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PICList Thread
'[EE]: Transformerless power supply for PIC'
2001\03\09@162514 by Charles Craft

picon face
I searched the archives and didn't come up with much.

Any gotchas before diving into this type of circuit?
Most of the other circuits I've seen on the web use a bridge rectifier instead of just two diodes like the MicroChip circuit.
Advantages of one over the other?

thanks
chuckc




http://www.piclist.com/techref/microchip/power.htm


http://www.microchip.com/download/appnote/category/pic16/91008b.pdf

In most non-battery applications, the power to the
microcontroller is normally supplied using a wall
mounted transformer, which is then rectified, filtered
and regulated. In most applications, this method of
generating the regulated voltage is cost effective and
can be justified. However, there are applications where
the PIC12/16/17 is the main controller and low voltage
is not required by other components except the PIC12/
16/17. In these instances, the cost of the transformer
becomes the sizable cost factor in the system. Transfor-merless
power supplies, thus, have a distinct advan-tage
in cost as well as in size. The disadvantages of
using a transformerless power supply are: (1) low cur-rent
supply and (2) no isolation from the AC line volt-age.
The PIC12/16/17 microcontrollers draw a
maximum of 10 mA, even at the highest frequency and
voltage of operation, therefore low current availability is
not an issue. AC line voltage isolation can be
addressed by using MOVs or transient suppressors on
the PIC12/16/17.

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2001\03\10@194309 by Bob

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For a simpler, more reliable, and possibly even a less expensive way to do this,
take a look at a part called the VB409 from ST Micro Electronics
(http://us.st.com).

It also has the advantage of producing two output voltages, if you need them (a
5vdc 5% regulated, and a 12~15vdc unregulated).  It only requires a 35~50v 220uf
electrolytic cap, two resistors, and a rectifier to operate (maybe a small
inductor too, for more efficient operation).  Using two diodes (half rectified)
on this part will give you a -2.5dc and +2.5dc (a 5vdc bias) from "true ground",
where using a full bridge will put the circuit at 1/2 line potential (but it
still generates a 5vdc bias).  It can generate upwards of 70 or 80ma at 5vdc,
and can have peaks upwards of 400ma on the 12~15 supply up to 10ms.

The only trick to using this part, is actually finding a distributor that stocks
it as a standard off the shelf part.  Let me know if you happen to run into a
distributor like that....  Arrow has it listed at $1.23 each, but doesn't show
any in stock (i.e., special order item).

Bob

{Original Message removed}


'[PICLIST] Transformerless Power Supply'
2001\04\27@021540 by Alexandre Domingos F. Souza
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       Dear PICsters,

       I'm looking for a circuit of a transformerless power supply of 12VCC / 100 mA. Can anyone help?

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2001\04\27@025935 by Vasile Surducan

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www.geocities.com/vsurducan/c520.htm
power.gif image it's a 5v transformerless supply, you must change serial
capacitor value and 3 pin stabilizer. It's unusefull if you can't short
your ground with neutral mains. In that case you need an isolated
switching supply.
V

On Fri, 27 Apr 2001, Alexandre Domingos F. Souza wrote:

>         Dear PICsters,
>
>         I'm looking for a circuit of a transformerless power supply of 12VCC / 100 mA. Can anyone help?
>
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>

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2001\04\27@065533 by mike

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On Fri, 27 Apr 2001 03:18:56 -0300, you wrote:

>        Dear PICsters,
>
>        I'm looking for a circuit of a transformerless power supply of 12VCC / 100 mA. Can anyone help?
Transformerless is not usually practical at this power level - a
transformer will be cheaper and probably smaller than any
safety-approvable alternative, unless you can burn off a lot of heat. You could use a capacitive dropper but the cap(s) would likely be
bigger and more expensive than a 12v 100mA transformer.

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2001\04\28@014026 by basam

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"Alexandre Domingos F. Souza" wrote:

>         Dear PICsters,
>
>         I'm looking for a circuit of a transformerless power supply of 12VCC / 100 mA. Can anyone help?
>
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MAX 610
                   Milan

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'[EE]: Transformerless power supply on 3 phases?'
2003\12\30@013101 by Anand Dhuru
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Hi,

There's been a few threads about transformerless power supplies on the
forum, so I'm hoping one of the EEs on the list can help me with this.

Would it be possible to build a transformerless power supply for a PIC based
circuit (max. current not more than 10 mA, including the LEDs) *using a 3
phase mains system*?

The idea here is that the PIC should get power even if a certain phase
fails, and would then be able to also determine which of the 3 has indeed
failed.

