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Post by lollygagger on Apr 7, 2017 16:53:19 GMT
Today I bought a light fitting. The mains powered ones had "mains" written on the box. This one didn't but is. Bugger!
It was cheap and if possible I'd rather bodge it up to run on DC than take it back. Inside is a circuit board. The led strip has a few things printed on it including 230v AC and 9v.
I have it in mind to simply connect 12v DC to where it expects 230v AC and see what happens.
Or connect 12v to the leads that attach to the led strip, there are 4 -ve and 1 +ve. Assuming again from the "9v" printed on the strip is what it expects, will it survive 14v from the charger?
I hate electricity.
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Post by lollygagger on Apr 7, 2017 16:54:38 GMT
Here's a picture, I know you like pictures.  |
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Post by Telemachus on Apr 7, 2017 17:29:43 GMT
Hard to be sure but it looks like the big oblong yellow capacitor (top right of the board) is the primary means of dropping the voltage from 230 to 9. It will thus only work on AC. I'd therefore very much doubt that putting 12v DC onto the terminals that expect 230v AC will cause anything at all to happen.
On the actual ring of LEDs there is no sign of any dropper resistors so I suspect if you put 14v directly onto them, they will glow very brightly shortly before going up to LED heaven.
I am not 100% convinced that the "9v" printed on the ring is actually the voltage, but presuming it is then I suggest a resistor to drop the voltage. There is no indication of the nominal power consumption of the LEDs but let's assume it is 100mA, so you need to drop 14-9= 5v at 100mA, which is 50ohms (47 ohms will do). It will dissipate 1/2 watt and thus get quite hot. I would suggest at least a 2w resistor so it doesn't get too hot, and you will need to position it so that it can dissipate the heat safely. If it doesn't seem bright enough, try a 33ohm resistor, or lower if it was really dim. |
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Post by lollygagger on Apr 7, 2017 18:08:34 GMT
Hard to be sure but it looks like the big oblong yellow capacitor (top right of the board) is the primary means of dropping the voltage from 230 to 9. It will thus only work on AC. I'd therefore very much doubt that putting 12v DC onto the terminals that expect 230v AC will cause anything at all to happen.
On the actual ring of LEDs there is no sign of any dropper resistors so I suspect if you put 14v directly onto them, they will glow very brightly shortly before going up to LED heaven.
I am not 100% convinced that the "9v" printed on the ring is actually the voltage, but presuming it is then I suggest a resistor to drop the voltage. There is no indication of the nominal power consumption of the LEDs but let's assume it is 100mA, so you need to drop 14-9= 5v at 100mA, which is 50ohms (47 ohms will do). It will dissipate 1/2 watt and thus get quite hot. I would suggest at least a 2w resistor so it doesn't get too hot, and you will need to position it so that it can dissipate the heat safely. If it doesn't seem bright enough, try a 33ohm resistor, or lower if it was really dim. Thanks, looks a non starter then realistically... It says it's 13.5w. 13.5w/9v=1.5a. At least that's whole numbers (you know what I mean). 38 LEDs in 4 bunches, not sure how the maths for that works! 9v would make sense if you also made a battery powered version? |
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Post by Telemachus on Apr 7, 2017 18:18:03 GMT
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Post by lollygagger on Apr 7, 2017 18:58:41 GMT
13.5w is for the LEDs. Thanks, that's an option. What a faff this is turning into! Maybe I should buy a strip of 12v leds and stick them on the fitting. The diffuser is nice.  |
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