After a few years service, the halogen incandescent MR16 bulb in my shower fan/light assembly stopped working - contacts had distorted with heat.
Put a replacement LED version in, and it worked for a week. But now, when the power is applied it just flashes.
I tried another LED bulb (they came as a 4 pack ...) and it does the same.
Does this mean the transformer is ****ed ? I've checked the new bulb is making good contact.
It might mean the contacts in the base have oxidised due to the heat from the incandescent and are forming a high resistance as seen by the LED. Might be work trying to clean them up, perhaps by reinserting the lamp a number of times.
Is the LED described as 'transformer independent?
Have you checked if the transformer has a *minimum* load? Many intended for halogen use won't work with LEDs.
I was hoping to avoid crawling around in the loft ...
The LED bulb worked for a week before acting funny ...
Did the second one work for a while first too? Can you describe the flashing?
It sounds like the LEDs are being overrun, and a bond wire or some other connection has turned into a 'thermostat', breaking contact when hot. While it may seem unlikely that two LEDs will exhibit the same symptoms, they're made in the same place by the same machines and probably at much the same time.
That might just reflect the time it took the transformer to overheat and die as a result of trying to drive a mismatched load :-)
(modern transformers (mostly switched mode PSUs in reality) will usually be rated from 0W to whatever maximum limit. However it was common for older ones to have a minimum load which a LED lamp may not satisfy)
No. It behaved the same as the first started to. Hence my deduction it was unlikely to be the bulb
Or the transformed is ****ed. I never thought to check the LEDs were "transformer friendly".
Oh well, the whole fan assembly was due an overhaul. I want to replace the 180 ducting with a straight-up through the roof vent ....
Not impossible. However product info does seem to suggest transformers will be OK ...
There is a peculiar kind of engineer who makes consumer electronics. Usually, the cost sensitive stuff. These people will make circuits that *only* work properly, if the *exact* components are used at all times.
You talk of a fan unit with light. What if I did this ?
Mains X------ fan ----- halogen_lamp ----+ | Mains X----------------------------------+
If a person was a cheapskate, perhaps they could adjust the electrical characteristics of the fan design, so a lamp in series with it, caused the lamp to light up. Such a design would shorten the life of the halogen bulb, due to the stall current of the fan. If the fan was impedance protected, there might not be sufficient current to light the bulb. Substituting a LED bulb here would be a disaster (circuit characteristic isn't similar enough).
*******A more safety minded person, might design like this. The transformer gives a more expected characteristics, where no matter what is connected to the MR16, it's "normal" from an application perspective.
Mains X---+-- fan -----+ | | Mains X-------+--------+ | | | +----- --- | xfmr lamp_socket +--------- ---
To understand what is wrong at the moment, you need to double-check the circuit topology for unexpected configurations like the first one.
*******How well does the LED bulb work, if some load is applied to the transformer in parallel with the LED ?
---------------+----------+ | | Halogen LED MR16 MR16 | | ---------------+----------+
---------------+----------+ | | Power LED Resistor MR16 | | ---------------+----------+
I can see mention on the web, of the usage of "electronic transformers" for this. Which seems kinda unnecessary, but I have to ask what the power source looks like. Maybe it is something bizarre and unexpected as power sources go ?
*******The MR16 itself is quite complicated. This circuit actually attempts to "load" the electronic transformer a bit to keep it happy. They have a table of transformers and not all of them are completely satisfied by the circuit.
Yes. It's a change over to LED from incandescent and needs a different driver.
When they changed over from gas lighting to electrical lighting it was also one or the other. There was no hybrid system
The first "about" says: "NOTE:It's better use a LED transformer.If you want to connect a halogen transformer,make sure that the entire power of LED bulbs should reach the lowest power of your transformers,otherwise they may flicker strongly and not work "
For example, the transformer I have feeding a track light in my kitchen is rated from 50W to 250W - it used to drive 4 x halogen. I need to use
5 x 6W LED, and a 20W halogen to keep it happy and not flickering. (one day I will get round to swapping it for the LED compatible driver I bought to replace it!)
IME flashing LED bulbs are very common at all voltage levels I just throw them away and get a different brand.
I have loads of 50W 12V spotlamp halogen bulbs left, BUT the last one that failed is at the top of a stairwell and needs a ladder to replace, so I went LED for longevity. The transformer there is a toroid and it drove the thing perfectly.
I got that one in Homebase - I think the brand was TCP.
I have a kitchen on three dimmers. At least two of the spots flicker and flash at certain settings.
LED technology is very imperfect especially in the cheaper brands
I haven't tried LEDS on electronic transformers, because frankly its easier to fit a mains LED if a transformer goes
Toroidal transformers run fine: I can confirm that.
Its the switched mode ones that may barf on being presented with whatever weirdness the LEDS present. Its not just a matter of power, its is the reactive component as well.
BUT why not replace MR16s with mains voltage lamps?
GU10s etc?
I've had similar - seven LED MR16s in the bathroom. They worked for over a year and then started flashing. I replaced the power supply (twice, with two different makes, both of) which quoted the right range of maximum and minimum loads. Both just flashed. I got fed up of climbing in and out of the airing cupboard and working through the hatch there and replaced one of the MR16s with a halogen one instead. All has been well since.
I'll get around to making my own power supply at some point.
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