Regards,

Anand Dhuru



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2003\12\30@014545 by Russell McMahon

face
flavicon
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> Would it be possible to build a transformerless power supply for a PIC
based
> circuit (max. current not more than 10 mA, including the LEDs) *using a 3
> phase mains system*?
>
> The idea here is that the PIC should get power even if a certain phase
> fails, and would then be able to also determine which of the 3 has indeed
> failed.

In its simplest form it's an essentially trivial extension of the single
phase designs. Just build 3 x 1 phase supplies and connect them to the
output capacitor with a diode from each. Each supply must not be able to
"see" the AC pumping of the zener clamp diode which is usually used.

eg simplest form with many "real world" parts omitted.
Capacitor from mains to point A.
Zener diode from point A to ground, (anode to ground).
Point A will rise to Vz on one half cycle and drop to 1 diode drop below
ground on the other.
Make 3 of these and connect point A on each via a diode to the output filter
capacitor.
Real solutions add series resistors to capacitors etc.
See archives for past threads on 1 phase versions.

As the problem is stated you actually only need 2 of these circuits !
If only 1 phase fails then 2 circuits will always have at least 1 phase
still running.

Detection of phase loss may be independent of the power supply or could
monitor the 3 x point A's
(With only 2 supplies you need some other means of monitoring the 3rd phase)



           Russell McMahon

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2003\12\30@020900 by Anand Dhuru

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Thanks for the insight, Russell.

> In its simplest form it's an essentially trivial extension of the single
> phase designs. Just build 3 x 1 phase supplies and connect them to the
> output capacitor with a diode from each. Each supply must not be able to
> "see" the AC pumping of the zener clamp diode which is usually used.

I left out the fact that a common (neutral) might not be available here;
would the same strategy still work? What I mean is, the I need to derive
power from just the 3 phase cables themselves.

> eg simplest form with many "real world" parts omitted.
> Capacitor from mains to point A.
> Zener diode from point A to ground, (anode to ground).
> Point A will rise to Vz on one half cycle and drop to 1 diode drop below
> ground on the other.
> Make 3 of these and connect point A on each via a diode to the output
filter
> capacitor.
> Real solutions add series resistors to capacitors etc.
> See archives for past threads on 1 phase versions.
>
> As the problem is stated you actually only need 2 of these circuits !
> If only 1 phase fails then 2 circuits will always have at least 1 phase
> still running.

True; just covering the contingency that 2 phases fail together. Or is that
unlikely in the real world without the third going down as well?

>
> Detection of phase loss may be independent of the power supply or could
> monitor the 3 x point A's
> (With only 2 supplies you need some other means of monitoring the 3rd
phase)
>

I understand; I intend to monitor all three phases individually as well.
Since the common (or neutral) might not be available, this again might pose
a problem for direct zero detection; in which case could I use an opto?

Regards,

Anand



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2003\12\30@022349 by Josh Koffman

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Anand Dhuru wrote:
> True; just covering the contingency that 2 phases fail together. Or is that
> unlikely in the real world without the third going down as well?

That depends on what you're using the power before. I've worked
extensively in the live entertainment industry, and in some venues it's
not too uncommon to get a lighting system drawing more instantaneous
power (as 100,000W of lighting turns on at once) than the fuse is rated
for. If you haven't balanced your load equally over all three phases,
you can blow only one or two phases. The interesting thing to watch is
what happens to the equipment afterwards. Most often the control
circuits are only powered off of one phase. If you blow that phase, the
equipment seems to go dead, but you still have dimmer modules getting
power on their output side...

Josh
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2003\12\30@045027 by Russell McMahon

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flavicon
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> Thanks for the insight, Russell.
>
> > In its simplest form it's an essentially trivial extension of the single
> > phase designs. Just build 3 x 1 phase supplies and connect them to the
> > output capacitor with a diode from each. Each supply must not be able to
> > "see" the AC pumping of the zener clamp diode which is usually used.
>
> I left out the fact that a common (neutral) might not be available here;
> would the same strategy still work? What I mean is, the I need to derive
> power from just the 3 phase cables themselves.

Should be "doable". But unless you need to do it your own way, as someone
else noted, there are existing phase failure solutions available
commercially. That would probably be the easiest answer for small volume
requirements.

_____________

Roll your own thoughts. Not backed by any practical playing:

3 capacitors, from a common point to 1 phase each, should produce the star
point for the 3 phases (Vr + Vg + Vb = 0). The capacitors would need to be X
rated for at least phase to star point voltage. .

If a zener was placed in series with each capacitor, between each capacitor
and the derived star point, anodes to common point, each would successively
produce either Vz or negative 1 diode drop at their cathodes relative to the
star point.

3 diodes taken from each of the cathodes to a filter cap whose other end
goes to the star point should produce a DC voltage of Vz - 1 diode drop
across this capacitor - use to power the processor. Monitoring the 3 zener
cathodes should also allow phase fail detection. eg diode from each cathode
to processor should produce positive going square wave with ~= 50% duty
cycle.

