I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring
plan type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring
and the wireless stat receiver, terminate in the airing cupboard, where
the tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

On 02/11/2016 13:06, Harry Bloomfield wrote:
I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring plan
type.

There is one just like that at my parents house. Which is just as well
since it is insanely complicated with multiple zones, two 3 way ported
valves, three thermostats and three independent clock timers together
with a bucket load of mechanical engineers relay based logic from well
before I understood electronics. Only the neon indicator lamps and a
multimeter allow me to figure out what is going on and to bodge round
the various failed or failing components to keep it all running. The
circuit diagram for this system if there ever was one is long gone.

The weakness is that you have to run a wire back to the indicator panel
from every point where you want to know the actual status.

When it was fully operational it could do hot water, upstairs,
downstairs or automatically switch to both and then upstairs at set
times choosing the right thermostat(s) accordingly. It was advanced for
its time but a bit over engineered and more like a process controller.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring and
the wireless stat receiver, terminate in the airing cupboard, where the
tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

Neon indicators are much easier where mains voltages are concerned. You
don't have to drop so much voltage in the load resistor that way.

Sensing actual valve position is one I would recommend since most
failures I have seen have been from one seizing up or motor failure
possibly triggered by water leakage. There is a nice stalagmite under
one of them now probably been growing since the 1970's.

I wouldn't bother with "pump running" as you can hear it in a quiet
house without needing an indicator lamp.

--
Regards,
Martin Brown

Martin Brown submitted this idea :
Neon indicators are much easier where mains voltages are concerned. You don't
have to drop so much voltage in the load resistor that way.

You can use a suitable diode, cap and resistor to run an LED on mains.


Sensing actual valve position is one I would recommend since most failures I
have seen have been from one seizing up or motor failure possibly triggered
by water leakage. There is a nice stalagmite under one of them now probably
been growing since the 1970's.

I will agree, 90% of our faults over the years, involved the valve
actuator, which is why I keep a spare to hand, ready to just plug in.


I wouldn't bother with "pump running" as you can hear it in a quiet house
without needing an indicator lamp.

Ours is all but inaudible, apart from when it first starts to run.

On Wed, 02 Nov 2016 13:06:56 GMT, Harry Bloomfield
wrote:

I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring
plan type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring
and the wireless stat receiver, terminate in the airing cupboard, where
the tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

Shortly after I moved in here in 1977 I made a control panel with four
neons, two to indicate that the CH and DHW were on, and the other two
to indicate when the cylinder stat and room stat were calling for
heat.
You really should take a little time to trace out your wiring first
though.
https://www.flickr.com/gp/g3zvt/ZE2P2h



--

Graham.

%Profound_observation%

On 02/11/16 13:06, Harry Bloomfield wrote:
I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring plan
type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring and
the wireless stat receiver, terminate in the airing cupboard, where the
tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

I want to do something similar.

I was thinking either:

a) Cheap and quick: Load of GRID neons in a shop lightswitch style panel
with dymo labels. But not very pretty.

b) Get a nice panel made up online with a proper legend with a system
schematic. Then use LEDs - you can get mains LED panel indicators (with
inbuilt resistors and diodes) to make this less Heath Robinson.

I have seen places that will do laser cut various materials, so in
theory it should be possible to get a plate engraved with any diagram
you can draw in a simple SVG editor (I plan to use Inkscape - it's
free). It might even be possible to get all the holes laser cut in the
same operation which would be dead cool.



In either case, I'd also like to have override switches for each
subsection to aid in priming/bleeding - and also in the event any
controller fails.

My system will need some relays anyway to combine:


2 UFH demand signals -- UFH mixer pump

then:

UFH mixer pump -v
General call for heat from rads -- Boiler demand
Air space heating (conservatory) -^



Probably use more relays than technically necessary so I don't need to
assume every control device has volt-free contacts (though most do seem
to). Plus the control device for UFH don't have enough guts to power the
surge current a mixer pump pulls at startup.

It also makes it easy to add override switches.


I am not sure if it's best to put the override switches in the panel
itself or on a separate panel or grid box.

To be super complete, I'd like centre-off 3 position rockers or toggles
so each override can be:

Manual On
OFF
Automatic

with Automatic being the nominal setting.

