Modulating 240v lights fluros

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Modulating 240v lights fluros

Postby Harry Dalek » Sat Jun 12, 2010 6:05 pm

Hi i have been thinking of using high voltage lights for NBTV for a while still working on my crt project but nothing stopping me thinking of those motors and things with holes in them !

I want to use High voltage lights for something different and want maximum light without using a bank of star leds .
So started to think about the light box i want and size of picture this time around .

I have finished the electronics and tested the circuit just using an amplifier handy to feed it ,it will modulated 240v fluros 240v Incedecent 12v what ever via 240v step down transformer the fluros have the speed for nbtv i should think ... i think the thing could do just about any 240v light that you can get flashing fast enough.... so its pretty interesting as you could test different types of lights .


I found the circuit its very safe for some thing like this i changed the triac
for the BT137 i think the 136 is live to the heatsink not a good thing !!!!!! and not safe ! so i'd do the same if i were you !

So if you want a lot of light there you go.
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Last edited by Harry Dalek on Sun Jun 13, 2010 12:16 am, edited 2 times in total.
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Modulation 240v Light Flouros

Postby Alan » Sat Jun 12, 2010 7:21 pm

Harry suggests that he would like to look at modulation of incandescent lamps as a light source. Problem here is the inertia of the heating and cooling of the filament - positively slow, infact too slow for NBTV (and audio, come to that).
An interesting 4 page PDF is available at http://www.international-light-associat ... Martel.pdf
You will see that the mod range is <1 to 20 c/s only.
Hope that this is of use,

Alan.
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Re: Modulation 240v Light Flouros

Postby Harry Dalek » Sat Jun 12, 2010 8:13 pm

Hi Alan
i know that they are no good for nbtv its just that this circuit will do just about any 240v light that will work ! For NBTV ....if the light can flash fast enough plug it into this it will modulate it to the speed it can flash on and off ...There are nbtvs with fluro lights so i'd say thats worth looking at if you want a bright display. If you want a projection tv say i think you will have to look at 240v lamps or even any thing close as bright to a crt .

Theres two ways to go with modulating nbtv light direct to the light device
or some sort of light valve which is harder but you can use any old high light device then .

Another idea on the light valve these days , small lap top displays lcds not sure if you can easly rip the things out of a dead laptop or what ever
and get it to turn all the diodes on and off without to much electronics ?
but it would make the best current day light valve ...
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Re: Modulation 240v Light Flouros

Postby gary » Sat Jun 12, 2010 10:07 pm

Alan wrote:Problem here is the inertia of the heating and cooling of the filament - positively slow, infact too slow for NBTV (and audio, come to that).


And yet it is my understanding that Baird did indeed use an array of 2,100 incandescent lamps for his "large screen" display at the London coliseum. I wonder if anyone has any more information on the nature of those lamps?
gary
 

Re: Modulation 240v Light Flouros

Postby Harry Dalek » Sat Jun 12, 2010 10:29 pm

Hi gary

I was more interested in the fluros but thinking about what you said about bairds matrix tv ? looking at the Incedecent flash way on the nbtv signal i think it could be because the lamp is mostly on not heating from dead cold....mmmm most likly too slow but if baird did it who are we to not try it ...whats the worst than can happen it not working and changing the light globe! :shock:
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Postby Marcus » Sat Jun 12, 2010 10:50 pm

I'm looking into this myself, I have read up about the fluro coating on the common fluro tubes and it should allow for quick enough modulation.

I went and bought a set of the small "neon" tubes used in and under cars. I got the 6" white versions that run from 180 - 300v. Been sitting there a while doing nothing though.

If I can get this to run from the output of a 6V6 tube then I have a nice bright strip of light for my mirror screw, with no need for diffusion.
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Postby Harry Dalek » Sat Jun 12, 2010 11:03 pm

Marcus wrote:I'm looking into this myself, I have read up about the fluro coating on the common fluro tubes and it should allow for quick enough modulation.

Hi Marcus

Try the circuit i am using its so simple no valves needed to drive those neons ,,,this thing could run a few globes neons would be nothing for it .

Its mainly getting a amp thats enough to light that internal led in the ic i am just using and old pc external stereo amp. ,that kicks it into life!
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Re: Modulating 240v lights fluros

Postby cool386 » Sun Mar 20, 2022 12:36 am

Apologies for resurrecting an ancient thread, but having been down this path I can relate my experience. When I first constructed my televisor I thought a 4W fluoro tube would make an excellent light source, being brighter than a neon and a preferable colour. Being a gas discharge lamp, it would modulate easily at the maximum required 30 line video frequency. And so I built said televisor with 4W tube modulated with a beam tetrode valve running at about 35mA plate current. It all looked good until I tried modulating it with a video signal...what killed it was the persistence of the phosphor, which was just too long even at 375Hz. You could see the modulation, but instead of a nice deep black was a light brown as phosphor lost its excitation. Pic of it here https://www.flickr.com/photos/13469158@ ... 070450870/ The first time I saw a recognisable picture on this televisor was when I swapped the fluoro tube for a LED array.
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Re: Modulating 240v lights fluros

Postby Panrock » Sun Mar 20, 2022 1:12 am

This 45-line Nipkow system (camera and monitor) that I built in the '90s used miniature fluorescent tubes for the modulated light, encased in tubes of red, blue and green gelatin filter material. The camera was shockingly insensitive and I never got a picture as such, though the coloured noise on the monitor's 'screen' looked convincing enough! The tubes were driven by EL34 valves. I do recall some yellow 'lag' from the tube phosphor when unfiltered.

Building this must have taught me useful lessons, because later on, I built another colour camera and monitor system that actually worked - the 'Grosvenor' - and Steve A designed the circuitry - but that's another story.

Steve O
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Re: Modulating 240v lights fluros

Postby Steve Anderson » Sun Mar 20, 2022 2:00 pm

Chris Long did many experiments with modulated light sources and detectors for long-range optical communication in the 60s and 70s, maybe into the 80s. The website is still up as of today...

http://www.modulatedlight.org or http://www.modulatedlight.com

The site is still valid today though many of the sources have improved since it was created...though not flouro's, perhaps with the exception of efficiency. As I recall he was just able to get voice bandwidth out of them, but that appears to be the limit, maybe 3kHz? Not really enough for NBTV, but worth a try...

Bairds matrix tv was an immense array of probably small low-current light bulbs with very thin filaments i.e. low thermal inertia...

Steve A.

P.S. When Harry mentions 'Globes' in previous postings he means light-bulbs, an Australian expression still used today...
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Re: Modulating 240v lights fluros

Postby Panrock » Mon Mar 21, 2022 4:15 am

I seem to remember I once did a plot of the response of the smallest thermal capacity 'pea bulbs' I could find (1.25v). By 1 KHz there was absolutely zero response and they were basically useless far below that. Effective equalisation would have been hard/impossible because of the fixed 'decay' time constant as distinct from the 'warm up' period varying with frequency... or something like that. :oops:

Anyway, my very first (8-line) system made at boarding school in 1966 used such a pea bulb in one version. My idea was to launch a 'television service' on this basis to serve the whole school! Another one that didn't work...

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Re: Modulating 240v lights fluros

Postby Harry Dalek » Mon Mar 21, 2022 10:25 pm

Shocked to see my postings back on this one ,of cause older and wiser sort of ! :roll: at the time i did not take into account bandwidth of the ac frequency i was using ,and the electronics in the fluo ...one to narrow 50 hz ! arrrrr i would give my younger self a slap on the back of the head /
Yes Steve O some times the ideas work other times not but you learn from your mistakes !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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