LED 12v Lamps

[ollieo]

Hello, I have some 12v LED lamps, on the data sheet it says:

Working current IF = 20mA

but it also says pulse forward current IFP = 150mA Pulse max width = 10ms

I was going to use 8 of these in parralel off of a transistor, but the max IC is 800 mA. I am only pulsing at 100ms min going up to 1 second max.

Will this maximum pulse current come into play here when turning the LEDs on? or will it just be the rated 20mA?

Help very much appreciated.

Thanks

 

[MikeMl]

Post a link to the data sheet for these Leds. I'm trying to figure out if they have an internal current limiting resistor, or not.

 

[ollieo]

**broken link removed**

The red, yellow green and blue ones.

Ta

 

[MikeMl]

It would appear that they have a built-in resistor, although I wish the idiot that wrote that spec sheet would have said so...

Are you planing to "pulse" these with much more than 12V applied? My take is that if driven from either 12ADC or 16VDC, the current will stay within spec.

 

[ollieo]

It's going to running off around 12V - 13.5V. Pulse range is variable from 100ms to 1 second, the pulse width will be a lot wider than the 10ms stated.

So will 8 of these be more than 800mA max IC for the transistor do you recon (when turning on being too much and breaking down the transistor)? Or do you mean the 20mA spec stated?

Thanks again

 

[MikeMl]

No, if you wire them to 16VDC, the current will be only 20mA each. If you PWM the 16V, the average current will be lower than 20mA each. If you parallel eight, then the total current would be 160mA on DC, and proportionally less on PWMed DC.

Because they have a built-in resistor, the only way to drive them at their peak current rating would be to pulse them with ~75V.

 

[ollieo]

Ahh, brilliant.

Thanks a lot for your help

 

[MikeMl]

Ahh, brilliant.

...

No, just Ohm's law