Will this setup work with this driver?

I had a little change of plans in the type of led I am using. I was wondering if using the this Flexblock with these led's in the series I have noted will work ok? I just don't want to burn them out on my first try. Thanks

Flex block 700ma in 48V boost mode. http://www.luxdrive.com/products/flexblock-a011/

4 - Philips Luxeon M ROYAL BLUE 12 Watt LEDs = Forward Voltage is 11.00V @ 700ma, 11.40V @ 1,000ma


1 - Philips Luxeon ES ROYAL BLUE 3 Watt LEDs = Forward Voltage is 2.75V @ 350ma, 2.95 @ 700ma, 3.00V @ 1,000ma

In this sequence ----12w + 12w + 3w + 12w + 12w

The sequence doesn't matter. All you need to worry about is if the total forward voltage is within the limits of the driver, which it seems to be.

So you want to run all 5 LED's in the same string? That wont work with 1 driver. If you have all 5 LED's in series they they all all get the same mA which is 700mA. I would recommend running the 4 Luxeon M's with 1 flex block and then the Royal Blue from a seperate driver that is 350mA, such as the buckblock drier.

Why cant I add the ES? it will allow 700ma also just like the M's ?? The M's are at 11.0V each and the ES is at 2.95V. 11v x 4 = 44 + 2.95v = 46.95v. The flexblock puts out 48v. ??

mnm99 said:

Why cant I add the ES? it will allow 700ma also just like the M's ?? The M's are at 11.0V each and the ES is at 2.95V. 11v x 4 = 44 + 2.95v = 46.95v. The flexblock puts out 48v. ??

Click to expand...

EDIT: Re-read post, and agree with evilc66.

mds82 said:

So you want to run all 5 LED's in the same string? That wont work with 1 driver. If you have all 5 LED's in series they they all all get the same mA which is 700mA. I would recommend running the 4 Luxeon M's with 1 flex block and then the Royal Blue from a seperate driver that is 350mA, such as the buckblock drier.

Click to expand...

He never said he was intending to run the Rebel ES at 350mA. He just posted the vf at given currents (notice the vf listed at 350mA, 700mA, and 1000mA). The Flex Block he listed is a 700mA version, so all LEDs connected to it would run at 700mA, which is well within the specs of both LEDs.

One more question. I also have a bunch of other led's. Should I be OK running these of the same flex block? The voltage only adds up to around 43.2v and the block puts out 48v

12 - 3w led in series. Says Forward Voltage :3.5V~4.0V Forward Current:700mA, but another spec says Forward Voltage (VF) MIN/TYP 3.2-3.6v. Reverse Current(IR)
VR=5V
(uA) 100

EDIT...I found this in another thread. If this is the way it works I understand now. Thanks

Led power (P) = The voltage drop across the LED (V) * The current passing through the LED (I)

Lets use some round numbers for an example.. Lets say you have 4 LED's.. each is rated for 10 volts and 1 amp.. so each led is theoretically 10 watts..
You hook up all four in series with a constant current power supply that delivers up to 48 volts at 1 amp..
The power supply will adjust the voltage to 40 volts because that is what it will theoretically take to "push" the 1 amp of current through.. Current will remain the same at 1 amp through all four LED's. In any series circuit, current is always the same.

1st LED: 40 volts @ 1amp goes in. >> 30 volts out
2nd LED: 30 volts @ 1amp goes in >> 20 volts out
3rd LED: 20 volts @ 1amp goes in >> 10 volts out
4th LED: 10 volts @ 1amp goes in >> 0 volts out and the current returns to the power supply negative.

mnm99 said:

I was wondering if using the this Flexblock with these led's in the series I have noted will work ok? I just don't want to burn them out on my first try.

Click to expand...

Yes, according to the math, the power supply should work with the setup you described.
The LEDs in your circuit have a combined voltage drop load of 46.95v at 700mA. This voltage drop is greater than the minimum voltage of the power supply.

From my experience, I would caution that (unless you are substantially underdriving the LEDs) it might be possible that a sudden power surge could cause a burn out. Just as a precaution, I would recommend not attaching the power supply to the LEDs until the power supply is first plugged in. There could be a power surge if the power supply is suddenly plugged in.

If there is a burnout, usually what will happen is one of the LEDs will burn out, while another one will be "damaged" (though still producing some light). The LED that burns out is the one with the lowest current rating. The LED will act as a fuse, so not all of them will burn out.

If you are extremely worried, one possible option would be adding just one more LED emitter into the circuit. This will slightly reduce the current through the circuit (since the flex block is limited to 48V).


But yes, that is what is so magical about a constant current power source, as long as the current (mA) is right, it does not matter how many LEDs you wire together in series , only so long as the total voltage of the LEDs is within the rated voltage range of the power supply.

I have to say that the easiest most fun way to learn about something is when you actually need to know because you are trying to build something.

