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Need some very basic help

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Torben

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Willie TwoFinger said:
Another question has come up...

"We need to find out the formula for the amps when we wire it series/parallel. Is it just straight up division?

If I had lets say 200 diodes wired into four groups of 50 -and each of those four was wired series, and I used a 12 volt adapter- then would the total amps be 1/4th what it would be?"

Hi Willie,

OK, for this I'm going to assume we're just using bare LEDs here (not laser modules with integrated electronics).

Assumptions: all LEDs are 3.2V LEDs which want 50mA; we have a 12V power supply. So Vled = 3.2V; Iled = 50mA, and Vsupply = 12V.

The short answer to your questions is "No, the total current drawn would not be 1/4 of of just wiring them all up in parallel. It would be 0." That is, 200 3.2V LEDs wired in 4 strings of 50 LEDs each would not even try to light up from a 12V power supply. Remember that you need (Vled * number of LEDs per string) volts to run the thing. (3.2 * 50) = 160V. You are not going to get a 160V device to run on a 12V power supply without some kind of boost converter. If you used a 160V+ power supply then the current draw would be 200mA (50mA * 4).

With a 12-volt supply your longest string of LEDs can be 3 LEDs long. Why? Because 3.2V goes into 12 at most 3 times. So you could do 66 groups of 3 LEDs (with 2 LEDs left over), or 100 groups of 2 LEDs.

Make sense?


Torben
 

audioguru

Well-Known Member
Most Helpful Member
Everybody is just guessing without detailed spec's.
The laser assemblies might need external current-limiting or not.
What is their minimum and maximum allowed voltage and current?
 
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