AC offline to low-V supply, with a cap

George Herold wrote:


> 
> > > 
> > > http://crcomp.net/electronic/securitylight/085-5411-MB.png
> > > 
> > 
> > 
> > ** Don't think so - no way that concoction could work or be safe. 
> It's a diode bridge with 24V zeners in half of the legs.
> 
> The first cap needs to be robust.. I'd guess.


** Learn to read a circuit some time -  pal.



....  Phil  

> 
> George H. 
> > 
> > > FWIW, Todd Harrison produced a video [2] that shows how to convert a 
> > > readily available medical grade isolation transformer into a tech iso 
> > > transformer.
> > 
> > 
> > ** Unfortunately his understanding of the safety issue is wrong.
> > 
> > Using an isolation tranny on the service bench all the time creates a false sense of security that could result in a fatal electric shock. 
> > 
> > 
> > > In the video Harrison also reviews safety considerations 
> > > apropos to dropper supplies.
> > > 
> > 
> > 
> > ** Rule 1: 
> > 
> > Never connect them to the AC supply plug earth pin unless you intend to kill someone. 
> > 
> > Ham radio guys should keep away from subjects they do not understand, which dos not leave much. 
> > 
> > 
> > ....   Phil

George Herold <gherold@teachspin.com> wrote:
> On Friday, March 8, 2019 at 8:54:26 PM UTC-5, Phil Allison wrote:
>> Don Kuenz wrote:
>>
>> >
>> >
>> > AC outdoor security lights [1] typically use a dropper. The dropper
>> > circuit inside of one looks like this:
>> >
>> > http://crcomp.net/electronic/securitylight/085-5411-MB.png
>> >
>>
>>
>> ** Don't think so - no way that concoction could work or be safe.
> It's a diode bridge with 24V zeners in half of the legs.
>
> The first cap needs to be robust.. I'd guess.

Indeed. The dropper cap is rated at +250V. You obviously see how the
zener diodes do double duty. A very interesting circuit, to those able 
see it.

Thank you, 73,

-- 
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

George Herold <gherold@teachspin.com> wrote:

> On Friday, March 8, 2019 at 9:11:01 PM UTC-5, Steve Wilson wrote:
 
>> Without an isolation transformer, ZD1 and ZD2 would be shorted by the 
>> connection between the incoming line neutral and the external
>> connection to ground. 
 
> Ahh OK... but if the load is floating, it looks OK to me.  
> (who has never done such a thing.. except for AC indicator lights.)
 
> George H. 

It's the same problem with a dropper or any other equipment connected 
directly to the line. If you short the output and line neutral, you will 
probably blow any GFI connected to that line.

The other problem is line droppers will transmit line spikes, which can be 
severe. The may disrupt sensitive electrics, such as timers, amplifiers, etc.

Best is to just get a walwart rated for the load. The transformer provides 
isolation from spikes and complete freedom to connect the output wherever you 
need it.

On Saturday, 9 March 2019 01:01:17 UTC, George Herold  wrote:
> On Friday, March 8, 2019 at 2:33:09 PM UTC-5, Don Kuenz wrote:
> > Winfield Hill <hill@rowland.harvard.edu> wrote:
> > >  Years ago we had threads about the ugly but
> > >  seemingly simple scheme to get 12V DC at 5mA,
> > >  etc, with a film capacitor straight to the AC
> > >  line.  We said, gotta have a series resistor
> > >  to minimize the startup inrush current.
> > >
> > >  Does anybody recall a specific instance of
> > >  this scheme being used commercially?
> > >
> > >  Paul and I are days away from turning in the
> > >  manuscript on our new x-Chapters book, and I
> > >  decided to add this and a few other cheap
> > >  AC-to-DC-power circuits, for entertainment.
> > >  So I created one with SPICE, 12V at 5mA, only
> > >  a few parts, cost under $1.50, and the series
> > >  resistor sized to limit the worst-case inrush
> > >  (cap with -170V, new line connection at +170V)
> > >  to 720 mA, with a 470-ohm 2-watt wirewound.
> > >
> > >  OK, the numbers look bad.  Yes the cap current
> > >  is 90-deg out of phase with the voltage, but
> > >  not so for the 470-ohm resistor, swallowing
> > >  up power.  The efficiency is less than 5%.  Yes
> > >  I could reduce the 470, but its maximum pulsed
> > >  instantaneous power (0.2ms) is already 245 W.
> > >
> > >  Maybe an NTC inrush limiter, but I don't know
> > >  if the time scales are right.
> > 
> > AC outdoor security lights [1] typically use a dropper. The dropper
> > circuit inside of one looks like this:
> > 
> > http://crcomp.net/electronic/securitylight/085-5411-MB.png
> Huh.. one resistor?  
> Ya gotta love diodes!
> George H. 

never seen that type of inbuilt psu before. If I were desperate to save the cost of a cap I'd just use a resistor for a very low current load.


