Need 60V, 1mA current source for testing LEDs with

Hello
We are using ten 34V CLU038 LED COBs on our mains connected product. We connect them as five lots of two-in-series. –So there are five connection wire pairs going off to them from the driver PCB.

CLU038 LED COB datasheet:
https://www.light.fi/assets/files/151210-CLU038-1206C4[Ra80-70]-DataSheet.pdf


Our assemblers unfortunately keep misconnecting them. Then when the whole luminaire is completely assembled, some or all of the five COB pairs don’t light up….
….We then have to spend ages disassembling the product so we can find out where the misconnection is and then correct it.
What we need is to test the LED COB pairs as they are assembled…to ensure they are correctly connected in.

So what we want is a 1mA current source with two probes so that we can touch the PCB pads to which the COB pairs should be connected, and check to see if the LEDs light up. Each COB pair needs about 59V to light up. We need the limitation to 1mA otherwise assembly staff may blind themselves.
We could make up a 1mA current source power supply ourselves, however, if there is something very cheap already available off-the-shelf, then we would prefer to use that. Does anyone know of such a product?
Do you agree that it’s not possible to electrocute yourself badly with 59V, with the 1mA limitation?

Also, supposing staff occasionally accidentally reverse bias the LEDs from time to time whilst testing them, do you agree that this could not cause damage to the LEDs? … because none of the individual LEDs within the COBs would get reverse biased by more than 4V, say. (the voltage would be limited to 60V)

I don't think that 1mA will light the LEDs. There is an LED tester on ebay for about $50 that could do the trick. Probably a better approach would be proper training for your assembly staff, with possible floggings for those that deviate from the instructions. Or, not as effective, you could have a check in the assembly instructions that assured that they put the "+" in the right place.

I don't think that 1mA will light the LEDs.

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We just need the lowest current that will very dimly just light the leds...so maybe a few mA , max 10mA.

There's an old saying: "you can't test-in quality" meaning no amount of testing can overcome a flawed manufacturing process. That should be fixed first. You'd think people could visually see the (+) markings.
Removing a COB LED and flipping polarity is highly stressful for the part and likely to make more failures.

Actually that CLU038 has a "protection device" prob. zener diode built in which helps somewhat. Can you test to the mid-point of the two LED's?

There are many (TV) LED backlight testers you could use for this.
If your 1mA CC source has any lag or overshoot/output capacitance, it can damage things.

IEC 61010 Hazardous live (death) is considered:
"a.c. voltage levels are 55V r.m.s., 78V peak and the d.c. voltage level is 140 V.
For equipment intended for use in WET LOCATIONS, the a.c. voltage levels are 33 V r.m.s, 46.7 V peak and the d.c. voltage level is 70V.
The current levels are:
1) 3.5mA r.m.s. for sinusoidal waveforms, 5mA peak for non-sinusoidal waveforms or mixed frequencies.


68V 1mA will bite and wet hands would not be good.

You'd think people could visually see the (+) markings

Click to expand...

Thanks, Aswell as getting them the wrong way round, they also sometimes snag the wire end insulation in the connector instead of the stripped metal bit.

So we can gaurantee no death or injury with <60V ?

Can you test to the mid-point of the two LED's?

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Thanks , yes, but thats not on the PCB...we need to test from the driver pcb pads so as to check they are properly connected to the pcb

I can't say that voltage level is safe- in the USA OHSA has a 50VAC/DC limit. You are in the UK; HSE appears to follow the same guideline.
So PPE gloves etc. required for people handling this voltage level.

I leave it to Manufacturing to pay for the materials to fix their screwups.
You can consider using a bunch of PP3's and resistors, or a DC-DC converter brick, it's likely you don't have time to make a luxury test jig.

Hi,

I don't think that 1mA will light the LEDs

Click to expand...

Every usual LED will give relatively bright light with 1mA.
Modern LEDs will be brighter with 1mA than usual LEDs 20 years ago with 20mA.
Even high power LEDs will send out fairly visible light ... as long as there is not other internal (parallel) circuitry that prevents this small current passing the LED's semiconductor.

Klaus

1 ma would tickle, I would get a transformer with a double center tap primary. typically 220/110 option on a small transformer , any low voltage secondary doesn't matter, your not going to need it. or a isolation transformer

Wire 110 VAC to the full primary, then wire a full wave bridge across the center tap, to one side of the other primary. This will drop the AC voltage in half and give you about 75 V pulse out of the full wave.

THIS IS STILL LIVE AC VOLTAGE, DANGER.

Limit the current with a 25K resistor (in series with the output) on both the + and the - output of the bridge.

I suspect the LEDs will be visible with 1ma of current. They don't have a threshold current, so roughly 1/500 the full current brightness.

Done right you will have an isolated, pulsing 75 volts with about 1.5 ma peak current. This will tingle if you touch it. but 1.5 ma won't stop your heart.
Still your tester should be build to minimize exposure.