Newbie needs info on led driver. - Page 1
Forum section: electronics / projects

author: Findingmyway
author_rank: Newbie
timestamp: December 14, 2015, 03:35:57 pm
content: I bought 10 - 10w LEDs but can't figure out what size driver I need to run all 10. Do I need 10 w or 100 w I keep getting different info online and confused... Thanks Newbie.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 03:43:48 pm
content: It all depends on the voltage and how you connect them.I don't know the forward voltage of your LEDs, let's imagine it's 12V.If you have enough volts to put them in series ( ie. 120V) then you only need one driver.If you have 60V available you can make two strings of six, using two drivers.If you only have a 12V supply then each LED will need a separate driver.nb. You actually need a little bit more than 12V to give the driver a bit of room to work.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 04:00:03 pm
content: Quote from: AcHmed99 on December 14, 2015, 03:44:09 pmNope.If they're in series then you can use a single 10W driver from 1 up to 1 billion LEDs (assuming you can find a 12 billion volt power supply).If they're in parallel you need ten 10W drivers.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 04:26:19 pm
content: Quote from: AcHmed99 on December 14, 2015, 03:44:09 pmNope.Quote from: AcHmed99 on December 14, 2015, 04:08:46 pmThe power is dissipated in the LEDs, not the driver. The driver sees the same number of amps no matter how many LEDs are in series.(Assuming the excess voltage is the same in both cases - you have to match the power supply voltage to the number of LEDs)Quote from: AcHmed99 on December 14, 2015, 04:08:46 pmYou can't share a single driver between multiple LEDs in parallel.

author: georges80
author_rank: Frequent Contributor
timestamp: December 14, 2015, 05:04:07 pm
content: Talking about Watts for a LED driver is confusing the entire issue.You need to know:What is the Vf (forward voltage) of ONE of your LEDs at If (the forward drive current you plan to drive it at).Next you need to decide how many LEDs you will connect together and whether you connect them all in series or some kind of parallel series matrix.e.g. 1 you have 10 LEDs you connect them all in series then the Vf will be 10X a single LED's and you drive at If (the current of a single LED).e.g. 2 you connect 2 strings in parallel, each string has 5 LEDs in series. Your Vf will be 5X a single LED's and you drive a 2X If (since the current will 'roughly' split 1/2 into one string and 1/2 in the other string -> giving each string If.The above allows you to get an idea of your total Vf (for the 10 LED wiring configuration you plan to use), lets call it Tot_Vf and your total If, lets call it Tot_If. This then allows you to look at whether you need a Buck driver or Boost driver (and whether it can handle the Tot_Vf and Tot_If). Next your input voltage range and whether it meets the specs of the driver you are looking to use.The ONLY need for you to know the total Watts (and yes, it would be around 100W for ten 10W nominal LEDs) is to determine the efficiency losses in the driver (say the drive runs at 90% efficiency, with 100W you would have 100W/0.9 = 111W at the input, meaning 11W of thermal losses in the driver - YES, it will need a heatsink and YES, it will need to be rated to be able to dissipate 11W).Designing/choosing a LED driver that can handle 100W of load (RELIABLY) requires you to determine the best configuration of LED load (Tot_Vf an Tot_If) AND your available input voltage range. It is somewhat of an iterative process. At that power level you do need some decent specs for the driver to determine its safe operating parameters (max input voltage, min input voltage, max input current, efficiency at operating input voltage and current, maximum thermal dissipation etc).cheers,george.

author: MikeW
author_rank: Regular Contributor
timestamp: December 14, 2015, 05:17:25 pm
content: Quote from: Fungus on December 14, 2015, 04:26:19 pmAbout a hundred thousand of the light fittings we make a year would disagree with you.Quote from: Fungus on December 14, 2015, 04:00:03 pmThey won't all be running at 10W though. It will still be 10W total across however many you use. Which is not the objective.If I want to power 10 x 10W LEDs at 10W each, then I will need something capable of giving out 100W in power, doesn't matter how you wire it.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 06:31:03 pm
content: Quote from: AcHmed99 on December 14, 2015, 06:15:55 pmOK, you can probably do it... but it's not theoretically correct engineering.eg. How do you keep current in each path balanced? They're probably quite close but each path will have slightly different resistance.

