# LED DIY question



## Bayinaung (Feb 24, 2012)

Hey guys,

If I have two different sets of LEDs with the following specs, can I drive them on the same series?

LED1:
DC Forward Voltage (VF): 3.2V~ 3.4 V
DC Forward Current (IF): Typ 600mA

LED2:
DC Forward Voltage (VF): 3.6-3.8V
DC Forward Current (IF): 650-700 mA


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## cica (Feb 10, 2013)

Yes you can but only with max 600mA. I am driving 3 different tipes but only with the current of the weakest (least mA) ones rating.


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## Bayinaung (Feb 24, 2012)

awesome thanks! 

If I'm going to use 20 of those leds (10 each) would I be able to wire them together to a single driver? total voltage is 72.. does such a driver exist? (I'm a newb. forgive me)


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## cica (Feb 10, 2013)

I don't know if such a driver exist. Drivers that I saw on the net go up to 36V I beleive. I think they are rated to 12-36V if I remember correctly. What you can do is make 2 or 3 circuits and use 2-3 drivers if you dont find a driver for 72V. I didn't use prefab drivers, I just made my owns.
And also, playing with 72V is already a bit dangerous, so if you go that way, make sure that everything is well insulated.
Sorry that I wasn't much of a help.


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## 50seven (Feb 14, 2010)

The highest you'll find would be around 48 volts. 

Wire multiple loops and use a driver with a higher amperage rating.

But I hate constant current drivers myself...


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## Bayinaung (Feb 24, 2012)

that's very informative thanks guys. yeah high voltage driver I didn't find. I did find this driver on ebay that might do the job with just two circuits:

http://www.ebay.com/itm/IP67-Waterproof-150W-Dimmable-Electronic-LED-Driver-DC30-42V-3-5A-Power-Supply-/221252871708?pt=US_Lighting_Parts_and_Accessories&hash=item3383b2e61c

it's 30-42v, 150w, 3.5A. Might be perfect actually. two rows of lights, two series.


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## cica (Feb 10, 2013)

I would wire the leds in two rows but in each row I would put 5 of led #1 and 5 of led #2. Than wire the two rows in paralel. This way the two rows would be somewhat balanced. If you put 10 led #1 in one row and 10 led #2 in the other, than the "lower voltage" row will drow much higher current than the "higher voltage" row. Make sure to adjust (dial down) the current to no more than 1.2 A (1200mA). If you leave the driver at 3.5A you will kill the leds in no time.


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## 50seven (Feb 14, 2010)

+1

Don't use the dimmer on the driver to actually dim the lights; you'll want to set it to limit the current to 1.2A. If you want a dimmer, use a third party one put in line just before the LED strings


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## Bayinaung (Feb 24, 2012)

cica said:


> I would wire the leds in two rows but in each row I would put 5 of led #1 and 5 of led #2. Than wire the two rows in paralel. This way the two rows would be somewhat balanced. If you put 10 led #1 in one row and 10 led #2 in the other, than the "lower voltage" row will drow much higher current than the "higher voltage" row. Make sure to adjust (dial down) the current to no more than 1.2 A (1200mA). If you leave the driver at 3.5A you will kill the leds in no time.


I like that idea. which value of the voltage do I use to calculate the resistor to use? 30V or 42V?



50seven said:


> +1
> 
> Don't use the dimmer on the driver to actually dim the lights; you'll want to set it to limit the current to 1.2A. If you want a dimmer, use a third party one put in line just before the LED strings


Ok I didn't know that. thanks for that!


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## cica (Feb 10, 2013)

Bayinaung said:


> I like that idea. which value of the voltage do I use to calculate the resistor to use? 30V or 42V?


I did not mean to use a resistor. What I meant is to use the driver's knob to adjust the current, just like 50seven said. 
To calculate the resistor is not that easy. You would have to go with the 42V (or even better measure the driver's maximum voltage, witch could be even higher). Than you would have to know the voltage needed for each row to drive 600mA throgh the row. This is impossible to calculate, because each led is different. If the led is rated 600mA at 3.2-3.4 V, that means that the led can have 600mA at a voltage anywhere between 3.2 to 3.4V. each led is different even from the same batch. If an led can sink 600mA at 3.2V, and you supply it with 3.4V, the amperidge will be dangeresly high, and kill the led. That is why leds are driven by current driver and not by voltage driver.
You will have to adjust the drivers knob to get 1.2A. If you want to use the dimmer, than glue a pice of plastic to the drivers housing and one to the knob, making a hard stop that you can not dial it more upwards, just down. This way you can dim it but can not drive it over the rated current.


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## 50seven (Feb 14, 2010)

BTW you'll need to use a multimeter to detect and set the max. current 

Sent from my Galaxy Nexus using Tapatalk 2


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## Bayinaung (Feb 24, 2012)

Ok great. I didn't know there was a dial on driver.  Is a cheap canadian tire multimeter ok for this? 

Lots of opinions on soldering irons too... 25w 45w


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## 50seven (Feb 14, 2010)

I had a couple MasterCrap multilmeters, but found them to be very innacurate, especially on DC voltage. I still have a brand new one, but I just don't trust it, so I only use it for general household AC stuff. Since I splurged for a good DC clamp meter, it's all I use.


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## Bayinaung (Feb 24, 2012)

50seven said:


> mastercrap multilmeters


lmao!!!!!!!!!!


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## lewig (Aug 4, 2013)

Bayinaung said:


> awesome thanks!
> 
> If I'm going to use 20 of those leds (10 each) would I be able to wire them together to a single driver? total voltage is 72.. does such a driver exist? (I'm a newb. forgive me)


Check INVENTRONICS outdoor drivers.
http://www.inventronics-co.com/cplb2p.aspx?c_kind=2&c_kind2=29

You can run both 700 and 600 mA LED from 700 mA supply, but need better heat dissipation - " ... DC Forward Current (IF): Typ 600mA..." shows you normal operational current , check in datasheet for your LED maximum current,you can not exceed max. rating.


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