DIY LEDs - The write-up
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One of you electrical smarties needs to comment on dantimdad's last post. It would be nice if we could use something that cheap.
But it sounds to good to be true.
Speaking of cheap. Deal Extreme has got crazy prices on the CREE XR-E Q5 Cool Whites.
1-3 $6.27 with free shipping.
3+ $5.38 with $1.70 flat rate shipping.
Prices just keep dropping from there.
Bummer is they dont have any blues. Just White
But it sounds to good to be true.
Speaking of cheap. Deal Extreme has got crazy prices on the CREE XR-E Q5 Cool Whites.
1-3 $6.27 with free shipping.
3+ $5.38 with $1.70 flat rate shipping.
Prices just keep dropping from there.
Bummer is they dont have any blues. Just White
I'll take a crack at it.
The unit that dantimdad pointed out has got the following
12Vdc Output Voltage
20W Output
1.7A Output
My very ameture mind sees it like this. I could run one string of up to 5 LED's per unit without an Amperage problem because they don't run above 1000mA
Good for small projects that don't need a lot of power. Plus we can still power our white and blue seperately at a reasonable price.
I don't know how the 24V vs 12V part factor is.
I know I am probably really wrong but how did I do?
The unit that dantimdad pointed out has got the following
12Vdc Output Voltage
20W Output
1.7A Output
My very ameture mind sees it like this. I could run one string of up to 5 LED's per unit without an Amperage problem because they don't run above 1000mA
Good for small projects that don't need a lot of power. Plus we can still power our white and blue seperately at a reasonable price.
I don't know how the 24V vs 12V part factor is.
I know I am probably really wrong but how did I do?
You'll most likely blow out the driver and LED's if five are run in series. LED's are current driven devices and the max amperage is the point where it can take current and give up heat without loosing life. Heat lessens the life of the LED. More current will make the LED brighter and produce more heat. That is how LEDs can burn out. They get too much current, get to hot, and die.
What you could do is run two parallel strands of 3 LEDs. For the Cree the forward voltage is about 3.7v. So 3.7 + 3.7 + 3.7 = 11.1 which is the max you could run on a 12v driver. (More burns it out.) To get the current in check you run two strands in parallel which divides the current in half. You would then get 850 mA through each strand, which is perfect.
However, if one LED in one strand burns out all of the current will go through the other strand, burning out that entire strand. You would need a current mirror to protect the strands.
What you could do is run two parallel strands of 3 LEDs. For the Cree the forward voltage is about 3.7v. So 3.7 + 3.7 + 3.7 = 11.1 which is the max you could run on a 12v driver. (More burns it out.) To get the current in check you run two strands in parallel which divides the current in half. You would then get 850 mA through each strand, which is perfect.
However, if one LED in one strand burns out all of the current will go through the other strand, burning out that entire strand. You would need a current mirror to protect the strands.
So the failing point is the voltage?
Other models have higher wattage and amperage for only a few dollars more but the voltage is still only 12V.
I dont like the idea of all my LED's blowing out and I don't know what a current mirror is so maybe its time to look somplace else for power.
Then again, maybe only 6 LED will be enough for me.
Other models have higher wattage and amperage for only a few dollars more but the voltage is still only 12V.
I dont like the idea of all my LED's blowing out and I don't know what a current mirror is so maybe its time to look somplace else for power.
Then again, maybe only 6 LED will be enough for me.
Ok try this one on for size.
I get two of little Ballastwise units for a total of $19.98
Then 4 white and 4 blue LEDs
I wire then up in parallel rows of 2. This lowers the risk of the initial burn out as well as the potential for the other string to blow rgiht?
That gives me a price of about $65 for the electrical components to LED light a nano. Not bad.
Unless I'm wrong again and it is bad.
I get two of little Ballastwise units for a total of $19.98
Then 4 white and 4 blue LEDs
I wire then up in parallel rows of 2. This lowers the risk of the initial burn out as well as the potential for the other string to blow rgiht?
That gives me a price of about $65 for the electrical components to LED light a nano. Not bad.
Unless I'm wrong again and it is bad.
james3370
Premium Member
<a href=showthread.php?s=&postid=15013325#post15013325 target=_blank>Originally posted</a> by dantimdad
well, in my case, 6 will be plenty. So, I will be the guinea pig and order one and get 6 LEDs.
