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Topic: Dimming compact fluorescent lights (Read 2986 times) previous topic - next topic


The scheme of dimming using variable phase control of a triac,  apparently doesn't work for compact fluorescent lamps.

It is my understanding that conventional dimmers work on the same principle as the arduino circuit discussed in the other thread today.
You can buy these ( with a manual knob, not an arduino ) for about $10.

A dimmer which claims to work for compact fluorescents is about $80.

Does anyone know the operating principle for these,  or how you could implement that with an arduino ?
Is it really actually possible to dim compact fluorescents at all ?  I am somewhat doubtful and don't recall
ever seeing it actually being done.


You may have a hard time to do that.

From wikipedia:

CFLs have two main components: a magnetic or electronic ballast and a gas-filled tube (also called bulb or burner). Replacement of magnetic ballasts with electronic ballasts has removed most of the flickering and slow starting traditionally associated with fluorescent lighting, and has allowed the development of smaller lamps directly interchangeable with more sizes of incandescent bulb.

Electronic ballasts contain a small circuit board with rectifiers, a filter capacitor and usually two switching transistors. The incoming AC current is first rectified to DC, then converted to high frequency AC by the transistors, connected as a resonant series DC to AC inverter. The resulting high frequency is applied to the lamp tube. Since the resonant converter tends to stabilize lamp current (and light produced) over a range of input voltages, standard CFLs do not respond well in dimming applications and special lamps are required for dimming service.
Only some CF lamps are labeled for dimming control. Using a dimmer with a standard CFL is ineffective and can shorten bulb life and void the warranty.  Dimmable CFLs are available. The dimmer switch used in conjunction with a dimmable CFL must be matched to its power consumption range; many dimmers installed for use with incandescent bulbs do not function acceptably below 40 W, whereas CFL applications commonly draw power in the range 7-20 W. Dimmable CFLs have been marketed before suitable dimmers are available. The dimming range of CFLs is usually between 20% and 90%, but many modern CFLs have a dimmable range of 2% to 100%, more akin to that of incandescent lights. There are two types of dimmable CFL on the market: Standard dimmable CFLs, and "switch-dimmable" CFLs. The latter use a standard light switch, and the on-board electronics chooses the light output level based on the number of times the switch is turned on and off quickly. Dimmable CFLs are not a 100% replacement for incandescent fixtures that are dimmed for "mood scenes" such as wall sconces in a dining area. Below the 20% limit, the lamp may remain at 20% or flicker or the starter circuitry may stop and restart. Above 80%, the bulb may operate at 100%. However, recent products have solved these problems so that they perform more like incandescent lamps. Dimmable CFLs are more expensive than standard CFLs due to the additional circuitry.

A further limitation is that multiple dimmable CFLs on the same dimmer switch may not have the same brightness level, if not of the same manufacturer and type.

Cold-cathode CFLs can be dimmed to low levels, making them popular replacements for incandescent bulbs on dimmer circuits.

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


So you need a special dimmer (  which I have seen,  about $80 ),  and ALSO special CFD lamps as well ?

I think LEDs might be a better solution then.


Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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