DIY LEDs - The write-up
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swenholz
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A picture of your intended wiring diagram and the actual wired up LEDs would be helpful.
My first thought is that #7 or 8 is backwards or you soldered to the same polarity for #8 by accident, but that shouldn't complete the circut so that may not make sense either. pictures always help.
My first thought is that #7 or 8 is backwards or you soldered to the same polarity for #8 by accident, but that shouldn't complete the circut so that may not make sense either. pictures always help.
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vietcu
New member
Here are some pictures, any help would be appreciated. I am no electrician by any means, so all help and simple terms would help out a lot.
This is the meter that I have to use but really not sure how to use it
What I did noticed while soldering the leds were that, once I got to led #7. Everytime I soldered on another one the led would actually light up only a little but light up when I touch the soldering iron to the solder points.
Please tell me how to go about testing and figuring out what my problems are.
I did the battery test again to the string and I found this out. I touched all Led + and - and they all light up. But when I touch the + to number 7, 10, 12, and 13, and the negative to the heatsink. Those Led would light up. How to fix this?
This is the meter that I have to use but really not sure how to use it
What I did noticed while soldering the leds were that, once I got to led #7. Everytime I soldered on another one the led would actually light up only a little but light up when I touch the soldering iron to the solder points.
Please tell me how to go about testing and figuring out what my problems are.
I did the battery test again to the string and I found this out. I touched all Led + and - and they all light up. But when I touch the + to number 7, 10, 12, and 13, and the negative to the heatsink. Those Led would light up. How to fix this?
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swenholz
New member
I would start by checking to make sure you haven't fried one of the LEDs. There is a resistance test mode on the meter at approximately 5:30 on the meter dial. touch the positive and negative leads to the corresponding terminal on each individual LED. if it lights up you are good. if it beeps it is bad. I recall having a similar issue after I fried a few my first time around.
vietcu
New member
vietcu
New member
Problem solved hopefully. I kept testing #7 with the probe and finally decided to resolder that LED. I move the wire from one + joint to the other + joint and seems to have fixed all. I guess there was something screwy or something with the original + joint that I used. I tested all the LED to make sure the voltage was not straying, and plugged it all in and viola . Everything is lit now, thanks swenholz for the help.
. Everything is lit now, thanks swenholz for the help.
vietcu
New member
After doing some research kcress changed his mind:
Heatsink Size
CJO found this information and I think he got it from lynxvs.
[QUOTE[I've posted this before I think but it might be helpful. I use just a flat plate of aluminum as my heat sink. I did some calculations below to justify heat sink size. I attach a PCB directly to the plate using screws.
Max Junction Temp = 150° C
Power of Single LED = 3.4 Forward Voltage X 700 mA = 2.38 W
Ambient Temp = 70° C ( A SWAG)
Thermal Resistance between Junction â€"œ Case (From Data Sheet) = 10° C/W
Thermal Resistance between Junction and PCB (From Rebel application note) = 7° C/W
Total Thermal Resistance = 10 + 7 = 17° C/W
Total Thermal Resistance between Junction and ambient air = (150 â€"œ 70)/ 2.38 = 33.61 ° C/W
Thermal resistance between Case and Ambient air = 33.61 â€"œ 17 = 16.61 ° C/W
The amount of heat dissipation that can be achieved with a flat plate of aluminum is indicated below.
Using a 3mm plate looks about 20 cm^2 per LED converting to inches is equal to 3.1 in^2 * 50 LEDs = 155 in^2 The plate I am using is 24 X 7.25 = 174 in^2 not sure if you can count both sides of plate as surface area… I also have two cooling fans to help [/QUOTE][/QUOTE]
My next question is heat dissipation. I am trying to understand the images Kress posted up about using aluminum plates. I have a 16"x48" plate 1/4" thick. I have a total of 78 LED on this plate. What I was planning on doing was suspend a piece of acrylic roughly 1" from the back of the plate. On the piece of acrylic itself, I will place 4 PC fans to draw the air through the 1" space between the acrylic and the aluminum and out through the fan. Any chance of overheating those LED?
Managed to get another string up and running now without a hitch this time around.
Heatsink Size
CJO found this information and I think he got it from lynxvs.
[QUOTE[I've posted this before I think but it might be helpful. I use just a flat plate of aluminum as my heat sink. I did some calculations below to justify heat sink size. I attach a PCB directly to the plate using screws.
Max Junction Temp = 150° C
Power of Single LED = 3.4 Forward Voltage X 700 mA = 2.38 W
Ambient Temp = 70° C ( A SWAG)
Thermal Resistance between Junction â€"œ Case (From Data Sheet) = 10° C/W
Thermal Resistance between Junction and PCB (From Rebel application note) = 7° C/W
Total Thermal Resistance = 10 + 7 = 17° C/W
Total Thermal Resistance between Junction and ambient air = (150 â€"œ 70)/ 2.38 = 33.61 ° C/W
Thermal resistance between Case and Ambient air = 33.61 â€"œ 17 = 16.61 ° C/W
The amount of heat dissipation that can be achieved with a flat plate of aluminum is indicated below.
Using a 3mm plate looks about 20 cm^2 per LED converting to inches is equal to 3.1 in^2 * 50 LEDs = 155 in^2 The plate I am using is 24 X 7.25 = 174 in^2 not sure if you can count both sides of plate as surface area… I also have two cooling fans to help [/QUOTE][/QUOTE]
My next question is heat dissipation. I am trying to understand the images Kress posted up about using aluminum plates. I have a 16"x48" plate 1/4" thick. I have a total of 78 LED on this plate. What I was planning on doing was suspend a piece of acrylic roughly 1" from the back of the plate. On the piece of acrylic itself, I will place 4 PC fans to draw the air through the 1" space between the acrylic and the aluminum and out through the fan. Any chance of overheating those LED?
Managed to get another string up and running now without a hitch this time around
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kcress
New member
vietcu: This is now the very best thread on build commissioning. What's described and backed with outstanding pictures is the exact process that should be followed in every build if you want a trouble-free build and start-up. It even documents balancing very unbalanced strings.
http://www.reefcentral.com/forums/showthread.php?t=1973462
http://www.reefcentral.com/forums/showthread.php?t=1973462
SC Reefaholic
Member
As with most, i'm sure this question has bee asked and answered but I'm not exactly an electronics guy and i'm a little confused by some posts on another thread.
If you have a Mean Well ELN 60-48D dimmed by an Apex and you set the pot on the 48D at 700mA. When the Apex dims the LEDs to 50% are they not now running at 350mA?
If you have a Mean Well ELN 60-48D dimmed by an Apex and you set the pot on the 48D at 700mA. When the Apex dims the LEDs to 50% are they not now running at 350mA?
I am not familiar with the Apex dimming, but that sounds logical to me (driver will send 700mA when the signal is at 100% and 350mA at 50%). I would assume it is the same as me dimming my manual potentiometers 1/2 way.
I have asked this before and this is the answer I got. When you dim the driver it reduces the current going to the leds. The pot sets the max current allowed or what will be your 100% setting. For you this is 700 mA. I tested this using my meter, when I dim the leds with the meter measuring the current the mA does in fact go down.
CJO
New member
It will be very close to that (it's actually around 315mA, based on the datasheet).
CJ
SC Reefaholic
Member
That's what I thought. Thanks for the confirmation.
brassmonkyballs
BMB
would normally use a fast blow fuse on parallel strings but since you are running one string per driver theres nothing much to do.
jrizo1
New member
is that good or bad?
brassmonkyballs
BMB
Perfectly fine. Many would say its the ideal way to run them.
jrizo1
New member
o i do not need a fuse then?
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