Care needs to be taken about how phase failure manifests itself.
In a fully unloaded system, phase failure caused by eg a breaker going OC
(open circuit) will result in the failed phase going open circuit. In a real
world situation with loads between phases, the failed phase will assume a
voltage part way between the other two phases, with actual voltage set by
the voltage divider formed by the loads. eg if loads R-G, G-B and B-R are
equal and phase G goes OC then the voltage on G will be a sinusoid midway
between the instantaneous value of B and R.

Intuitively this is identical to what G would be if still present. This is
of course ludicrous (who needs G anyway ? ;-) ) so I've probably done
something obvious wrong but I'll leave it to you to sort out, having made
the point that an OC phase feed does not lead to a "dead" phase if loads are
connected phase to phase (delta connection).

Optos sound like an easy way to do phase detection but the zener cathode to
derived star point method above sounds cheaper.

Once you have your result you may well wish to use an opto to do something
with it as your PIC is at nominal ground but not a ground that I would care
to trust with my life.




       Russell McMahon

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2003\12\30@051140 by Anand Dhuru

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Thanks for the detailed suggestion, Russell. Things are much clearer now.

>
> Care needs to be taken about how phase failure manifests itself.
> In a fully unloaded system, phase failure caused by eg a breaker going OC
> (open circuit) will result in the failed phase going open circuit. In a
real
> world situation with loads between phases, the failed phase will assume a
> voltage part way between the other two phases, with actual voltage set by
> the voltage divider formed by the loads. eg if loads R-G, G-B and B-R are
> equal and phase G goes OC then the voltage on G will be a sinusoid midway
> between the instantaneous value of B and R.
>
> Intuitively this is identical to what G would be if still present. This is
> of course ludicrous (who needs G anyway ? ;-) ) so I've probably done
> something obvious wrong but I'll leave it to you to sort out, having made
> the point that an OC phase feed does not lead to a "dead" phase if loads
are
> connected phase to phase (delta connection).

I'm hoping this suituation can still be recognised by software that detects
a missing cycle on one of the phases, rather than looking at voltages.

Thanks again,

Anand

>
>         Russell McMahon
>
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2003\12\30@055157 by Russell McMahon

face
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part 1 952 bytes content-type:text/plain; (decoded 7bit)

> I'm hoping this suituation can still be     recognised by software that
detects
> a missing cycle on one of the phases, rather than looking at voltages.

That's fine but do note my point about the effects of phase to phase loads.
They will/may produce a voltage on the dead phase. Your detector needs to be
able to distinguish between full voltage and partial voltage.

If all phase-phase loads are equal then if a phase feed goes OC the DEAD
phase will have a voltage half the normal value and phased intermediate
between the two live phases - this is exactly the inverse of the normal
phase relationship when the phase is live. . See attached graph. This could
fool a detector
based on pulse detection alone if the trigger thresholds were wrong.



       Russell McMahon


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part 2 8796 bytes content-type:image/gif; (decode)

2003\12\30@074423 by Olin Lathrop

face picon face
Russell McMahon wrote:
> 3 capacitors, from a common point to 1 phase each, should produce the
> star point for the 3 phases (Vr + Vg + Vb = 0). The capacitors would
> need to be X rated for at least phase to star point voltage. .

You would also need bleeder resistors accross the capacitors.  Otherwise an
arbitrary DC voltage could build up.  The capacitors still handle the bulk
of the current.


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'[PIC] Transformerless power supply'
2006\10\25@124534 by slippyr4
picon face
Hope this counts as PIC, not EE

I've seen circuits for very simple, efficient, transformerless,
non-isolated power supplies such as
http://www.aaroncake.net/circuits/supply5.htm .

Would I have a chance of running a very low frequency PIC16 on this
type of supply? would i need to stick a 7805 in too? or is it simply
too noisy?

thanks

jon

2006\10\25@131037 by stef mientki

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face
slippyr4 wrote:
> Hope this counts as PIC, not EE
>
> I've seen circuits for very simple, efficient, transformerless,
> non-isolated power supplies such as
> http://www.aaroncake.net/circuits/supply5.htm .
>
> Would I have a chance of running a very low frequency PIC16 on this
> type of supply? would i need to stick a 7805 in too? or is it simply
> too noisy?
>
>  
And what about safety ?
Better use a battery cr2032 or so.
Stef
> thanks
>
> jon
>  

2006\10\25@131844 by Harold Hallikainen

face
flavicon
face

> Hope this counts as PIC, not EE
>
> I've seen circuits for very simple, efficient, transformerless,
> non-isolated power supplies such as
> http://www.aaroncake.net/circuits/supply5.htm .
>
> Would I have a chance of running a very low frequency PIC16 on this
> type of supply? would i need to stick a 7805 in too? or is it simply
> too noisy?
>
> thanks
>
> jon


These sort of supplies have a tremendous shock hazard, so be careful!
Also, I'd add a resistor in series with the capacitor to limit the current
when it's plugged in at a line voltage peak. The zener is probably enough
of a voltage regulator for the circuit (a pic works over a wide range).
The output of the circuit is similar to a constant current source with the
current splitting between the zener and your load. If the load current
varies substantially, you need to dissipate quite a bit of power in the
zener to regulate it.

