So, I know I don't have enough information but I am hoping someone can give me some guidance.

I have 4 halogen work lights .... all died in the past 6 months.

Two have 500 watt lamps.

The other two have dual heads each have two 300 watt tubes in each.

So in total 6 heads .... two with 500 watts and four with 600 watts.

Anyway, were relatively expensive with stands and such and I hate to just get rid of them.

I am thinking that I need about a 100 Watt led floodlight to be roughly equivalent.

New 100 watt led heads (from Amazon) start at about $40 each .... so $180 ... ouch!

Soooooo ..... I found "50 Watt LED floodlight with integrated smart IC driver"

I would need two in each light but they are super cheap ... $2 each.

None of the lights have a flat back so I would need to put in an aluminum plate to mount them on .... say $30

Now the problem ..... I know I will need a heat sink.

Other than guess, how do I choose one?

I see ones that are 150 mm x 60 mm x 25 mm for $4 .... I can cut the back out of the lights to make sure I get air flow and then put two of these in each light ..... but how can I tell if that will be enough?

No one I know has ever tried one of these led modules so I have no idea how hot they get or how much cooling I will need.

Any suggestions would be great.

Thanks so much .... Mike

 

The manufacturers’ data sheet would be helpful since they usually address this issue. If you can’t find it, and it wouldn’t surprise me if you cannot, go look at the Cree site and look for a similar LED. They have excellent documentation that might help you.

 

So, I know I don't have enough information but I am hoping someone can give me some guidance.

I have 4 halogen work lights .... all died in the past 6 months.

Two have 500 watt lamps.

The other two have dual heads each have two 300 watt tubes in each.

So in total 6 heads .... two with 500 watts and four with 600 watts.

Anyway, were relatively expensive with stands and such and I hate to just get rid of them.

I am thinking that I need about a 100 Watt led floodlight to be roughly equivalent.

New 100 watt led heads (from Amazon) start at about $40 each .... so $180 ... ouch!

Soooooo ..... I found "50 Watt LED floodlight with integrated smart IC driver"

I would need two in each light but they are super cheap ... $2 each.

None of the lights have a flat back so I would need to put in an aluminum plate to mount them on .... say $30

Now the problem ..... I know I will need a heat sink.

Other than guess, how do I choose one?

I see ones that are 150 mm x 60 mm x 25 mm for $4 .... I can cut the back out of the lights to make sure I get air flow and then put two of these in each light ..... but how can I tell if that will be enough?

No one I know has ever tried one of these led modules so I have no idea how hot they get or how much cooling I will need.

Any suggestions would be great.

Thanks so much .... Mike

Hello there,

Whenever you want to heat sink something you simply go by the watts and the rating of the heat sink and the allowed temperature rise or apply a rule of thumb in some cases.

Let's say you have a 20 watt LED that can take 100 degrees C without burning out too soon.
You find a heat sink that is rated for 5 degrees C per watt.
The power is 20 watts, and the temperature rises 5 degrees C for every watt, so the total temperature RISE is 100 degrees C.
This sounds good, but the trouble is that the temperature RISE is the rise above ambient, so if you have a 30 degree ambient the
final temperature is 30+100 and that's 130 degrees C so that's too high.
So you look around and find a heat sink that is 3 degrees C per watt.
Now the rise is 3*20=60,and so with an ambient of 30 C we get 30+60=90 degrees C final temperature, so this heat sink is OK, as long as the ambient does not go over 40 C.

Unfortunately, the hotter a component is the more likely it is to fail, so if you want long life you look for the biggest heat sink you can fit into the application and after checking to make sure it works at all, that's what you use.

A flat plate however is a different donkey. The heat distribution is not as good as a well designed heat sink, and the effective radiating surface area is no where near good enough. The two combined make a very crummy heat sink unless you have just a little power to dissipate. Thus a heat sink purchased that is made to be used as a heat sink and comes with complete spec's is the best way to get it right.

