Hi Andrew ... in the post below you asked me for data on the LED
Standard W10 Silicon Bridge Rectifiers ...

-----------------

Can you point to the datasheet for your LEDs?
My calculation assumed 40mA non-repetitive peak current.

What design constraints have you got (such as max power
dissipation per indicator)?


Here is datasheet on Br Rectifiers ...
http://pdf.datasheetcatalog.com/data...y/mXyzsrux.pdf

LED are standard 5mm LED (100mcd) ... forward Voltage 1.8-2.2V
20mA nominal current, 40mA maximum.

Capacitor are X2 rated, Polypropylene MPX 0.47uF
Withstand Voltage 275V AC
Rating Voltage 250V AC

No specific design constraint on display, just something that will
illuminate them.

I have purchased the capacitors, Br Rectifiers & LED so keen not to
waste these ...


Were you able to take a look at cct to see if there is suitable a
resistor or modification that allows use of these components, while
reducing the risk you (thankfully ) pointed out of blowing the LED's

One suggestion was to increase resistor to 680R

Welcome your advice.




--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

In article , Rick Hughes
writes
Hi Andrew ... in the post below you asked me for data on the LED
Standard W10 Silicon Bridge Rectifiers ...

-----------------

Can you point to the datasheet for your LEDs?
My calculation assumed 40mA non-repetitive peak current.

What design constraints have you got (such as max power
dissipation per indicator)?


Here is datasheet on Br Rectifiers ...
http://pdf.datasheetcatalog.com/data...y/mXyzsrux.pdf

LED are standard 5mm LED (100mcd) ... forward Voltage 1.8-2.2V
20mA nominal current, 40mA maximum.


Delve a bit more into the data for the LEDs to find their peak rating, I
suspect the values given are the nominal and maximum _continuous_
values.

If you can't find it on the sheet then give us a link to the data sheet.

There are other issues as well but one step at a time.
--
fred
it's a ba-na-na . . . .

On 31/01/2014 17:24, fred wrote:


Delve a bit more into the data for the LEDs to find their peak rating, I
suspect the values given are the nominal and maximum _continuous_ values.

If you can't find it on the sheet then give us a link to the data sheet.

There are other issues as well but one step at a time.

I did try that, and contacted seller ... all he has is what he provided
.... he has no other data, he bought a job lot and has no data sheet.
All he could give me was:

100mcd ... forward Voltage 1.8-2.2V
20mA nominal current, 40mA maximum.

I'm happy if we set 20mA as the design criteria, need indication only
not light the room :-)


--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

In article , Rick Hughes
writes
On 31/01/2014 17:24, fred wrote:


Delve a bit more into the data for the LEDs to find their peak rating, I
suspect the values given are the nominal and maximum _continuous_ values.

If you can't find it on the sheet then give us a link to the data sheet.

There are other issues as well but one step at a time.

I did try that, and contacted seller ... all he has is what he provided
... he has no other data, he bought a job lot and has no data sheet.
All he could give me was:

100mcd ... forward Voltage 1.8-2.2V
20mA nominal current, 40mA maximum.

I'm happy if we set 20mA as the design criteria, need indication only
not light the room :-)

Without full data for the LEDs it's difficult to say what the pulse
handling capability of the LEDs you have is. Some are better than others
and the different materials used to generate the light make a huge
difference, red generally being more pulse capable than other colours.

After looking at some typical device data and with finger in the air,
I'll say that your nondescript leds will take 75-100mA as an occasional
short duration peak at switching time.

240V peak is 338V which would need 3k9 or 4k7 to limit switch on current
to 87 or 75 mA.

Now consider dissipation in the res with led on:

You have gone for a 470nF dropper which gives a hefty 35mA rms current.
This will be pushing 5W in each resistor which is really too much (even
with a 10W res, it would be too hot to touch). In addition, you will be
running at a peak led operating current of 50mA which again is too much.

Best to see if you can get sufficient illumination with a lower
operating current, even if it means scrapping those leds (Experiment
with a dc supply and a few resistors).

Lets try a 100nF dropper (Xc of 32k).

