Remove some leds

A

AK

Guest
I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
 
On 4/28/2019 8:47 AM, AK wrote:
I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
Click to expand...

Probably - depending upon which ones that you remove and the current
that they are now running on and the maximum current that they can run.

Easier would be to keep all the LED's and replace one of the resistors
with a higher value one. That would reduce the current in the LED's and
their brightness. Put a pot in place of one of the resistors and
experiment.
 
On Sun, 28 Apr 2019 05:47:54 -0700 (PDT), AK wrote:

I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?
Click to expand...

Since the leds are in opposite ways round it assume it's run from an ac
transformer (if all of them work). Just remove L4 and then only L1 and
L2 will light and the resistors will be correct for that half of the
power cycle.

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail rpont (at) gmail (dot) com
 
I noticed that 1 resistor is for ac line. Does that reduce 120 v to around 3 v? Do i modify the other resistor? Any idea what the box like item is?
 
On 04/28/2019 10:08 AM, Andy wrote:
I noticed that 1 resistor is for ac line. Does that reduce 120 v to
around 3 v? Do i modify the other resistor? Any idea what the box
like item is?
Click to expand...

That's a smoke box.

Get a black Sharpie pen, and color over the LEDs that you don't like.
That's what I did to fix some annoying LEDs in my car instrument panel.
 
On 4/28/2019 1:08 PM, Andy wrote:
I noticed that 1 resistor is for ac line. Does that reduce 120 v to around 3 v? Do i modify the other resistor? Any idea what the box like item is?
Click to expand...

Both resistors are in the AC line - one on each side. Don't know they'd
use 2, unless it is a feeble attempt to isolate the LED's from the line.
Yes, their purpose is to drop the voltage.

The box is in parallel to one of the resistors & I have no idea what it is.
 
On 28.04.19 21:07, Bob Engelhardt wrote:
On 4/28/2019 1:08 PM, Andy wrote:
I noticed that 1 resistor is for ac line. Does that reduce 120 v to around 3 v? Do i modify the other resistor? Any idea what the box like item is?


Both resistors are in the AC line - one on each side. Don't know they'd
use 2, unless it is a feeble attempt to isolate the LED's from the line.
Yes, their purpose is to drop the voltage.

The box is in parallel to one of the resistors & I have no idea what it is.
Click to expand...
a capacitor maybe? as an element to drop voltage.
The resistor in parallel is to discharge the cap.
 
On Sun, 28 Apr 2019 05:47:54 -0700 (PDT), AK
<scientist77017@gmail.com> wrote:

I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
Click to expand...
They are using capacitive reactance to limit current to the LEDs and
they have each set of LEDs wired +/- so that a rectifier isn't
required.

One pair conducts on the positive part of the sine wave and another
pair on the negative.

The LEDs need each other. Reverse breakdown of LEDs is on the order
of 5V or so. The conducting pair protect the non-conducting pair by
limiting the voltage.

To ditch two of the LEDs you could put a rectifier diode (a 1N2004
would be a good choice) in place of them. The rectifier would be
conducting and shunting the current limiting the voltage to ~0.6 V
protecting the remaining LEDs. There'd be more flickering and you may
find that annoying.

There's no transformer isolation so you'd get a nasty shock if you
fool with it cover-off and plugged in.

I'm guessing that if you plug it in then remove it from the outlet and
touch the prongs the led would come on for a short time as the cap
discharged through your fingers.

Or you could just put some paint on the LEDs or mask them with tape.
 
On Sun, 28 Apr 2019 21:13:39 +0200, Sjouke Burry
<burrynulnulfour@ppllaanneett.nnll> wrote:

On 28.04.19 21:07, Bob Engelhardt wrote:
On 4/28/2019 1:08 PM, Andy wrote:
I noticed that 1 resistor is for ac line. Does that reduce 120 v to around 3 v? Do i modify the other resistor? Any idea what the box like item is?


Both resistors are in the AC line - one on each side. Don't know they'd
use 2, unless it is a feeble attempt to isolate the LED's from the line.
Yes, their purpose is to drop the voltage.

The box is in parallel to one of the resistors & I have no idea what it is.

a capacitor maybe? as an element to drop voltage.
The resistor in parallel is to discharge the cap.
Click to expand...

The cap is dropping the voltage, the resistors are there as inrush
current limiting and as fuses in case the cap shorts.

I've got a Fairchild opto electronics applications manual that shows
the circuit. Capacitive reactance is a lot cheaper than a
transformer or power supply and is very efficient.

They use the same thing in some consumer things like coffee machine
digital timers.

If you want to use it yourself - the cap must be AC rated for voltage
or a film type DC 3-4 X higher voltage. You use the formula for
capacitive reactance to calculate the reactance at a particular
frequency and it is expressed in ohms.

Another neat trick is to wire a cap across a light switch that
controls LED bulbs. A point 5 microfarad cap will turn the LED into a
night light when the switch is in the off position. (some require a
little higher capacitance to light at all, but .5 is a good place to
start.)

