Starboard UVa and far red light


I attempted to make an LED light from Starboard and a forum post (this one). Unfortunately, I think I did not choose the right power source … The lamp worked for more or less 5 minutes.

Here is the material used:
1 X Starboard UVa 365nm
1 X Starboard UVa 385nm
2 X Starboard far red 730nm
Power supply
Heat sink

I had connected this in series but I do not believe that is the cause.

I do not absolutely want to put UV and far red on the same circuit. I am ready to change the LEDs for others who are specialized for horticulture.

I would like to know what would be the best diet to use. In addition, the LEDs on the boards are completely screwed up?

Do I need to add anything else to this circuit?

Thank you

Hi @KKirouac! At first glance, I notice you have three different types of LEDs and specs:

1672-1124-ND - 3.4V and 500mA
1672-1123-ND - 3.6V and 500mA
2 of the 1672-1057-ND - 1.9V and 350mA

1866-1114-ND - driver with constant current 350mA and 9~36VDC output.

If you have these 4 LEDs in series, you have quite the unbalanced load. Your voltage is in the right range for the driver (10.8V) but the issue was mismatching the current needs of the LEDs with the 350mA driver and 350mA LED.

I’d recommend redesigning with LEDs that have matched current needs. I’d also include a current limiting resistor in the design. It wouldn’t be a bad idea to split the design apart into a UV and a far red circuit.

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I am completely lost, I would need help finding the power supply to plug in and the resistance to add.

2 x UVA

Also I would like to know what would allow me to connect the following:

2 x UVA

thank you in advance

Can’t really help with your question, but wanted to make sure you saw the warning on the last page of the UV LED data sheet.


Yes, I know the dangers of UV. I already have horticultural glasses with UV protection. And I use these UVs in a closed area, before entering to work this area we close the UVs. We keep our glasses because it also protects from other spectra and I believe that there is some UV in the strip LEDs that we use.

I know a little electronics, more horiticulture and I am safe on two levels.

Hi KKirouac,

Running those four LEDs in series at 350mA should be fine with that driver. You don’t need a current limiting resistor with a constant current type driver like the APC-12-350. As long as the LEDs are rated for 350mA or more, your are good to go. The only stipulation in this regard is that you will not be able to control the relative brightness of each LED individually, so you may get the wrong ratio of brightness for the various colors using this method.

Now about the failure. What happened? Did the power supply die, did one or more of the LEDs fail, or something else?

It’s pretty unlikely that the power supply failed, as it is current limited. More likely one or more of your LEDs died. Two things to consider there – first, LEDs are somewhat sensitive to ESD, so they could be damaged by a static discharge event. You really should take ESD precautions when handling them. However, more likely is that one or more of them overheated. You mention using a heatsink, but you did not mention using a thermal interface material (TIM) between the LEDs and the heat sinks. Without a decent TIM, the heat conduction between the LED and the heat sink is quite poor due to the microscopic irregularities of the two surfaces. The TIM fills those gaps and allows more effective thermal transfer.

Interface between LED star board and heat sink:

Here are a couple TIM’s cut in a star pattern specifically for LED star boards:



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The power supply is not dead. The UV seems clearly dead, for the far RED it seems to be still in good condition. When first plugged in, everything worked (2 minutes). I put it in place and notice a red led stop lighting after 1 minutes. I plug into another outlet and 3 these are turned on and off.

I checked the connections, everything was OK.

The UV has a point that seems burnt.

The connection was in series and I had to install on a heatsink with star sticky and one with thermal paste and screws.

I have nothing against connecting the different LEDs to a specific power supply. I would have the optimal power of each.

Do you have any advice?

thank you in advance

Hey KKirouac,

Hmm, based off what you said, it sounds like heat may not have been the cause of the damage. My thinking is similar to Lindsay’s. The power supply you have isn’t quite right for your applications. Let me offer some suggestions.

For the Far Red LEDs: The supply you already have is nearly there. It has the correct current output, but the output voltage is actually a bit too high. I would recommend putting a resistor is series with those two to protect them. Using our handy LED Series Resistor Calculator we can figure out that you’ll need something around 15-25ohm and 2-3W to safely reach the lower end of your driver’s voltage output. I recommend A105927CT-ND to get you comfortably within those values.

For the UV LEDs: Luckily these both have a current rating of 500ma, so that makes our lives easier. By adding up our LED forward voltages, it looks like we need a supply with an output of 7V @ 500ma.
Something like 945-2934-ND, should do nicely for those values.

Does all that make sense?

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First of all, thank you and everyone for the involvement! It’s very appreciated.

Indeed, all of them make sense. My knowledge is not at the level of all my projects!

I have a quick question still going in this direction, how can I calculate maximum leds for a circuit?

For example RACD04-500
with LST1-01G01-UV01-00
, if I understood correctly I would like to check:

each LED we need 1.8w for a total of 2.2 LEDs?

Using this one RACD07-700, could I increase to two more on the circuit?

I got with this power supply for the moment but, i have a lot a project and i want to understand well!


Hi KKirouac,

To figure out valid combinations of LEDs and constant current power supplies, you need to look at the range of output voltage for any supply and the forward voltage of each LED at the current you intend to drive them.

Your LED, the LST1-01G01-UV01-00, can actually handle up to 1A, with sufficient cooling, but it is generally better to run it at the test current of 500mA. According to the datasheet, its forward voltage can range anywhere between 3V and 4V.

The RACD04-500 will output 500mA at any voltage between 3V and 8V. This means that you could supply one or two LST1-01G01-UV01-00 LEDs in series with it, since the minimum voltage for one is 3V and the maximum voltage for two in series is 8V.

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I tried to connect the far red with the power supply, but no reaction. The power supply is OK. In total, it makes 6 starboards which do nothing or we cease to function after a few seconds. It is possible to know exactly what I need as current, I can explain everything you need.

I am currently waiting for the power supply for the UV, I hope it will be the one I need I have already burned 5 starboard uv.

I would like to finalize my project, there are only these LEDs left and for the moment after several hundred dollars I am at the same point. For the rest everything went well

Thank you

Hi KKirouac,

Your far red LED, the XPEFAR-L1-0000-00601-SB01, will typically have a forward voltage in the neighborhood of 1.8V to 1.9V at a forward current of 350mA, according to the datasheet (see graph below from page 17 of datasheet):

So, if you run two in series at about 350mA each, you will need a supply which can provide 350mA with an output voltage which can range from below 3.5V to above 4.0V (giving a little margin on each end). If you used the APC-12-350 to drive fewer than 5 of these LEDs in series (5 x 1.8V per LED = 9V), you would likely kill them since its minimum output voltage is 9V.

Here are a couple of LED power supplies which meet the requirements for two XPEFAR-L1-0000-00601-SB01 LEDs in series:

RACD04-350 3V ~ 12V, 350mA, 4W supply with wire leads
RACD06-350 3V ~ 24V, 350mA, 6W supply with screw terminals

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