That gives 7.5mA rms or 10mA pk which I'm guessing will give you
reasonable brightness indoors.

That will give just over a quarter watt in a 4k7 pulse limiting res
which will be fine for a half watt resistor (always best to derate).

Next, peak power dis in the res at switching, 75mA in 4k7 gives 26W peak
meaning that we really need this to be a pulse capable resistor such as
carbon composition (yes they do still make them).

We also need the res to withstand at least the peak volts of the mains
(338V) plus a bit for transients so a 350-500V resistor.

These parts would do the job at a cost of 45p per chain:

http://cpc.farnell.com/CA07116 100nF 300Vac X2
http://cpc.farnell.com/RE06293 4k7 0.5W 350V Carbon composition

Bear in mind that the above is entirely theoretical and should be used
only as a starting point for experimentation.

In your place I would set up one of these on a switching rig (one red,
one green or a few of each) and absolutely hammer them to make sure the
leds and other components survive. At its most simplistic, this could be
running them connected to an old fashioned mechanical plug in timer with
alternating 15min on-off periods.


Starting from scratch I would probably search for some really low
current (say 2mA) but bright and pulse capable leds which would result
in reduced component stress, values and hence cost.


Finally the safety stuff:

1. Safe distances between L & N (and any series components carrying
same) on a board or through air (creepage and clearance) is 4mm. That
will mean removing intervening tracks if using veroboard.

2. Same for between L or N and Earth on an earthed (Class 1) setup is
6mm. 8mm to exposed unearthed metal parts on Class 2 I think.

3. Only use X2 rated caps and 350V or above pulse capable resistors.

4. IMO, it would not be safe to mount the LEDs in a metal panel (even if
earthed), the insulation will not have been specified for mains use. Use
a plastic panel and mount so that even if damaged, the LED junction
would be some way behind the front face of the panel.


Are you sure you don't want to scrap it all and use some skinny neons
;-)

Otherwise, good luck.
--
fred
it's a ba-na-na . . . .

On 01/02/2014 20:51, fred wrote:



Now consider dissipation in the res with led on:

You have gone for a 470nF dropper which gives a hefty 35mA rms current.
This will be pushing 5W in each resistor which is really too much (even
with a 10W res, it would be too hot to touch). In addition, you will be
running at a peak led operating current of 50mA which again is too much.



4. IMO, it would not be safe to mount the LEDs in a metal panel (even if
earthed), the insulation will not have been specified for mains use. Use
a plastic panel and mount so that even if damaged, the LED junction
would be some way behind the front face of the panel.


Are you sure you don't want to scrap it all and use some skinny neons ;-)



Box will be all fully insulated nylon ...


Never use neons ... what would cct look like with these .... although I
would prefer to use what I just bought .... (if it is possible)

The whole reason for going to capacitor dropper was to avoid dissipating
heat in resistors which many of the simple ccts do.

Just so annoying I followed the design as per here ....
http://www.marcspages.co.uk/tech/6103.htm

(I have had contact from page owner he insists with 220R it works fine,
but for additional reliability it could be increased to 680R )

--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

In article , Rick Hughes
writes

Box will be all fully insulated nylon ...

Never use neons ... what would cct look like with these .... although I
would prefer to use what I just bought .... (if it is possible)

The whole reason for going to capacitor dropper was to avoid dissipating
heat in resistors which many of the simple ccts do.

Just so annoying I followed the design as per here ....
http://www.marcspages.co.uk/tech/6103.htm

(I have had contact from page owner he insists with 220R it works fine,
but for additional reliability it could be increased to 680R )


If you want to test the reliability of the circuit with the original
values then set up a circuit to switch the mains to it every second or
so and if it lasts more than 24hrs then stick with those values to
monitor your occasionally switched heating zones, if they don't last
then you have your answer.

220R will result in 1.5A peak LED current when switched on at the peak
of the ac waveform, 500mA for 680R. I'd say that the former will pop all
but the toughest pulse capable LEDs in short order and that the latter
will be a 50-50 risk.

You still risk popping the LEDs for excessive forward current when lit,
things last longer when derated, which is why they have a nominal and a
max rating, they'll last 10-100 times longer when operated at nominal
over what they will when operated at max.

