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| Thread ID: 129256 | 2013-02-13 08:47:00 | Very strange LED issue... almost supernatural!? | The Error Guy (14052) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 1327876 | 2013-02-13 08:47:00 | My 100pc LED's just showed up and I have started making the light for my "lightbox" for scanning my film negatives. I am wiring the LEDs in series parallel, with 5 LED's in each cell/cluster, probably looking to make 10-15 clusters. Anyway, I tested all the LEDs are working fine, and soldered the first cluster together, when It came to testing the cluster it wouldn't light, but I noticed a strange phenomenon, now I'm positive (no bad electrical pun intended) that someone will explain this out but when I attached one of the electrodes (positive or negative) and held the LED's other leg it glowed dimly. The especially strange thing is if I connect the positive electrode from the power supply to either the correct + or - leg of the diode it STILL glows dimly if I hold the other leg.... dafuq!? To me this goes against every single piece of physics I know (I don't know much :D) The light flickers, I'm guessing at 50Hz, it's probably to do with the power supply since the battery doesn't do it. That's one thing, but the OTHER one is my series cluster won't light (the whole cluster does this weird dim light thing though!) , at first I thought the polarity might be wrong but I have checked, it's good. Each LED is working but no matter where I put the probes from my power supply it will only ever light one LED, and only if the probes are either side of it. I have taken 2x separate LED's and tried to get them to light to no avail, they just glow dimly by themselves or not at all. The only way they will both light is in parallel. Can someone point me in the right direction and explain my dim glowing? I'm rather confused. Have I discovered free power maybe? Not very useful power. Far too dim! I'll try put some pics up. EDIT - pics are in this Picassa album picasaweb.google.com |
The Error Guy (14052) | ||
| 1327877 | 2013-02-13 08:59:00 | Voltages? | KarameaDave (15222) | ||
| 1327878 | 2013-02-13 09:19:00 | Power supply is 3.2v 500mA, LED's are Forward Voltage (V) : 3.2 ~ 3.8 Luminous Intensity Typ Iv (mcd) : Average in 9000 Max Power Dissipation : 80mw Max Continuous Forward Current : 30mA |
The Error Guy (14052) | ||
| 1327879 | 2013-02-13 09:25:00 | Is that not then your problem? If your power supply is rated at 3.2v and the LED's are too, then they will all need to be in parallel. Won't they? |
KarameaDave (15222) | ||
| 1327880 | 2013-02-13 09:35:00 | *brain freeze* derp, of course. There is a reason why my 6th form physics wasn't too hot. I got my ohms law muddled!! Series I/Current is the same and V is divided between the components, parallel and the current get divided. I feel stupid :p What about the dim glowing though, that has me intrigued, esp as charge polarity doesn't seem to affect it. |
The Error Guy (14052) | ||
| 1327881 | 2013-02-13 09:38:00 | Not sure. | KarameaDave (15222) | ||
| 1327882 | 2013-02-13 09:49:00 | Actually, I think you want them in Series to avoid the voltage being reduced. As for the 'supernatural'... it's not an AC output from the power supply is it? |
Paul.Cov (425) | ||
| 1327883 | 2013-02-13 10:06:00 | It's *supposed* to be DC, it's an Aixiz laser power supply unit. | The Error Guy (14052) | ||
| 1327884 | 2013-02-13 20:08:00 | Actually, I think you want them in Series to avoid the voltage being reduced. Nup. Components connected in parallel are connected so the same voltage is applied to each component. from en.wikipedia.org |
KarameaDave (15222) | ||
| 1327885 | 2013-02-13 20:33:00 | Yes you will need to put them in parallel on your supply. Five in series will need at least 16 volts! Of course it didn't work. However, I would get a different power supply, something with a higher voltage. Matching the supply to the LED voltage drop is not the proper way to do it. You should have a higher supply and correct current limiting resistors. The voltage drop of the LEDs will not be exactly the same on all of them. Unless your supply is constant current limited, then you can probably get away with it. As for the flickering while holding one end of the string... I am guessing (but have no real clue) that it's some kind of interference from mains supply. You said it flickered at a low frequency - this seems to make sense. Maybe something similar to this: www.electronics-related.com |
Agent_24 (57) | ||
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