Not terribly difficult to add in as all the logic is in one place, and
avoids lots of arguments with plumbers when the boiler needs a service:
"It's your CH controls guv"
"No, see here - this green light says "Boiler Demand On"

On Wed, 02 Nov 2016 14:38:27 +0000
Graham. wrote:

On Wed, 02 Nov 2016 13:06:56 GMT, Harry Bloomfield
wrote:

I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone
has done something similar? Idea is to be able to quickly diagnose
any problems, so I can fix them. I have long since forgotten the
wiring plan type.

I have - a condensing boiler, stored hot water, radiators on a
wireless room stat, LCD time clock, pump and three port valve. All
the wiring and the wireless stat receiver, terminate in the airing
cupboard, where the tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call
for water heating, valve position indication, time clock says
heating on, time clock says water on.

Shortly after I moved in here in 1977 I made a control panel with four
neons, two to indicate that the CH and DHW were on, and the other two
to indicate when the cylinder stat and room stat were calling for
heat.
You really should take a little time to trace out your wiring first
though.
https://www.flickr.com/gp/g3zvt/ZE2P2h




I had wondered about making LED-sized holes in the cover of the
Honeywell junction box, and then fixing LEDs so that they poked through
the holes.

--
Davey.

On 02/11/16 13:06, Harry Bloomfield wrote:
I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring plan
type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring and
the wireless stat receiver, terminate in the airing cupboard, where the
tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

Yes, very useful. Had done the same with my old S-plan.

Had neon indications for 'call for water', 'call for heating' and
'boiler on'. All proving when lit that valves were in their correct
positions and the micro-switches working. If not, failed valve head
motor replaced in 10 minutes and heating back on!

--
Adrian C

Tim Watts used his keyboard to write :
I want to do something similar.

I was thinking either:

a) Cheap and quick: Load of GRID neons in a shop lightswitch style panel with
dymo labels. But not very pretty.

b) Get a nice panel made up online with a proper legend with a system
schematic. Then use LEDs - you can get mains LED panel indicators (with
inbuilt resistors and diodes) to make this less Heath Robinson.

I have now got this under way...

I am ordering a second CH joint box - double socket box with a blanking
plate. I will drill a row of holes in that for the LED's once I know
how many, then design a labelling panel to stick over the top.

The LED's I already have in stock, so I ordered up 10x 470nF 630v, 10x
220Ohm, 10x 1n4148 and some Vero- board. I'll add a 250mA fuse - I
suspect I will not have much choice but to install that in the common
neutral for the LED's. Rather naughty, but better than no fuse at all.

The live inputs will be fault current limited by the 220Ohm resistors.

L ---- 220 -- 470 -- 4148 + LED (back to back) ---- N

My intention is to mount the above display, directly above my CH joint
box in the airing cupboard and see what signals I can pick up from it.
That location is where I usually end up fault finding, so most useful
installed there.

I did originally draw a wiring diagram for the system, but it has been
hacked about since then by A N Installer, whilst I was out at work. New
boiler, new time controller, new wireless room stat, new pump, new
valve actuator, during which the wiring was well hacked about.

On 11/2/2016 1:06 PM, Harry Bloomfield wrote:
I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring plan
type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring and
the wireless stat receiver, terminate in the airing cupboard, where the
tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

I'd been thinking about setting up a Raspberry Pi with a temperature
logger, to give me flow and return temperatures on CH (2 circuits) and
DHW, plus tank temperature (I suspect I have a slight leak on a diverter
valve where pipes are normally inaccessible). And outside and some room
temperatures while I am at it.

On 02/11/2016 13:06, Harry Bloomfield wrote:
I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring plan
type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring and
the wireless stat receiver, terminate in the airing cupboard, where the
tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.


Well here's most of those:

http://wiki.diyfaq.org.uk/index.php/...h_ indicators


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 02/11/2016 13:06, Harry Bloomfield wrote:
I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring plan
type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring and
the wireless stat receiver, terminate in the airing cupboard, where the
tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

Seems like a chunk of work for something that you might (or might not)
need once every 10-20 years - why not just feel the pipes and measure
the voltage in the relevant locations? That's worked for me on the rare
occasions things have failed.
If you're short of something to do I can find you a few (dozen) jobs ;-)

brought next idea :
Seems like a chunk of work for something that you might (or might not) need
once every 10-20 years - why not just feel the pipes and measure the voltage
in the relevant locations? That's worked for me on the rare occasions things
have failed.
If you're short of something to do I can find you a few (dozen) jobs ;-)

Well, much more frequently than that, every few years in fact. I derive
great enjoyment from finding ways to make my life easier, such would
make my life easier - call it a hobby or even DIY.