A rule of thumb is that 1 watt creates a temperature rise of 60 degrees C per watt, but heat distribution and conduction enter into the picture when the power gets higher, so going by the heat sink manufacturer's spec for a given heat sink is better.

 

Thanks so much guys!

Both the led module and the heat sink have specifications given.

I just did a quick search .... found the same 150 x 60 x 25 (151 to 156 g) heat sink on everyone's site ... but no other specifications.

I will probably just take a chance ... keep my thermometer on it for a while and see what happens.

Thanks again ... Mike

 

Also be aware that some heat sinks are designed for use with forced air, these usually have the fins much closer together than the type designed for passive cooling.

 

Funny you say that. I did the same module in "kit" form with a fan and a heat sink that looked much more like it was made of foil or sheet aluminum then an extruded piece of aluminum.

Thanks again!!!!!

 

I think a link to your 50 Watt LED floodlight would be a better start.

 

Thanks so much guys!

Both the led module and the heat sink have specifications given.

I just did a quick search .... found the same 150 x 60 x 25 (151 to 156 g) heat sink on everyone's site ... but no other specifications.

I will probably just take a chance ... keep my thermometer on it for a while and see what happens.

Thanks again ... Mike

Hi,

Experimentation is our friend

If you can get just one heatsink then you can test it with just one LED, then decide if it is good or not.

Generally you go for a temperature rise of around 60 degrees C max, but less is better.

A while back i had two 1 watt LEDs i didnt feel like buying a heat sink for, so i used thermal epoxy to glue one to a shot piece of angle aluminum. It worked pretty well, so i glue the other one to it also but used a different kind of epoxy.
One epoxy was made for thermal applications, the other one was just PC Fahrenheit epoxy, but they both worked well.
So that experiment worked just fine

Oh yeah one more little note, and that is if the LED gets too hot and you can reduce the power electrically and put up with just slightly less light output, then you can lower the temperature that way too if needed. LED aging does down exponentially with lower drive current so you can push the half life into the double or triple decades.

 

maybe some form of a cots CPU heatsink that has cooling fan built-in would work. you would however need to wire in a wall-wart to power the fans, which is ez to do.

in this specific scenario though, engineering the temp rise is perhaps not so important. adding any AL heatsink with more surface area than you had before will help increase MTBF related to temp.

all that said, might be more cost effective to just switch out to LED style work lights vs trying to place heatsinks onto the existing halogens.

also, instead of heatsink, i would 1st try mounting some simple 120vac boxer fans (1 per lamp) to keep them cool. simple & ez.

 

Typically one would use the published thermal resistance when using a heatsink from a quality manufacturer..
sadly you aren't dealing with quality manufacturers so you are left to experiment or do some fairly complex mathematical calculations..

Be aware you are also dealing with lethal voltages and cheap construction/less than ideal dielectric properties prone to electrical leakage creating a shock/electrocution hazard..

Also..
A 500W halogen typically provides about 8000 lumens of light..
A 300W halogen typically provides about 6000 lumens of light..
So 2 x 8000 + 4 x 6000 =
That 50W led you talk about is 5,000 to 6000 lumens..
So you need 8 x 50W LEDs....

Maybe you want to buy ones like this?
https://www.ebay.com/itm/Pair-50W-W...m=272991667598&_trksid=p2045573.c100705.m4780

Note: there are numerous reports of them catching fire..

Just saying...

 

Thanks for the warning!

I am a safety fanatic ..... everything I build is grounded.

That is cheaper then any I found.

I was planning on putting two 50W in each of the heads ... so 100W in each head .... but thus a lot of heat I fear.

I will definitely take a good look again.

Thanks ..... Mike

 

FWIW.. I've used cheap Duron CPU heatsinks/fans to cool 50W LEDs without problems in the past and larger computer heatsinks for 100W LEDs..
These work great..
http://www.mpja.com/Duron_Athlon-Socket-A-CPU-Heatsink-Fan/productinfo/17045+HK/

$5 each and plenty to cool 50W LEDs
Drill/tap and apply some thermal grease and away you go..