NT

Don Kuenz wrote:

> 
> >> >
> >> >
> >> > AC outdoor security lights [1] typically use a dropper. The dropper
> >> > circuit inside of one looks like this:
> >> >
> >> > http://crcomp.net/electronic/securitylight/085-5411-MB.png
> >> >
> >>
> >>
> >> ** Don't think so - no way that concoction could work or be safe.
> > It's a diode bridge with 24V zeners in half of the legs.
> >
> > The first cap needs to be robust.. I'd guess.
> 
> Indeed. The dropper cap is rated at +250V.
>
>

 ** The cap is not shown - why ??

 Active, Neutral and Earth are not shown  - why ?? 

 The dropper cap needs to be rated for AC volts, not just DC. 

 The fact the circuit unit is "hard wired " to the supply is CRUCIAL too. 
   

> You obviously see how the zener diodes do double duty.


 ** What does the symbol on the bottom right of the schem indicate?? 

    
 > A very iteresting circuit, to those able to see it.


 ** Shame you did not draw it correctly. 


 
> Thank you, 73,
> 
> -- 
> Don Kuenz KB7RPU


** Ham radio dickhead 



....  Phil 



> There was a young lady named Bright Whose speed was far faster than light;
> She set out one day In a relative way And returned on the previous night.

Phil Allison <pallison49@gmail.com> wrote:
> Don Kuenz wrote:

>> >> > AC outdoor security lights [1] typically use a dropper. The dropper
>> >> > circuit inside of one looks like this:
>> >> >
>> >> > http://crcomp.net/electronic/securitylight/085-5411-MB.png

>> >>
>> >> ** Don't think so - no way that concoction could work or be safe.
>> > It's a diode bridge with 24V zeners in half of the legs.
>> >
>> > The first cap needs to be robust.. I'd guess.
>>
>> Indeed. The dropper cap is rated at +250V.
>>
>
>  ** The cap is not shown - why ??
>
>  Active, Neutral and Earth are not shown  - why ??
>
>  The dropper cap needs to be rated for AC volts, not just DC.
>
>  The fact the circuit unit is "hard wired " to the supply is CRUCIAL too.
>
>
>> You obviously see how the zener diodes do double duty.
>
>
>  ** What does the symbol on the bottom right of the schem indicate??
>
>
>  > A very iteresting circuit, to those able to see it.
>
>
>  ** Shame you did not draw it correctly.

Bear in mind that this is a reverse engineering work in progress. 
Additional labels are now present on the schematic. The ground shown in
the bottom left side is the virtual ground. It's not the frame ground.
Here's a photo of the top side of the PCB:

http://crcomp.net/electronic/securitylight/pcbtopfront.png

The black wire and barely visible white wire are the 120VAC input. The
red wire is controlled by the blue relay at the upper middle of the PCB.
The relay's under command of a onboard microcontroller. (More about that
in a moment.) When the relay closes the red wire supplies 120VAC to a
pair of AC flood lights. 

The heart of the dropper shown in my schematic appears in the upper 
right hand corner of the PCB. In addition, the two large electrolytics 
to the left of the relay are the smoothing capacitors for the +24VDC and
+5VDC rails. R19 and ZD3 are SMD devices on the bottom of the PCB. (More
about that in a moment.) 

A PIR is under the three electrolytic capacitors beneath the relay. To
the right of the PIR is an LED and further right is the microcontroller, 
which is glob top encapsulated chip and therefore almost impossible for
me to access. The glob top chip shows up better in this photo:

http://crcomp.net/electronic/securitylight/pcbtopleft.png

My goal is to add a couple of features by modifying the PCB with the
replacement of the existing glob top microcontroller with a more user
friendly microcontroller. Here's a photo of the PCB bottom:

http://crcomp.net/electronic/securitylight/pcbbottom.png

The largest copper area on the middle left is the virtual ground shown
in my schematic. ZD3 is the middle of three devices shown on the upper
edge of the largest copper area. R19 is above it.

