# Actual design question.

Discussion in 'Electronic Design' started by Homer J Simpson, Mar 11, 2007.

1. ### Homer J SimpsonGuest

Can CFLs be reconfigured to run off a DC supply? Minimum voltage?

2. ### Phil AllisonGuest

"Homer J Simpson"

** With most CFLs there is no need to do anything.

** Depends on the CFL of course - dickhead.

Ones I have here ( rated for 220 - 240 volt AC operation) light up at
anywhere from 70 to 200 volts DC and reach full brightness at about 300.

The light up voltage depends greatly on the temperature with many CFLs while
brightness is roughly proportional to the voltage - ie half rated voltage
= half max light output in lux.

YOU will just have to try some out.

......... Phil

3. ### Paul Hovnanian P.E.Guest

I suppose it depends on the CFL ballast design. I cut one open once. The
120 Vac line input drives a rectifier and a filtering cap. I'd guess
that one could feed 170 Vdc in at this point.

4. ### Homer J SimpsonGuest

So the other way is to dump the electronics and add a fluo inverter / driver
I guess.

7. ### Phil AllisonGuest

"Bob The Tenth Wit **** "

you post anything.

........ Phil

8. ### Homer J SimpsonGuest

12v CFL Light Bulbs Price Ex VAT = £ 10.50

As compared to 99 cents for 120 VAC.
He's a sad case, no? And he can't read : "Can CFLs be reconfigured to run
off a DC supply? Minimum voltage?"

9. ### Phil AllisonGuest

"Homer J Simpson Fucking IDIOT "

** Shame it says not ** one tiny thing ** about 12 volts.

YOU ASD FUCKED BRAIN DEAD **** !!!

........ Phil

10. ### EeyoreGuest

Anything you like within reason. 12V DC versions exist.

Graham

11. ### Robert BaerGuest

*Any* fluorexcent lamp can run off of DC; the problem is to first
strike that arc, which takes high voltage.
When the arc is present, then it is wise to use current limiting so
as to not overheat the poor lamp; typical voltage drop is the first
ionizationpotential of mercury ~32V.

12. ### Robert BaerGuest

That is with an inverter AKA "ballast".
What i answered was relative to the bulb itself absent electronics.

13. ### EeyoreGuest

By CFL I expected he meant the latter.

Graham

14. ### Homer J SimpsonGuest

ISTR some fairly compact designs to run the tube off a low voltage supply.

15. ### RobboGuest

I recall reading something about premature blackening at one end of the
"tube" and early failure if dc is used with fluoro's????

16. ### Phil AllisonGuest

"Robbo"

** All modern CFLs use electronic ballasts - ie high frequency inverters -
to drive the tube.

The AC supply is rectified and used as a source of DC voltage for that
inverter !!!!!

Eg: http://www.repairfaq.org/sam/cflamp1.pdf

....... Phil

17. ### John LarkinGuest

I just picked up eight 18-watt spiral-tube cfl's at Cole Hardware, 50
cents each, subsidized by PG&E. They're guaranteed for 12 years. I
don't believe that. My experience with cfl's is that they blow up
fairly often, especially if started/stopped a lot.

John

18. ### Homer J SimpsonGuest

And they don't much like outside light fittings.

19. ### EeyoreGuest

I've never had one 'blow up' in some 15 years of using them.

Almost all have been Philips or Osram though.

Graham

Why's that ?

Graham