workbench lighting - Page 1
Forum section: electronics / general

author: electrolust
author_rank: Unknown
timestamp: July 26, 2017, 01:26:33 am
content: How are people lighting their workbenches? I have steel shelves and under them I have magnetic LED strips. The LED strips chain together, and so the single cap touch power switch on any of them will turn them all on. This is highly convenient, the light quality is pretty decent, and the strips were damn cheap, probably under $15 ea strip. Also I just bought them at the local Home Depot so that also made it easy and later if I have to replace one it will be easy.But the strips are super noisy EMI wise. Any circuit I'm working on picks up the noise either through the circuit itself (generally breadboard stuff) or through the probe ground clip. I'm getting tired of turning the light off to read the scope, then back on to do any work.I could try a clip-on incandescent bulb for that fiddling time, but I thought if someone had some cool and non-EMI-crazy lighting I might steal the idea.

author: floobydust
author_rank: Super Contributor
timestamp: July 26, 2017, 02:43:57 am
content: It's a good question, I was going to put it out there.I am using Ikea & Luxo task (desk) lights withCree BR30 100W equivalent PAR38 lamp 2700K 1,500 lumens.The EMI from the LED bulb helps my designs against noise/interference, lol. Welded up a decent mounting bracket in stead of crap clamp.Also use a 20W halogen 12V desk lamp with no flicker, no EMI, and hotter colour-temperature so I can see better.I've tried working with cheap LED's & bulbs off eBay, like strips, 3W beads and 30-100W big modules. They have poor quality light - shadows, blue/yellow fringing, small spots of light, gross colour temp (blueish), run hot etc. Just too much hassle so for now I settled on a screw in bulb.My next workbench lighting project, I'll take an old two-tube fluorescent desk fixture out of the garbage/flea market, gut it and install LED's GU-10 base.You can get mains constant-current SMPS on eBay for LED's and they are pretty much DC, so much quieter than a screw-in bulb for EMI and flicker.

author: cdev
author_rank: Super Contributor
timestamp: July 26, 2017, 02:54:46 am
content: Electrolust, once the DC leaves the buck boost converter or whatever that thing uses, filter the noise out of it.I would start out by trying some cheap and easy to use ferrite beads on the power cord and perhaps also try putting some on your scope probes. If you can pass the power cord for the light (the AC power cord) multiple times through a big toroid core that might help even more. If thats not enough, add the components the manufacturer should have put there but scrimped on. Add a pi filter on the DC to smooth out the noise.

author: Cubdriver
author_rank: Unknown
timestamp: July 26, 2017, 05:58:03 am
content: Figure out what voltage and current the strips require and build an appropriately sized linear supply to power them? It might be easier than trying to suppress the hash from the 'built as cheaply as possible' switcher that's likely powering them now.-Pat

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 26, 2017, 06:31:06 am
content: I had some LED bulbs to replace the GU10 style halogens in my spot strips, but as they fail I am going back to halogens as the tiny, 11 component, switchers in the LEDs destroy HF reception completely. I can't even listen to a ball game on the local medium wave AM station if they are on.

author: GerardWassink
author_rank: Contributor
timestamp: July 26, 2017, 06:48:48 am
content: If radio reception is a problem you might wannatry this website.More on topic: I am using a daylight lamp with a built-in loupe. It's on an arm so I can draw it closer when needed...Cheers,Gerard

author: electrolust
author_rank: Unknown
timestamp: July 26, 2017, 09:08:11 am
content: Quote from: cdev on July 26, 2017, 02:54:46 amMight be hard. These don't have a separate wall wart or power brick, just a mains cord and polarized 2 prong plug. The power supply is fully internal to the housing. It isn't a bare strip of LEDs, it's a finished under cabinet housing, with a small opaque section which houses the power supply.Quote from: Cubdriver on July 26, 2017, 05:58:03 amThat sounds like a great project. Maybe I can just rip out the PSU and use a lab supply in the short term.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: July 26, 2017, 01:53:40 pm
content: "I've tried working with cheap LED's & bulbs off eBay, like strips, 3W beads and 30-100W big modules. They have poor quality light - shadows, blue/yellow fringing, small spots of light, gross colour temp (blueish), run hot etc. Just too much hassle so for now I settled on a screw in bulb."The COB LEDs are significantly better in terms of giving a uniform wide field of light, with good colour and no fringing. Flicker is also a problem with some readymade LED bulbs if they run from unfiltered rectified AC. Unfortunately the only way to find out is to buy and try.As mentioned you can get readymade constant current SMPS, and they seem to have a relatively ripple-free output compared to the tiny regulators in readmade LED bulbs.Flicker is a concern for anyone doing close work because it can give you headaches even if you don't notice it.I have a converted halogen desk lamp for PCB inspection work. This originally used a 12v 20w capsule fed from an ironcore transformer, and while it was a good light source, heat was a problem for close work. I gutted out the head and fitted a video card hs/fan with a 10w COB. In the base I added a bridge, decent size filter cap and one of those cheap Chinese buck units, the type with current limiting. A pot on the base, replacing the ten-turn which was on the buck unit, provides brightness control. Now cool running, and brighter than the halogen on max setting.

author: electrolust
author_rank: Unknown
timestamp: July 26, 2017, 10:41:27 pm
content: I bought an LED tape strip from the local supplier. I'll try successively more expensive power supplies until I find one that is good. Anyone know of a linear design that is COTS? I have decided not to build my own because I want something UL listed. None of the LED drivers / supplies I can find actually state if they are SMPS or linear, so I assume they are all SMPS.There's a tekpower TP3005T on amazon for $80. I'd be willing to pay a bit more than that to have something compact that isn't getting underfoot. Lutron Hi-Lume 1% is $200, that's a bit too much and also likely SMPS anyway.

author: Kjelt
author_rank: Super Contributor
timestamp: July 26, 2017, 10:47:25 pm
content: Most if not all modern led drivers are made for high efficiency, ergo they are smps.Then there are two tastes, isolated and non-isolated drivers.

author: cdev
author_rank: Super Contributor
timestamp: July 26, 2017, 11:18:26 pm
content: Clip on ferrite beads might help. They are cheap, and always useful to have around, so its definitely worth a try.