My heating failed yesterday. It took me a while to work out that the
room stat wasn't calling for heat due to its batteries having failed.
This would make it quickly obvious why the heating wasn't working - no
call for heat.

On 02/11/2016 21:12, Harry Bloomfield wrote:
brought next idea :
Seems like a chunk of work for something that you might (or might not)
need once every 10-20 years - why not just feel the pipes and measure
the voltage in the relevant locations? That's worked for me on the
rare occasions things have failed.
If you're short of something to do I can find you a few (dozen) jobs ;-)

Well, much more frequently than that, every few years in fact. I derive
great enjoyment from finding ways to make my life easier, such would
make my life easier - call it a hobby or even DIY.

My heating failed yesterday. It took me a while to work out that the
room stat wasn't calling for heat due to its batteries having failed.
This would make it quickly obvious why the heating wasn't working - no
call for heat.

When I did some extension work about 10 years ago I fitted a new boiler
and pressurised DHW cylinder and split my system into 2 heating zones
(with individual timer/stats), 1 towel rad zone (with timer), 1 DHW
"zone" (with timer) and added a DHW recirculation loop (timer integrated
with pump) - all with 2-port valves. Since then the boiler and the
expansion vessel have each failed once and I've changed the stat
batteries once (the LCD display being blank was the hint I needed) but
everything else has been fine.
Apart from this, and in other houses, over forty years I think I've had
to replace two dead pumps, three 3-port valve heads (two of them had
broken microswitches), one room stat, one immersion heater and one ABV.
All were easy to identify and fix.
Based on my experiences, if you've got a 3-port valve and want to
improve reliability you might get more bang for your time by replacing
it with two 2-port valves rather than devising a monitoring system.

Harry Bloomfield has brought this to us :
The LED's I already have in stock, so I ordered up 10x 470nF 630v, 10x
220Ohm, 10x 1n4148 and some Vero- board. I'll add a 250mA fuse - I suspect I
will not have much choice but to install that in the common neutral for the
LED's. Rather naughty, but better than no fuse at all.

The live inputs will be fault current limited by the 220Ohm resistors.

L ---- 220 -- 470 -- 4148 + LED (back to back) ---- N

{EDIT] My 6mm superbright LED blew with the 470nF. The 470nF will be to
large a value, amend it to 0.1uF / 100nF 630volts and it works fine.

I really don't know why anyone uses neons as indicators - horrible things. They are always wire ended and have about as short a life span as a filament bulb. Just try looking at your cooker and see how many of them are flickering behind the temperature control, etc.

The problem with bespoke CH control systems is that the designer - and aren't we all one of those - knows how to operate it but never educates anyone else, nor leaves written instructions or a proper circuit diagram / manual for anyone else coming after them. And I plead guilty to this too, having a back-boilered wood burning stove and an oil CH boiler controlled with some resistor/diode/relay logic to switch between them and control valves, etc... The system has run happily for 25+ years without an electronic failure, but I've just spent the day giving the stove some TLC and am wondering how long before I have to do a repeat restoration operation on the oil burner.

On 02/11/2016 13:06, Harry Bloomfield wrote:
I have long had an urge to buy or build a small panel with a row of
LED's which shows the status of my CH system and wonder if anyone has
done something similar? Idea is to be able to quickly diagnose any
problems, so I can fix them. I have long since forgotten the wiring plan
type.

I have - a condensing boiler, stored hot water, radiators on a wireless
room stat, LCD time clock, pump and three port valve. All the wiring and
the wireless stat receiver, terminate in the airing cupboard, where the
tank and its stat are located.

I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

I purchased a couple of HIVE thermostat/controllers for my heating
system. 2 zones: upstairs and downstairs.

The receivers have very clear status LEDs *and* the best thing is I can
check status on my phone from bed (or indeed anywhere else on the
planet). I think it's great but my wife simply thinks I am mad.

Harry Bloomfield expressed precisely :
Harry Bloomfield has brought this to us :
The LED's I already have in stock, so I ordered up 10x 470nF 630v, 10x
220Ohm, 10x 1n4148 and some Vero- board. I'll add a 250mA fuse - I suspect
I will not have much choice but to install that in the common neutral for
the LED's. Rather naughty, but better than no fuse at all.

The live inputs will be fault current limited by the 220Ohm resistors.