I seem to recall some chips that were especially for this sort of supply.
I thought maybe Maxim, but can't find it on their website.

Harold

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2006\10\25@133554 by Mike Harrison

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On Wed, 25 Oct 2006 17:45:32 +0100, you wrote:

>Hope this counts as PIC, not EE
>
>I've seen circuits for very simple, efficient, transformerless,
>non-isolated power supplies such as
>http://www.aaroncake.net/circuits/supply5.htm .
>
>Would I have a chance of running a very low frequency PIC16 on this
>type of supply? would i need to stick a 7805 in too? or is it simply
>too noisy?
>
>thanks
>
>jon

You can get a few mA out of circuits like this, so possible to run PICs at normal clock rates,
obviously you'd use a 5V1 zener instead of 11V.
You'll want to add a little bit of series R (~100R fusible) to limit inrush current if it's plugged
in at the top of the cycle.



2006\10\25@140455 by Bob Axtell

face picon face
Mike Harrison wrote:
{Quote hidden}

I never saw the original post. Please contact me. You have to be careful
with these, because power line spikes can cream your PS and PIC.
I have a commercial version of this with all the safeties needed to make
use of it, supplying 10-15mA for an AC motor control using a PIC12C
device. Hundreds were made, been in the field working without a single
failure after 3 years.

--Bob

2006\10\25@142102 by Shawn Wilton

picon face
Seeing as this is a "commercial" version, I don't suppose you would be
interested in posting it to the list?

On 10/25/06, Bob Axtell <spam_OUTengineerTakeThisOuTspamneomailbox.com> wrote:
{Quote hidden}

> -

2006\10\25@144710 by Bob Axtell

face picon face
part 0 44 bytes
his is a multi-part message in MIME format.
part 1 2108 bytes content-type:text/plain; charset=ISO-8859-1; format=flowed (decoded 7bit)

I have posted it before, but I will post it again. Gotta find it...
I can only tell you that it is driving a small 120VAC 60hz
gearmotor.

--Bob


Shawn Wilton wrote:
{Quote hidden}

>> --

2006\10\25@154438 by Wouter van Ooijen

face picon face
> I've seen circuits for very simple, efficient, transformerless,
> non-isolated power supplies such as
> http://www.aaroncake.net/circuits/supply5.htm .

Note that the explanation states: "You may want to add a resisor in
series with C1 to limit current if the circuit is plugged in and the
mains is at its full voltage." I don't see how you could avoid plugging
in at the top voltage, so that resistor definitely belongs in the
circuit.

The other problem with this type of circuit is the voltage on the mains
plug after uplugging...

Wouter van Ooijen

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2006\10\25@155222 by Dwayne Reid

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At 10:45 AM 10/25/2006, slippyr4 wrote:
>Hope this counts as PIC, not EE
>
>I've seen circuits for very simple, efficient, transformerless,
>non-isolated power supplies such as
>http://www.aaroncake.net/circuits/supply5.htm .
>
>Would I have a chance of running a very low frequency PIC16 on this
>type of supply? would i need to stick a 7805 in too? or is it simply
>too noisy?

Yes.  Do note that the schematic as presented is missing a current
limit resistor in series with the input capacitor (I normally draw
mine in series with the bottom AC input line, underneath C1).

The PIC supply can simply be another zener supply: input resistor of
about 470R feeding a 5.1V zener diode.

dwayne

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2006\10\25@164345 by Jinx

face picon face

> Would I have a chance of running a very low frequency PIC16
> on this type of supply? would i need to stick a 7805 in too? or
> is it simply too noisy?

They can be made pretty clean, more like this

http://home.clear.net.nz/pages/joecolquitt/txless.html

The X2 capacitor determines how much current is available, up
to you how much filtering you need/add

Wouter said -

"The other problem with this type of circuit is the voltage on the
mains plug after uplugging..."

A suitably-rated bleeder resistor would fix that

2006\10\25@173049 by Wouter van Ooijen

face picon face
> Wouter said -

> "The other problem with this type of circuit is the voltage on the
> mains plug after uplugging..."

