slow turn-on of a lamp

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aucklander

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#295901 3-May-2022 21:41

Hi all,

what would be your recommendation if I want to achieve the slow turn on of a mains lamp? Application will be on halogen spotlights installed outdoors, they get those long skinny bulbs R7s (78mm long in my case), I want them to turn on from off state to full brightness over a period of - say - one or two seconds? It would be quite a wow factor. The lights will also be controlled by a PIR sensor.

I heard of dimmers which can get an external "control" signal, in that case a light sensor was used to control the dimmer, with the lights slowly coming on to compensate for sunset! But even if I would have one of those, I need something to generate the control signal (presumably 0-10V DC?) from 0 to 10V over a period of 2 seconds, then stay at max brightness until turned off...

I did find few schematics on internet but I was wondering if there is a "ready-made" solution available?

Thank you.

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davidcole

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#2909966 4-May-2022 08:55

Probably relatively easy if you're in the home automation space, with dimming relays, or "smart" bulbs and getting a feed from the PIR sensor. But there's a few ifs there.

Not sure what options there are for say, PDL modules for doing that, I know they have a PIR module, and I know they have diming....but can they talk together?

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aucklander

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#2909973 4-May-2022 09:04

Thanks,

I will do some reading about dimming relays (it will be a learning curve).

Any suggestion for a supplier in NZ to get an idea of the price? Could not find much info in NZ at a quick first search...

davidcole

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#2910023 4-May-2022 11:34

aucklander:

Thanks,

I will do some reading about dimming relays (it will be a learning curve).

Any suggestion for a supplier in NZ to get an idea of the price? Could not find much info in NZ at a quick first search...

Depends which way you're going, home automation stuff - shelly.cloud, Active automation (zwave), PBtech (smart bulbs etc), or something from an electrician, ie idealm ja russel etc.

DonH

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#2910134 4-May-2022 14:16

Put an NTC (Negative Temperature Coefficient) resistor in series with each fitting. They are used for soft start of lamps and motors etc.

I don't know offhand who sells them. An online search for something like "inrush current ntc" could be a good place to start.

People hear what they see. - Doris Day

richms

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#2910178 4-May-2022 16:18

Replace them with smart LED floodlights and save a crapload on power and get more controllability of them?

Richard rich.ms

neb

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#2910200 4-May-2022 17:34

DonH:
Put an NTC (Negative Temperature Coefficient) resistor in series with each fitting. They are used for soft start of lamps and motors etc.

In more general terms what the above is is an inrush current limiter, but given the voltages and power levels involved you probably want to put a bit more engineering effort into it than just wiring an NTC into the circuit. If you're in Orkland I have an electronic one for controlling power tools that you could borrow to test on the lamps, with halogens you may not be able to do what you want since they may not start below a certain power level so you may not be able to go all the way down to near-zero light.

Alternatively, you can actually get specialised but still quite cheap lamps that do exactly what you want as part of their normal operation. Go to your local supermarket and look for something called a "CFL bulb". Damn sight cheaper and less of a fire risk than R7s as well.

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SomeoneSomewhere

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#2910207 4-May-2022 18:06

Halogens are incandescent at heart so should work fine down to zero brightness at zero voltage. I agree that they're an absolute waste of energy, though.

An appropriately sized NTC may work but will probably dissipate quite a bit of heat given the amount of current being drawn.

A lot of higher-end high-power LED floods ramp up over a second or two by default.