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Post by ricco on Nov 2, 2022 8:46:15 GMT
OK it's not on a boat but the same principles apply, I think. I have two sets of ceiling lights in the kitchen. Two of the bulbs in one set have recently blown. I've checked this is the case, it's not something more sinister, by swapping over a remaining working bulb. The bulbs are G4 12v so there's some kind of conversion system hidden in the void above the ceiling, changing the 240v to 12v.
Looking on Ebay I could get replacement led bulbs for all the lights for very little money. On the ad though it says: 'In order for the led lights to work properly a DC adapter is needed rather than an AC adapter. Many houses are fitted with AC adapters. Please ensure you choose a DC adapter.
There's no way I can identify what's changing the power to 12v, it's very tight up there. I don't understand why it would matter, isn't 12v simply 12v?
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Post by GUMPY on Nov 2, 2022 9:07:42 GMT
No
AC changes polarity 50 x a second
DC is fixed polarity
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Post by telemachus on Nov 2, 2022 9:08:57 GMT
OK it's not on a boat but the same principles apply, I think. I have two sets of ceiling lights in the kitchen. Two of the bulbs in one set have recently blown. I've checked this is the case, it's not something more sinister, by swapping over a remaining working bulb. The bulbs are G4 12v so there's some kind of conversion system hidden in the void above the ceiling, changing the 240v to 12v. Looking on Ebay I could get replacement led bulbs for all the lights for very little money. On the ad though it says: 'In order for the led lights to work properly a DC adapter is needed rather than an AC adapter. Many houses are fitted with AC adapters. Please ensure you choose a DC adapter. There's no way I can identify what's changing the power to 12v, it's very tight up there. I don't understand why it would matter, isn't 12v simply 12v? It’s a matter of 12v DC vs 12v AC. Mains is AC. Incandescent bulbs don’t care whether they get ac or dc. So a 12v transformer thingy for 12v incandescent lighting doesn’t need to rectify the ac into dc. However an LED is a polarised device, it needs positive on the anode and negative on the cathode. So it needs a dc (rectified) output. You can put a multimeter onto the bulb socket terminals. Set to a dc range it will show 12v if the supply is dc. It will show more or less zero if the supply is ac. Change the meter to ac range to check that it now shows 12v to confirm the socket was live. All that said, decent led bulbs have built in rectification so they can run off ac (but might flicker slightly) and also so it doesn’t matter which way round you insert the bulb. I would argue against very cheap eBay bulbs, they don’t last long in my experience. Buy cheap, buy twice. Somewhere like Screwfix sells decent LED bulbs at a good price. |
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Post by ricco on Nov 2, 2022 9:14:03 GMT
OK it's not on a boat but the same principles apply, I think. I have two sets of ceiling lights in the kitchen. Two of the bulbs in one set have recently blown. I've checked this is the case, it's not something more sinister, by swapping over a remaining working bulb. The bulbs are G4 12v so there's some kind of conversion system hidden in the void above the ceiling, changing the 240v to 12v. Looking on Ebay I could get replacement led bulbs for all the lights for very little money. On the ad though it says: 'In order for the led lights to work properly a DC adapter is needed rather than an AC adapter. Many houses are fitted with AC adapters. Please ensure you choose a DC adapter. There's no way I can identify what's changing the power to 12v, it's very tight up there. I don't understand why it would matter, isn't 12v simply 12v? It’s a matter of 12v DC vs 12v AC. Mains is AC. Incandescent bulbs don’t care whether they get ac or dc. So a 12v transformer thingy for 12v incandescent lighting doesn’t need to rectify the ac into dc. However an LED is a polarised device, it needs positive on the anode and negative on the cathode. So it needs a dc (rectified) output. You can put a multimeter onto the bulb socket terminals. Set to a dc range it will show 12v if the supply is dc. It will show more or less zero if the supply is ac. Change the meter to ac range to check that it now shows 12v to confirm the socket was live. All that said, decent led bulbs have built in rectification so they can run off ac (but might flicker slightly) and also so it doesn’t matter which way round you insert the bulb. I would argue against very cheap eBay bulbs, they don’t last long in my experience. Buy cheap, buy twice. Somewhere like Screwfix sells decent LED bulbs at a good price. Great thanks, I have a multimeter that measures AC and DC so I'll try that test. |
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Post by Deleted on Nov 2, 2022 19:34:55 GMT
I have found the cheap ones sold at supermarkets to be perfectly adequate.
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