G9 LED bulbs that don't flicker?

[PenguinWithHair]

Hey everyone, I bought a pack of G9 LED 5 watt bulbs and they have a noticable high frequency flicker effect. The light is alright to see generally but it's when you look at something moving is had that strange 'low frame rate' effect. I've replaced b22, gu10 and e14 bulbs with LED with no problems, just this pack of G9s.

Anyone recommend G9s that don't do this, or anything in the specs to look out for which may indicate they might create a strobe effect?

Cheers.

 

[ericmark]

At what voltage? You can get both 12 volt and 230 volt G9 bulbs plus a load of other voltages. A 230 volt G9 should be same as any other LED bulb, but at 12 volt you have to have some power supply, and question is then is it the bulb or the power supply or a combination of both?

To control an LED bulb you need some current limiting device. This can be a simple resistor or a complex pulse width modulated chip. With the latter it switches on/off at a very high frequency, however the voltage dropping device also uses the same method, the switch mode power supply is very common. So unless it converts the output to DC and has a smoothing capacitor then one device and upset the other and cause the flickering. In the main when converting from 12 volt quartz to 12 volt LED we also swap the power supply from high frequency AC to DC. Because the LED is a diode it can also result with radio transmissions if connected to a high frequency AC supply.

Most likely it is the power supply not the bulb which is the problem assuming using 12 volt. If using 230 volt bulbs then no idea why the bulbs should flash.

 

[ban-all-sheds]

Poor quality rectification/smoothing coupled with the very fast response times and zero lag of LEDs could easily produce a lamp with a significant 50Hz variation in output.

I've got an LED R80 lamp which does the same as the OP's G9. Never had that problem with those wonderfulandnowthebastardshaveruinedorstoppedmakingthem Genuras.

 

[ericmark]

Fluorescent lamps unless HF have got a 100 Hz on/off but I have never noticed it. I would not expect you to notice it with a LED. Even with very cheap LED's they seem to use full wave so 100 Hz not 50 Hz.

I expect to find they are 12 volt and the supply and bulb are not compatible. Likely the supply is under loaded. Most supplies will have both a maximum and a minimum output, check that the minimum is exceeded.

 

[bernardgreen]

Fluorescent lamps unless HF have got a 100 Hz on/off but I have never noticed it.

The phosphors used in (most) fluorescent lamps have an after glow which significantly smoothes out the 100 Hz variation in luminous intensity.

Likewise a good quality LED element will use phosphors with a significant after glow to smooth out the luminous intensity.

Many cheap LED elements do produce light that varies in intensity with the current through the element and this could be 100 Hz or several thousand Hz depending on the way the current is controlled by the driver in the lamp.

 

[ban-all-sheds]

Many cheap LED elements do produce light that varies in intensity with the current through the element and this could be 100 Hz or several thousand Hz depending on the way the current is controlled by the driver in the lamp.

I feel like I could guarantee that someone, somewhere, is doing something to make a cheap LED lamp and getting a 50Hz flicker.

 

[ericmark]

They have not returned to say if 12 volt or 230 volt. I would expect 12 volt. Having seen lamps dismantled it seems some are really cheap, but oddly it is likely the cheap ones work OK and it is the more expensive versions which have problems. A LED typically can give 100 lumen per watt, and those with PWM controllers actually do give a 100 lumen per watt, however using a simple capacitor as a current control and likely we are looking at more like 60 lumen per watt.

However the 60 lumen per watt type can easy be dimmed and also are not really worried if the supply is 50 Hz or 50 kHz from a PWM power supply (Assuming at extra low voltage resistor rather than capacitor used). But the supply voltage is rather important. With the PWM chip controlling the LED the dimming switch needs to talk to the chip, and some chips are not designed to read wave form clipping as an instruction to reduce current output. Some will power the LED with same current with a huge variation in voltage.

Where the power is sent through a PWM volt dropper and then fed to a lamp with a PWM chip it is likely the odd wave form shape from the first PWM device will upset the PWM chip in the second device. The cure is to move to DC, if the first PWM controllers output is DC then this can be smoothed so that it will not upset the second PWM chip.

