incandesent bulbs dimmer

Thread Starter

Voltboy

Joined Jan 10, 2007
197
Hello guys.
I want to do a light system for my bedroom. I want it to have about 3 light states and I don't know if use a PWM to control the dimming or a simple potentiometer. What would be the better?
And if anyone know how to instead of a switch use a touch plate it would be great.

Best Regards,
Yoda
 

beenthere

Joined Apr 20, 2004
15,819
If it's a bedside lamp, you can get a socket adapter that it touch operated and gives 3 levels of operation. I got mine at an Ace Hardware several years ago. I've never popped it apart to see what the controller is.
 

eeboy

Joined Sep 27, 2007
90
Depends... what LED(s) are you driving? If you truly are lighting your bedroom it may be best to look in the direction of an IC dedicated to controlling LEDs. This would be the most efficient method.
 

Thread Starter

Voltboy

Joined Jan 10, 2007
197
Eeboy, I'm not using LED's, i know that a LED driver is best for LED's but I'm using incandescent lamps and not for illuminating all the room. Just about 3 small bulbs to give some ambient and to read.
I think that the best for incandesent bulbs is a potentiometer, so I think maybe I'll use a digital pot.
About the touch operated mode, I think something of sensing the resistance because when you touch it the resistance increase because of the body (or I'm wrong)
 

eeboy

Joined Sep 27, 2007
90
Not sure where I got LED's from... sorry.

Are you indicating you are going to use a digital pot to limit the current to the lamps? This is not a good idea. Most digital pots have current limits in the mA range. They are not suitable for this application.

Take a look at triacs for your dimming control... http://en.wikipedia.org/wiki/Triac .
 

hgmjr

Joined Jan 28, 2005
9,029
Greetings Yoga,

I'm pretty sure that the digital potentiometers will need some additional circuitry since the pots themselves are fairly low power devices.

Perhaps you had in mind to incorporate a power MOSFET as the controlling device and use the digital potentiometer in the gate circuit. That should work well.

hgmjr
 

Thread Starter

Voltboy

Joined Jan 10, 2007
197
Perhaps you had in mind to incorporate a power MOSFET as the controlling device and use the digital potentiometer in the gate circuit. That should work well.

hgmjr
I like your idea hgmjr. Do you think instead of a MOSFET I could use a power transistor?
 

hgmjr

Joined Jan 28, 2005
9,029
Yes, the lamps are going to be powered of DC source. Why is it bad to control it with a transistor?
A MOSFET transistor and a digital potentiometer could be a useful combination.

You will most likely need a heatsink depending on the wattage of the lamps you intend to use.

hgmjr
 

eeboy

Joined Sep 27, 2007
90
I assumed you were using an AC source.

DC control makes it much simpler. I would use a FET as hgmjr stated and use PWM at the gate to control current. You could substitute a BJT for the FET as well.

The implementation really depends on what you have available to you.
 
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