--
fred
it's a ba-na-na . . . .

Rick Hughes wrote:
Hi Andrew ... in the post below you asked me for data on the LED
Standard W10 Silicon Bridge Rectifiers ...

-----------------

Can you point to the datasheet for your LEDs?
My calculation assumed 40mA non-repetitive peak current.

What design constraints have you got (such as max power
dissipation per indicator)?


Here is datasheet on Br Rectifiers ...
http://pdf.datasheetcatalog.com/data...y/mXyzsrux.pdf

LED are standard 5mm LED (100mcd) ... forward Voltage 1.8-2.2V
20mA nominal current, 40mA maximum.

Capacitor are X2 rated, Polypropylene MPX 0.47uF
Withstand Voltage 275V AC
Rating Voltage 250V AC

No specific design constraint on display, just something that will
illuminate them.

I have purchased the capacitors, Br Rectifiers & LED so keen not to
waste these ...


Were you able to take a look at cct to see if there is suitable a
resistor or modification that allows use of these components, while
reducing the risk you (thankfully ) pointed out of blowing the LED's

One suggestion was to increase resistor to 680R

Welcome your advice.




Thought a bit more about this. If these are low efficiency red leds,
then the Vf will be about 2V---roughly. This is about twice the level of
a 4148 diode which will withstand 1A for 1 second (data sheet).
This indicates that the leds will probably withstand 300mA for 1 second
so, I'd guess that 1A at 10mS would be survived. So personally, I'd go
with 4(400V) resistors to make up 1K and survive any transient voltages.
I'd also reduce the capacitor to 0.1uF. Over run leds don't last long,
as the chinese are proving in lamps. My rule of thumb for capacitative
droppers is 80mA/uF, so peak running currents of 12mA should be
adequate. These are off the cuff thoughts, others may differ. I've seen
1500V transients on our house mains supply and I would normally scope
this circuit to make sure that things are behaving as expected.

Capitol wrote:
Rick Hughes wrote:
Hi Andrew ... in the post below you asked me for data on the LED
Standard W10 Silicon Bridge Rectifiers ...

-----------------

Can you point to the datasheet for your LEDs?
My calculation assumed 40mA non-repetitive peak current.

What design constraints have you got (such as max power
dissipation per indicator)?


Here is datasheet on Br Rectifiers ...
http://pdf.datasheetcatalog.com/data...y/mXyzsrux.pdf

LED are standard 5mm LED (100mcd) ... forward Voltage 1.8-2.2V
20mA nominal current, 40mA maximum.

Capacitor are X2 rated, Polypropylene MPX 0.47uF
Withstand Voltage 275V AC
Rating Voltage 250V AC

No specific design constraint on display, just something that will
illuminate them.

I have purchased the capacitors, Br Rectifiers & LED so keen not to
waste these ...


Were you able to take a look at cct to see if there is suitable a
resistor or modification that allows use of these components, while
reducing the risk you (thankfully ) pointed out of blowing the LED's

One suggestion was to increase resistor to 680R

Welcome your advice.




Thought a bit more about this. If these are low efficiency red leds,
then the Vf will be about 2V---roughly. This is about twice the level of
a 4148 diode which will withstand 1A for 1 second (data sheet).
This indicates that the leds will probably withstand 300mA for 1 second
so, I'd guess that 1A at 10mS would be survived. So personally, I'd go
with 4(400V) resistors to make up 1K and survive any transient voltages.
I'd also reduce the capacitor to 0.1uF. Over run leds don't last long,
as the chinese are proving in lamps. My rule of thumb for capacitative
droppers is 80mA/uF, so peak running currents of 12mA should be
adequate. These are off the cuff thoughts, others may differ. I've seen
1500V transients on our house mains supply and I would normally scope
this circuit to make sure that things are behaving as expected.

Was the original designed for 110V?

On 03/02/2014 01:43, Capitol wrote:
Capitol wrote:


Was the original designed for 110V?


No ... the guy has a page with his design (and theory) if you want a look :

http://www.marcspages.co.uk/tech/6103.htm

I did reach out to him, and although he advises his circuit works fine
he is adamant the 220R stops any excess in-rush current,though he did
add that increasing that to 680R might be worthwhile.

