Does anyone make high efficiency ac/dc LED indicators

[John Gilmer]

With Google I found a company that has a line of LED indicator assemblies
from 6 volts up to 24 volts. As far as I can tell from the power
consumption data, they just take two LEDs in parallel and put in the
appropriate resistor. At 24 volts, we are talking about 1/2 watt and that
can get downright WARM.

BUT, why couldn't "they" put several "tiny" LEDs in series and adjust the
resistor so that the same light could be obtained with, say, 5 mA as
compared to the more or less standard 20 mA.

OR, for AC use, how reasonable would be it to use a capacitor or coil to
drop most of the voltage.

It would be "nice" to have a pilot lamp than can run cool and have a
expected lifetime longer than whatever it is monitoring. At 120/240 neon
based indicators just don't seem to last very long.

 

[John Gilmer]

If you use a capacitor how do you guarantee that there will be
nothing other than the line frequency get to the input? Harmonics and
impulse noise will not be treaded the same a a clean sine wave at line
frequency.

You can't.

That's why:

1) you "back up" the cap with a resistor which will help with the impulses.

2) you "protect" youself with a "60 Hz, _% harmonics label.)

 

[Paul Hovnanian P.E.]

With Google I found a company that has a line of LED indicator assemblies
from 6 volts up to 24 volts. As far as I can tell from the power
consumption data, they just take two LEDs in parallel and put in the
appropriate resistor. At 24 volts, we are talking about 1/2 watt and that
can get downright WARM.

BUT, why couldn't "they" put several "tiny" LEDs in series and adjust the
resistor so that the same light could be obtained with, say, 5 mA as
compared to the more or less standard 20 mA.

Poor current regulation, particularly for the lower voltage assemblies.
The more LED drop (with a negative Vf vs temperature characteristic) in
the circuit, the more sensitive it will be to temp. variations.

OR, for AC use, how reasonable would be it to use a capacitor or coil to
drop most of the voltage.

It would be "nice" to have a pilot lamp than can run cool and have a
expected lifetime longer than whatever it is monitoring. At 120/240 neon
based indicators just don't seem to last very long.

It all boils (no pun intended) down to cost. Most buyers are comparing
these things to cheapo incandescent or neon units. As long as the lamps
last a little longer than the warranty, the manufacturer doesn't care.

 

[Mike Lamond]

Poor current regulation, particularly for the lower voltage assemblies.
The more LED drop (with a negative Vf vs temperature characteristic) in
the circuit, the more sensitive it will be to temp. variations.


It all boils (no pun intended) down to cost. Most buyers are comparing
these things to cheapo incandescent or neon units. As long as the lamps
last a little longer than the warranty, the manufacturer doesn't care.

The LED lamps that IDEC sells for their industrial pilot lights have an
internal
resistor and what looks like multiple elements on a flat surface. They have
a
bayonet base and are rated 20mA for 6, 12 and 24 volt models, and 10mA
for 120 and 240 volt models. I think some of them are brighter than the 1
watt incandescent, but none of them match a 3 watt 120MB lamp.

Mike

 

[Spokesman]

The LED lamps that IDEC sells for their industrial pilot lights have an
internal
resistor and what looks like multiple elements on a flat surface. They have
a
bayonet base and are rated 20mA for 6, 12 and 24 volt models, and 10mA
for 120 and 240 volt models. I think some of them are brighter than the 1
watt incandescent, but none of them match a 3 watt 120MB lamp.

So far there is no LED lamp that can match the effieciency of an ordinary
incandescent let alone being as efficient as a HPS lamp. Someday..