> A suitably-rated bleeder resistor would fix that

True, but the circuit as shown does not have that resistor, and the text
that goes with it admits that another resistor is needed. Two key
components missing in a circuit that has how many - 10 components? That
does not exactly raise my confidence in the engineering behind the part
of the circuit that is shown.

Wouter van Ooijen

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2006\10\25@180733 by I. Forse

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Take a look at http://www.edn.com/archives/1994/021794/04di2.htm#fig1
this uses a high voltage current regulator from IXYS

Ian

2006\10\25@181134 by Jinx

face picon face
> That does not exactly raise my confidence in the engineering
> behind the part of the circuit that is shown

"a little knowledge is a dangerous thing" ?

A potentially, no pun intended, harmful circuit that raises
as many questions (if you know you ask them that is) as
it answers. In a situation like this I would much rather
over-engineer for safety's sake

2006\10\25@205930 by Mark Jordan

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       Another circuit attached.

       Mark Jordan

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2006\10\25@211030 by Bob Axtell

face picon face
I. Forse wrote:
> Take a look at http://www.edn.com/archives/1994/021794/04di2.htm#fig1
> this uses a high voltage current regulator from IXYS
>
> Ian
>  
I think you will not be able to locate these parts anywhere, because
these chips didnt hold up.
Maxim took a stab at this, too, and then quietly faded away.

--Bob

2006\10\25@215246 by Xiaofan Chen

face picon face
On 10/25/06, Bob Axtell <.....engineerKILLspamspam.....neomailbox.com> wrote:
> I. Forse wrote:
> > Take a look at www.edn.com/archives/1994/021794/04di2.htm#fig1
> > this uses a high voltage current regulator from IXYS
> >
> I think you will not be able to locate these parts anywhere, because
> these chips didnt hold up.
> Maxim took a stab at this, too, and then quietly faded away.
>

Supertex has some interesting ICs.

I've tested SR036 before and it works fine for its target application.
1) Linear IC low current
http://www.supertex.com/products/selector_guides/107/100

2) "pseudo switch-mode" for pure AC supply
http://www.supertex.com/feature_sr03x.html

Regards,
Xiaofan

2006\10\25@224140 by Charles Rogers

flavicon
face
.
>
> Would I have a chance of running a very low frequency PIC16 on this
> type of supply? would i need to stick a 7805 in too? or is it simply
> too noisy?
>
> thanks
>
> jon

Jon:

Why don't you try microchip.com.  AN954 might be just what you
are looking for.

CR

2006\10\25@230140 by Bob Axtell

face picon face
Xiaofan Chen wrote:
{Quote hidden}

Now THOSE look interesting. Thanks for the heads up.

--Bob

2006\10\25@230738 by Bob Axtell

face picon face
Let me make it very clear: these transformerless designs are
dangerous because they operate with exposed lethal voltages.
The only reason I did the gig was because it was to be potted
in plastic.. and it was.

It also followed the general UL principles and would pass if
tested.

--Bob

Bob Axtell wrote:
{Quote hidden}

2006\10\25@230850 by Jinx

face picon face

> Why don't you try microchip.com.  AN954 might be just what you
> are looking for.

> Why don't you try microchip.com.  AN954 might be just what you
> are looking for.

There has been discussion, on this list and at Microchip's forum,
about the safety of Microchip transformerless supplies, at least
as presented by them

>From a thread about AN521 last year

======================

You are completely right, of course. This thread started with many
very clear statements against AN521.

In another thread, discussion of the infamous AN954 - resistive
transformerless supply triggered a host of warnings by forum members,
pointing out the various safety hazards and reliability issues that
both ApNotes failed to mention.

I agree that both ApNotes are incredibly misleading. A complete
reliability discussion should be included in the ApNotes, and resistor
failure modes should be analysed more carefully. Actually, in the
AN521 the author seems to have no knowledge of the concept of
reliability and failure analysis. I completely agree that it should be
removed from MCP site, along with AN954.

Unexperienced developers might risk their lives, and even design
hazardous equipment that can risk the end users' lives

2006\10\26@041530 by peter green

flavicon
face
> Unexperienced developers might risk their lives, and even design
> hazardous equipment that can risk the end users' lives
also doesn't transformerless imply not isolated from the mains? mains
neutral cannot be depended on to stay at near eath potential!


2006\10\26@051105 by Ariel Rocholl

picon face
I did never implement it myself, but I consider this AN from STM very
detailed and good design with all the rationale in place:
http://www.st.com/stonline/products/literature/an/8313.pdf


2006/10/25, Wouter van Ooijen <wouterspamspam_OUTvoti.nl>:
{Quote hidden}

> -

2006\10\26@060314 by slippyr4

picon face
Thanks everyone for your comments...


