unloaded/malfunctioning. The
operating frequency of an unloaded SMPS is sometimes in the audible human
range.
Power factor Low for a regulated supply because current is drawn from
the mains at the peaks of the voltage sinusoid. Ranging from low to medium
since a simple SMPS without PFC draws current spikes at the peaks of the AC
sinusoid. Active/passive power factor correction in the SMPS can offset this
problem and are even required by some electric regulation authorities,
particularly in Europe.
Risk of electric shock Supplies with transformers allow metalwork to
be grounded, safely. Dangerous if primary/secondary insulation breaks down,
unlikely with reasonable design. Transformerless mains-operated supply
dangerous. In both linear and SM the mains, and possibly the output
voltages, are hazardous and must be well-isolated. Common rail of equipment
(including casing) is energised to half mains voltage, but at high
impedance, unless equipment is earthed/grounded or doesn't contain EMI/RFI
filtering at the input terminals. Due to regulations concerning EMI/RFI
radiation, many SMPS contain EMI/RFI filtering at the input stage before the
bridge rectifier consisting of capacitors and inductors. Two capacitors are
connected in series with the Live and Neutral rails with the Earth
connection in between the two capacitors. This forms a capacitive divider
that energises the common rail at half mains voltage. Its high impedance
current source can provide a tingling or a 'bite' to the operator or can be
exploited to light an Earth Fault LED. However, this current may cause
nuisance tripping on the most sensitive residual-current devices.
Risk of equipment damage Very low, unless a short occurs between the
primary and secondary windings or the regulator fails by shorting
internally. Can fail so as to make output voltage very high. Can in some
cases destroy input stages in amplifiers if floating voltage exceeds
transistor base-emitter breakdown voltage, causing the transistor's gain to
drop and noise levels to increase.[3] Mitigated by good failsafe design.
Failure of a component in the SMPS itself can cause further damage to other
PSU components; can be difficult to troubleshoot. The floating voltage is
caused by capacitors bridging the primary and secondary sides of the power
supply. A connection to an earthed equipment will cause a momentary (and
potentially destructive) spike in current at the connector as the voltage at
the secondary side
"Alasdair" <ma...@bobaxter.coo.uk> wrote in message
news:0jteq5dtm2ngribdd...@4ax.com...
Chris Kirby
>c...@NOSPAM.netunix.com wrote:
>
>>Light bulbs often fail to a short circuit
>
>Quite. Especially these new-fangled GU10 spotlights. I have some in
>the kitchen and 50% of the times they have failed, they have blown the
>lighting circuit fuse.
I tested a GU10 which took out my trip and found it to be open
circuit. I reckon that, on filament failure, the gap in the filament
strikes up an arc which has much lower resistance than the filament
itself. Once the bulb has cooled off, a test with an ohmmeter will
then show an open circuit.
Also, have you noticed how much dimmer a 50w GU10 is than a 50w 12v
halogen bulb of the same shape and size?
--
Chris
Jimbo in the bedroom ...
> Alasdair.
think the problem is all watson stuff is junk...I only kept my watson PSU a
couple of months .....buzzing away it was ........
Gareth Evans G4SDW
news:91hfq5h71cl9a4dn2...@4ax.com...
> My W25AM has served me well for years and has survived
> running bulbs and motors, if not charging batteries.
Remind me, was that in the Ranger or Cambridge series?
Jeff
Neither, I think it would have been a Westminster had they made a W25.
They made W15 and W30's as I recall.
Jeff
Jeff
Oops, take it all back it appears that they did make a Westminster
W25FM, but not AM
Jeff
Gareth Evans G4SDW
news:9j0gq5tu2jjnuj4vu...@4ax.com...
> I tested a GU10 which took out my trip and found it to be open
> circuit. I reckon that, on filament failure, the gap in the filament
> strikes up an arc which has much lower resistance than the filament
> itself.
An interesting discussion proposal, but even then, wouldn't the
arc still be in series with the higher-resistance filament? (The
negative resistance characteristic of arcs referring to the slope
of the curve and not to the measured resistance)
Jimbo.GM4DHJ
"Walt Davidson" <g3...@invalid.invalid> wrote in message
news:21chq556a5mgf7nbo...@4ax.com...