Thanks again..Here's one more. How much brighter will 1000ma be compared to 700ma??? I have a 700ma driver that puts out 48v. The LEDs I have to power are the Luxeon M ROYAL BLUE 12 Watt LEDs = Forward Voltage is 11.00V @ 700ma, 11.40V @ 1,000ma and Luxeon ES ROYAL BLUE 3 Watt LEDs = Forward Voltage is 2.75V @ 350ma, 2.95 @ 700ma, 3.00V @ 1,000ma. Now I can't find a driver to power 4 of the M's and 1 of the ES in series (5 total). The only way I found is with a AC/DC driver that will do 1000ma at 48v, BUT I would then have to buy a DC to AC inverter to power the AC driver. Cost of the drives would be around $50 each and the inverter I could get for around $40. Is it worth the expense of doing all that for 300ma?


Boat transom lights......Here is some progress on the light / heat sink. This is the first set with the cheap EBAY led's 3w using 2 drivers for each light, embedded in thermal epoxy. The second will be with the above Luxeon ones. The led's will be encapsulated and under water. I did it this way for water flow behind them. Should cool them pretty good.

Anders Hoveland said:

I would recommend not attaching the power supply to the LEDs until the power supply is first plugged in. There could be a power surge if the power supply is suddenly plugged in.

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Ignore this bad advice. Generally much better to have the LEDs connected BEFORE you plug in the driver, not the other way around. The driver may charge up capacitors to a high open circuit voltage which is discharged into the LEDs when they are connected .... hence connect the LEDs first so this does not happen.

SemiMan said:

Ignore this bad advice. Generally much better to have the LEDs connected BEFORE you plug in the driver, not the other way around. The driver may charge up capacitors to a high open circuit voltage which is discharged into the LEDs when they are connected .... hence connect the LEDs first so this does not happen.

Click to expand...

I understand. That kinda answers the switch question. I would connect the on off switch between the driver and battery right?

Yes that is correct.

mnm99 said:

I had a little change of plans in the type of led I am using. I was wondering if using the this Flexblock with these led's in the series I have noted will work ok? I just don't want to burn them out on my first try. Thanks

Flex block 700ma in 48V boost mode. http://www.luxdrive.com/products/flexblock-a011/

4 - Philips Luxeon M ROYAL BLUE 12 Watt LEDs = Forward Voltage is 11.00V @ 700ma, 11.40V @ 1,000ma


1 - Philips Luxeon ES ROYAL BLUE 3 Watt LEDs = Forward Voltage is 2.75V @ 350ma, 2.95 @ 700ma, 3.00V @ 1,000ma

In this sequence ----12w + 12w + 3w + 12w + 12w

Click to expand...

it should work, i used that driver many times. you are close to limits but not over them. also this driver has open circuit protection, it does not matter if led connected or not, prior to turinig it on.

alpg88 said:

it should work, i used that driver many times. you are close to limits but not over them. also this driver has open circuit protection, it does not matter if led connected or not, prior to turinig it on.

Click to expand...

Thanks. So far so good. My next part is encapsulating them. I'm going to go with the MG clear. Do you think I'll have a problem?

ecapsulating what???? leds?? hard to say since i do not see what, and how you'll be encapsulating, but, in general, if you leave heatsinks out, so they can be cooled by air, than you should be ok.

SemiMan said:

Ignore this bad advice. Generally much better to have the LEDs connected BEFORE you plug in the driver, not the other way around. The driver may charge up capacitors to a high open circuit voltage which is discharged into the LEDs when they are connected .... hence connect the LEDs first so this does not happen.

Click to expand...

+1

alpg88 said:

ecapsulating what???? leds?? hard to say since i do not see what, and how you'll be encapsulating, but, in general, if you leave heatsinks out, so they can be cooled by air, than you should be ok.

Click to expand...

The LED's. Making for underwater. Does the picture show up? I'm looking at Clear encapsulation made by MG.

Question about the first post. Would taking out the 3w still work using the flexblock? Would the higher voltage cause a problem or does the Flexblock regulate that?

Flex block 700ma in 48V boost mode. http://www.luxdrive.com/products/flexblock-a011/

4 - Philips Luxeon M ROYAL BLUE 12 Watt LEDs = Forward Voltage is 11.00V @ 700ma, = 44Volts

if you making them for underwater, you can get away with even smaller heatsink, but it still has to be exposed. you can not encapculate it.

yes you can add and remove any amount or type of leds, as long as voltage drop across all is not over 48v under 700ma current, you should be fine. driver does not care about types or amount of leds.

Thanks. Why cant I encapsulate?

Also I'm doing a terrible job soldering led to led. I tried 18ga solid wire and tinned it first and 16ga stranded tinned first. Put a dab of solder on the terminal and tried to solder together. Maybe my iron is too small, because it wouldn't bond if I put the iron on top. What gauge wire should I use?