On 25/10/06, Harold Hallikainen <@spam@haroldKILLspamspamhallikainen.org> wrote:
> These sort of supplies have a tremendous shock hazard, so be careful!
> Also, I'd add a resistor in series with the capacitor to limit the current
> when it's plugged in at a line voltage peak.

I realise that - but they have a very low part count and are efficient.

On 25/10/06, Mike Harrison <KILLspammikeKILLspamspamwhitewing.co.uk> wrote:
> obviously you'd use a 5V1 zener instead of 11V.
> You'll want to add a little bit of series R (~100R fusible) to limit inrush current if it's plugged
> in at the top of the cycle.

What do you mean fusible? (in the context of a resistor)?

On 25/10/06, Bob Axtell <RemoveMEengineerTakeThisOuTspamneomailbox.com> wrote:
> I have posted it before, but I will post it again. Gotta find it...
> I can only tell you that it is driving a small 120VAC 60hz
> gearmotor.

Thanks for the post bob

On 25/10/06, Wouter van Ooijen <spamBeGonewouterspamBeGonespamvoti.nl> wrote:
> The other problem with this type of circuit is the voltage on the mains
> plug after uplugging...

This is going to be used for fixed equipment (if I actually get round
to making it).

On 26/10/06, Charles Rogers <TakeThisOuTcrogersEraseMEspamspam_OUTtotelcsi.com> wrote:
> Why don't you try microchip.com.  AN954 might be just what you
> are looking for.

Taking a look...

On 26/10/06, Bob Axtell <RemoveMEengineerspamTakeThisOuTneomailbox.com> wrote:
> Let me make it very clear: these transformerless designs are
> dangerous because they operate with exposed lethal voltages.
> The only reason I did the gig was because it was to be potted
> in plastic.. and it was.

The design will be used in plastic cased fixed equipment, and an earth
is present so I can design the innards in a safe fashion.


On 26/10/06, peter green <plugwashEraseMEspam.....p10link.net> wrote:
> > Unexperienced developers might risk their lives, and even design
> > hazardous equipment that can risk the end users' lives
> also doesn't transformerless imply not isolated from the mains? mains
> neutral cannot be depended on to stay at near eath potential!

In what context do you mean "rely" ? In my houses electricity supply
(designated TN-S in UK terminology), the neutral and earth are joined
at the substation (ie the star point of the REC's transformer where
the neutral originates is grounded). So only in major fault conditions
can the potential differ much - only due to a break in neutral or
earth, or a major fault current on the earth causing a voltage drop on
the earth.


Anyway, for everyone's information, the project i'm considering is
making an intelligent, anticipating room thermostat for my central
heating. My current electromechanical stat is rubbish in it's
performance. It's supplied by a 3 core + earth cable - phase, neutral,
switched live. The neutral is only present to power the anticipator
resistor.

Of course, I could use a battery to power the pic, and relay to switch
the mains volts. But that'd annoy me. Batteries need to be changed,
and unless I put a bunch of effort into circuit and firmware design to
reduce power consumption then the battery could go flat real quick.
And when there's mains voltage in the thermostat, why not use it?

I'd plan on using my current thermostat housing, gutting it and
fitting a new PCB with a VR for the control knob.

thanks

jon

2006\10\26@065733 by Bob Axtell

face picon face
slippyr4 wrote:
{Quote hidden}

It sounds like a good idea, and that design, if potted could be made
safe enough. As long
as you crush the spikes with a transorber, the design will live forever.
If you plan to get it
UL approved, it will need to have an internal fuse so that when it DOES
get damaged,
it won't catch fire..

--Bob

> thanks
>
> jon
>  

2006\10\26@080428 by olin piclist

face picon face
> Unexperienced developers might risk their lives,

Gee, you almost make it sound like N-1 morons is a bad thing.

********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2006\10\26@081030 by Gerhard Fiedler

picon face
peter green wrote:

>> Unexperienced developers might risk their lives, and even design
>> hazardous equipment that can risk the end users' lives

> also doesn't transformerless imply not isolated from the mains? mains
> neutral cannot be depended on to stay at near eath potential!

Of course, and there's also nothing inherent in the design that says that
the circuit potential has to be anywhere near neutral. It can be near phase
voltage just as well, or anywhere in the middle, depending on the circuit.

That's why this has to be well encapsulated with no active parts that can
be touched, and when working on it it's best to use an isolation
transformer.

Gerhard

2006\10\26@092859 by Howard Winter

face
flavicon
picon face
Jinx,

On Thu, 26 Oct 2006 11:11:30 +1300, Jinx wrote:

> > That does not exactly raise my confidence in the engineering
> > behind the part of the circuit that is shown
>
> "a little knowledge is a dangerous thing" ?
>
> A potentially, no pun intended, harmful circuit that raises
> as many questions (if you know you ask them that is) as
> it answers.