L ---- 220 -- 470 -- 4148 + LED (back to back) ---- N

{EDIT] My 6mm superbright LED blew with the 470nF. The 470nF will be to large
a value, amend it to 0.1uF / 100nF 630volts and it works fine.

Sorry, and another [EDIT] of values....

I was using ideas and values found on the Internet, plus a bit of rule
of thumb.

It blew the LED and diode again, after an extended period on soak. So
47nF seems OK at the moment. It was also possible to get it to blow on
surge, repeated switching on and off, so I upped the surge resistor
value 1k2 seems to make it more robust. My present offering is...

L ---- 1K2 -- 47nF -- 4148 + LED (back to back) ---- N

On 09/11/2016 12:34, Harry Bloomfield wrote:
Harry Bloomfield expressed precisely :
Harry Bloomfield has brought this to us :
The LED's I already have in stock, so I ordered up 10x 470nF 630v,
10x 220Ohm, 10x 1n4148 and some Vero- board. I'll add a 250mA fuse -
I suspect I will not have much choice but to install that in the
common neutral for the LED's. Rather naughty, but better than no fuse
at all.

The live inputs will be fault current limited by the 220Ohm resistors.

L ---- 220 -- 470 -- 4148 + LED (back to back) ---- N

{EDIT] My 6mm superbright LED blew with the 470nF. The 470nF will be
to large a value, amend it to 0.1uF / 100nF 630volts and it works fine.

Sorry, and another [EDIT] of values....

I was using ideas and values found on the Internet, plus a bit of rule
of thumb.

It blew the LED and diode again, after an extended period on soak. So
47nF seems OK at the moment. It was also possible to get it to blow on
surge, repeated switching on and off, so I upped the surge resistor
value 1k2 seems to make it more robust. My present offering is...

L ---- 1K2 -- 47nF -- 4148 + LED (back to back) ---- N

That is ~10mA into the LED and it won't take much more to kill it.

It will invariably blow the LED to kingdom come every time there is a
fast mains transient glitch on the power line.

If you put a choke in series as well and/or a capacitor in parallel with
the LED it might survive but you would be safer with 1 or 2mA.

Try R = 100k C = 10n as a starting point - nominal 1mA drive.

Only the LED forward biassed by the 4148 will be lit. You may as well
put the diodes in series with a capacitor across the LED to avoid mains
flicker and smooth out any glitches. I am not sure that I should be
encouraging someone so inept to play with mains voltages.

You do this at your own risk.

--
Regards,
Martin Brown

In article ,
Tim Watts wrote:
I'm thinking - LED's for pump running, call for space heating, call for
water heating, valve position indication, time clock says heating on,
time clock says water on.

I want to do something similar.

I was thinking either:

a) Cheap and quick: Load of GRID neons in a shop lightswitch style panel
with dymo labels. But not very pretty.

b) Get a nice panel made up online with a proper legend with a system
schematic. Then use LEDs - you can get mains LED panel indicators (with
inbuilt resistors and diodes) to make this less Heath Robinson.

Since it's basically electrical, get a blank plate of the same make as
your wiring accessories in that room, and drill it for suitable LEDs or
whatever. The normal back box and fixing makes it as easy to install as a
socket, etc.

I have seen places that will do laser cut various materials, so in
theory it should be possible to get a plate engraved with any diagram
you can draw in a simple SVG editor (I plan to use Inkscape - it's
free). It might even be possible to get all the holes laser cut in the
same operation which would be dead cool.

You could have the blank plate engraved and filled with wax of the colour
you want.

Grid systems do seem like an easy way - but are restricted to module
width. Likely to be far wider than needed for a LED. And often aren't a
good match to your existing wiring accessories.

--
*Ambition is a poor excuse for not having enough sense to be lazy *

Dave Plowman London SW
To e-mail, change noise into sound.

on 09/11/2016, Dave Plowman (News) supposed :
Since it's basically electrical, get a blank plate of the same make as
your wiring accessories in that room, and drill it for suitable LEDs or
whatever. The normal back box and fixing makes it as easy to install as a
socket, etc.

That is the plan! I'm mounting it vertically, to make the labelling
easier and I have a labelling maching to hand.

Martin Brown has brought this to us :
That is ~10mA into the LED and it won't take much more to kill it.

It will invariably blow the LED to kingdom come every time there is a fast
mains transient glitch on the power line.

They are 30mA LED's.

