| Electronics > Beginners |
| LED strip tester will it work |
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| DarkZero:
Sorry to bring this old post up. I actually built it and it works quite well. the problem occurs when i reverse bias the led strip or individual led it immediately kills them but in a funny way they illuminate but quite dimly. i measured that current limit is 6mA. i think they are burning up because of high voltage reverse break down and that current that destroys the led is less than 6mA when reverse biased. now i didn't try it but i was thinking i add some diode with high reverse voltage breakdown and low reverse bias current in series to stop them from going kaput but maybe im wrong so i tought i would ask here first |
| PTR_1275:
What is the highest voltage strip you’ll be testing? I did some reverse bias tests on a 3mm led (because why not) and it started to glow at around 30v, I got it up to a decent brightness before it lives no more. Most led strips are 3 (or 6 for 24v) LEDs in series with a limiting resistor. If you’re only testing 24v strips, reduce that input voltage and you shouldn’t have issues killing strips when reverse polarity. |
| Brumby:
If you want to test the LED backlight of a TV, for example, you might want a much higher compliance voltage. I checked out such a problem on a TV that had 5 strips of LEDs wired in series. It required 160V to drive them normally and over 100V to get them to glow visibly. You could check each strip individually, but it would require removing the complete front of the TV (LCD panel, filters and diffusers) to gain access to all the intermediate connection points, where 30V would be enough. |
| PTR_1275:
Very good point. I suppose it really comes down to the application and what the user will most likely be testing. I have bench supplies that can do 120vdc and if need be I can always series a few up if I need higher voltages. Not everyone has that equipment though and it is something I take for granted |
| DarkZero:
i made the circuit spec suggested in the post above and it works well, im powering it from 220/220 5VA transformer but like i said they die once i reverse bias them so im wondering if i can do something to stop that from happening like the tester in this video i know that 320v is well over reverse break down but i just cant think of a way to add some protection to it i lack some knowledge https://youtu.be/IuHZBE2NP7c?t=442 |
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