Now, I have to remember to go to HD and get the aluminum rails. Been 3 times since this started and forgot them every time!
dantimdad
did you see my posts showing the aluminum u-stock that i used for mine??? worked great & gives an area to hide all the wire
...got it at lowesin case you didn't (& to save the trouble of looking for it pre-split) here is the post (w/ pics)
http://reefcentral.com/forums/showthread.php?s=&postid=14835287#post14835287
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kcress
New member
Dang it!! I swear I answered earlier today before all the speculation.. But I don't see it. Hmmm I wonder where I did post it? DOH!
That supply is full on marketing BS. It is nothing more than a DC power supply that puts out up to 1.7A at 12VDC. It is NOT a LED driver. Nosirrebob.
A bunch of cheap international power supply sellers put labels on their supplies. They think that providing a supply in and cheap housing somehow makes it The Supply for LED builders. Then they mis-label them.
With that unit you still need a LED driver as all that is a power supply. It's actually a very lousy power supply for what we want to do since it's only 12V. We want at least 24V to reduce the number of drivers we need. RUN AWAY. MAKE SYMBOL of the CROSS WITH GARLIC PLANTS.
That supply is full on marketing BS. It is nothing more than a DC power supply that puts out up to 1.7A at 12VDC. It is NOT a LED driver. Nosirrebob.
A bunch of cheap international power supply sellers put labels on their supplies. They think that providing a supply in and cheap housing somehow makes it The Supply for LED builders. Then they mis-label them.
With that unit you still need a LED driver as all that is a power supply. It's actually a very lousy power supply for what we want to do since it's only 12V. We want at least 24V to reduce the number of drivers we need. RUN AWAY. MAKE SYMBOL of the CROSS WITH GARLIC PLANTS.
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I agree with Kcress.
For future drivers we find we want to try and see if they are constant current sources, with variable voltage. This is opposite of the power source last reviewed. (And which I missed that part of.)
Basically LEDs need a constant current and the driver needs to only put out the added forward voltage of the LEDs in the string.
This is also why you can have anywhere from one LED to the max it can handle without being concerned with a true LED driver. The driver will put out only the voltage needed at the same constant current.
This lessens the risk only in that you have fewer LEDs that could burn out in the initial strand. Ignoring that the risk and issues are the same because the current will be identical.
For future drivers we find we want to try and see if they are constant current sources, with variable voltage. This is opposite of the power source last reviewed. (And which I missed that part of.)
Basically LEDs need a constant current and the driver needs to only put out the added forward voltage of the LEDs in the string.
This is also why you can have anywhere from one LED to the max it can handle without being concerned with a true LED driver. The driver will put out only the voltage needed at the same constant current.
This lessens the risk only in that you have fewer LEDs that could burn out in the initial strand. Ignoring that the risk and issues are the same because the current will be identical.
dtech
New member
I am going to purchase some stuff soon I hope and would like to know what you think of these
http://www.dealextreme.com/details.dx/sku.1445
https://www.dealextreme.com/details.dx/sku.1775,if not I will go with the CREE I read that one of the light manufacturers use these in their fixture. Also I am going to go with 30 of each and no optics over a 75 to get it a touch brighter, I have a clam that I want to keep low, thoughts on that too maybe it would not be needed, I am planning more SPS and LPS than softies but will have some of them as well lower in the tank.
http://www.dealextreme.com/details.dx/sku.1445
https://www.dealextreme.com/details.dx/sku.1775,if not I will go with the CREE I read that one of the light manufacturers use these in their fixture. Also I am going to go with 30 of each and no optics over a 75 to get it a touch brighter, I have a clam that I want to keep low, thoughts on that too maybe it would not be needed, I am planning more SPS and LPS than softies but will have some of them as well lower in the tank.
HD Fatboy®
New member
First off this is on great thread, I started reading it today at around noon.
Can someone please help me out here. What is the differnce in these two power supplies other than cost?
The specs seem the same.
http://www.mpja.com/prodinfo.asp?number=17829+PS
http://www.mpja.com/prodinfo.asp?number=16854+PS
TIA!
Can someone please help me out here. What is the differnce in these two power supplies other than cost?
The specs seem the same.
http://www.mpja.com/prodinfo.asp?number=17829+PS
http://www.mpja.com/prodinfo.asp?number=16854+PS
TIA!
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