Acrylic paint and a small artist's brush was used to highlight the
power and ground traces. Green is for ground, cadmium red is for +24VDC,
and cadmium yellow is for +5VDC. 

Thank you, 73,

-- 
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

Phil Allison <pallison49@gmail.com> wrote:
> Don Kuenz wrote:

>> >> > AC outdoor security lights [1] typically use a dropper. The dropper
>> >> > circuit inside of one looks like this:
>> >> >
>> >> > http://crcomp.net/electronic/securitylight/085-5411-MB.png

>> >>
>> >> ** Don't think so - no way that concoction could work or be safe.
>> > It's a diode bridge with 24V zeners in half of the legs.
>> >
>> > The first cap needs to be robust.. I'd guess.
>>
>> Indeed. The dropper cap is rated at +250V.
>>
>
>  ** The cap is not shown - why ??
>
>  Active, Neutral and Earth are not shown  - why ??
>
>  The dropper cap needs to be rated for AC volts, not just DC.
>
>  The fact the circuit unit is "hard wired " to the supply is CRUCIAL too.
>
>
>> You obviously see how the zener diodes do double duty.
>
>
>  ** What does the symbol on the bottom right of the schem indicate??
>
>
>  > A very iteresting circuit, to those able to see it.
>
>
>  ** Shame you did not draw it correctly.

Bear in mind that this is a reverse engineering work in progress. 
Additional labels are now present on the schematic. The ground shown in
the bottom right side is the virtual ground. It's not the frame ground.
Here's a photo of the top side of the PCB:

http://crcomp.net/electronic/securitylight/pcbtopfront.png

The black wire and barely visible white wire are the 120VAC input. The
red wire is controlled by the blue relay at the upper middle of the PCB.
The relay's under command of a onboard microcontroller. (More about that
in a moment.) When the relay closes the red wire supplies 120VAC to a
pair of AC flood lights. 

The heart of the dropper shown in my schematic appears in the upper 
right hand corner of the PCB. In addition, the two large electrolytics 
to the left of the relay are the smoothing capacitors for the +24VDC and
+5VDC rails. R19 and ZD3 are SMD devices on the bottom of the PCB. (More
about that in a moment.) 

A PIR is under the three electrolytic capacitors beneath the relay. To
the right of the PIR is an LED and further right is the microcontroller, 
which is glob top encapsulated chip and therefore almost impossible for
me to access. The glob top chip shows up better in this photo:

http://crcomp.net/electronic/securitylight/pcbtopleft.png

My goal is to add a couple of features by modifying the PCB with the
replacement of the existing glob top microcontroller with a more user
friendly microcontroller. Here's a photo of the PCB bottom:

http://crcomp.net/electronic/securitylight/pcbbottom.png

The largest copper area on the middle left is the virtual ground shown
in my schematic. ZD3 is the middle of three devices shown on the upper
edge of the largest copper area. R19 is above it.

Acrylic paint and a small artist's brush was used to highlight the
power and ground traces. Green is for ground, cadmium red is for +24VDC,
and cadmium yellow is for +5VDC. 

Thank you, 73,

-- 
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

Phil Allison <pallison49@gmail.com> wrote:
> Don Kuenz wrote:

>> >> > AC outdoor security lights [1] typically use a dropper. The dropper
>> >> > circuit inside of one looks like this:
>> >> >
>> >> > http://crcomp.net/electronic/securitylight/085-5411-MB.png

>> >>
>> >> ** Don't think so - no way that concoction could work or be safe.
>> > It's a diode bridge with 24V zeners in half of the legs.
>> >
>> > The first cap needs to be robust.. I'd guess.
>>
>> Indeed. The dropper cap is rated at +250V.
>>
>
>  ** The cap is not shown - why ??
>
>  Active, Neutral and Earth are not shown  - why ??
>
>  The dropper cap needs to be rated for AC volts, not just DC.
>
>  The fact the circuit unit is "hard wired " to the supply is CRUCIAL too.
>
>
>> You obviously see how the zener diodes do double duty.
>
>
>  ** What does the symbol on the bottom right of the schem indicate??
>
>
>  > A very iteresting circuit, to those able to see it.
>
>
>  ** Shame you did not draw it correctly.

