A lot of times the asian folks selling stuff are nontechnical, best toOn Friday, August 9, 2019 at 6:21:27 PM UTC-5, Phil Allison wrote:
AK wrote:
I bought some 12 VDC 5 mm red leds.
They work find but...
when I touch the wires going into the led, they were hot enough that I had to remove my hand.
That does not seem normal.
** The heat is from a resistor in series with the 5mm LED.
Red LEDs only take 1.7 volts so the rest is dropped by a resistor.
..... Phil
I found out that the led is actually 9 volt.
It was labeled at 12 volts which was way too much.
After switching to 9 volts, it runs much cooler.
Andy
P.S. I wonder if the Chinese fighter jets have similar mistakes.
On Fri, 09 Aug 2019 18:35:03 -0700, AK wrote:
I found out that the led is actually 9 volt.
It was labeled at 12 volts which was way too much.
After switching to 9 volts, it runs much cooler.
They're 'current-orientated devices' for want of a better term for it. To
make things a bit easier, manufacturers will quote the Vf for each LED
which is the recommended level of forward bias voltage required to
provide the optimum amount of current vs. longevity allowing for such a
device's dynamic resistance as its barrier height potential is overcome.
I could have probably written that better, but not on a Sunday afternoon
after a decent bottle of Claret.
--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.