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We have just recently bought LED lighting and transformers from a local store. After installing, there's a noticeable flicker, most notably in the "little room" where you have ample time to look (and get annoyed by it).

I have already switched that single LED with another one to verify it's not a defect LED. Now that I'm convinced it's not the LED, I started looking for possible causes.

It seems that this might be caused by not using the right transformer. As I'm just a layman and before going to my local seller to confront him with this, I'd like to be sure I'm on the right track.

Technical details

The transformers are Niko ere 320-00002. and the LED lights are Lightplus Megaman .03285 12V 8W.

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closed as off-topic by Kaz, Leon Heller, Matt Young, Dave Tweed, PeterJ Aug 9 '13 at 1:44

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I'm no lighting expert (Russell is the man for lighting) but I think it's a safe bet that it's the transformer, and the fact that it's designed for halogen lamps.
As far as I am aware, halogen lamps have quite a long time constant (> 1s) so variation in supply will be not noticable unless it's very slow. Contrast with LEDs which have time constants in the nanoseconds and they would flicker.
So for LED driving you need a very smooth supply, which other technologies don't usually need - for instance an incandescent buld can be driven directly from an AC source at a relatively low frequency and you won't notice any flicker due to the long time constant.

I think getting a transformer specified for LEDs should solve the issue. To confirm there is variation in levels you could test the output with an oscilloscope if you have access to one. Also make sure the cables connecting the lamps are not too long and of a decent diameter (in case there is excess resistance which can cause voltage drops)

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  • \$\begingroup\$ thx Oli. I'll have a talk with my vendor and see if we can work something out (I don't have access to an oscilloscope and buying one for this purpose is a bit overkill :)) \$\endgroup\$ – Lieven Keersmaekers Aug 8 '13 at 18:12
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LED-strings are polarized, you realized that? And you transformer outputs alternating current. So the LED strip will only light during half periods. When you are in a 50Hz mains grid country, you'll see a 50Hz flicker which is quite noticable. Connect two LED strings in anti-parallel. When you move the strings close enough together, both strings will flicker but in alternate order (when one is off the other will be on and the other way around). Moving the strings close together effectively reduces the visible flicker.

You can also consider using a power supply that outputs DC instead of AC.

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  • \$\begingroup\$ Just saw the LED bulb is actually AC/DC. I'll remove my answer in a couple of minutes. \$\endgroup\$ – jippie Aug 8 '13 at 17:48
  • \$\begingroup\$ I knew about the LED's being polarized but I didn't notice the transformer outputting alternating current (I'm just a layman remember :)). I do consider this to be something the vendor should know, not me. \$\endgroup\$ – Lieven Keersmaekers Aug 8 '13 at 17:50
  • \$\begingroup\$ Just saw your comment but if it's not the transformer, what else could it be? (and the LED being AC/DC, does that mean it would work with either one?) \$\endgroup\$ – Lieven Keersmaekers Aug 8 '13 at 17:51
  • \$\begingroup\$ If it says AC/DC on it, I'd expect it to work with both. You linked in an interesting article yourself into your question. \$\endgroup\$ – jippie Aug 8 '13 at 17:58
  • \$\begingroup\$ It's this line in the article that gets me worried, both about the transformer being the problem and the possibility of damage: Why you may ask? Electronic transformers cannot provide a smooth current output to LED's and instead output tiny bursts of current causing LED's to flicker. These tiny bursts of current not only causes flicker but can actually result in permanent damage to the LED's. Sometimes you may not notice the flicker because it is too faint, nevertheless, the electronic transformer will still cause damage to your LED and reduce its lifetime severely \$\endgroup\$ – Lieven Keersmaekers Aug 8 '13 at 18:02

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