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12 Vdc led running hot

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AK
Guest

Fri Aug 09, 2019 3:45 am   



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.

Helmut Wabnig
Guest

Fri Aug 09, 2019 8:45 am   



On Thu, 8 Aug 2019 19:03:46 -0700 (PDT), AK <scientist77017_at_gmail.com>
wrote:

Quote:
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-

Tom Biasi
Guest

Fri Aug 09, 2019 3:45 pm   



On 8/8/2019 10:03 PM, AK wrote:
Quote:
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?


Bob Engelhardt
Guest

Fri Aug 09, 2019 4:45 pm   



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.

George Herold
Guest

Fri Aug 09, 2019 8:45 pm   



On Thursday, August 8, 2019 at 10:03:49 PM UTC-4, AK wrote:
Quote:
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

Phil Allison
Guest

Sat Aug 10, 2019 12:45 am   



AK wrote:
Quote:

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

default
Guest

Sat Aug 10, 2019 12:45 am   



On Thu, 8 Aug 2019 19:03:46 -0700 (PDT), AK <scientist77017_at_gmail.com>
wrote:

Quote:
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
Guest

Sat Aug 10, 2019 2:45 am   



On Friday, August 9, 2019 at 6:21:27 PM UTC-5, Phil Allison wrote:
Quote:
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. Smile

Rheilly Phoull
Guest

Sat Aug 10, 2019 2:45 am   



On 10/08/2019 9:35 am, AK wrote:
Quote:
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. Smile

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.

Cursitor Doom
Guest

Sun Aug 11, 2019 6:45 pm   



On Fri, 09 Aug 2019 18:35:03 -0700, AK wrote:

Quote:
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. :)



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This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
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AK
Guest

Thu Aug 15, 2019 10:45 pm   



On Sunday, August 11, 2019 at 11:57:38 AM UTC-5, Cursitor Doom wrote:
Quote:
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.


Thanks Mr. Doom

Andy

Tobias Gadelha
Guest

Mon Sep 16, 2019 6:45 pm   



On Friday, August 9, 2019 at 4:00:35 AM UTC-3, Helmut Wabnig wrote:
Quote:
On Thu, 8 Aug 2019 19:03:46 -0700 (PDT), AK <scientist77017_at_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-


It's a easy way to make a test in LED during the commissioning.

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