Driving Leds

[FlyMario]

Hi,  for Halloween I have several props that are going to use about 350 to 400 LED's each.  About 1000 LEDs are going to be 2v 20ma. Instead of soldering so many resistors,  I am wondering if I just used a Buck converter putting out 2V at 2A could I just drive a lot of LED's straight off that or would that be LED suicide.  Of course, I know I am only going to drive 2A worth of LED's max.  As long as I stay under 2A pull from the Buck Converter should I be ok?

Thanks,
Pete

[Benta]

No. What you do is connect the LEDs in series and give each series string 20 mA. Depending on your supply voltage, you can decide how many LEDs to each string. Allow for extra voltage for current limiting (~5 V).

[Brumby]

As Benta has said, series strings are the way to go.

50 strings of 20 LEDs; 20 strings of 50 LEDs; 23 strings of 42 LEDs plus one string of 34.  There are a lot of ways to go about this.  How many LEDs in each string will depend on the capabilities of the power supply you have available and safety considerations of the voltage applied.

Running LEDs in parallel isn't the best idea anyway as there will be small differences in their V_f - so some will be brighter (ie drawing more current) than others.  There are some products that do this out of cost reduction objectives, but these tend to work because the LEDs are well matched, having come from the same batch.  However, I would expect than in a thousand LEDs, you wouldn't be so lucky.

[FlyMario]

Yeah thanks guys,  I was trying to be lazy.  I have so much soldering to do as it is for these monster heads.  Just don't need to focus on how many I need to do but instead on how good it will look

FlyMario