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12 Vdc led running hot

Started by AK August 8, 2019
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.

Thanks.
On Thu, 8 Aug 2019 19:03:46 -0700 (PDT), AK <scientist77017@gmail.com>
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. > >Thanks.
Don*t touch them, that would be normal. Who in the world touches LED wires? w-
On 8/8/2019 10:03 PM, 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. > > Thanks. >
At what current are you running them?
On 8/9/2019 10:06 AM, Tom Biasi wrote:
> At what current are you running them?
Right. More specifically - how are you running them? I.e., what are you using to supply the 12v? E.g., a plain old 12v battery will cause way too much current (& heat). LED supplies need to be current limited.
On Thursday, August 8, 2019 at 10:03:49 PM UTC-4, 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. > > Thanks.
Sounds broken, got a picture/ link of what you bought? GH
On Thu, 8 Aug 2019 19:03:46 -0700 (PDT), AK <scientist77017@gmail.com>
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. > >Thanks.
Maybe you could supply some info like the datasheet on the leds? Too hot to touch is usually too hot.
 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
On 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 10/08/2019 9:35 am, AK wrote:
> On 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. :-) >
A lot of times the asian folks selling stuff are nontechnical, best to take any descriptions with a grain of salt and form your own opinion as to suitability and accuracy.
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.