T8 LED Tube flicker! - Page 1
Forum section: electronics / general

author: K3mHtH
author_rank: Regular Contributor
timestamp: November 18, 2016, 01:32:38 am
content: Hey guys,I recently installed some T8 LED tubes in my shop, from two different brands. Brand A is fantastic, and Brand B is driving me nuts - I swear it's flickering (probably at 120Hz) although most people don't notice it I certainly do.Brand A tubes are "ballast compatible" and Brand B the flickery ones aren't. Both are in fixtures without ballasts. Could it be that the extra electronics required to make Brand A tubes "ballast compatible" also includes filter capacitors that the others do not have?The manufacturer of Brand B did say they would refund my money, but I'm going to set up some test equipment in the next few days just to see if the problem actually exists. It's just on the edge of perceptibility, but I don't want to be working under lights like that - they'd drive me bonkers.

author: GreyWoolfe
author_rank: Unknown
timestamp: November 18, 2016, 02:55:05 am
content: For now, I have an Envirolite 6 tube, 4 ft LED fixture over half my workbench, soon to be joined by another. The bulbs themselves are marked Espen Technologies. I have not noticed any flicker and the fixture has no effect on my VHF or HF radio equipment. I thought about buying the ballast compatible bulbs, but read too many mixed opinions/reviews to want to deal with it.The light is VERY bright and a much cleaner light, which is what I want and I can't wait to get the second fixture. On the other half of the bench is a standard 6 bulbs of T-8 fluorescent lights that look almost dim compared to the LEDs. SWMBO recently had me replace the T-12 fixtures in the kitchen ceiling with LED fixtures, she loves the extra light and the price made her very happy. It won't be a hard sell to replace all the CFL bulbs with LEDs as they go out.

author: tronde
author_rank: Frequent Contributor
timestamp: November 18, 2016, 06:22:39 pm
content: I guess brand B cheaped on capacitors. Either half of the LEDs are driven from the positive part of the sinewave, and the other half from the negative or they use a bridge rectifer. Both will give 120Hz flicker with a mains frequency of 60Hz. LEDs are not "slow" like an incandescent bulb, so flicker will be very visible. Even fluorescent tubes are rather quick, so they will give flicker if driven from mains frequency. You need about 30kHz for them to be constant lit.

author: K3mHtH
author_rank: Regular Contributor
timestamp: November 19, 2016, 01:40:26 am
content: Quote from: tronde on November 18, 2016, 06:22:39 pmYikes! So the LED's are alternating?? That doesn't seem like a good design. These are getting sent back. Can't say enough good things about the Brand A ones though.. Fintronx 6-bulb fixtures from amazon.com that came loaded with their 5000K T8 LED "ballast compatible" tubes give off great light and don't bug my eyes.

author: amyk
author_rank: Super Contributor
timestamp: November 19, 2016, 05:43:27 am
content: Alternating is still better than having all the LEDs light on only half the mains cycle... but a full-wave rectifier with good bulk capacitance is the best.You may use a simple mechanical stroboscope to see the flicker frequency, or if they are alternating.

author: tronde
author_rank: Frequent Contributor
timestamp: November 19, 2016, 04:11:08 pm
content: Quote from: K3mHtH on November 19, 2016, 01:40:26 amYou will get flicker at double mains frequency with both alternating and a bridge rectifier without a capacitor. Alternating is of course a waste, but when it comes to cheap LED-lights from China almost everything is possible. I have seen it all. It can very well be that your lamp uses a bridge rectifier with a capacitor but that the capacitor suffers from a bad solder joint too. Quality control cost money...