XPost: uk.d-i-y, alt.home.repair
From: rod.speed.aaa@gmail.com
"William Gothberg" <"William Gothberg"@internet.co.is> wrote in message
news:op.zudk28kzo5piw3@desktop-ga2mpl8.lan...
> On Fri, 21 Dec 2018 04:11:46 -0000, Rod Speed
> wrote:
>
>>
>>
>> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message
>> news:op.zucm99ypo5piw3@desktop-ga2mpl8.lan...
>>> On Fri, 21 Dec 2018 01:06:46 -0000, Rod Speed
>>> wrote:
>>>
>>>>
>>>>
>>>> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in message
>>>> news:op.zucezsmio5piw3@desktop-ga2mpl8.lan...
>>>>> On Thu, 20 Dec 2018 22:14:31 -0000, Rod Speed
>>>>>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in
>>>>>> message
>>>>>> news:op.zucb6od6o5piw3@desktop-ga2mpl8.lan...
>>>>>>> On Thu, 20 Dec 2018 21:35:49 -0000, Rod Speed
>>>>>>>
>>>>>>> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in
>>>>>>>> message
>>>>>>>> news:op.zub8lqzpo5piw3@desktop-ga2mpl8.lan...
>>>>>>>>> On Thu, 20 Dec 2018 19:11:36 -0000, Rod Speed
>>>>>>>>>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> "William Gothberg" <"William Gothberg"@internet.co.is> wrote in
>>>>>>>>>> message
>>>>>>>>>> news:op.zubnqbkho5piw3@desktop-ga2mpl8.lan...
>>>>>>>>>>> On Thu, 20 Dec 2018 09:36:02 -0000, Jon Fairbairn
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> "William Gothberg" <"William Gothberg"@internet.co.is> writes:
>>>>>>>>>>>>> Agreed. All I can detect (with my digital camera) is that
>>>>>>>>>>>>> one brand of LED light I have flickers about 5 times less
>>>>>>>>>>>>> (not sure if it's smother or faster) than the others.
>>>>>>>>>>>>
>>>>>>>>>>>> Try a longer exposure and move the light rapidly relative to
>>>>>>>>>>>> the
>>>>>>>>>>>> camera.
>>>>>>>>>>>
>>>>>>>>>>> I wonder, if I fed the lamps with mains voltage DC, simply a
>>>>>>>>>>> bridge
>>>>>>>>>>> rectifier and a huge capacitor, they'd reduce their flicker.
>>>>>>>>>>
>>>>>>>>>> Wont work at all if they use capacitor droppers and
>>>>>>>>>
>>>>>>>>> I made a few of those to power LEDs to indicate the function of my
>>>>>>>>> central
>>>>>>>>> heating. I'm looking inside the flickery lamp just now (£15,
>>>>>>>>> 20W).
>>>>>>>>> Without undoing the glue holding the PSU onto the inside of it,
>>>>>>>>> all
>>>>>>>>> I
>>>>>>>>> can
>>>>>>>>> see is probably: the mains going through a large bipolar cap, a
>>>>>>>>> tiny
>>>>>>>>> resistor (to discharge it safely?), a bridge rectifier, another
>>>>>>>>> very
>>>>>>>>> large
>>>>>>>>> resister (to limit the LED current more accurately?), then a 400V
>>>>>>>>> 4.7uF
>>>>>>>>> capacitor (which is bulged).
>>>>>>>>
>>>>>>>>> A capacitor dropper with a rectifier and smoothing capacitor after
>>>>>>>>> it?
>>>>>>>>
>>>>>>>> Yep, that's what it is.
>>>>>>>>
>>>>>>>>> The one I made has no smoothing cap, just mains to cap to resistor
>>>>>>>>> to
>>>>>>>>> bridge to LED.
>>>>>>>>
>>>>>>>> Yeah, not need for one if you don't mind the 100Hz flicker.
>>>>>>>
>>>>>>> It was just indicator LEDs to tell me what water circuit was
>>>>>>> running.
>>>>>>> 3
>>>>>>> zones from the one boiler switched with valves.
