Can Badboy and Madmax be used to drive 5mm Nichias?

[Cemoi]

Hello,

Using two NiMH AAs in series, can I use the Badboy or Madmax (designed to drive high power LEDs) to drive two Nichia GS* in parallel?
*Vf=3.2V @ 20 mA, max specified If = 30 mA.

 

[dat2zip]

Madmax is not adjustable and would overdrive the two Nichias.

The badboy can be set to 30mA using a two resistors (2 ohm, 10 ohm). That would give you the desired output current.

Wayne

 

[Cemoi]

The badboy can be set to 30mA using a two resistors (2 ohm, 10 ohm)

Thanks. I tried to calculate this myself using your resistor calculator, but if I enter 0.03 A (=30mA) as the desired current I get a message saying "Desired current is invalid (ie 0.1A - 1.5A)", whereas the calculator instructions say "Legal values are between 0 and 1.5" :thinking:
On the other hand:

• Why should I use two resistors?
• Where should the resistors be connected?
• If the above value make the Badboy supply a 30 mA current, each LED will only get 15 mA if they are in parallel. If I want 30 mA in each LED, the resistor(s) should be designed for a 60 mA total current.
• Is connecting the LEDs in parallel the best option, could the Badboy drive them in series?

 

[dat2zip]

Thanks. I tried to calculate this myself using your resistor calculator, but if I enter 0.03 A (=30mA) as the desired current I get a message saying "Desired current is invalid (ie 0.1A - 1.5A)", whereas the calculator instructions say "Legal values are between 0 and 1.5" :thinking:
On the other hand:

• Why should I use two resistors?
• Where should the resistors be connected?
• If the above value make the Badboy supply a 30 mA current, each LED will only get 15 mA if they are in parallel. If I want 30 mA in each LED, the resistor(s) should be designed for a 60 mA total current.
• Is connecting the LEDs in parallel the best option, could the Badboy drive them in series?

The resistor calculator had limits for low and high. Must be 0.1A for the low end.

It took two resistors to get the correct value for 30mA. There are limited resistor values and the computed one is not a standard value so it took two to get it correct.

Yes, you can make it 60mA using different values. A 0.86 ohm resistor will give you 60.9mA or so.

The formula for computing the output current is 0.05 / Rsense = LED_Current.

0.05 / 0.82 = 0.06097 Amps

Valid values of resistors below 1 ohm are E12 values. You can see all of them here. Look at the E12 column. 100 would be 0.100, 120 would be 0.120 etc.

Yes, you can drive two or more LEDs in series with the Badboy. I don't recall ofhand, but, you can drive multiple LEDs as long as it's less than 16V or possibly higher (might be 22V or so).

Wayne