CMB16D and high power led's

[scubado]

I just got my new cards and started to play and ran into a problem. I made my own colored floods using using high powered leds. During the making of these I was using a battery pack for testing to avoid damage to the power supply in case of a mistake. Now I've got them hooked up to the card and power supply and burned out two red ones in about 2 seconds, apparently can't handle 12V as advertised. Blue and green, no problems. I looked in the hardware utility to limit a single channel to say 90% and could't find a way. I thought I read somewhere that the latest software would be able to do that, or was it a future release? I still need to contact the dealer where I got them and get new ones.

[Max-Paul]

I dont think this is going to help. Is not the voltage / current going through the load (in this case LED floods) PWM? So this means that at some point you will still have the full voltage value applied across the load. Its just how long that the voltage is applied that makes the LED appear dimmer? Much like what happens on the AC cards.

So, being that the Red LEDs require less voltage to operate than say blue, green or white. Means that you either need to have more red LEDs in series or a current limiting resistor in series with the red LEDs. Otherwise you are going to continue to blow your red LEDs.

I think that this is your problem and solution.

[JBullard]

What was the battery voltage you were testing with?

What is the actual DC output voltage of your power supply ? (under load and at no load)

Is the output voltage regualated? Or does it vary depending on the current load?

Is your power supply constant current rated?

How much current are your LEDs drawing in your flood circuit?

What is the max forward voltage and current your LEDs rated for? (An LED is usually rated for a max current drop and max forward voltage. Exceed either in your design and the LED is toast)


A link to the LEDs you purchased would help.


Did you calculate the values of your dropping resistors yourself or were they built into your LED package?

Did you design your flloodlights circuit yourself or was it a published design circuit?

All anyone can do is make wild assumptions and guesses with out knowing more information about your power supply, LEDs, dropping resistors (if any) and the type of circuit design for the floods you made.

Many of us would be glad to offer help with complete information on your application.

[scubado]

I just found my answer looking up the specs of the led.  The 10w led's run on 12v without any resistors except the particular red ones that I used.  The red ones run on 6.5-7v.   Arrrrrg! 

This is the type that I used for this project:

http://cgi.ebay.com/10W-Red-Hi-brightness-260LM-Save-Power-LED-NEW-f-/400154203227?pt=LH_DefaultDomain_0&hash=item5d2b0c945b

Can someone suggest a circuit for me that will allow me to use these on a 12v supply. I'm not sure what type of resistor will work with the current draw of 1000mA.

[mnkyboy]

scubado wrote:

I just found my answer looking up the specs of the led. The 10w led's run on 12v without any resistors except the particular red ones that I used. The red ones run on 6.5-7v. Arrrrrg!

This is the type that I used for this project:

http://cgi.ebay.com/10W-Red-Hi-brightness-260LM-Save-Power-LED-NEW-f-/400154203227?pt=LH_DefaultDomain_0&hash=item5d2b0c945b

Can someone suggest a circuit for me that will allow me to use these on a 12v supply. I'm not sure what type of resistor will work with the current draw of 1000mA.

using the specs from the link you show, and this is for the RED only..


a 5.6 ohm resistor should work for a single LED ands its gonna have to dissapate quite a bit of heat!.

Solution 0: 1 x 1 array uses 1 LEDs exactly

The wizard says: In solution 0:

• 
  
• each 5.6 ohm resistor dissipates 5600 mW
  
• the wizard thinks the power dissipated in your resistors is a concern
  
• together, all resistors dissipate 5600 mW
  
• together, the diodes dissipate 6500 mW
  
• total power dissipated by the array is 12100 mW
  
• the array draws current of 1000 mA from the source.
  
• The wizard thinks arrays of a single LED are cool too.

IMHO, My concern would be 2 things

Cooling that 10w LED would be the most important issue. Once these HO LEDS get hot they go into thermal runaway. Once they do that, well they die a VERY quick death.

DC current being applied, even on the other colors, without either some form of current limiting, or being driven by a constant current device which does not need limiting resistors ( which is the correct way with HO LEDS.)

[cenote]

You could bump up the LED floods to redesign them using 24v.
Than you could run the reds in series with a (5watt) 3.3 ohm resistor. A 5watt would handle the load. But you would also have to redesign the other two in, and that would get tricky. If the forward volts equals the same as the input voltage, you need a volt or two extra to be able to control the current with a resistor or even a constant current chip.

[scubado]

I'm sorry, but I'm lost with your explanation. What's a 1 x 1 array? I know the leds get very hot, they are mounted in an aluminum housing as a heat sink. You also mention the wizard, what is it?

[cenote]

scubado wrote:

I'm sorry, but I'm lost with your explanation. What's a 1 x 1 array? I know the leds get very hot, they are mounted in an aluminum housing as a heat sink. You also mention the wizard, what is it?

A lot of folks use this: http://led.linear1.org/led.wiz

It's good, but not exact. I always use a current meter in front of the led's and test as I build.

A 1 x1 array just means that there is 1 LED in 1 Series.

[JBullard]

Here is one example of a "wizard" that can be used to assist in calculating dropping resistors for LED circuits

http://theledlight.com/resistancecalculator.html

EDIT: cenote posted while I was typing. I like the wizard he posted also.

[scubado]

Thanks guys. I liked the http://theledlight.com/resistancecalculator.html better because it gives you what wattage resister you will need. In my case I needed a 5ohm 5W resistor, I happened to have on hand two 10ohm 10W resistors that I wired in parallel to get me the 5ohms and it worked. I'll need to stop at RadioShack to see if they have 5W resistors that are smaller to fit easier in the housing.

[cenote]

scubado wrote:

Thanks guys. I liked the http://theledlight.com/resistancecalculator.html better because it gives you what wattage resister you will need. In my case I needed a 5ohm 5W resistor, I happened to have on hand two 10ohm 10W resistors that I wired in parallel to get me the 5ohms and it worked. I'll need to stop at RadioShack to see if they have 5W resistors that are smaller to fit easier in the housing.

Chances are, it will not. For some reason, simple math does not work when putting multiple resistors together. Best way is to but them together, than take a reading from a simple meter.