If you put a choke in series as well and/or a capacitor in parallel with the
LED it might survive but you would be safer with 1 or 2mA.

They do not light at such low currents..

Only the LED forward biassed by the 4148 will be lit. You may as well put the
diodes in series with a capacitor across the LED to avoid mains flicker and
smooth out any glitches.

I can see the mains flicker, but that is not an issue - it is just a
diagnostic aid.

I am not sure that I should be encouraging someone
so inept to play with mains voltages.

That is offensive. You don't know my qualifications, so where does the
inept come from?

On 10/11/2016 11:07, Harry Bloomfield wrote:
Martin Brown has brought this to us :
That is ~10mA into the LED and it won't take much more to kill it.

It will invariably blow the LED to kingdom come every time there is a
fast mains transient glitch on the power line.

They are 30mA LED's.

If you put a choke in series as well and/or a capacitor in parallel
with the LED it might survive but you would be safer with 1 or 2mA.

They do not light at such low currents..

You are clueless. Modern LED dies are visibly lit on 10's of uA.
You only need a higher current if they are in sunlight.

Only the LED forward biassed by the 4148 will be lit. You may as well
put the diodes in series with a capacitor across the LED to avoid
mains flicker and smooth out any glitches.

I can see the mains flicker, but that is not an issue - it is just a
diagnostic aid.

I am not sure that I should be encouraging someone so inept to play
with mains voltages.

That is offensive. You don't know my qualifications, so where does the
inept come from?

Your original posting. You have no idea what you are doing.

--
Regards,
Martin Brown

Martin Brown submitted this idea :
Your original posting. You have no idea what you are doing.


--

Really! Just for reference - I designed and wrote the software for the
very first micro-based home central heating system controller. It did
all of the temperature sensing and timing in the one unit, it included
variable timed temperatures as well as the basic on off and frost
protection. This was long before the Internet appeared and in the very
early days of home computers.

The fact that what I suggested works and continues to work, is cheap to
implement sort of proves that I do know what I am doing. Your comments
suggest you are a troll.

Harry Bloomfield wrote
Martin Brown wrote

Your original posting. You have no idea what you are doing.

Really! Just for reference - I designed and wrote the software for the
very first micro-based home central heating system controller. It did
all of the temperature sensing and timing in the one unit, it included
variable timed temperatures as well as the basic on off and frost
protection. This was long before the Internet appeared and in the very
early days of home computers.

The fact that what I suggested works and continues to work, is cheap to
implement sort of proves that I do know what I am doing. Your comments
suggest you are a troll.

Not a troll, just another that leaps to unwarranted conclusions
and doesn't have the balls to admit that he can be wrong.

On Wed, 09 Nov 2016 12:34:57 +0000, Harry Bloomfield wrote:

Harry Bloomfield expressed precisely :
Harry Bloomfield has brought this to us :
The LED's I already have in stock, so I ordered up 10x 470nF 630v, 10x
220Ohm, 10x 1n4148 and some Vero- board. I'll add a 250mA fuse - I
suspect I will not have much choice but to install that in the common
neutral for the LED's. Rather naughty, but better than no fuse at all.

The live inputs will be fault current limited by the 220Ohm resistors.

L ---- 220 -- 470 -- 4148 + LED (back to back) ---- N

{EDIT] My 6mm superbright LED blew with the 470nF. The 470nF will be to
large a value, amend it to 0.1uF / 100nF 630volts and it works fine.

Sorry, and another [EDIT] of values....

I was using ideas and values found on the Internet, plus a bit of rule
of thumb.

It blew the LED and diode again, after an extended period on soak. So
47nF seems OK at the moment. It was also possible to get it to blow on
surge, repeated switching on and off, so I upped the surge resistor
value 1k2 seems to make it more robust. My present offering is...

L ---- 1K2 -- 47nF -- 4148 + LED (back to back) ---- N

Mine (as best as I can recall) went:

L...2k2...33nF(or maybe 47nF)...LED in antiparallel with cheap Si
diode...N (Earth in the case of the top floor "Protected Mains" twin
socket where the cct was rearranged as L...2k2...LED & Si
diode...33nF...E purely for ease of mounting the components - the
resulting 2.5mA flowing to earth being an acceptable compromise,
especially in the absence of ELCB protection on a cct intended to power
PC kit with its own earth leakage issues via 47nF caps (at least one per
PC ATX psu)).

