DMX Controlled High Power LED Driver - Page 1
Forum section: electronics / projects

author: CarnivalBen
author_rank: Contributor
timestamp: November 25, 2015, 01:22:27 pm
content: My hobby is to be part of a team that builds an illuminated carnival float every year for carnival parades in south west England. My job is to wire it all up. Check this out to see what I'm talking about:In the past, we've used a 800kVA generator to power around 12,000 x 40w incandesant lamps, but times are changing and it's getting difficult to buy 40w lamps, and the festoon sockets to put them in, so I've been thinking about alternative lighting for future years.What I'd really love to do, is use these 100w RGB LEDs:http://www.ebay.co.uk/itm/161035396404and build a load of drivers to power them controlled by DMX, with the aim of being able to dim and change the colour of 1000's of these LEDs all over the carnival float.In the past I've designed and built DMX controlled dimmers using a triac to control resistive loads, but I'm not sure how to do something similar with these types of LEDs. Can anyone suggest a rough schematic to get me started...? I'm ok with the DMX side of things, I just need help with the LED driver bit.I propbably have a budget of around 10000 GBP.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 25, 2015, 01:28:05 pm
content: Quote from: CarnivalBen on November 25, 2015, 01:22:27 pmI think you'll do better looking at ready-made fixtures - LEDs like that will take a lot of heatsinking and careful driving. Also, for an application like that, you probably don't need that density - more, lower power fixtures spread out more will have much lower cooling requirements.Chinese LED products and drivers are so cheap that it's unlikely to make sense to roll your own. Spend a few hours on Aliexpress to see what's available.Also bear in mind that white will give the most bang for buck/power, so a mix of white for brightness and RGB for colour is probably the way to go.

author: CarnivalBen
author_rank: Contributor
timestamp: November 25, 2015, 01:44:26 pm
content: Thanks.... I've seen plently of PSUs for 100w LEDs, but they're never controllable. I want to flash, dim, and change their colour in time to the music.Cooling is not necessarily a problem, as the carnival float is made from a steel frame... so lots of metal to bolt them to, to dissipate the heat.Good point about the mix of white/RGB though

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 25, 2015, 01:46:48 pm
content: Quote from: CarnivalBen on November 25, 2015, 01:44:26 pmIt is very much a problem, as you need to get the heat out from the immediate vicinity of the LED to keep the temp within sensible limits, so a steel frame isn't going to be much help.For something on that scale, you may find that LED tape is a good way to cover large areas with easy controllability.

author: CarnivalBen
author_rank: Contributor
timestamp: November 25, 2015, 01:57:47 pm
content: Ok... So I can see there are some challengesI don't think I'm ready to give up on the idea yet though... I'd at least like to do something small scale using this type of LED, and see what I can come up with.

author: Towger
author_rank: Super Contributor
timestamp: November 25, 2015, 02:51:13 pm
content: As Mike said, those 100w (90W) LEDs will be over kill. If you cover your float with them LEDs, people will not be able to look at it! I have a few here I bought to build LED PAR64 cans. I mocked one up using 3 of these LED PWM drivershttp://store.sure-electronics.com/le-ll51111,controlled by an Arduino. The 100w LEDs required serious cooling, mounting them on to large P4 heatsink with fan, gives you the best bang for buck. In the end it was simpler to buy cans from China and at the time A6211 ICs (which are very nice) used by Sure were always out of stock, so I could not build my own driver board.BTW I remember seeing floats like yours on a trip to France as a young fellow. The business ends consisted of banks of phone relays driven by multiple Apple IIe computers. The noise of the chattering relays was louder than the generators.

