Is there any circuit to make incandescent bulbs (60-100W) light up more gradually?
I've seen many different devices but none of them would work for me. I do not want to just stop the high current spike while the filament is warming up. I want the bulb to have 1.5-2 seconds delay before glowing fully bright. My only find is this Russian video of a light bulb soft start(Sadly I can't just buy it from the Russian store) Most other designs just focus on the inrush current limitation. I want is because I just like the effect of a bulb gradually increasing its brightness.
Can this be done without fancy micro controllers or specialized IC's?
Could you send any schematics that would work?
(The mains voltage in my country is 230V AC)
Electrical – Incandescent Light Bulb Soft Start
dimminglightmainsschematics
Related Solutions
I am going to assume it's an incandescent bulb of the "artistic" type with interesting filament structure. If it's an LED or CFL bulb, the below comments do not apply.
It's possible to connect a silicon diode in series with the bulb to permanently dim it. The behavior is not linear because the light bulb proportionally sucks more juice (technically speaking) when the tungsten filament is not running at full temperature. There's no way to adjust the brightness, so it's either acceptable to you or not.
The diode part number would be different depending on the bulb wattage, but a 1N4007 should work for anything up to 100W or so, and a 1N5407 for about any bulb you'd be likely to use. Be prepared to occasionally replace the diode after the bulb blows- the symptom would probably be the new bulb operating at full brightness. There's less chance of that happening with the 1N5407. They're less than 50 cents each.
If you have a bunch of them, you could install them in random orientation (which end of the diode goes to which side of the power) to be nice to the power company.
Note: I have no opinion on whether this is acceptable to fire, insurance or other codes and regulations in whatever 240V country you're in. Electronically it will work.
The surge is called inrush current, the cold filament has a much lower resistance than the hot filament.
This is why bulbs usually fail as they're turned on.
The simplest solution might be to fit a regular light dimmer, and turn them up slowly. Or a suitably rated Negative Temperature Coefficient device could be used as an inrush current suppressor.
try this search for a lot or articles and manufacturers.
Best Answer
You can run LEBs (light emitting bulbs) with PWM. In fact, soft start actually increases their lifetime.
It is possible to chop AC, but generally easier to rectify the AC then chop the resulting DC. Four diodes and a capacitor are good enough to make DC to run the bulb from. You also need to make a small low voltage supply to run the processor from.
The switch itself is probably most easily realized by a NPN transistor rated for the voltage. It can be controlled directly from the low voltage output of the microcontroller PWM.
Note that the rectified DC will have a higher RMS voltage than the AC. You compensate for that by not going to 100% duty cycle for full on. You could even measure the DC and adjust the duty cycle on the fly to make the light intensity relatively insensitive to voltage fluctuations of the AC. You could even make a "universal" powered light. That's one that can run from 90 to 250 V, 50 to 60 Hz.