DiY LED - Cree CXA3070
- Thread starter SupraSPL
- Start date
Organix420
Member
Looks good Supra and you are right about those heatsinks I bought one of those temp guns and within a few minutes the cxa was up to ~45C. Do you have a link for the heatsinks you are using?
SupraSPL
Well-Known Member
Those are from HeatsinkUSA the 10.08" profile. I had them cut into 10"X6 pieces. Each piece is 5454cm². They can fit four pieces into a flat rate box. I added a 140mm fan and was able to dissipate 100W in each heatsink with heatsink temps only 4 degrees C over ambient. I suspect you could run as much as 150W on each heatsink and I plan on testing that soon. The total cost ends up about $0.90/Watt for passive cooling.
Another option is customhydronutrients heatsinks. They are great if you need a long thin option or you could strap 2 pieces together so a single 80mm or 120mm fan could cool it. An 8" piece would be 1400cm².I recommend 110cm²/Watt for passive cooling or 40cm²/Watt for active cooling so the cost is $0.70/Watt for passive.
Another option is customhydronutrients heatsinks. They are great if you need a long thin option or you could strap 2 pieces together so a single 80mm or 120mm fan could cool it. An 8" piece would be 1400cm².I recommend 110cm²/Watt for passive cooling or 40cm²/Watt for active cooling so the cost is $0.70/Watt for passive.
RedCarpetMatches
Well-Known Member
I want to implement these cobs in a vertical set up. I seen a 1 1/4 x 1/8 wall square heatsink on Steve's. Do you think this fan http://shop.stevesleds.com/Pressurizing-Cooling-Fan-with-Power-Regulator-Pressurizing-Cooling-Fan-w-plug.htm would be good enough to cool 8 cobs?
Organix420
Member
Has anyone used the thermocouple attach point? My understanding is that it is a way to measure the temperature.
Yes. 1 water /2days, 1/4 jack classic, molasses - boiled banana tea.
I did. My method was ghetto because all I have is a an Infrared sensor I bought(Forgot they make oven thermometers...). I soldered some unstranded wire to a small piece of stranded to the COB and coiled the stranded wire to gather heat as it is copper it conducts heat easily and put my thermometer right on it. I'm sitting at 55c.
Let's see a picture of that! Do you have a thread?
Supra how is the growth on your bud sites? Would you say your far enough along to tell if the 3000k gives the plant more leaf matter?
I have design idea's for the 3070 I really want to get on but I am hesitant on the 3000k color temp.
RedCarpetMatches
Well-Known Member
Can someone answer post 287. Please and thank you 
SupraSPL
Well-Known Member
That is a very interesting fan. I use bathroom fans to build small carbon filters but that fan could make a really small filter for a drying box etc. Not sure about the idea of using aluminum tubing actively cooled. That would be an good experiment.
SupraSPL
Well-Known Member
I havent tried using a thermocouple but I have experimented with a very accurate infrared thermometer. First thing I noticed is that you can't get the temperature of the surface of the cob when it is turned on because it does create some infrared light of its own. You have to switch it off and take the temp immediately.
Another way to estimate the junction temp is by measuring the ambient temp and forward voltage at ambient and then letting the junction temp rise and remeasuring the forward voltage. If you have an accurate voltmeter, that gives you a good estimation of the junction temp if you know the coeeficient, which we do. For the CXA3070, for every .1 volts the vF falls, the junction temp has increased by 1 degree Celsius over ambient.
The Tc (case temp) is assumed to be about 30C lower than the Tj (junction temp). You can see this demonstrated in the Cree manual on this graph. They set the Tj 85C, 1925mA test current as 100% on the graph and the 100% intersection on the graph is at Tc 55. Therefore junction temp in this case is 30C above the case temp.
Of course if you are running softer the difference between case temp and junction temp would be much less. In my case I am aiming for Tj of 50C or less. Since it is winter my ambient temps are very reasonable ~21C and my Tj has been as low as 40C. Hopefully I can stay under 50C during the warm season.
SupraSPL
Well-Known Member
Cannabare so far I am very happy with the look of the bud sites that are directly under the 3000K. It seems they have enough blue to control node distance and to induce plenty of frosting in all the varieties I have tried so far.
This is a blue widow at 19 days directly under 3000K on both sides.
This is a blue widow at 19 days directly under 3000K on both sides.
RedCarpetMatches
Well-Known Member
Thanks for answer! I could probably screw in some heatsinks on top of the tubular heatsink with the fan. Maybe something along these lines.
And then have some rear lighting angled at backs of plants.
And then have some rear lighting angled at backs of plants.
nestor
Well-Known Member
A really great way to get cheap heatsink/fan combos is to go to a local computer shop. I went in the other day asking for exactly that. They brought out a box from the back with a bunch of heatsinks from old AMD socket 939/AM2/AM2+ etc. I was able to take my pick of 2 for 5 bucks. They were happy to be rid of them. I was happy to have them. Win/win.
I don't have access to an IR gun so I can't speak to the temps, but just hooking up the fan to an old cell phone charger running at less voltage and amps than the fan was rated for dropped the temps significantly. First the bottom of the heatsink was hot to the touch. Turning on the fan dropped it to being pleasantly warm to the touch within minutes.
EDIT: I should also add that I was running a 3070 COB @ 1.4mA.
The overall layout of the board. 5000k in the center with space for two 3000k marked out on the sides.
View of the COB on the bottom the heatsink.
Single chip hooked up and shelf replaced in cabinet.
SupraSPL
Well-Known Member
Hey nestor welcome to riu. I like yr design. Ya it doesnt take much fan speed to keep those heatsinks cool. If you are curious yo can get an IR thermometer from Walmarts baby section for $10. The one that reads the temp of baby food.
If you power a 12V .2A fan at 5v it will only draw about .05A so you can get away with almost any 5V cell phone adapter. On the other hand since you are running the COB at 1.4A it might benefit you to run the fan speed higher. Good luck with your grow!
If you power a 12V .2A fan at 5v it will only draw about .05A so you can get away with almost any 5V cell phone adapter. On the other hand since you are running the COB at 1.4A it might benefit you to run the fan speed higher. Good luck with your grow!
SupraSPL
Well-Known Member
That is an interesting COB and heatsink redcarpet where did you find that?
@ cannabare - ya I am trying to keep training to a very minimum. I fim them early if necessary and I will bend tops down when necessary or strap the stalk to the bucket if they start to flop over. I used to use LST and that is how I learned that it is too much work for my grow lol.
@ cannabare - ya I am trying to keep training to a very minimum. I fim them early if necessary and I will bend tops down when necessary or strap the stalk to the bucket if they start to flop over. I used to use LST and that is how I learned that it is too much work for my grow lol.