author: ajb
author_rank: Super Contributor
timestamp: November 25, 2015, 03:42:58 pm
content: In addition to everything else, those massive COB arrays have some serious disadvantages. Because they're a whole array of point sources, you'll never be able to properly shape the output--a simple lens system will give you an ugly mess of overlapping blobs of red, green, and blue with stepped edges due to the grid arrangement of the individual chips. You'd need a complicated grid lens with one lens per chip to really do anything with it optically. The cheap eBay ones also tend to have loads of leakage resistance, so the efficiency is pretty bad and current sharing is uneven across the array. If you slowly ramp the voltage to the array you'll see that the individual chips don't come on all at once.If you decide you really want to roll your own, I'd look at smaller 1-3W RGB or RGBW LEDs which you can get inexpensively on star boards from eBay. The power density is easier to manage, and driving them is easier as well. I also expect that they'll be a more appropriate brightness for your application, and you can wire several in series to one set of drivers if you want. Speaking of drivers, there are a number of options for the lower-power LEDs. For a ready-made solution the Meanwell LDD series is cheap, and can be easily PWMed by a microcontroller.

author: Jr460
author_rank: Regular Contributor
timestamp: November 25, 2015, 04:07:10 pm
content: I have to agree that ready made fixtures would be the way to go. Many, many of them about, and many are cheap. Look for the low end DJ stuff, it can all be driven with DMX, and you can get lots of Free/Shareware software that can do whatever you want.One thing with the LED fixtures and colors...... One would think full Red, Green, and Blue and you have white. Not really. You start dealing with color temp. So while your "white' might look fine all alone, it will look very blue-ish compared to standard lamps. Unless you adjust, the float will look pale blue and people's skin will look sick. Yellow is also very hard for RGB LED fixtures to do well.Highend fixtures are balanced better. I use a set that are 5 channel. Red, green, blue, amber, and white.

author: Fungus
author_rank: Super Contributor
timestamp: November 25, 2015, 04:26:10 pm
content: Quote from: CarnivalBen on November 25, 2015, 01:22:27 pm1000s of 100W LEDs is waaay too much.Have a play around with WS2812 RGB LED strips:http://www.ebay.com/sch/i.html?_nkw=ws2812+led+stripThey have built-in controllers and you can set the color of every LED individually. They should be plenty bright enough. If not, add more of them!You can also mix and match the strips with WS2811 'pixels' in all sorts of formats:http://www.ebay.com/sch/i.html?_nkw=ws2812+pixelshttp://www.ebay.com/itm/221753410090

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 25, 2015, 04:42:46 pm
content: The problem with WS2812 type strips in quantity is you need 5V at huge currents, so cabling becomes hard to manage unless you use local PSUs or DC-DC convertersYou may be better off with 12 or 24V strips, or LED products that have a few LEDs per pixel in series, so the current is more manageable.

author: Fungus
author_rank: Super Contributor
timestamp: November 25, 2015, 04:57:50 pm
content: Quote from: mikeselectricstuff on November 25, 2015, 04:42:46 pmTrue.You can get them in 12V versions with a controller for every 3 LEDs. That makes power much more manageable.eg.http://www.ebay.com/itm/252057934748You can still mix/match those with the 5V ones if needed (nb. only data/ground lines, not power lines).PS: I forgot to mention the other big advantage of those strips: You can cut them into pieces with scissors so they're great for decorating stuff.