 

That would work great ... $2 for the led and $5 for the heat sink .... $14 per head would be awesome. Problem, then I need a 12 volt supply for the flood light. I was hoping to keep everything 120. The module I found had the supply built in so it takes 120 vac directly to it.

Also, although a fan would be ok inside, I use these lights outside sometimes. The heads are waterproof. Even inside while using them in a shop, the fans tend to get clogged up with things like sawdust.

Good idea but I think a passive heatsink .... although larger .... would make more sense for this application.

Thanks .... Mike

 

Maybe you want to buy ones like this?
https://www.ebay.com/itm/Pair-50W-Warm-White-LED-FloodLight-Outdoor-Waterproof-Flood-Garden-Daylight-Lamp/272991667598?_trkparms=aid=555019&algo=PL.BANDIT&ao=1&asc=20170105155410&meid=65c157e4331b443b98a7abd73092232e&pid=100705&rk=1&rkt=1&&itm=272991667598&_trksid=p2045573.c100705.m4780

Note: there are numerous reports of them catching fire..

Just saying...

i would just tie a 120vac boxer fan to the back of those 50w led lamps. blow ambient air onto the fins, etc.

 

That would work great ... $2 for the led and $5 for the heat sink .... $14 per head would be awesome. Problem, then I need a 12 volt supply for the flood light. I was hoping to keep everything 120. The module I found had the supply built in so it takes 120 vac directly to it.

Also, although a fan would be ok inside, I use these lights outside sometimes. The heads are waterproof. Even inside while using them in a shop, the fans tend to get clogged up with things like sawdust.

Good idea but I think a passive heatsink .... although larger .... would make more sense for this application.

Thanks .... Mike

if they run uber hot then why is sawdust on them? they make IP rated fans. you could get 12vdc fans IP rated "wet" and just run them from a wall wart. will work in or outside just fine.

if you cannot get good surface contact onto the lamp housing with a heatsink, it will likely do little good. really needs to be flat mating surface with a touch of thermal paste between.

 

I agree ..... just thinking of my computer here beside me.

We are in the middle building our house (and living in it at the same time).

I literally blow out the computer once a month .... lets not say "sawdust" as that makes most people think of shavings. Lets just say a fine power / dust ... enough to clog the filter (fine mesh screen) over my computer fan. Funny that this is the only computer I have ever had with a "filter" over the fan .... probably a very good thing.

Everything in here is covered with a fine layer of dust ... you can just see it sticking to the walls.

I thought about the work lights as they ran very hot .... but my guess is that they are engineered to stay below say 140 deg so you don't burn your hand when touching them.

They do make work lights that are LED ... they look large to me ... maybe because it takes that much heat sink (the entire back of the unit) to keep them cool under the worst case conditions.

Thanks again!!!!!

Mike

 

put panty-hose over your PC
this will help keep fine dust out.

 

A "50W" Led that is selling for only $2.00 is probably a 5.0W LED but the decimal point is too small to see.

 

Here is a link to the ones I found .... $1.49 with free shipping.

They are availible through lots of vendors.

It says 50 Watts .... 110 volts

https://www.ebay.com/itm/110v-220v-...hash=item33dff975b7:m:mTic42-SDbbxhaFwvRwq01A

Here is a link to the heat sink I am thinking about .... one per 50 W LED ( I was planning on two 50W led's per head to two heat sinks per head).

https://www.ebay.com/itm/150mm-X-60mm-X-25mm-Heat-Sink-Aluminum-Heatsink-Cooling-Fin-for-Power-Amplifier/282452296708?epid=860592625&hash=item41c3780404:gEgAAOSwN2VZShHG

Thanks ...... Mike

 

the mount is not flat, what good does a heatsink do?
attach IP wet rated fans.