> Jimbo.
>
> 73 de Wlat
>
yes I can...I just get rid of things pronto that turn out to be crap .......
Jimbo in the bedroom ...
> I may shortly decide to replace the GU10 light fitting with a standard
> bayonet socket and start using my newly-purchased supply of 100 watt
> incandescent light bulbs. One 100 watt bulb would be cheaper to run
> than three 50 watt GU10s, anyway.
> :-)
Good man .......
>
> My brother says the Polish shops in London have been importing 100
> watt incandescent bulbs from Poland and are now selling them as "99
> watt bulbs", which can legally be retailed in the UK!
>
> 73 de Wlat
>
you will always be able to get BC 100 150 and 200 watt bulbs branded for
industrial use .....
Jimbo in the bedroom ...
"Walt Davidson" <g3...@invalid.invalid> wrote in message
> On Tue, 23 Mar 2010 13:10:18 -0000, "Jimbo in the bedroom ..."
> <jim.g...@multibandcb.com> wrote:
>
>>you will always be able to get BC 100 150 and 200 watt bulbs branded for
>>industrial use .....
>
> boxed and each one bears the legend "SupaLite 240v 100w BC". They
> have a "CE" mark on them. There is no indication of the country of
> manufacture.
>
> On each box is marked "RoHS" with a green tick through it. This means
> they are compliant with the "Restriction of Hazardous Substances"
> regulations.
>
> 73 de G3NYY
>
be still my heart ..........
Brian Gregory [UK]
you after a news server than belongs to a lying thieving incompetent rip-off
cable company, that's really cruel. You have my sympathy.
"news.virginmedia.com" <rep...@report.com> wrote in message
news:QsSpn.59525$E66....@newsfe22.ams2...
> Switch mode power supplies have the advantage of being smaller and also
> cost less because they do not have a transformer in them
They typically have a smaller transformer in them so that the output is
isolated from the mains input.
> and thats one of the expensive parts in a linear power supply....Switch
> mode power supplies work differently and do not like --->>>>Inductive
> loads<-----.
It depends what they're designed to cope with.
> This could be like a electric motor or even a fluorescent lamp or
> fluorescent tube....Switch mode power supplies are more energy
> efficient... cost less and weigh less...I deal for many more purposes like
> mobile phone charging...... I personally dont like them for running radio
> equipment.. I prefer linear power supplies..
Yes many, but not all, switch mode power supplies create interferance when
used to supply radio equipment.
> Comparison of a linear power supply and a switched-mode power supply
> Linear power supply Switching power supply Notes
> Size and weight If a transformer is used, large due to low operating
> frequency (mains power frequency is at 50 or 60 Hz). Small if
> transformerless. Smaller due to higher operating frequency (typically 50
> kHz-1 MHz) A transformer's power handling capacity of given size and
> weight increases with frequency provided that hysteresis losses can be
> kept down.
That's weight of the core.
You still need thick windings to carry high currents.
> Therefore, higher operating frequency means either higher capacity or
> smaller transformer.
Ah, so now you're admitting that switch mode power supplies have
transformers in them.
> Output voltage With transformer used, any voltages available; if
> transformerless, not exceeding input.
Not true. You don't need a transformer to increase the voltage.
See http://en.wikipedia.org/wiki/Boost_regulator
I've known SMPSUs that apparently meet safety requirements where this
leakage current is enough to give a nasty jolt.
> Risk of equipment damage Very low, unless a short occurs between the
> primary and secondary windings or the regulator fails by shorting
> internally. Can fail so as to make output voltage very high. Can in some
> cases destroy input stages in amplifiers if floating voltage exceeds
> transistor base-emitter breakdown voltage, causing the transistor's gain
> to drop and noise levels to increase.[3] Mitigated by good failsafe
> design. Failure of a component in the SMPS itself can cause further damage
> to other PSU components; can be difficult to troubleshoot. The floating
> voltage is caused by capacitors bridging the primary and secondary sides
> of the power supply. A connection to an earthed equipment will cause a
> momentary (and potentially destructive) spike in current at the connector
> as the voltage at the secondary side
--
Brian Gregory. (In the UK)
n...@bgdsv.co.uk
To email me remove the letter vee.