author: CarnivalBen
author_rank: Contributor
timestamp: November 29, 2015, 10:51:46 am
content: Ok... so it looks like 100w LED chips are not gonna work.Thanks for the idea of LED strips. I actually have already tried these on this year's float, for small parts of it... It was a LOT of work to get them working though and would not be feasible to cover the entire float with them. I used them to cover some dolphins made of ply, and they were spinning around, and I only had 2 slip rings available to get the power to them, so I ended up wiring them in groups of 4 strips in series so I could power them with 48v to reduce the current required. I then butchered 4 old ATX PSU's that I managed to blag from a school that were getting rid of some old computers... and connected them in series to give me a decent 48v supply.This was the result:Anyway, it's going to be far too difficult to do this for the entire float... it was hard enough doing this for 10 dolphins!So given that a lot of people have said that 1000's of 100w will be far too bright, I've put together a spreadsheet to try to work out what types of different lighting would give an equivalent brightness. We normally use 40w incandescants, which based on the average of a few references on the internet are I think about 450 lumens. So 12,000 of these would make my entire carnival float around 5.4 million lumens.Looking at a few different types of lighting as comparison, I've worked out that to give the same amount of brightness, I'd need 540 x 100w LEDs to give the same brightness as 12,000 x 40w. But given the supply and cooling issues I've also looked at several types of LED GLS B22 lamps... here is what I came up with:Anybody have any other ideas that might work...?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 29, 2015, 11:19:04 am
content: With LEDs you have a lot more scope to do stuff with colour, shape & control - does it actually need to match the brightness? Quality over quantity perhaps?Again, you may find some ready-made stage or architectural products that have already joined together a decent number of LEDs at Chinese labour prices.When I was in Shenzen there were a couple of products that were absolutely everywhere - white LED strips approx 1m long in various densities, usually 12v, may also have been some 24v ones,this sort of thinghttp://www.aliexpress.com/item/two-color-rigid-strip-100pcs-1m-SMD5630-rigid-strip-white-warm-white-double-color-DC12V-144pcs/32508869658.html?spm=2114.01020208.3.103.S0Tg93&ws_ab_test=searchweb201556_1_79_78_77_80,searchweb201644_5,searchweb201560_1and strings of typically 3 1W LEDs per module pre-wired, in various colours :http://www.aliexpress.com/store/product/20pcs-strand-5050-SMD-white-color-led-module-DC12V-input-60-66lm-size-66mm-16mm-with/701799_32273610332.htmlRay Wu's store on Aliexpress is a good place to start browsing for the sort of thing that's available :http://www.aliexpress.com/store/all-wholesale-products/701799.html

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 29, 2015, 11:21:45 am
content: There are also some mains voltage flexible strips available :http://www.aliexpress.com/item/led-strip-220v-1m-Waterproof-220V-5050-SMD-60-LED-Flexible-Strip-Light-14-4W-M/32426432087.html?spm=2114.01020208.3.85.S0Tg93&ws_ab_test=searchweb201556_1_79_78_77_80,searchweb201644_5,searchweb201560_1AIUI all that's in the little box is a rectifier - you could also make up your own 20x12v or 10x24v series strings for mains voltage.

author: CarnivalBen
author_rank: Contributor
timestamp: November 29, 2015, 11:38:07 am
content: Quote from: mikeselectricstuff on November 29, 2015, 11:21:45 amAh really...? That would make it considerably easier. But if I rectified mains... wouldn't I need to base the series strings on the peak 340v rather than 240v...? i.e. 28x12v?

author: CarnivalBen
author_rank: Contributor
timestamp: November 29, 2015, 11:43:47 am
content: Quote from: mikeselectricstuff on November 29, 2015, 11:19:04 amThese are great!!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 29, 2015, 11:52:59 am
content: Quote from: CarnivalBen on November 29, 2015, 11:38:07 amNot if you don't smooth it ( which you probably don't want to, to avoid bad power factor). It would be 340 peak but 240-ish avarage.Of course you might want to build in some safety margin - a small decrease in power isn't going to be too noticeable

author: Zero999
author_rank: Super Contributor
timestamp: November 29, 2015, 12:01:03 pm
content: Not only is that 100W LED array overkill but I doubt it will actually work at 100W. Going from the maximum specified VF(36V for blue & green and 24V for red) at the rated IF, the maximum power dissipation is 86.4W. Given the low price, I also doubt it's capable of full power operation over long periods without overheating, even with a good heat sink so it's sensible to de-rate it considerably.Using lower power RGBW LEDs is a good idea. I've been burnt by buying cheap LEDs before and would recommend a proper brand such as Cree.https://www.led-tech.de/en/High-Power-LEDs-Cree/CREE-MC-E-Series/CREE-MC-E-RGBW-Emitter-LT-1568_120_133.html