>>>>>>>
>>>>>>>>> Perhaps this bulged cap is why I'm getting flicker, I'll try
>>>>>>>>> replacing
>>>>>>>>> it
>>>>>>>>> tomorrow.
>>>>>>>>
>>>>>>>>>> they very likely do because those are the only cheap
>>>>>>>>>> droppers for dropping such a large voltage.
>>>>>>>>
>>>>>>>>> Aren't miniature SMPS units pretty cheap?
>>>>>>>>
>>>>>>>> Not as cheap as the cap and the bridge rectifier.
>>>>>>>>
>>>>>>>>> I just bought a 12V 6A SMPS for £4.50.
>>>>>>>>
>>>>>>>> Yeah, I did too.
>>>>>>>>
>>>>>>>>> Designed for powering LEDs
>>>>>>>>
>>>>>>>> Mine will run anything 12V. I currently use it to power a water
>>>>>>>> pump.
>>>>>>>
>>>>>>> It was sold for LEDs, presumably it will run anything provided I
>>>>>>> don't
>>>>>>> exceed the 6A.
>>>>>>>
>>>>>>> However I've noticed they scrimp on the caps (or cooling). Loads of
>>>>>>> them
>>>>>>> get bulged caps after a while, in particular a 3A PSU I ran 2A of
>>>>>>> LEDs
>>>>>>> 24/7 from, failed in 1 year. It kept cutting out - I discovered the
>>>>>>> bulk
>>>>>>> capacitor had dried out. Same happened (over a longer period) with
>>>>>>> two
>>>>>>> monitor PSUs.
>>>>>>>
>>>>>>>> The LEDs I use are all Hues and have their
>>>>>>>> own power supply with the led strips.
>>>>>>>
>>>>>>> The one I mentioned above was for an insectocuter, I removed the
>>>>>>> flours
>>>>>>> and ballast and fitted strips of UV LEDs instead.
>>>>>>>
>>>>>>>>> - but I've looked inside it and it's definitely a switched mode,
>>>>>>>>> not
>>>>>>>>> a
>>>>>>>>> capacitor dropper. Now this flickery LED lamp I'm looking inside,
>>>>>>>>> it's
>>>>>>>>> about 20W, so 12V at 2A is all that's required, it could have had
>>>>>>>>> an
>>>>>>>>> SMPS
>>>>>>>>> in it similar to the one I just described.
>>>>>>>>
>>>>>>>> Yeah, but the cap and bridge are cheaper.
>>>>>>>
>>>>>>> Well I've got 9W £4 strips with a switched mode PSU in them, so they
>>>>>>> can't
>>>>>>> cost that much.
>>>>>>>
>>>>>>>>> I'm now looking inside one of the better LED lamps (the
>>>>>>>>> non-flickery
>>>>>>>>> model). It has a basic SMPS inside it. They're 9W and £4 each
>>>>>>>>> for
>>>>>>>>> the
>>>>>>>>> whole lamp. I'm sure it's more than just a standard SMPS though,
>>>>>>>>> because
>>>>>>>>> when some LEDs fail short circuit (it has about 40 in series), the
>>>>>>>>> voltage
>>>>>>>>> coming from the PSU drops, to maintain the correct current for the
>>>>>>>>> remaining good LEDs.
>>>>>>>>
>>>>>>>> Yeah, its best to drive leds in constant current mode.
>>>>>>>
>>>>>>> I'm surprised that the LEDs always fail short circuit, new type of
>>>>>>> LED
>>>>>>> designed to do this?
>>>>>>
>>>>>> Think its just the way leds fail naturally
>>>>>> with the higher powered lighting leds.
>>>>
>>>>> What's quite weird is with the decent strips I've got, the LEDs are
>>>>> wired
>>>>> in pairs. Each pair is in parallel, then there are 20 such pairs in
>>>>> series. When one single LED fails, I'd expect either it shorts and
>>>>> the
>>>>> neighbouring one in the pair gets 0 volts, or it fails open circuit
>>>>> and
>>>>> the neighbouring one gets double current and soon dies. But neither
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