Fuller Fan Club@sgt.co.uk.com Count de Monet
"Jimbo in the bedroom ..." <jim.g...@multibandcb.com> wrote in message
news:ho9tjb$dea$1...@news.eternal-september.org...
>
>> Alasdair.
>
> think the problem is all watson stuff is junk...I only kept my watson PSU
> a couple of months .....buzzing away it was ........
I own a 30 Amp Zetagi 1230 s PSU. If there were such a thing as a beauty
contest for amps, this would win it hands down ;-)
CdM
Chris
> "Alasdair" <ma...@bobaxter.coo.uk> wrote in message
> news:0jteq5dtm2ngribdd...@4ax.com...
>>I have just purchased a Watson 25-amp power supply model W-25AM. I
>> am surprised to see the second thing on the istruction manual is
>> "WARNING - This unit must not be used to charge lead acid batteries,
>> run light bulbs, or operate any equipment containing a motor".
>>
>> Please, can someone tell me why there is this restriction? What harm
>> can these uses do to the power supply so long as the maximum current
>> is not exceeded?
>
> I suspect the reasons differ between the "loads".
>
> Lead Acid batteries: A normal lead acid battery would be in a sorry state to
> sink 25A when discharged, so I doubt it is the load current. Maybe the maker
> is concerned what happens if the mains is turned off while the battery is
> connected. If this is correct, a series diode would solve the problem. I've
> certainly been asked to repair similar style PSUs in the past which were
> used to "float charge" a battery and provide a UPS type supply.
If you leave a voltage source connected to the PSU when off the "warning"
lamp comes on and a not unreasonable current flows into the supply....
astral...@gmail.com
nemesis
> I have just purchased a Watson 25-amp power supply model W-25AM. I
> am surprised to see the second thing on the istruction manual is
> "WARNING - This unit must not be used to charge lead acid batteries,
> run light bulbs, or operate any equipment containing a motor".
>
> Please, can someone tell me why there is this restriction? What harm
> can these uses do to the power supply so long as the maximum current
> is not exceeded?
>
> Alasdair.
It may look the part,
But i found mine made a lot of noise under a 100w load.
The field from the big transformer would rattle the units case.
It eventually gave up the ghost and i have went back to my switch mode supply which i have never had a bit of trouble with.
The newer design switch mode units do not have the noise that some complained about in rx, i have never noticed this issue and this is comparing them to linear units.
More compact and a helluva lot lighter i prefer this type.
nemesis
> Hello i have purchased the w-25am transformer how ever i seem to have a big problem with it when you turn the machience on it jumps straight to full power and i cant turn it down could somebody please help me
Chuck it in the bin and buy a switch mode supply instead.
Watson linear psu's are just unreliable crap.
Sonny
>
> As for the problem, some initial thoughts:
>
> Pass transistors failed short circuit collector to emitter.
>
> Fault in feed back circuit, this measures output, feeds to the control IC,
> which then controls the pass transistor circuit. Could be anything from a
> bad joint to a failed device.
>
> I'd imagine there is a circuit on the net.
>
> The Watson supplies aren't that bad, I have one on my work bench. It does
> the job.
Faulty v. adj pot seems to be quite common - circuit here:
<http://g3zjo-radio.blog.co.uk/2013/02/15/the-zurich-watson-25-30amp-13-8v-power-supplies-15536757/>
Jim GM4DHJ in the shack ...
<astral...@gmail.com> wrote in message
news:cacd64ca-73ad-4460...@googlegroups.com...
> big problem with it when you turn the machience on it jumps straight to
> full power and i cant turn it down could somebody please help me
binned mine.....only an idiot would have one on their bench......
Brian Howie
<james.st...@ntlworld.com> writes
Gurl qba'g xabj gur jbeqf
B
--
Brian Howie
Jim GM4DHJ in the shack ...
"Brian Howie" <br...@nospam.demon.co.uk> wrote in message
news:9CgsGNLW...@b-howie.demon.co.uk...