In my bedroom I have a three position switch on the wall so I can run
the overhead light at reduced power when I'm searching for my clothes
in the dark and don't want to wake my wife. In the living room it is
across the standard light switch, and much better than the ordinary
night lights because it is the overhead light and not behind some
furniture like so many plug-in night lights. It only dissipated a
watt in night light mode so it is still very efficient.

AND unlike lamp dimmers controlling LED lamps there's no flicker to
speak of. (although there is a strobe effect with rotating things
like fans)
 
On Sun, 28 Apr 2019 17:35:36 -0400, default <default@defaulter.net>
wrote:

On Sun, 28 Apr 2019 05:47:54 -0700 (PDT), AK
scientist77017@gmail.com> wrote:

I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
They are using capacitive reactance to limit current to the LEDs and
they have each set of LEDs wired +/- so that a rectifier isn't
required.

One pair conducts on the positive part of the sine wave and another
pair on the negative.

The LEDs need each other. Reverse breakdown of LEDs is on the order
of 5V or so. The conducting pair protect the non-conducting pair by
limiting the voltage.

To ditch two of the LEDs you could put a rectifier diode (a 1N2004
would be a good choice) in place of them. The rectifier would be
conducting and shunting the current limiting the voltage to ~0.6 V
protecting the remaining LEDs. There'd be more flickering and you may
find that annoying.

There's no transformer isolation so you'd get a nasty shock if you
fool with it cover-off and plugged in.

I'm guessing that if you plug it in then remove it from the outlet and
touch the prongs the led would come on for a short time as the cap
discharged through your fingers.

Or you could just put some paint on the LEDs or mask them with tape.
Click to expand...

I just went back and looked at the circuit again. R1 looks like it is
across the cap so it discharges the cap when unplugged, so you
wouldn't see it light by putting your fingers on the plug prongs.
 
On Sunday, April 28, 2019 at 6:08:31 PM UTC-5, default wrote:
On Sun, 28 Apr 2019 17:35:36 -0400, default <default@defaulter.net
wrote:

On Sun, 28 Apr 2019 05:47:54 -0700 (PDT), AK
scientist77017@gmail.com> wrote:

I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
They are using capacitive reactance to limit current to the LEDs and
they have each set of LEDs wired +/- so that a rectifier isn't
required.

One pair conducts on the positive part of the sine wave and another
pair on the negative.

The LEDs need each other. Reverse breakdown of LEDs is on the order
of 5V or so. The conducting pair protect the non-conducting pair by
limiting the voltage.

To ditch two of the LEDs you could put a rectifier diode (a 1N2004
would be a good choice) in place of them. The rectifier would be
conducting and shunting the current limiting the voltage to ~0.6 V
protecting the remaining LEDs. There'd be more flickering and you may
find that annoying.

There's no transformer isolation so you'd get a nasty shock if you
fool with it cover-off and plugged in.

I'm guessing that if you plug it in then remove it from the outlet and
touch the prongs the led would come on for a short time as the cap
discharged through your fingers.

Or you could just put some paint on the LEDs or mask them with tape.

I just went back and looked at the circuit again. R1 looks like it is
across the cap so it discharges the cap when unplugged, so you
wouldn't see it light by putting your fingers on the plug prongs.
Click to expand...

I decided to paint 2 of the leds. :)

Andy
 
On Sun, 28 Apr 2019 05:47:54 -0700 (PDT), AK
<scientist77017@gmail.com> wrote:

I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
Click to expand...

You would have to short two of the LEDs. Black paint is easier.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
On 2019-04-28, AK <scientist77017@gmail.com> wrote:
I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
Click to expand...

The thing controlling the brighness is that big capacitor.

The easiest way to make that nightlight dimmer is to take a marker pen
or some paint and darken the LEDs a bit.

Or since they are two series strings you could remove two from
opposite corners and replace them with wire links.

Or add a resistor parallel with the LED string, (from the T shape to
the C shape) about 330 ohms could be a good starting point.

Next easiest would be to replace the capacitor with one of lower
capacitance, you need one that's X1 rated.

--
When I tried casting out nines I made a hash of it.
 
On Sunday, April 28, 2019 at 8:47:57 AM UTC-4, AK wrote:
I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.
Click to expand...

How about some black tape? or more permanent black goop.

George H.
 
On Tuesday, April 30, 2019 at 8:24:59 AM UTC-5, George Herold wrote:
On Sunday, April 28, 2019 at 8:47:57 AM UTC-4, AK wrote:
I would like to reduce the light output of this nightlight by removing two of the leds.

"https://www.dropbox.com/s/nd0mo8uidmz5w4h/20190428_073812.jpg?dl=0"

"https://www.dropbox.com/s/156rgctzo5bxihf/20190428_073751.jpg?dl=0"

Would I need to change one of the resistors?

Thanks.

How about some black tape? or more permanent black goop.

George H.
Click to expand...

I painted two of the leds.

Andy
 
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