So changing from 12v Halogen to 12v LED (bollox ?)

Surely ( not shirley ) the heat generated within the bulb is more from the pcb than the led´s? Cannot ever remember coming across a hot led. My dog´s collar had several led´s and ran off a 3v lithium battery, as do many " Christmas hats " and assorted paraphernalia sold at various times of year. No heat, just pretty lights. I also have about three types of led work lights that run on standard batteries or re-chargeable, never got hot yet.
Or am I using the wrong led´s?
 
Milamber said:
Surely ( not shirley ) the heat generated within the bulb is more from the pcb than the led´s? Cannot ever remember coming across a hot led. My dog´s collar had several led´s and ran off a 3v lithium battery, as do many " Christmas hats " and assorted paraphernalia sold at various times of year. No heat, just pretty lights. I also have about three types of led work lights that run on standard batteries or re-chargeable, never got hot yet.
Or am I using the wrong led´s?
Click to expand...
Well ..fwiw ..these high power high brighness leds do generate a fair amount of heat ..
If you don't believe me ...open up an LED TV screen/panel ..if you're brave enough ..
On larger TVs the actual LEDs are mounted on heatsinks not just pcbs ..
In the case of the led bulbs ..I doubt a single LED can generate enough heat to be an issue ...but 12 in close proximity ?
I've yet to check the heat generated ...it's on my to do list ..
Personally I don't believe it to be that excessive but heated air rises ..and will heat any air trapped in the confined space within the glass chamber ..this may result in thermal runaway..
is this chamber sufficiently evacuated even ..?
I simply dont have those answers..
does anyone here know for sure ?
certainly when I smashed that glass it did not pop like a conventional lightbulb.
rgds
VS
 
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Vipersan said:
Well ..fwiw ..these high power high brighness leds do generate a fair amount of heat ..
If you don't believe me ...open up an LED TV screen/panel ..if you're brave enough .. ( yes I´m brave enough, just not stupid enough)
On larger TVs the actual LEDs are mounted on heatsinks not just pcbs ..
In the case of the led bulbs ..I doubt a single LED can generate enough heat to be an issue ...but 12 in close proximity ? ( gathering of the clan)
I've yet to check the heat generated ...it's on my to do list .. (get on with it)
Personally I don't believe it to be that excessive but heated air rises ( as we all know, we all fart ).and will heat any air trapped in the confined space within the glass chamber ..this may result in thermal runaway..( and the need for a chilled toilet roll )
is this chamber sufficiently evacuated even ..? ( I doubt it )
I simply dont have those answers..
does anyone here know for sure ? ( only one I can think of )
certainly when I smashed that glass it did not pop like a conventional lightbulb. ( nah! more like microwave popcorn )
rgds
VS
Click to expand...
 
Vipersan said:
Can't see it being lethal at 12v 1amp..but still..
Click to expand...

Like I say, if it was using an capacitive dropper (versus an isolated transformer), which is referenced to mains, give it a path direct to earth, zappy times, I should know, I did just that recently, after I made this quick instagram vid actually:

@twocvbloke on Instagram: “Hand of god, or current leakage due to crappy household wiring? You decide... :P”

Suffice to say, I shall not be touching broken LED filament bulbs again, but I do need to investigate why the live and neutral is swapped in this house, cos that lamp was off, so must have been switching the neutral, not the live...
smiley_electrocute.gif
 
2cvbloke said:
Like I say, if it was using an capacitive dropper (versus an isolated transformer), which is referenced to mains, give it a path direct to earth, zappy times, I should know, I did just that recently, after I made this quick instagram vid actually:

@twocvbloke on Instagram: “Hand of god, or current leakage due to crappy household wiring? You decide... :P”

Suffice to say, I shall not be touching broken LED filament bulbs again, but I do need to investigate why the live and neutral is swapped in this house, cos that lamp was off, so must have been switching the neutral, not the live...
smiley_electrocute.gif
Click to expand...
We get that all the time in Spain, NEVER trust Spanish wiring, ALLWAYS turn the mains off.
 
So here are some temperature readings take(n) from the exposed pcb it having run hanging just under the downlight fitting for about 16 hours non stop..
LED in centre cluster 29.7 c
LED in outer cluster 28.8 c
one of the 43 ohm resistors .. 30.2 c
the bridge rectifier .. 30.4c
the pcb around the point of resoldering .. 35.1 c
These are minimum values as holding onto the pcb whilst checking temeratures for more than a minute was actually painful ..
yes the pcb is that hot ..
and remember it is now air cooled having no glass envelope..
So ..the question remains does the pcb get hot enough in a closed space to partially liquify certain solders ?
I'm guessing yes ..
The unclothed LED lamp pcb is not showing any signs of failing after 16 hours straight running ..
rgds
VS
 
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Vipersan said:
So here are some temperature readings taked from the exposed pcb it having run hanging just under the downlight fitting for about 16 hours non stop..
LED in centre cluster 29.7 c
LED in outer cluster 28.8 c
one of the 43 ohm resistors .. 30.2 c
the bridge rectifier .. 30.4c
the pcb around the point of resoldering .. 35.1 c
These are minimum values as holding onto the pcb whilst checking temeratures for more than a minute was actually painful .. ( whimp )
yes the pcb is that hot .. ( as I suspected )
and remember it is now air cooled having no glass envelope..
So ..the question remains does the pcb get hot enough in a closed space to partially liquify certain solders ? ( yes, as I suspected )
I'm guessing yes ..
The unclothed LED lamp pcb is not showing any signs of failing after 16 hours straight running ..
rgds
VS
Click to expand...

Enough said! ( and it should have been temperatures ) ( taken ) etc.
 
Sorry, totally off topic. Please chuck all unwanted and obviously unrelated posts on the scrap heap, or however it is correctly written!
 
Well ...they took about 3 weeks to arrive ...and I would much prefer a warm white ....but hey ..
at about £2 each were the cheapest I could find ..
unbranded plain white box ..but I'm sure they are the same ones that are sold in the UK ..but in a nice coloured box at around £5 each..
All the way from HK ..
So far I'm impressed with the amount of light they give out ...and unpowered from a distance look like conventional filament BN22 clear candle lamps..
After the Chinese New Year ...I'll go in search of the same lamp in warm white..
and possibly a dimable version ..
here are a couple of pix..
Now to see how long they last...
rgds
VSDSCF0002.webp DSCF0003.webp
 
Is that ceiling flammable? :oops:
 
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