Yes it seems rather pointless to have two units, having a proper driver supplying say 340 mA at 6 ~ 50 volt would drive the LED chip directly. But that means it becomes harder to produce units which have replaceable LED's fitted. All the LED's must be same type and wired in series to the true driver. Where we have got use to lamps wired in parallel and each lamp has a voltage rating not a current rating. So as little packages for easy use we have to convert the raw LED with is current dependent to and user replaceable LED lamp with is voltage dependent.

Because of the host of true drivers (current limited output DC) and pretend drivers (voltage limited output DC) electronic transformers (with odd waveform and high frequency with minimum output) and true transformers (with sine wave output at 50 Hz) the easy method with LED replacement is stick to low voltage (230 ac) and kick extra low voltage to touch. The whole point with extra low voltage was the element in the quartz envelope was thicker so lasted longer, and the voltage could be controlled to very fine limits with electronic transformers (really switch mode power supplies) so the quartz envelope was maintained at a temperature which would not allow the tungsten to adhere to it so it returned to the element thus again extending the life. All this has gone with LED lamps, so no point any longer using extra low voltage.

 

[PenguinWithHair]

Hey everyone, thanks for the replies! Apologies I didn't state this previously, I'm talking about a wall light fixing, so 240 odd volts and 220-240 volt bulbs at five watts each.

 

[endecotp]

Do they claim to be dimmable? If so, try a non-dimmable version. Having seen how some of the dimmable ones work, it's possible that that could result in 50Hz or 100Hz flicker even at full brightness.

 

[ericmark]

Unless there is an electronic controller, be it a dimmer switch or a PIR then the lamps should not really flicker. I would seem you have simply got a set of faulty bulbs.

Likely even replacing with same make and model the new bulbs will not flicker (unless from same batch). It is really a case for returning the bulbs as faulty.

I also got caught out with modern bulbs, in my case I paid a fortune for 16 CFL 8W globe bulbs for Philips which I assumed was a good make, a year latter and 6 had failed, and 2 years latter and not one still in use. So today I buy cheap bulbs and only a few at a time so if they are poor not too much spent. It would be nice to say get good quality and all will be OK. But that's not the case, up to now not had a single bad bulb from Lidi so trying to stick to their bulbs.

 

[PenguinWithHair]

Ah thanks for the replies, I do totally agree sometimes you've just got to trial and error and see what works and go from there.

Interesting to report, I don't think they're described as dimmable but I tried them with a dimmer switch with some very interesting results!

They do dim, sort of. They have three stages of brightness, but they don't smoothly dim like a standard bulb would, but they do sort of dim in three jagged steps. Anyone experience similar? Is this how LED bulbs dim?

 

[endecotp]

No, that's not how dimmable LED bulbs dim - so they aren't dimmable.

 

[David Maloney]

One way I have found to be quite effective for determining the extent of an LED bulb's stroboscopic effect is by putting my smartphone camera close to the bulb and watch the camera screen. If the bulb flickers, the camera will show thick moving black stripes across the whole screen. Experiment for yourself and try using this to test for strobing before making any purchase.

 

[DetlefSchmitz]

My son is very sensitive to this flicker. He recently took apart one of these LED (230V) G9s. What he found was a large number of LEDs in series, and the power supply was a series capacitor to drop the voltage down feeding a bridge rectifier. The output of the bridge rectifier had a position on the pcb for a smoothing capacitor, but the manufacturer had left the capacitor out to save costs - hence the flicker.
He added the capacitor, but failed to adjust the remaining component values, and for 24 hours the flicker was completely gone. Then the bulb exploded and destroyed the light fitting.

 

[ban-all-sheds]

My son is very sensitive to this flicker.

Mine is complaining about it with a lamp we have in the hallway right now. If I, for example, wave an outspread hand in front of it I can detect a strobing effect, but other than that, nada.

Maybe their eyes are young and fast, and ours are old and slow.