Help With Power Supplies

[billw2]

Hello. I’m trying to get organized on my first model lighting project which is the Polar Lights 1/350 Enterprise. As I surf the web I’ve found many great resources on LED’s, circuit boards, resisters… but clear understanding of one piece of the puzzle eludes me. How to you calculate the wattage or amperage of a plug in DC power supply. There is a lot of information about batteries which I don’t think would be particle for this project.

I’ve found calculators to figure resisters on wiring series and parallel LEDs. They all ask for the voltage of the power supply (12 volt DC) and most have a max of 32 LEDs. Due to the size of this project I anticipate more than 32 LEDs. Do I design them as circuits and add up the milliamps for each circuit to determine the power supply? Do you look at each circuit as an independent part to figure resistor values? If you use a calculator and specify 10 LEDS in parallel or 20 LEDS in parallel you get different resistor values. What if you have 10 and 20 LED circuits running off the same power supply? Finally I was thinking of using cold cathode lighting for the Warp engines. How do figure the draw of other components in the plan? Finally circuits may on and off. Does that change things?

I’m very much a newbie here – but maybe someone can offer some guidance.

Thanks.

[USS Atlantis]

Hello. I’m trying to get organized on my first model lighting project which is the Polar Lights 1/350 Enterprise. As I surf the web I’ve found many great resources on LED’s, circuit boards, resisters… but clear understanding of one piece of the puzzle eludes me. How to you calculate the wattage or amperage of a plug in DC power supply. There is a lot of information about batteries which I don’t think would be particle for this project.

Can't answer ALL your questions, but lets get a start going here

I’ve found calculators to figure resisters on wiring series and parallel LEDs. They all ask for the voltage of the power supply (12 volt DC) and most have a max of 32 LEDs. Due to the size of this project I anticipate more than 32 LEDs. Do I design them as circuits and add up the milliamps for each circuit to determine the power supply?

You can do that, or just total all the LED's you think you'll use and get a power supply hefty enough to handle it

Example - 100 LED's at 20ma each is 2000 ma or 2 amps - so you'd need a power supply that could push out 2 amps

Do you look at each circuit as an independent part to figure resistor values? If you use a calculator and specify 10 LEDS in parallel or 20 LEDS in parallel you get different resistor values. What if you have 10 and 20 LED circuits running off the same power supply?

Each string of LED's needs it's own resistor, so calculate the resistor values for each group of LEDs

Finally I was thinking of using cold cathode lighting for the Warp engines. How do figure the draw of other components in the plan?

I'm not up on CCL - some one else will have to field this one

Finally circuits may on and off. Does that change things?

Nope - if at any one point in time - even for just a fraction of a second, the LEDs are lit, consider them as lit all the time for the resistor and power requirements - I would separate any blinking LEDs into distinct circuit runs

I’m very much a newbie here – but maybe someone can offer some guidance.

Thanks.

We're here to help

Just remember, the only stupid question is the one un-asked

[Scott Hasty]

How to you calculate the wattage or amperage of a plug in DC power supply. There is a lot of information about batteries which I don’t think would be particle for this project.

First, be careful with common wall warts. They are unregulated (unless noted otherwise). That 9V wart can actually be pumping out 18V so you will need a voltage regulator. If you want a nicely regulated supply, I suggest a laptop power supply.

Power (watts) can be calculated by multiplying the voltage and current (amps). If your supply is rated at 12V 1A, it has the power capability of 12 watts.

You will have to utilize series/parallel circuits when using extensive LED's. Other components (such as CCFL's) will have their ratings on them and will have to be figured into your circuit totals.

[robiwon]

While I can not contribute a whole lot to this thread, I will add this. I am running 21 white LEDs for my Anigrand Bad Guy Pie Cruiser and I wanted to use a walwart. I picked up at RadioShack an adjustable regulated power supply. You can set it at 3, 4.5, 6, 9,and 12 volts. It puts out 1 amp. Set at the 3v setting it powered my 21 LEDs with no resisitors. I let it run for about 3 hours and nothing heated up or went "POOF".