Indeed, a "Trap for the unwary" - which will catch out those who just copy circuits as they are without underestanding them, and just expect they
will be OK.  I've been known to do this (I started out doing just that when my age only needed one digit) so I know it happens!  :-)  In those days, of
course, it was in magazine articles, so the amount of available material was limited.

Cheers,




Howard Winter
St.Albans, England


2006\10\26@092902 by slippyr4

picon face
On 26/10/06, Bob Axtell <spamBeGoneengineerSTOPspamspamEraseMEneomailbox.com> wrote:
> It sounds like a good idea, and that design, if potted could be made
> safe enough. As long
> as you crush the spikes with a transorber, the design will live forever.
> If you plan to get it
> UL approved, it will need to have an internal fuse so that when it DOES
> get damaged,
> it won't catch fire..

UL approved?

it's just a hobby project

2006\10\26@094135 by Howard Winter

face
flavicon
picon face
Peter,

On Thu, 26 Oct 2006 09:14:15 +0100, peter green wrote:

> > Unexperienced developers might risk their lives, and even design
> > hazardous equipment that can risk the end users' lives

> also doesn't transformerless imply not isolated from the mains? mains
> neutral cannot be depended on to stay at near eath potential!

Quite!  And under UK regulations Neutral conductors are to be treated as live, and isolated from touch contact in the same way.  A design such as the
one under discussion would only be allowed if it was double-insulated (Class II) such that nothing metal could come into contact with people.  And
the dropper-capacitor would have to be properly rated ("X2", possibly?) for series connection with the mains, which includes the provision that
failure must be open-circuit, which the article doesn't mention.  I can just see people grabbing the nearest electrolytic of the right value...

Darwin applies!  :-)

Cheers,



Howard Winter
St.Albans, England


2006\10\26@095937 by Michael Rigby-Jones

picon face


{Quote hidden}

To be fair, this is exactly how you learn from a young age.  How many people got stuck into a semiconductor theory book at the age of 8?

I think the point is that we would have been using PP3 batteries* rather than transformerless supplies as these are most certainly not suitable to design in without full knowledge of their design and shortcommings.

Regards

Mike


*Except my dad somewhat foolishly let me have a 12v Lead Acid battery from his motorcyle to use for powering experiments.  Had many happy hours welding bits of wire together!

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2006\10\26@123324 by Dwayne Reid

flavicon
face
At 09:07 PM 10/25/2006, Bob Axtell wrote:
>Let me make it very clear: these transformerless designs are
>dangerous because they operate with exposed lethal voltages.
>The only reason I did the gig was because it was to be potted
>in plastic.. and it was.
>
>It also followed the general UL principles and would pass if
>tested.

My versions are both CSA & UL certified.  None of them are potted but
they are all enclosed such that the consumer cannot touch any part of
the circuit.  One unit does have a pot shaft but that is plastic.

Interestingly enough, one of the current generation of LED Christmas
lights that I am working with uses a capacitive power supply in every
single bulb.  Each bulb is completely self-contained and replaces a
standard C5 lamp.  Reasonably bright and runs at about 0.8 Watts -
but with an extremely capacitive power factor.

These transformerless power supplies do have their place.

dwayne

--
Dwayne Reid   <@spam@dwayner@spam@spamspam_OUTplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
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2006\10\26@143053 by Wouter van Ooijen

face picon face
> I did never implement it myself, but I consider this AN from STM very
> detailed and good design with all the rationale in place:
> http://www.st.com/stonline/products/literature/an/8313.pdf

But the capacitive version still has the 'shock from the mains plug'
syndrome..

Wouter van Ooijen

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


2006\10\26@145229 by alan smith

picon face
Is this something you can share as well?

Dwayne Reid <spamBeGonedwaynerspamKILLspamplanet.eon.net> wrote:  
My versions are both CSA & UL certified. None of them are potted but
they are all enclosed such that the consumer cannot touch any part of
the circuit. One unit does have a pot shaft but that is plastic.

               
---------------------------------
Do you Yahoo!?
Get on board. You're invited to try the new Yahoo! Mail.

2006\10\26@154057 by Gerhard Fiedler

picon face
Olin Lathrop wrote:

> Gee, you almost make it sound like N-1 morons is a bad thing.

I've been missing you lately :)

Gerhard

2006\10\26@231050 by John Chung

picon face
Copying code or schematics is a bad idea. Just maybe
you have created your own virus or bomb!