It looks like I will have to buy a new set of capacitors ... seems to be
form your & Freds comments hat 0.22uF will be better at ~20mA


--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

In article , Rick Hughes
writes
On 03/02/2014 01:43, Capitol wrote:
Capitol wrote:


Was the original designed for 110V?


No ... the guy has a page with his design (and theory) if you want a look :

http://www.marcspages.co.uk/tech/6103.htm

I did reach out to him, and although he advises his circuit works fine
he is adamant the 220R stops any excess in-rush current,though he did
add that increasing that to 680R might be worthwhile.

It looks like I will have to buy a new set of capacitors ... seems to be
form your & Freds comments hat 0.22uF will be better at ~20mA

I'm sure this hole is getting bigger as we speak but please don't buy
_sets_ of anything until you have fully tested the concept for light
output and durability.

Your 470n caps are not totally wasted as you can combine them in chains
to experiment with circuit values. If you weren't already aware, 2 x
470n in series will create 235nF so a suitable test for 220n or 5 x 470n
will create 94nF which will test for 100n. Obviously more bulky than
correct replacements but this is only for testing.

Note that if you go for 20mA then you will limit your pulse resistor
size to about a quarter of the sizes I suggested (power = I sqrd x R),
you will be limited to 1k or so make sure you test for durability of
your non spec'd leds at those pulse levels before building in quantity.

Reet, that's enough digging, I'm out . . . .
--
fred
it's a ba-na-na . . . .

On 03/02/2014 23:39, fred wrote:


Note that if you go for 20mA then you will limit your pulse resistor
size to about a quarter of the sizes I suggested (power = I sqrd x R),
you will be limited to 1k or so make sure you test for durability of
your non spec'd leds at those pulse levels before building in quantity.




OK went and ordered some 0.22uF X2 caps ... so when they arrive will
try them out ... so with the aim to be at 20mA, am I following you
correctly to use 1k 1/4 resistors ?

--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

Rick Hughes wrote:
On 03/02/2014 23:39, fred wrote:


Note that if you go for 20mA then you will limit your pulse resistor
size to about a quarter of the sizes I suggested (power = I sqrd x R),
you will be limited to 1k or so make sure you test for durability of
your non spec'd leds at those pulse levels before building in quantity.




OK went and ordered some 0.22uF X2 caps ... so when they arrive will try
them out ... so with the aim to be at 20mA, am I following you correctly
to use 1k 1/4 resistors ?

The problem now is not the wattage, it's the voltage across the
resistor. You need to use 4 off 400V rated resistors to avoid the
coating breaking down when a transient hits the circuit. Check the
resistor voltage ratings. There are some special high voltage reistors
around, Philips used to make some, Multicomp do some 1W carbon film
resistors which will withstand 1KV but only down to 1K I believe. You'd
need two of those in series.

In article , Rick Hughes
writes
On 03/02/2014 23:39, fred wrote:

Note that if you go for 20mA then you will limit your pulse resistor
size to about a quarter of the sizes I suggested (power = I sqrd x R),
you will be limited to 1k or so make sure you test for durability of
your non spec'd leds at those pulse levels before building in quantity.

OK went and ordered some 0.22uF X2 caps ... so when they arrive will
try them out ... so with the aim to be at 20mA, am I following you
correctly to use 1k 1/4 resistors ?


Actually no, the values I recommended are those given in my second post
in this thread[1] but you have chosen to ignore them.

My mention of 1k was a warning that that was the maximum value you could
use at your new current level without the resistor bursting into flames,
it was not a recommendation to use that value.

If you insist on using those values then you do so at your own risk but
in the interests of safety for you and yours, I will point you at:

http://cpc.farnell.com/RE06270 1k0 0.5W carbon comp 350V working, 700V
permitted overload

1/4W is not suitable, nor is anything other than a pulse capable, high
voltage resistor.


