Picking high power leds.  - Page 1
Forum section: electronics / projects

author: David97
author_rank: Contributor
timestamp: January 20, 2016, 12:51:03 pm
content: I do alot of work under cars on my driveway. Quite often I end up working in the dark. The lighting system we have is terrible just being some ligtbulb fixtures on a peice of wood. The bulbs are big, so hard to get in position, and prone to being broken when they are kicked or something falls on them.I've been wanting a better system for awhile now. I am looking at some of the cheap ebay high power leds, and thought, wouldn't it be great if I mounted some of those to blocks of aluminium, then put magnets on the back. That way I could just stick them to any piece of steel, like the gearbox tunnel, chassis rails, bottom of the bonnet. Place them so I can have lighting from all angles.I was thinking 5 smaller led's that were mounted on small bits of aluminium with magnets to light the hard to see places, and be strategically positioned on whatever was being worked on. Then 2 or 3 bigger ones that would be placed on the ground, and fill everything else with light.Anyway I'm wanting recommendations on what power ratings I should pick. I'm wanting something that will provide plenty of light, but not dazzle and blind me when I'm using them. I might put some paper over some of them to diffuse the light. You can get 10W leds for less than 50C a piece from ebay, but would that be too bright? I probably will be using a dimmer anyway, but it would be terrible if they were too bright turned right down.Thanks, David.

author: Fungus
author_rank: Super Contributor
timestamp: January 20, 2016, 02:27:18 pm
content: Quote from: David97 on January 20, 2016, 12:51:03 pmA 10W LED produces aLOTof light when you're close-up. Probably too much.But "too bright" is good for what you're doing because:a) LEDs don't have a brightness cutoff, they can go right down to 0.000000001%. There's no possible way they could be too bright if you have a dimmer (unless your dimmer is rubbish, obviously).b) Running eBay specials at the full 10W is a bad idea anyway. They'll get awfully hot. Better to run them at much less than that.c) Once in a while youmightneed full power for something.So ... 10W is a good power IMHO.Edit: Because they're so cheap you might want to buy a few different packs of LEDs from different sellers and pick the best ones. You can get good LEDs on eBay but you might get bad ones. It's about 50:50 in my experience and not really the sellers fault - they get ripped off too and they can't test every single component they sell. If you get some bad LEDs just relax and remember how cheap they were (and even the 'bad' ones will still produce a lot of light).Watch this video:

author: bxh
author_rank: Contributor
timestamp: January 20, 2016, 03:09:56 pm
content: Consider using LED strips for the wider areas. I've played with powerful LED arrays, small like a coin but powerful enough to light my entire room, and they're not particularly comfortable to look at and require a massive heatsink. On the other hand, LED lighting strips run fairly cool and light the area in a less harsh way.

author: Fungus
author_rank: Super Contributor
timestamp: January 20, 2016, 03:29:20 pm
content: Quote from: bxh on January 20, 2016, 03:09:56 pmYou can get them on sticks, too:http://www.ebay.com/itm/331756144903

author: bookaboo
author_rank: Frequent Contributor
timestamp: January 20, 2016, 05:25:54 pm
content: Yes with lighting it's always best to have as wide a source as possible. You can have all the lumen output you want but if it's coming from only 2-3 points then you are going to have shadowing, especially in that application.Dimmable IP65 LED strip light on aluminium could well be your best bet.If you were indoors I'd suggest painting the floor white to help whatever lights you end up using. In professional lighting planning software changing the colour of the floor & walls affects the entire recommendation.

author: picandmix
author_rank: Frequent Contributor
timestamp: January 20, 2016, 05:37:38 pm
content: Depends on how much work and money you want to spend on leds, which for your short working range you might find have a very narrow beam, plus the larger ones will virtually blind you if catching them direct.Find this type of cheapo multi led torch as a very good light; has a hook and magnet on the back.Also use one of the similarly cheap floodlights attached to heavy baseplate, gives a good even spread.You might also want to consider a 4ft flourescent tube covered with a sturdy metal mesh/grill as they give an execellent wide beam without blindling you; like the floodlight, both should be use with a RCD device in case of damage.

author: Fungus
author_rank: Super Contributor
timestamp: January 20, 2016, 05:46:31 pm
content: Quote from: picandmix on January 20, 2016, 05:37:38 pmWellobviouslyyou can buy one, but this is EEVBLOG.

author: picandmix
author_rank: Frequent Contributor
timestamp: January 20, 2016, 06:33:08 pm
content: Quote from: Fungus on January 20, 2016, 05:46:31 pmYes, I know, but as the OP says he does not want to be blinded by the light , and as I also work under the car in a similar manner I know from using single chip 10w leds they will certainly do that, cannot imagine what a 100w single chip led would do if you looked directly into them at short range..

author: Fungus
author_rank: Super Contributor
timestamp: January 20, 2016, 08:04:20 pm
content: Quote from: picandmix on January 20, 2016, 06:33:08 pmIfyou run them at 10W (which I don't advise...)

author: David97
author_rank: Contributor
timestamp: March 10, 2016, 10:02:08 pm
content: Hi everyone again. So I'm going to make a start on this project finally. So Here's my draft idea, if it sounds good to everyone here?So I'm thinking to base it around cheap 10W led's. Because most of the cheap ebay ones seem to have a forward voltage of about 12V, which it perfect for automotive. If there isn't power available, just have a input from the car battery. I know it's not a good idea to draw down the car battery but I do alot of 4X4 that requires repair at night with no power. There will be a PSU inside for running off the mains when it's being used at home.I'm going to use a arduino as the brain of the system, it's what I know. So I'm not too sure on how to sense the current Via the arduino. Been looking at the max471 current sense chip. It will measure up to 3A and has a internal sense resistor, making it really simple. Then just feed this into a analogue pin? Then I will write some code that works out the current, and then varies the PWM output to a fet to control the current? Use a LC filter to smooth it back out.I will have a pot to set the current, that way I can use small LED as well as big ones.I was also looking at putting a resistor across the LED, then I could have different value resistors for different power leds. Then read the resistance at a low voltage, so the arduino could automatically set the current limit before powering it up. This is just thinking forward. Ill worry about this after I actually get it to work.So what's the thoughts? Have I got the right idea about how to do this. Is the max471 a good chip to use? Am I doing this completely wrong and should l be using the arduino as a current controller? I could be completely off the mark here, haven't really designed many projects by myself before, other than really simple stuff.Thanks, David.