John

--- Howard Winter <.....HDRWspam_OUTspamH2Org.demon.co.uk> wrote:

{Quote hidden}

> --


'[PIC] Transformerless power supply'
2007\06\15@092057 by alan smith
picon face
Bob....hope your still around reading the list.  Or if anyone else is familiar with his power supply design....wondering how you can get a little more current from it?  I built it but I'm thinking that under load it isnt giving quite enough for what I am trying to drive (micro and rf module).  Without the RF module, appears to function perfectly but the main power LED and status LED (both low current devices) "flicker" that tells me the regulator isn't able to provide enough current (its a 1A regulator so thats not the problem per say). pulling the RF module out allows the micro to work fine.  I'm not really that familiar with these transformerless supplies,   I need about 60mA.....maybe I'm just asking for too much from his design?

Bob Axtell <TakeThisOuTengineer.....spamTakeThisOuTneomailbox.com> wrote:  I have posted it before, but I will post it again. Gotta find it...
I can only tell you that it is driving a small 120VAC 60hz
gearmotor.

--Bob


Shawn Wilton wrote:
{Quote hidden}

>> --

2007\06\15@100713 by Peiserma

flavicon
face
piclist-bounces@mit.edu wrote:
> Bob....hope your still around reading the list.  Or if anyone
> else is familiar with his power supply design....wondering
> how you can get a little more current from it?

First, I don't have a copy of that ciruit, but I assume its a
proper one, not the one posted in the link...

Basically you need to increase the capacitance of the main
cap (the one that is in series with the supply). Use ohms
law but work with the impedance of the capacitor at line
frequency for w=2*PI*f

Don't forget to take the zener into account. It may need
a higher power rating.

2007\06\15@103029 by Jinx

face picon face

> Basically you need to increase the capacitance of the main
> cap (the one that is in series with the supply). Use ohms
> law but work with the impedance of the capacitor at line
> frequency for w=2*PI*f

An approximation is I = 6fCV

230V, 50Hz, 1uF, I = 6 * 50 * 0.000001 * 230 = 0.069A
120V, 60Hz, 1uF, I = 6 * 60 * 0.000001 *120 = 0.043A

2007\06\15@110602 by alan smith

picon face
part 1 1050 bytes content-type:text/plain; charset=iso-8859-1 (unknown type 8bit not decoded)

I'm including the pdf for the schematic that Bob had previously posted, so I'm sure its OK with him if I do so again (implied consent)
 
 The cap is a 0.82uF so following the formula, it would provide a max 35mA and makes sense that the LED's were flickering because it was trying to provide it, but was perhaps..pulsing trying to keep the voltage level up while the current draw was being demanded (assumption because I didnt have a scope or isolation transformer with me).
 
 Interesting tho his comments said...good up to 1A so I blindly went forth and built assuming this fact.
 

Jinx <TakeThisOuTjoecolquittKILLspamspamspamclear.net.nz> wrote:
 
> Basically you need to increase the capacitance of the main
> cap (the one that is in series with the supply). Use ohms
> law but work with the impedance of the capacitor at line
> frequency for w=2*PI*f

An approximation is I = 6fCV

230V, 50Hz, 1uF, I = 6 * 50 * 0.000001 * 230 = 0.069A
120V, 60Hz, 1uF, I = 6 * 60 * 0.000001 *120 = 0.043A

2007\06\15@120931 by Vasile Surducan

face picon face
On 6/15/07, alan smith <.....micro_eng2spamRemoveMEyahoo.com> wrote:
> I'm including the pdf for the schematic that Bob had previously posted, so I'm sure its OK with him if I do so again (implied consent)
>
>  The cap is a 0.82uF so following the formula, it would provide a max 35mA and makes sense that the LED's were flickering because it was trying to provide it, but was perhaps..pulsing trying to keep the voltage level up while the current draw was being demanded (assumption because I didnt have a scope or isolation transformer with me).
>
>  Interesting tho his comments said...good up to 1A so I blindly went forth and built assuming this fact.

The load men! The one connected to "swiched AC", pole 3 of JP1. That's
probably 1 A
It's a good example about how a well commented schematic may kill good
software programmers...
:)
Vasile

2007\06\15@124512 by alan smith

picon face
exactly your comment....assumption "load" was loading from the power supply, not the load on the relay.

Vasile Surducan <RemoveMEpiclist9spamspamBeGonegmail.com> wrote:  On 6/15/07, alan smith wrote:
> I'm including the pdf for the schematic that Bob had previously posted, so I'm sure its OK with him if I do so again (implied consent)
>
> The cap is a 0.82uF so following the formula, it would provide a max 35mA and makes sense that the LED's were flickering because it was trying to provide it, but was perhaps..pulsing trying to keep the voltage level up while the current draw was being demanded (assumption because I didnt have a scope or isolation transformer with me).
>
> Interesting tho his comments said...good up to 1A so I blindly went forth and built assuming this fact.

The load men! The one connected to "swiched AC", pole 3 of JP1. That's
probably 1 A
It's a good example about how a well commented schematic may kill good
software programmers...
:)
Vasile

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