[1] In my earlier post I suggested a 4k7 0.5W 350V Carbon composition
resistor for use in a 7.5mA circuit but incorrectly gave the part number
for a 680R resistor. The correct part number for 4k7 is:

http://cpc.farnell.com/RE06278
--
fred
it's a ba-na-na . . . .

On 04/02/2014 20:55, fred wrote:
In article , Rick Hughes
writes
On 03/02/2014 23:39, fred wrote:

Actually no, the values I recommended are those given in my second post
in this thread[1] but you have chosen to ignore them.




No ... not intending to ignore value, apologies if you think that.. but
you posted for 7.5mA which would seem too low, I want to get closer to
20mA nominal for LED ........ but accept your warning over 0.47uF
capacitor being too big.

I had assumed in your post when you wrote:
"if you go for 20mA then you will limit your pulse resistor size to
about a quarter of the sizes I suggested (power = I sqrd x R), you will
be limited to 1k "


Assumed that this meant use 1K as the current limiting resistor .... if
this is incorrect, what value should be used with a 0.22uF capacitor ?

I will also try the 100nF & 4k7 option you give .... so I can test both







--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

In article , Rick Hughes
writes
On 04/02/2014 20:55, fred wrote:
In article , Rick Hughes
writes
On 03/02/2014 23:39, fred wrote:

Actually no, the values I recommended are those given in my second post
in this thread[1] but you have chosen to ignore them.

No ... not intending to ignore value, apologies if you think that.. but
you posted for 7.5mA which would seem too low, I want to get closer to
20mA nominal for LED ........ but accept your warning over 0.47uF
capacitor being too big.

Ok, fair enough.

The general point I was aiming for was that you want to minimise both
the operating and transient current in the droppers where you have
fragile elements (the LEDs and to a lesser extent, the resistors).

Without any real data available for the LEDs I made some assumptions
(perhaps conservative ones) that 100mA repetitive peak would be a safe
max current and that was where my 4k7 pulse/inrush/transient resistor
came from (actually gives 75mA pulse limit) and that is what I think is
a safe value so as not to pop LEDs or overstress the resistor under
maximum switch-on pulse. This is the same for all LED operating currents
(cap sizes) but you can't use 4k7 at operating currents above 7.5mA
(rms) as the resistor will fry.

Reducing the transient limiting resistor will increase the risk of
popping the LEDs so that is why I am not happy about it.

Capitol has suggested 300mA might be a safe peak limit and that may be
closer to the mark but we just don't know.

Trying 300mA peak pulse gives 1k1 as a resistor value so 1k0 may be
something you want to try. The 20mA you mention with 220n is actually
closer to 16.5mA (rms) which will give 272mW in a half watt resistor
which is safe. The peak power at switch on is a hefty 90W which is a lot
or a half watt resistor to take so the res may pop as well as the LED
(or neither . . . ).

I had assumed in your post when you wrote:
"if you go for 20mA then you will limit your pulse resistor size to
about a quarter of the sizes I suggested (power = I sqrd x R), you will
be limited to 1k "

Assumed that this meant use 1K as the current limiting resistor .... if
this is incorrect, what value should be used with a 0.22uF capacitor ?

What I meant was 1k0 is the max you can use (for resistor power
dissipation reasons) when running at 20mA (16.5mA actual) and I didn't
think that would be enough to avoid popping LEDs but if you want to give
it a go then it may work (no guarantees).

I will also try the 100nF & 4k7 option you give .... so I can test both

Do try for the lowest current you can.

Designing this properly is tricky, if I was doing a product design with
something like this in I'd be choosing my LEDs carefully from low
current, high efficiency but pulse capable ranges and operating it at as
low a current as possible, 2-5mA max, to reduce component stress.

--
fred
it's a ba-na-na . . . .

On 05/02/2014 17:52, fred wrote:


Designing this properly is tricky, if I was doing a product design with
something like this in I'd be choosing my LEDs carefully from low
current, high efficiency but pulse capable ranges and operating it at as
low a current as possible, 2-5mA max, to reduce component stress.



Thanks for the details .... it was the extreme simplicity of the cct
that was attractive .... I'm at the point of changing the whole
concept and use Mains neon indicators instead ... :-(

Would also avoid need to create a PCB ...



--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/