Gradual On for Lamp

[Nehmo Sergheyev]

Gradual On for Lamp



I dislike the rude assault you get when you flip on a light switch.



Instead of an abrupt on-off switch on a 120 V circuit, I want something
that gradually turns on. In other words, you throw a control switch and
the resistance in the load's circuit goes from infinity to zero in the
span of, let's say, three seconds. The load would be a 500 W
incandescent lamp.



Is there a commercially available product that could accomplish this?
Or is there a simple way to make this circuit?

 

[Ken Taylor]

Gradual On for Lamp



I dislike the rude assault you get when you flip on a light switch.



Instead of an abrupt on-off switch on a 120 V circuit, I want something
that gradually turns on. In other words, you throw a control switch and
the resistance in the load's circuit goes from infinity to zero in the
span of, let's say, three seconds. The load would be a 500 W
incandescent lamp.



Is there a commercially available product that could accomplish this?
Or is there a simple way to make this circuit?

Google is your friend. (Someone else coined that phrase, but I like it!)

http://www.hometech.com/modules/plugin.html
Plenty of others like it but that was the first hit. Search for a circuit
diagram the same way.

Ken

 

[Anthony Fremont]

Instead of an abrupt on-off switch on a 120 V circuit, I want
something that gradually turns on. In other words, you throw a
control switch and the resistance in the load's circuit goes from
infinity to zero in the span of, let's say, three seconds. The load
would be a 500 W incandescent lamp.

Is there a commercially available product that could accomplish this?

x-10 might do this, but I don't really know.

Or is there a simple way to make this circuit?

A PIC chip, a TRIAC, and a few other parts could do this job perfectly.
There are quite a few examples on the net, just Google 'em up by
searching for "PIC" and "dimmer". ;-) You would just need a slight
variation on the code to make it do what you wish.

 

[Beachcomber]

The official lingo for this is "Soft Start" ... may help during the
searches....

Beachcomber

 

[Repeating Decimal]

Gradual On for Lamp



I dislike the rude assault you get when you flip on a light switch.



Instead of an abrupt on-off switch on a 120 V circuit, I want something
that gradually turns on. In other words, you throw a control switch and
the resistance in the load's circuit goes from infinity to zero in the
span of, let's say, three seconds. The load would be a 500 W
incandescent lamp.



Is there a commercially available product that could accomplish this?
Or is there a simple way to make this circuit?

use candles

 

[anthony wooldridge]

In days of old they used a power NTC thermistor as a surge arrestor in valve
TV's to do this.
On switchon it has high resisance to limit the initial surge current
for all those discharged capacitors and cold valve heater elements.
When it heats up it due to the load current it consumes minimum power as the
resistance drops right down.
It would have to be carefully matched to the load.
Whether you can find one the right power for this job, I don't know,
but I often wondered why someone didn't coin this potential market.
I guess the lamp manufacturers would soon buy them out.
Anthony

 

[JeffM]

Start here.
http://www.google.com/search?num=10...F-8&oe=UTF-8&q=ramp+dimmer&btnG=Google+Search

....and it's not done with resistance; it's done with duty cycle.

 

[r_p_bayly]

Start here.
http://www.google.com/search?num=10...F-8&oe=UTF-8&q=ramp+dimmer&btnG=Google+Search

...and it's not done with resistance; it's done with duty cycle.

Try a DIMMER switch !

 

[Reg Edwards]

Connect a thermistor in series with the lamp. As the thermistor warms up
its resistance goes down and the lamp gets brighter.

 

[JeffM]

True--in theory--but even the slowest thermistor
is too fast to achieve what he wants.

 

[Nam Paik]

True--in theory--but even the slowest thermistor
is too fast to achieve what he wants.

I think there are special turn-on (sliding) switches which does what
you want to do - it is probably expensive $20 maybe per switch. But
churches & some expensive homes use this kind of sliding scale
brightness switch. You can slide the switch as fast as you want or as
slowly as you want.

Side benefit will be that brightness can be controlled precisely (I
guess it is really a more elegant dimmer switch - since the SCR or
TRIAC controls the pulse width, you will still have 99% efficiency. If
you try to do it with resistors, it can become pretty dangerous
(failure of circuitry will make the whole circuit glow & you'll be
lucky not to burn down your house).

Worst thing that a TRIAC or SCR can do is become OPEN (bulb does not
turn on at all) or become SHORT (bulb is always on at max. brightness
& you lose soft-start & brightness control). Either way, nothing will
get hot & definitely no fires are started.

I would still buy a professional dimmer switch in metal box just in
case the SCR or TRIAC decides to become a flame thrower for a few
seconds (some cheap dimmer switches did cause housefires in the past &
I am sure there will always be cheap & dangerous products available
since 95% of people buy on price only !!!)