35mA led with 25mA pic output?

[xnihilo]

It may be that the 35mA rating for the LED you describe is a maximum, do-not-exceed rating. If you can find the data sheet for the LED, see if it also gives a typical operating current.

People sometimes forget that most LEDs will produce full brightness long before maximum rated current is reached.

A couple of replies have suggested a 220 ohm resistor; that or even a 180 ohm resistor would be a good starting point. Depending on the Vf of the LED, that will give you something between 14 and 19 mA. You may be surprised to find that the LED is quite bright.



Piezo tone/buzzer devices are basically voltage-driven; the greater the voltage, the louder the sound. The 9 mA rating is probably for the 12 VDC maximum; at 5 volts, it will likely draw only 4 or 5 mA.

They say "max dc forward current" and "Typical" FC is 35 mA
See: http://www.futurlec.com/LEDR3R.shtml

About the buzzer, thanks for the info, I'm surprised it needs only 9mA (7mA in fact) at 12V. That's cool.

I lear so many things here.

[RussMartin]

They say "max dc forward current" and "Typical" FC is 35 mA
See: http://www.futurlec.com/LEDR3R.shtml

You are misreading the table.

The third line is saying that the maximum DC forward current is typically 35 mA. It means that for some of the LEDs, it may be a little more and for others a little less, but what it is telling you for sure is, "Don't exceed 35 mA."

The first line of the table is probably more indicative, where it shows a typical forward voltage (Vf) of 2 VDC when run at 12 mA. This sounds like a typical operating condition and is probably as bright as it needs to be.

So you need a series resistor of 220 ohms (13.6 mA), but you can probably use down to 150 ohms (20 mA).

[xnihilo]

You are misreading the table.

The third line is saying that the maximum DC forward current is typically 35 mA. It means that for some of the LEDs, it may be a little more and for others a little less, but what it is telling you for sure is, "Don't exceed 35 mA."

The first line of the table is probably more indicative, where it shows a typical forward voltage (Vf) of 2 VDC when run at 12 mA. This sounds like a typical operating condition and is probably as bright as it needs to be.

So you need a series resistor of 220 ohms (13.6 mA), but you can probably use down to 150 ohms (20 mA).

... Right. Thank you.
Stuff like "Vcc=Min,Iol=MAX,Vih=MAX" is not yet so obvious for me.

[skimask]

.....Information removed at the risk of annoying RussMartin......
See post below....

[RussMartin]

Most of those abbreviations are listed at the bottom of the pages of the datasheets.
If not there, usually a Google-search and/or Wiki will get you the answer on whatever the abbreviation means. In this case:
Vcc = voltage common-collector, generally positive voltage input
Iol = current, output, low (sinking current)
Vih = voltage, input, high

. . . and which have nothing to do with either his question or his LED. I believe he was conveying his thanks to me, not asking another question.

[skimask]

. . . and which have nothing to do with either his question or his LED. I believe he was conveying his thanks to me, not asking another question.

Well excuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu uuuuuuuuuuuuuuuuuuse me