LED flood causing interference - Page 1
Forum section: electronics / beginners

author: Seamus16
author_rank: Contributor
timestamp: May 08, 2017, 08:43:38 pm
content: I am hoping that someone can help me.I have just installed some cheap Chinese lamps over my bench - like thesehttp://www.ebay.co.uk/itm/332076773650.They have the led driver in an enclosed unit at the back leading through to the led. All enclosed in an alloy housing.They are causing serious interference on my scope. I am guessing that I should fit a capacitor somewhere but don't know where this is best placed.Would welcome some guidance on this please.

author: Zero999
author_rank: Super Contributor
timestamp: May 08, 2017, 08:50:45 pm
content: Quote from: Seamus16 on May 08, 2017, 08:43:38 pmUnder what circumstances do you see the interference on the oscilloscope?If it's with nothing connected to the probe, i.e. open circuit, then this is normal and to be expected.Try shorting the probe to the earth clip. If it still is causing interference, then you have a problem, most likely with the LED lamp not complying with the regulations for EMI emissions.

author: Seamus16
author_rank: Contributor
timestamp: May 08, 2017, 09:09:22 pm
content: Thanks for the reply.I was just using the scope square wave test. Interference stopped when I switched the lights off.

author: David Hess
author_rank: Super Contributor
timestamp: May 08, 2017, 10:56:04 pm
content: An external conducted EMI filter at the bulb socket should help. Internally they include differential and common mode LC filter sections.

author: tautech
author_rank: Super Contributor
timestamp: May 09, 2017, 01:25:56 am
content: In a similar vein, my son put a 30" LED light bar on one of his excavators and indeed the the radiated and/or conducted EMI is that bad it overpowers his radio. Conducted I suspect moreso as when wearing a pair of radio muffs in the machine they don't suffer the same issue.Dad has yet to get his hands on this and sort it, probably with some local bypassing and line chokes/toroids to quiet these damn things some.Way back when, we had similar issues with radios in cars, those with generators and old school points ignition systems and a single suppressor cap close to the noise source and maybe another near the radio normally fixed it fine.

author: Zero999
author_rank: Super Contributor
timestamp: May 09, 2017, 09:56:13 am
content: Quote from: Seamus16 on May 08, 2017, 09:09:22 pmThen the LED lamp doesn't comply with the EMI regulations. If you bought it recently, then you have good grounds to return it for a refund.If you don't want to or can't return the lamp, then you need to install an EMI filter as close to the lamp as possible, as David said.

author: CJay
author_rank: Super Contributor
timestamp: May 09, 2017, 10:01:57 am
content: I've had similar, terrible radio interference and visible distortion on 'scope traces.Percussive maintenance on the offending LED fixture solved the problem, I now run 12V LED strip from a spare bench PSU and am able to see signals again.

author: Seamus16
author_rank: Contributor
timestamp: May 11, 2017, 04:43:59 pm
content: Thanks for all the replies.I have tried a plug in Transient Mains Spikes RFI filter but makes no difference, in fact worsens it.I have been watching Dave's video on filtering but that only covers tracking the source, not on how to cure it.