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 Post subject: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 3:39 pm 
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What is the mechanism that makes a neon bulb start to flicker? I talking about the common little NE-2 bulbs. Many times you'll see these in power strips flickering away. I want to recreate this flicker for a Halloween project. The only neon bulbs that I could find made specfically to ficker are the larger candelabra or medium based neon bulbs with the flame looking electrodes. I want an NE-2 or NE-2H to do this. Has anyone seen this size bulb made to flicker like a candle? I've tried underdriving them by increasing the series resistor but that only makes them dimmer. I was thing about overdriving them but have a feeling that would take a long time to achieve the "ageing" that I'm looking for. Any thoughts on this one?


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 3:56 pm 
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To save the trouble of making it, you can buy battery operated tea lights that have the flicker. I haven't taken one apart to see what inside, but can.


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 4:15 pm 
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Model railroaders simulate campfire flames using a flickering LED. It's a pretty old technique. The LED is driven from the output of a linear feedback shift register (LFSR) clocked at a relatively low frequency. The output bit-string from the LFSR is pseudo-random. That produces the flickering effect.

I believe that the same mechanism is used in the tea lights.

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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 4:36 pm 
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Location: Santa Rosa, CA
Quote:
Flickering bulbs

You can buy neon lights deliberately designed to flicker, for example to simulate candle light. There are two electrodes within the glass bulb – a pair of closely spaced, but not quite parallel, metal plates. The spot where the glow is produced is sensitively dependent on the gap at that point and also probably the temperature and pressure in that region. The result is that the glow randomly moves around between the plates, looking rather like a candle flame flickering in a breeze.


https://edu.rsc.org/feature/trade-secrets--neon-lights-flicker-bulbs-and-chaos/3007420.article

Since neon bulbs require 70 to 90 V to operate, you are safer using LEDs. "Flickering" LEDs actually have a simple Integrated Circuit chip in the structure that causes random blinking.

https://shop.evilmadscientist.com/productsmenu/189

Neon bulbs ARE sensitive to radiation, including light. I had an old neon bulb pilot light that would not illuminate, unless I pointed a laser pointer at it. The internal gas needed a bit more energy to ionize and glow.

Rich

PS: Over-driving a neon bulb will cause it to overheat and die.


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 5:57 pm 
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Location: Montreal, Quebec
I assume the "candles" Alan mentioned are using pseudo-random generators. A specific use, so really easy to out in a small IC, or maybe part of the LED.

Forty years ago there were ICs for "white noise" (often followed by a filter for "pink noise"). Those were shift registers arranged as a pseudo-random generator. A much longer shift register, and clocked fast.

In both cases, if done with common logic ICs, it gets bulky because of multiple ICs with output pins not used. But for a dedicated purpose, no flexibility needed, and hence only a few pins needed.


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 6:23 pm 
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No need for logic ICs or invention.

100 flickering white LEDs plus resistors for $10!

https://www.amazon.com/EDGELEC-Flickeri ... B077XFPJ2W

Rich


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 8:55 pm 
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Location: Arlington, VA USA
Thanks for the suggestion guys. Just had a bunch of these neon bulbs laying around and thought I might be able to use them for this project. I guess I am curious why these can flicker when they are not designed to in the first place. And then if there was a technique that I could use to get them to.


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Mon 20, 2021 11:34 pm 
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There were projects in Popular Electronics in the early sixties that used neon bulbs. But I can't remember details.

I can picture something with a few neon bulb oscillators connected for a sort of random display. I can't remember if this was standalone, or used to give flicker to an incandescent bulb.

I hadn't noticed flashing LEDs at Amazon. Seems like a good price. I could have everything flashing.


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 2:22 am 
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ErikD wrote:
Thanks for the suggestion guys. Just had a bunch of these neon bulbs laying around and thought I might be able to use them for this project. I guess I am curious why these can flicker when they are not designed to in the first place. And then if there was a technique that I could use to get them to.

I think the ones you have seen are either worn out or the gas in then is not the right concentration. The available voltage from the AC line is not quite high enough to reliably light them. If you have a variac, you might try running some neon bulbs at reduced voltage and see what happens.

