Voltage drop over a resistor?

[NoFair]

Anybody have an estimate of voltage drop over a 60 ohm resistor in series with led drop in using 2 cr123s?

I'm looking at the feasibility of using my C2 with 60 ohm 2-stage tailcap from the sandwich shoppe with 2 cr123s and a 3.7V LumensFactory led drop in. This would be emergency only and the light would normally be run using a 17670.

Discussed it briefly with Mark at LF, who said not to try it

Sverre

 

[PaulNYC]

I think:

V= 2*3 - 3.7 = 2.3V

I = V / R = 2.3 / 60 = 0.03833A

 

[CampingLED]

What you need to know is the specs of the drop-in at lower currents. My estimate is that the current will be anything between 40 and 70mA. If anybody has that answer, you have your answer.

 

[NoFair]

Mark at LumensFactory says not to try it, but I want to know a bit more since I have spare cr123s for emergencies both at work and at home..

Normally I'll run it on a 17670.

I'd think the voltage should drop and the current be severely limited.. Been awhile since my electronics courses in high school

Sverre

 

[Blindasabat]

LED-Pro says 45 mA at 3.3V from 6V.

What you need to know is the specs of the drop-in at lower currents. My estimate is that the current will be anything between 40 and 70mA. If anybody has that answer, you have your answer.

 

[NoFair]

LED-Pro says 45 mA at 3.3V from 6V.

Thank you :twothumbs

Will test a bit before I try (hopefully not fry:green

Sverre

 

[CampingLED]

Thank you :twothumbs

Will test a bit before I try (hopefully not fry:green

Sverre

You are usually safe with an inline resistor, especially as high as 60 ohm. Just remember that 45% of the power will be lost over the resistor. Keeping in mind other inefficiencies of the driver and you should be running less than 50% effective.

 

[NoFair]

You are usually safe with an inline resistor, especially as high as 60 ohm. Just remember that 45% of the power will be lost over the resistor. Keeping in mind other inefficiencies of the driver and you should be running less than 50% effective.

This is for emergencies only.

It will normally run unresistored on a 3.7V 17670.

Sverre