Soft-start for mains LEDs?

[ardhuru]

Hello Everyone!

I have absolutely no experience in this, and had no idea where to begin; Google hasnt really made things clear(er).

I am looking for a readymade module (or, if not, designs, or ideas to make one) that would soft start an existing LED lamp. I'm talking about controlling an LED bulb, the kind that directly plugs into the mains (240v in my case).

Ideally, the soft-start should ramp up the lamp to full in about 5 seconds or so after switch on, although the ramp-up time isnt critical.

Does such a beast exist? Or doable??

Hoping the huge pool of talent on this forum would have some pointers!

Best Regards,

Anand

[mackrackit]

Use PWM and and ramp that up or down over a time period.

[ardhuru]

Dave, this is not an exposed LED; its one of those LED bulbs that directly replace an incandescent or CFL lamp in its mains holder.

[peterdeco1]

Hi Anand. I did this so long ago I forgot how. But I remember using a triac and diac configured as a lamp dimmer. It started as dim and gradually ramped up by charging a capacitor. I also remember one of my attempts blew everything up. Be careful. An exploding capacitor is like a firecracker with electrolyte inside.

[ardhuru]

Hi Peter, thanks for that information; now I know at least that its possible!

Do you have any tips at all, from whatever you can remember? Those would go a long way towards not re-inventing the wheel.

I'm familiar with triacs and phase control, as can be applied to incandescent bulbs, or resistive, or inductive loads. Its just that I cant figure out how to control something like these, to ramp up to full intensity spread over a few seconds. http://www.shopclues.com/philips-led...B&gclsrc=aw.ds

Regards,

Anand

[peterdeco1]

Sorry Anand. This was at least 20 years ago. All I remember is building a dimmer circuit and modifying the section that used the potentiometer to control the brightness. If I had to do it all over again, I would probably buy a dimmer and modify it. It's probably cheaper than buying all the parts and making it yourself.

[ardhuru]

Peter, LED lamps (bulbs) 20 years ago?

[peterdeco1]

Yes. In about 1980 a buddy of mine had a digital LED wristwatch, LED calculators and alarm clocks were becoming popular. Google it. LED's were around since the 70's.

[peterdeco1]

I'm sorry I wasn't clear in my original post. Of course I didn't do the brightness thing with an LED replacement bulb. It was to slowly start an AC motor but the same process would work with AC lighting.

[Jerson]

Hi Anand

The LED bulb which you speak about may be of the non-dimmable variety. These will turn on at a certain operating voltage. They are NOT dimmable.

There are other LED bulbs which are dimmable in the old-traditional way. These are a different breed altogether and you will find them on ebay/such

Techniques - I do remember seeing dedicated ICs for doing such kind of dimming from a phase angle dimmed voltage wave.

Jerson

[ardhuru]

Peter, I *was* referring to the control of replacement bulbs; in the late 70's a TI watch with an LED display was my most prized possession too!

Jerson, thanks for that; thats a very conclusive answer. I'll do more research on the kind of LED bulbs which are dimmable.

Thanks again, guys.