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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 2:59 am 
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This is the first electronic kit I built when I was 10 or 11 years old from a old copy my cousin gave me of July 1963 issue of Popular Electronics. My father went to Canal Street in New York City to buy the parts for me. I remembered vividly I wrote the parts list down and for the capacitors the guy behind the counter sold my father 600v .5uf film capacitors and for the resistors I wrote the resistor values I needed at 117 volts each. The guy explained to my father there are no voltage requirement as the capacitors have. I learned something new that day.

Till this day I love to play with neon bulbs, except now its Nixie tubes.

Sal


Attachments:
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Popular Electronics 2.jpg
Popular Electronics 2.jpg [ 226.89 KiB | Viewed 612 times ]

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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 3:28 am 
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The tea light is even simpler than I expected. Here are the parts of it (minus a second screw that's now somewhere on the floor):
Attachment:
IMG_20210921_102303.jpg
IMG_20210921_102303.jpg [ 345.57 KiB | Viewed 602 times ]

The black thing is the on/off switch. It just pushes the contact into the battery. Other than the bulb and the battery, there are no other electronic parts. No resistors, capacitors, or chips of any kind.
Attachment:
IMG_20210921_103029.jpg
IMG_20210921_103029.jpg [ 303.9 KiB | Viewed 602 times ]

Attachment:
IMG_20210921_121119.jpg
IMG_20210921_121119.jpg [ 281.67 KiB | Viewed 577 times ]


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 4:51 am 
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I use the flicker LEDs as a signal source to drive brighter LEDs.
One pot controls the voltage to the flicker LED, the other sets the bias level for the FET. A capacitor couples the flicker signal to the FET.
I've built maybe 30 of these to create my Halloween display. One of them will be driving a 27 watt bumper-mount LED spotlight hidden in a cauldron with orange plastic.
I hooked three of them to an LED strip with RGB inputs. It was very disorienting!
Attachment:
2 Flicker 3 boards.jpg
2 Flicker 3 boards.jpg [ 320.27 KiB | Viewed 585 times ]

Attachment:
4 Flicker circuit.jpg
4 Flicker circuit.jpg [ 132.23 KiB | Viewed 585 times ]



Bob

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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 4:59 am 
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Location: Montreal, Quebec
45 years ago, there were LEDs with built in zener, so they'd turn on when voltage went above that level. There were also LEDs that didn't need resistors, they had a constant current source ibside the package.Somewhat later, Radio Shack (so someone else made it), had a red LED that flashed. Not really a surprise. An LED is a chip inside all that plastic, so why not have other electronics built in?

Fifty years ago, most ICs were flexible, useful for miltiple purpises. But more and more, ICs are specific. No unneeded pins, and less useful for other purposes.

These tea lamps, and the Christmas flashers that sequence through colours, they are just very specialized ICs that also include the LED. I hadn't even thought to look for such LEDs at Amazon, they never used to be an item abpvailable through mainstream sources.


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 9:22 am 
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Alan Voorhees wrote:
To save the trouble of making it, you can buy battery operated tea lights that have the flicker. I haven't taken one apart to see what inside, but can.

So it's a chopper that makes the flicker?

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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 1:04 pm 
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This may be of interest: https://www.physicsforums.com/threads/f ... er.442225/

Read it all the way through... there are as usual some replies that don't exactly apply to the question....

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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 1:32 pm 
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The flicker LED have a chip built into them that causes the flicker.

https://hackaday.com/2013/12/16/reverse ... icker-led/

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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 3:15 pm 
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ErikD wrote:
What is the mechanism that makes a neon bulb start to flicker? I talking about the common little NE-2 bulbs. Many times you'll see these in power strips flickering away.


Those are neon lamps that are beginning to fail.

What you're looking for is a circuit that will cause a neon bulb to flicker.

You will need a minimum of two neon lamps for the following circuit. Also they must be the same type of neon lamp for it to work properly.

I cannot remember if I lowered the value of the 470K resistor for 120Vac operation.

