# Need some very basic help

Status
Not open for further replies.

#### Willie TwoFinger

##### New Member
Also, how big of a resister can be placed on each diode if I so desired? I know that is a lot but... I'd do it... is it even feasible?

#### Torben

##### Well-Known Member
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

#### Willie TwoFinger

##### New Member
Torben...

Yeah, it's starting to sink in... Much thanks!

#### audioguru

##### Well-Known 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?

Status
Not open for further replies.

Replies
21
Views
6K
Replies
24
Views
3K
Replies
16
Views
2K
Replies
7
Views
1K
Replies
7
Views
1K