doll house 5mm led project, need advice on power supply

[VegasF6]

As title says, I have a doll house lighting project going. Don't have all the details yet, but probably 9-12 5mm white leds, 14,000 mcd from DX. I used the led array tool here:http://led.linear1.org/led.wiz

So, rather than a constant current circuit, I want to power this from a wall wart power supply and resistors. I feel it will be "good enough."

My concern is what will be the effect of a switch mode power supply vs a simple transformer? I am considering this power supply here:

http://www.allelectronics.com/make-a-store/item/PS-1236/12VDC-300MA-SWITCHING-POWER-SUPPLY/-/1.html

A switch mode power supply varies current to attempt to keep voltage at the same level? Or varies voltage to keep current the same under a load? According to the tool I will only have a draw of around 80mA.

Thanks.

 

[2xTrinity]

As title says, I have a doll house lighting project going. Don't have all the details yet, but probably 9-12 5mm white leds, 14,000 mcd from DX. I used the led array tool here:http://led.linear1.org/led.wiz

So, rather than a constant current circuit, I want to power this from a wall wart power supply and resistors. I feel it will be "good enough."

My concern is what will be the effect of a switch mode power supply vs a simple transformer? I am considering this power supply here:

http://www.allelectronics.com/make-a-store/item/PS-1236/12VDC-300MA-SWITCHING-POWER-SUPPLY/-/1.html

A switch mode power supply varies current to attempt to keep voltage at the same level? Or varies voltage to keep current the same under a load? According to the tool I will only have a draw of around 80mA.

Thanks.

Whether the supply reglates current or voltage depends on the supply, though all wall-wart type switching supplies that I know of are 5V or 12V voltage-regulated, with a maximum current limit. So voltage will be kept level unless current would exceed some limit (300mA in the one you have listed).

So in the case of your LEDs, clustered in groups of three with small resistors in series with each (around 100 ohm or so), should work.

 

[VegasF6]

Ah, thank you.
Any problems then with installing a potentiometer between the power supply and my array? I am imagining that the PS would attempt to overcome the pot and not let me lower voltage until I get enough resistance to overcome the limitations of the PS, there by generating more heat than is ideal?

How would I go about figuring the value for a pot? Both resistance and wattage I guess.

 

[Black Rose]

As title says, I have a doll house lighting project going. Don't have all the details yet, but probably 9-12 5mm white leds, 14,000 mcd from DX. I used the led array tool here:http://led.linear1.org/led.wiz

I discovered that site the other day when I was looking for some info to create a Nichia light array for our shed (not electricity in there).

Pretty neat.

 

[ken2400]

I use cell phone power supplies myself. They almost give them away at garage sales. I have used pots BUT have burned up two LEDs so far, the multi chip ones, so I now put resistors in front of the pot to insure I don't give the LEDs too much power.

Good luck with the project

Ah, thank you.
Any problems then with installing a potentiometer between the power supply and my array? I am imagining that the PS would attempt to overcome the pot and not let me lower voltage until I get enough resistance to overcome the limitations of the PS, there by generating more heat than is ideal?

How would I go about figuring the value for a pot? Both resistance and wattage I guess.