Attachment:
Neon flicker circuit.jpg
Neon flicker circuit.jpg [ 21.68 KiB | Viewed 506 times ]


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 5:00 pm 
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Location: New York, NY
I know this is very tangential to the OP's question, so perfunctory apologies for the sidebar. But if anyone's interested in Philip's Hue bulbs, read on.

We have one of these in our living room:

Image

And I wanted a subtle flickering effect. It's easy to find info about the API for talking to the "bridge" controller, so I wrote this simple bash script, with clear indications of my being empirical. :)

#!/bin/bash

# Flicker dah lights

# TM 2/14/21


. functions

trap "alloff ; exit" 0 1 2 15

# First turn all the lights on

curl -s -X PUT -d '{"on":true}' $dest/1/state >/dev/null
curl -s -X PUT -d '{"on":true}' $dest/2/state >/dev/null
curl -s -X PUT -d '{"on":true}' $dest/3/state >/dev/null
curl -s -X PUT -d '{"on":true}' $dest/4/state >/dev/null

while true ; do

for light in 1 2 3 4 ; do

duration=`echo "scale=2 ; $RANDOM / 131068" | bc`
intensity=`echo "(($RANDOM / 1000)^2)/20 + 10" | bc`
echo $intensity

curl -s -X PUT -d \{\"bri\":$intensity\} $dest/$light/state >/dev/null

# sleep .1

# curl -s -X PUT -d \{\"bri\":10\} $dest/$light/state >/dev/null

sleep $duration

done

dwell=`echo "scale=2 ; $RANDOM / 13106" | bc`

# sleep $dwell

# Check to see if someone turned them off

if isoff ; then

exit

fi

done

[tim@centos hue]$ cat functions
#!/bin/bash -x

# Functions and declarations for Hue scripts

# TM 11/4/19

dest=http://192.168.3.40/api/w5e3kxXNBterrsVgTCn4sJWm1Af9gLM-9cysrc-P/lights

isoff()
{
# Check to see if the lights are off

# on=$(curl -s -X GET $dest/1 | jq '.state.on?')
test "$on" = false
}

allon()
{
curl -s -X PUT -d '{"on":true}' $dest/1/state >/dev/null
curl -s -X PUT -d '{"on":true}' $dest/2/state >/dev/null
curl -s -X PUT -d '{"on":true}' $dest/3/state >/dev/null
curl -s -X PUT -d '{"on":true}' $dest/4/state >/dev/null
}

alloff()
{
curl -s -X PUT -d '{"on":false}' $dest/1/state >/dev/null
curl -s -X PUT -d '{"on":false}' $dest/2/state >/dev/null
curl -s -X PUT -d '{"on":false}' $dest/3/state >/dev/null
curl -s -X PUT -d '{"on":false}' $dest/4/state >/dev/null
}


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 5:08 pm 
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Location: Santa Rosa, CA
There is a difference between "blinking" and "flicker."

R/C circuits will make a blinker... a distinct ON and OFF sequence with fixed time intervals. The "flicker" LEDs are more random and actually vary the apparent brightness.

National used to make an LED flasher/driver: https://hackaday.com/2018/01/04/there-once-was-an-ic-dedicated-to-blinking-an-led/

Sadly, no one wants to make LM3909 any more. It's a hobbyist circuit, so no real volume of sales. Starting in the early 90s (I was at Siliconix), ASIC was the way to make money. Application Specific Integrated Circuit. No one wants to make NE555-type products. Not designed into new OEM equipment and no profit in hobbyist sales.

Rich


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 Post subject: Re: How to Create Neon Bulb Flicker
PostPosted: Sep Tue 21, 2021 6:09 pm 
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simplex1040 wrote:
The flicker LED have a chip built into them that causes the flicker.

https://hackaday.com/2013/12/16/reverse ... icker-led/


I've encountered two different versions. The older ones worked fine driving incandescent bulbs. but the newer ones pulse too quickly for the filament to follow. They do work fine with LEDs. I don't have a logic analyzer, but the pulses do look very different on a regular scope.

I have also built many neon flashers, including several pin-on Christmas decorations, and a panel of 100 NE-2 flashers.

Bob

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