I'd have sketched the original cct on a scrap of paper about a decade
ago... a quick look through my permanent collection of such scraps of
paper and a notepad failed to find such a cct diagram so memory it has to
be (that plus a sanity check with an on line reactance calculator).

The 3mm dia LEDs were 1990s vintage, recovered afaicr, from scrapped IT
kit. Despite their vintage, they give a bright enough indication despite
the simple half wave rectifier cct being used.

If you care to use blue LEDs of any vintage (by definition, recent
vintage), you could probably use 4.7nF and a 10K resistor with a halfwave
silicon diode in antiparallel across the LED. :-)

--
Johnny B Good

On Sat, 05 Nov 2016 12:32:03 +0000, Harry Bloomfield wrote:

Harry Bloomfield has brought this to us :
The LED's I already have in stock, so I ordered up 10x 470nF 630v, 10x
220Ohm, 10x 1n4148 and some Vero- board. I'll add a 250mA fuse - I
suspect I will not have much choice but to install that in the common
neutral for the LED's. Rather naughty, but better than no fuse at all.

The live inputs will be fault current limited by the 220Ohm resistors.

L ---- 220 -- 470 -- 4148 + LED (back to back) ---- N

{EDIT] My 6mm superbright LED blew with the 470nF. The 470nF will be to
large a value, amend it to 0.1uF / 100nF 630volts and it works fine.

Just how *bright* an indicator lamp did you need?[1] Even 100nF seems
like 'overkill' imo (ISTR using 47 or 33nF caps for my own LED
indicators).

Using a current inrush limiting resistor of only 220 ohms was likely the
main reason the LED blew up (3.2A peak worst case[2] being possible on
switch on) but the 16mA average current flowing through the LED may also
have contributed towards its demise.

[1] From your next post, I gather you didn't really need it to be quite
as bright as all that. :-)

The 1.2K resistor was a move in the right direction but I chose a larger
value again, 2.2K (peak inrush of c 300mA worst case scenario), or
possibly 6.8K (I couldn't see all the colour bands on the resistor when
checking an unused "protected supply" socket whilst the cct was still
live).

[2] Worst case scenario in this circuit being that the power is
disconnected just as the cap is charged to peak voltage followed by being
reconnected during an opposite peak voltage event resulting in a peak
voltage of some 700v being applied across the resistor.

The larger the capacitor used, the wider the destructive pulse of
current going through the resistor and LED/diode. A 1 amp rated diode
might be ok with such surges but the LED won't (with a 1 in 2 chance of
it being fried by such a pulse).

Even using a 1k2 resistor is going to result in a 583mA pulse of
current. I have a sneaking suspicion I may have actually used 6k8 inrush
limiting resistors in my own cct. A 6k8 resistor would have dropped 24v
and dissipated 84mW, leaving the bulk of the volt drop (almost 90%) to
the lossless capacitor dropper part of the circuit with a 47nF capacitor.
A 6k8 resistor in this case would have limited the worst case peak
current to 109mA.

In general, with narrow and low enough duty current spikes, diodes and
LEDs can withstand current peaks 2 or 3 orders of magnitude greater than
their maximum average ratings. You need to examine the data sheets to
best decide on the current limiting resistor if you want to keep
resistive losses to a minimum without needlessly endangering the diodes
and LEDs chosen for this type of circuit.

--
Johnny B Good

On Thu, 10 Nov 2016 15:58:09 +0000, Harry Bloomfield wrote:

Martin Brown submitted this idea :
Your original posting. You have no idea what you are doing.


--

Really! Just for reference - I designed and wrote the software for the
very first micro-based home central heating system controller. It did
all of the temperature sensing and timing in the one unit, it included
variable timed temperatures as well as the basic on off and frost
protection. This was long before the Internet appeared and in the very
early days of home computers.

The fact that what I suggested works and continues to work, is cheap to
implement sort of proves that I do know what I am doing. Your comments
suggest you are a troll.

To be fair and by your own admission, your foray into the design of LED
based mains indicator lamps seems to have been more experimental than
theoretical. At least you got to a working model (by my count) in only 3
iterations. :-)

By that example, I would say you *do* have *some* idea of what you were
doing, contrary to Martin Brown's thesis. It just seemed to me that you
CBA with those pesky calculations to check out the consequences of your
original choices of component values.

Now I, when it comes to powered circuits, am of a rather nervous
disposition so tend to calculate the consequences of component choices
before allowing "The Experiment" to go 'Live'. :-)

--
Johnny B Good