Bear in mind that this is a reverse engineering work in progress. 
Additional labels are now present on the schematic. The ground shown in
the bottom right side is the virtual ground. It's not the frame ground.
Here's a photo of the top side of the PCB:

http://crcomp.net/electronic/securitylight/pcbtopfront.png

The black wire and barely visible white wire are the 120VAC input. The
red wire is controlled by the blue relay at the upper middle of the PCB.
The relay's under command of a onboard microcontroller. (More about that
in a moment.) When the relay closes the red wire supplies 120VAC to a
pair of AC flood lights. 

The heart of the dropper shown in my schematic appears in the upper 
right hand corner of the PCB. In addition, the two large electrolytics 
to the left of the relay are the smoothing capacitors for the +24VDC and
+5VDC rails. R19 and ZD3 are SMD devices on the bottom of the PCB. (More
about that in a moment.) 

A PIR is under the three electrolytic capacitors beneath the relay. To
the right of the PIR is an LED and further right is the microcontroller, 
which is glob top encapsulated chip and therefore almost impossible for
me to access. The glob top chip shows up better in this photo:

http://crcomp.net/electronic/securitylight/pcbtopleft.png

My goal is to add a couple of features by modifying the PCB with the
replacement of the existing glob top microcontroller with a more user
friendly microcontroller. Here's a photo of the PCB bottom:

http://crcomp.net/electronic/securitylight/pcbbottom.png

The largest copper area on the middle right is the virtual ground shown
in my schematic. ZD3 is the middle of three devices shown on the upper
edge of the largest copper area. R19 is above it.

Acrylic paint and a small artist's brush was used to highlight the
power and ground traces. Green is for ground, cadmium red is for +24VDC,
and cadmium yellow is for +5VDC. 

Thank you, 73,

-- 
Don Kuenz KB7RPU
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

Don Kuenz is a Kunt wrote:


 Phil Allison 
> 
> >> >> >
> >> >> > http://crcomp.net/electronic/securitylight/085-5411-MB.png
> 
> >> >>
> >> >> ** Don't think so - no way that concoction could work or be safe.
> >> > It's a diode bridge with 24V zeners in half of the legs.
> >> >
> >> > The first cap needs to be robust.. I'd guess.
> >>
> >> Indeed. The dropper cap is rated at +250V.
> >>
> >
> >  ** The cap is not shown - why ??
> >
> >  Active, Neutral and Earth are not shown  - why ??
> >
> >  The dropper cap needs to be rated for AC volts, not just DC.
> >
> >  The fact the circuit unit is "hard wired " to the supply is CRUCIAL too.
> >
> >
> >> You obviously see how the zener diodes do double duty.
> >
> >
> >  ** What does the symbol on the bottom right of the schem indicate??
> >
> >
> >  > A very iteresting circuit, to those able to see it.
> >
> >
> >  ** Shame you did not draw it correctly.
> 
> Bear in mind that this is a reverse engineering work in progress.


** I bear no such damn thing in mind since you did NOT mention it before. 

 
> Additional labels are now present on the schematic.


** That is the SLEASIEST  thing I have ever seen anyone do on usenet !!!

The bullshitting prick has posted a NEW circuit under that SAME address as the previse entirely faulty one.

What a bloody deceit !!! 

Previous completely correct comments are now all rendered moot as no-one can see the old schem.

What a fucking cunt and ham radio asshole !!! 




....  Phil 

On Friday, March 8, 2019 at 9:30:58 PM UTC-5, Phil Allison wrote:
> George Herold wrote:
> 
> 
> > 
> > > > 
> > > > http://crcomp.net/electronic/securitylight/085-5411-MB.png
> > > > 
> > > 
> > > 
> > > ** Don't think so - no way that concoction could work or be safe. 
> > It's a diode bridge with 24V zeners in half of the legs.
> > 
> > The first cap needs to be robust.. I'd guess.
> 
> 
> ** Learn to read a circuit some time -  pal.

That's what I like about Phil.  He is always happy to give useful advice.  

Rick C.