author: Findingmyway
author_rank: Newbie
timestamp: December 14, 2015, 06:58:05 pm
content: Wow I never realized LEDs are so technical and now I understand why I couldn't find a real answer out there..still confused .lol here are the specs...DcFV : Dc 9-11vDc forward current : (IF) : 1050 mAOk so I still by all comments don't know which one. I will run them in series as for tep I am turning a shop light into the led light it has space between that I can put a small fan to. Keep the heat down. It used to be a 4 ft grow fluorescent light. Now I know I said 10 LEDs and will I use all 10? Not sure... What do you guys think? Is 10 to many for a 4" area will this create to much heat? I didn't know what I was getting into before I bought them.now have extra is better than not enough. Just need to light my work area which is about 5"x 2" . So again wiring them up in series going to have a cooling fan. The base is made of thin metal not aluminum but I do have a bunch of aluminum heat sinks I pulled of old computers I can use if need be and hide it all nice and neat. So now with more in do I can hopefully get an idea on what I need. Thanks guys for all your help...I am learning a lot.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 07:42:10 pm
content: Quote from: Findingmyway on December 14, 2015, 06:58:05 pmLEDs are specified in Amps, power supplies come in Volts. It always creates chaos in newbie's heads.Quote from: Findingmyway on December 14, 2015, 06:58:05 pmWhat that means is that the voltage across the LED will be somewhere between 9 and 11V when you apply 1050mA to it (Ohms Law!)Quote from: Findingmyway on December 14, 2015, 06:58:05 pm100W of LEDs will be WAY brighter than a 4ft fluorescent.To get the same amount of light you probably only need 20-30W (depending on the quality of the LED).Me? I'd put four or five LEDs each with its own 900mA driver. The drivers are cheap and having one driver per LED means that if one set fails the others will keep on working. (nb. You look at the driver's output current,notthe wattage - LEDs work by current)Something like this would do it:http://www.ebay.com/itm/310924747774(randomly picked eBay item)That can output up to 12V so it has your LED's voltage range covered.Yes ... you're running the LEDs at slightly less power than their maximum power but that's allowed and you'll avoid a lot of heat/burnout problems that way (especially in an enclosed space like a grow tent). The extra 150mA would create more heat than light...

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 08:13:00 pm
content: Quote from: AcHmed99 on December 14, 2015, 06:39:34 pmI guess, but it just feels ....dirty.

author: Seekonk
author_rank: Super Contributor
timestamp: December 14, 2015, 08:43:03 pm
content: You have entered the land of the damned. Just how do you decide who to listen to? If you think you can drive 10W into those LED, you may already be smokin what you are trying to grow. Even when they sell them as a 10W unit with driver the LED is over driven at 5W.

author: Findingmyway
author_rank: Newbie
timestamp: December 14, 2015, 09:56:34 pm
content: Quote from: Seekonk on December 14, 2015, 08:43:03 pmIt's really not for what your thinking. That I do know what I'm doing..lol I was just trying to get xplain what type of light fixture I am using its different than a reg shop light. Ya it is hard, but I aThink I'm getting a bit a of grip on this.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 09:58:18 pm
content: Quote from: Seekonk on December 14, 2015, 08:43:03 pmTherearesome good ones.But yeah, if you sort results by price and buy the ones at the top of the list theymightnot be top quality.(Yet another reason to slightly underpower them, and maybe buy some spares )

author: Findingmyway
author_rank: Newbie
timestamp: December 14, 2015, 10:00:29 pm
content: Quote from: AcHmed99 on December 14, 2015, 09:08:40 pmThis is the eBay pagehttp://www.ebay.ca/itm/261409999817?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITYes they are EBay and yes I made a mistake.lol but I am here to learn. I won't have a product code until they get here.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 10:00:54 pm
content: Quote from: Findingmyway on December 14, 2015, 09:56:34 pmThat's what they all say...Quote from: Findingmyway on December 14, 2015, 09:56:34 pmYou just have to swap amps and volts in your head. LEDs want amps.

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 10:31:12 pm
content: Quote from: Findingmyway on December 14, 2015, 10:00:29 pm$1.30 each? Who knows what you'll get...Another way to do it might be to get some LED strips.You can get rigid ones like this:http://www.ebay.ca/itm/251685975664Each strip puts out 6W (apparently*). 10 of those would be 60W (360 LEDs!) and they're much easier to install and power than big 10W LEDs. They give better area coverage, too (good for plants!)All you need to power them is a beefy 12V power supply. I like to run all power supplies at half rating so this would run 10 strips:http://www.ebay.ca/itm/201346346052One of those and 10 LED strips would cost about $23 and give alotof light.(or you could save money and recycle an old PC ATX power supply...)(*) By my math that gives 40mA per LED. Are there two LEDs in each 7020 package?

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 10:38:53 pm
content: Quote from: AcHmed99 on December 14, 2015, 10:13:42 pm

author: Seekonk
author_rank: Super Contributor
timestamp: December 15, 2015, 08:57:55 am
content: It is not just about LED quality. I love those 10W units for the packaging and they are cheap. I have an off grid camp and build all my custom lighting. I run them at low power and just hot melt glue them onto metal and run them a little over a watt. Slap 10 or 20 on an old light fixture and you have 80W of heat to get rid of. Does you mounting method give you enough thermal transfer and do you have enough metal area to keep the temperature low enough? The forward voltage and current will change with temperature as they get hot. Run them near the edge and you need complicated constant current electronics. If operating at greatly reduced power you can forget about thermal drift issues. I just go to my junk box ans use what I have that is free. Sting them together and that is a lot of voltage with insulation issues. A lot of posters like to hit it and quit it. They tell you what little they know and disappear. A lot of issues to deal with and multiple ways to do it.

author: Fungus
author_rank: Super Contributor
timestamp: December 15, 2015, 12:31:27 pm
content: Quote from: Seekonk on December 15, 2015, 08:57:55 amIf it's only for human beings to be able to see at night then you can do stuff like that, yes. Remember we used to get by with candles. I'm sure a 1W LED is better than that.If you're installing a lot of them though it's more important that all (or most) of the LEDs on the module are producing light. Every LED that isn't working is just wasted electricity (that you're paying for!). Plus you have to install more of them to get the required amount of light - more expense!