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Compact Flourescent Flash Rate
By wooferhound, Section Homebrewed Electricity Posted on Sun Jun 20th, 2004 at 08:17:22 PM MST
What Frequency does Compact Flourescent Flash at ?

I have been playing with flourescent lights for a long time. I was playing with a chart recorder that had a photo cell as it's input, I accidently pointed it at a flourescent fixture and it went crazy trying to show a 120 hz flash rate.
Well, Does anybody know if the Flash Rate on a Compact Florescent is different than the Grid Frequency, or does it create it's own Flash Frequency ?

Compact Flourescent Flash Rate | 9 comments (9 topical, 0 editorial)

Re: Compact Flourescent Flash Rate (3.00 / 0) (#1)
by baggo (baggo@copperstream.co.uk) on Mon Jun 21st, 2004 at 03:37:34 AM MST
(User Info) http://www.baggo.copperstream.co.uk

In compact flourescents the incoming AC line voltage is rectified to DC through a bridge rectifier and then fed to a DC to AC converter to drive the tube. The DC to AC converter operates in the 10 to 200 KhZ range, usually around 50KhZ. At these frequencies the gas in the tube does not have time to de-ionise (i.e. go out) and so the tube should not produce any flicker at all.

Re: Compact Flourescent Flash Rate (3.00 / 0) (#2)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Mon Jun 21st, 2004 at 08:14:31 PM MST
(User Info)

The fluorescent lamp you tested has a magnetic choke BALLAST to limit the current of the lamp and the operating pulses would be twice the operating frequency because you have 60 Hertz power.

The new electronic ballast operates differently, it has a switching circuit that may operate from 13 to about 50 Kilohertz which with the storage time of the phosphor in the lamp, the light is almost without flicker and of course the low level flicker is twice the high operating frequency.

Higher than 50 Khz is not necessary since the phosphor does not decay in its fluorescence.

I hope this helps

Nando

Re: Compact Flourescent Flash Rate (3.00 / 0) (#3)
by Edward (chemfor_me2@yahoo.com) on Mon Jun 21st, 2004 at 11:45:33 PM MST
(User Info) http://geocities.com/magnetstoo

Off the subject a bit,I took a fluorescent light bulb (by itself),connected one end to an AM radio antennae,and moved it toward my television screen,if you listen
to the sounds coming from the radio,you will hear a popping noise in one direction
and what sounds like a suction going the other,you can also discern the 'sawtooth'
pattern of the voltage powering the screen.The electric field emanating from the
screen is similiar in shape to a magnetic field,i.e.the electric field lines appear to dissipate as a square of the distance from the screen.I also took the back off the TV and held the bulb close to the back of the screen,and was able to slightly power up the bulb-Watch OUT ,there is a potential 20,000 volts back there,it got me going through the bulbs metal end.I also used the HV from a color TV to power up a HeNe Laser,but the small Laser (had a metal case)generated so much heat I had to make and wrap a finned aluminum sheet (heat sink) around it,and that Laser still could not warm a piece of cigarette paper,but it could shoot a visible beam clear across the street!

Re: Compact Flourescent Flash Rate (3.00 / 0) (#4)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Jun 22nd, 2004 at 10:22:15 AM MST
(User Info) http://wooferhound.com

Thank Ya'll for the comments, I feel better about using them now. I thing a regular 4 foot Flourescent that is flashing at 120hz is hard on the eyes even though you cant really see it flashing.

)}=- W o o f -={(

Re: Compact Flourescent Flash Rate (3.00 / 0) (#5)
by baggo (baggo@copperstream.co.uk) on Tue Jun 22nd, 2004 at 01:24:52 PM MST
(User Info) http://www.baggo.copperstream.co.uk

Hi again,

I am in the process of converting my house to RE. At the present time all the lights are powered by a Prowatt 12 volt 800 Watt MSW inverter. I found that the ordinary flourescent fittings with choke ballasts did not like the MSW at all. The chokes buzzed like hell and the tubes flickered badly. What I did was change the choke ballasts for electronic ones from RS ( I live in the UK ). They now work perfectly and are more efficient than before. The tubes should also last a lot longer and no flicker!

John

Re: Compact Flourescent Flash Rate (3.00 / 0) (#6)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Jun 22nd, 2004 at 06:44:48 PM MST
(User Info) http://wooferhound.com

I did'nt know that they make an electronic replacement for the standard ballasts. I have about 5 fixtures that I would like to convert to the more efficent less flashy ballasts.

)}=- W o o f -={(

[ Parent ]

Re: Compact Fluorescent Flash Rate (3.00 / 0) (#8)
by BT Humble (bt_humble@bigpond.com) on Thu Jun 24th, 2004 at 08:12:44 PM MST
(User Info) http://www.humbletown.org

My shed[1] has two 4-foot fluorescent fittings, and a 2-foot one. Due to time issues I was initially running them from my (mod sine) inverter, and it worked OK except for a VERY long startup time[2] and the fact that I had to remove the capacitors from inside the fittings in order to be able to run more that one at a time!

I recently bought and installed 3 of these:

http://www.rpc.com.au/products/inverters/otherbrands/fluoro_inverters.html

So now I not only have instant-on lights which don't rely on the inverter, but the current draw has gone down from 2.5A @ 24VDC for a single 4-foot tube through the inverter, to 2.1A for all three simultaneously.

At ~$40 Australian per unit, I heartily recommend them!

BTH
[1] http://www.otherpower.com/images/scimages/236/shed3.jpg
[2] Flick, flick, flick, flick, flick, flick, ahh, there we go!

[ Parent ]

Re: Compact Fluorescent Flash Rate (3.00 / 0) (#9)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Fri Jul 2nd, 2004 at 08:38:18 PM MST
(User Info)

BTH:

What you have done is to place the lamps to operate at 120 times a second at the rate that the electronic ballasts switch ( 15 to 50 Kilohertz)

The modified sine wave inverter has a square wave that is positive for a 1/3 cycle then is negative for 1/2 cycle ( in Australia at 50 Hertz rate) ALSO the modified sine wave does not produce any voltage for about 15 to 20 % of the time, so it looks like = positive pulse - dead time -- negative pulse -- dead time etc .

The solution is not to take the INTERNAL capacitors of the electronic ballast BUT TO INCREASE value about 3 to 5 times for the starting flicker to stop.

I have designed electronic ballast for many years.

Regards

Nando

[ Parent ]

Re: Compact Flourescent Flash Rate (3.00 / 0) (#7)
by baggo (baggo@copperstream.co.uk) on Wed Jun 23rd, 2004 at 08:36:57 AM MST
(User Info) http://www.baggo.copperstream.co.uk

Just do a Google search for electronic ballast and you will find plenty of suppliers in the US. RS only do 240 volt ones over here. It's very straightforward to change the ballast to the electronic version and the cost is not much more than that of a new fitting.

John

Compact Flourescent Flash Rate | 9 comments (9 topical, 0 editorial)

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