Led lamp - won't work in cold enviroment

[Gabriel]

Re: Led lamp - won't work in cold enviroment

if that is like one my neighbor put up last summer the caps are baked.
his is a dim blue now.several rows of leds are out too.it runs too hot to touch.

No, had a few of these on for two hours and they get warm but you can still touch the housing just fine and even touch glass without fingers getting stuck.

[stj]

Re: Led lamp - won't work in cold enviroment

i think he means baked by the sun.

[Gabriel]

Re: Led lamp - won't work in cold enviroment

Oh, I realize that ..now

[kc8adu]

Re: Led lamp - won't work in cold enviroment

it hit 200f at the led pad on the case at 85f ambient.after sunset.
i knew it wasnt going to last.i will wind up with it soon.3 altilon 1x4 will do nicely in it.

[Behemot]

Re: Led lamp - won't work in cold enviroment

What about adding a fan to move some air within it while the sun is baking it?

[kc8adu]

Re: Led lamp - won't work in cold enviroment

its sealed and daytime heating is not the issue.
the horrible efficiency of the cob led is.
the owner got it for less then $20 shipped from china.
he knew when i helped him install it to not expect much.

[Gabriel]

Re: Led lamp - won't work in cold enviroment

Winter is back and my led lamps is again not working.

I replaced the Su'scon on the secondaryside with Kyb (-40) and the small startupcaps with Lza (-55).

Still the lap won't turn on - it almost seems like the lamp with Su'scons turn itself on before the lamp with Kyb and Lza when brought inside and heated up.

Any ideas ? perhaps I will try to modify with ceramic startupcaps and runcap but will that shorten other components life and what size would I aim for ?

[ben7]

Re: Led lamp - won't work in cold enviroment

If you haven't already, check (when the driver is cold) to see if the PWM chip's VCC voltage is high enough. It might or might not still be a cap problem ... there ARE other parts which could go too far out of tolerance in the cold, my first thought would be resistors.

By the way, is it totally dead, or does it flash briefly and then not work?
Any little details like those can sometimes help!

-Ben

[Gabriel]

Re: Led lamp - won't work in cold enviroment

Ah I thought the caps were the only problem in the cold, don't have the lamps here right now but I will see if I figure out the vcc voltage.

No, the laps is completely lifeless, no flash or anything like that.

I wonder how cars manage to start in icecold, resistors and caps in the ecu's should suffer from the same problem as this laps does.

[ben7]

Re: Led lamp - won't work in cold enviroment

Ah I thought the caps were the only problem in the cold, don't have the lamps here right now but I will see if I figure out the vcc voltage.

Practically everything is affected by temperature in some way. Some more than others though!

Another idea is that the LED COB itself might require too high of a forward voltage when cold, which is causing the driver to not work. (I would think this would result in the lamp flashing for a brief moment though, which you say it is not.)

I wonder how cars manage to start in icecold, resistors and caps in the ecu's should suffer from the same problem as this laps does.

Well it's possible this power supply wasn't designed with low temperatures in mind. I know they take that into consideration most of the time these days when designing cars. Also, modern cars are better at starting their engine when cold because of better alloys, which will help keep enough compression to start it when it's very cold (the pistons shrink slightly in the cold).
(Also there are other things, like oil flow and what not. Our Toyota Sienna minivan is noisy when cold, the engine sound is more like a diesel ... it goes back to normal once it warms up enough and the oil flows where it needs to go. Apparently it is normal for the 2GR engines. (The 2GR engines are decent engines by the way.))

-Ben

[kc8adu]

Re: Led lamp - won't work in cold enviroment

yes find datasheet for the chip.make sure its supply is well above uvlo.
could be just on the edge.

[kaboom]

Re: Led lamp - won't work in cold enviroment

also check output voltage from working vs not working

that PS could be working, but Vo setpoint may be too low for some reason (resistors?) and too low to overcome the Vf of the cheap LED array- itself having higher Vf at low temps

kc8adu, to see how bad they are, use a variable supply and resistor to bring it up slowly- some LEDs in some of the strings won't even light while passing current!

example here:
https://www.youtube.com/watch?v=NjKgPLeJ79Q

[linuxguru]

Re: Led lamp - won't work in cold enviroment

You probably don't want to use aqueous electrolytics (ultra-low ESRs) in which the water is likely to freeze. Older non-aqueous electrolytics like NCC LXV/LXY/LXZ or Nichicon PJ/PW or Panasonic FC, etc. should be OK. Most modern electrolytics are aqueous for various regulatory, compliance and competitive reasons.

[stj]

Re: Led lamp - won't work in cold enviroment

they wont freeze because of the salts,
most are rated down to -55'

[Behemot]

Re: Led lamp - won't work in cold enviroment

Most are -40 actually (the oil lytes are -55), but still more than enough.

[imp]

Re: Led lamp - won't work in cold enviroment

Could it be because of an inrush current limiter (NTC) that never gets warm enough to pass enough current through?

[Behemot]

Re: Led lamp - won't work in cold enviroment

At 230 V even if the thermistor had 10 ohm all the time that still gives you 23 A at slightly lower voltage. At such situation it woulf off course heat so much it would drop the resistance immediatelly. This thing should take quarter an amp on average.