MadModder
Gallery, Projects and General => How do I?? => Topic started by: RussellT on November 17, 2015, 04:26:01 AM
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I need to get a new bulb for a milling machine work lamp which has a 48V AC supply. The bulb holder is a conventional (for the UK) bayonet fitting as used for 240V bulbs.
It has occurred to me that it might work with a modern LED type lamp as these incorporate a switch mode power supply. I have only found one spec sheet which says 100 - 240 V AC - but that's clearly what they expect it to be used with.
What does anyone think? :zap:
Russell
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Russell I have a feeling that I have some 48v bulbs tucked away somewhere, let me do a search after lunch
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Thanks Andrew
It's not that I can't get a 48V bulb - more that it would be more convenient and cheaper if I could use one from the supermarket.
Russell
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Here if you need it :)
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I need to get a new bulb for a milling machine work lamp which has a 48V AC supply. The bulb holder is a conventional (for the UK) bayonet fitting as used for 240V bulbs.
It has occurred to me that it might work with a modern LED type lamp as these incorporate a switch mode power supply. I have only found one spec sheet which says 100 - 240 V AC - but that's clearly what they expect it to be used with.
What does anyone think? :zap:
Russell
50v to GU10 LED conversion
http://madmodder.net/index.php/topic,10254.msg115604.html#msg115604
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Thanks Andrew
It's not that I can't get a 48V bulb - more that it would be more convenient and cheaper if I could use one from the supermarket.
Russell
So why cant you wire the holder from a 240 v supply rather than the 48v one?
That said there's a safety issue involved which is why its 48v to start with....no winners with this one...! :zap:
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Thanks for the suggestions.
So why cant you wire the holder from a 240 v supply rather than the 48v one?
I could. First I'd have to add a neutral to the machine etc etc. :bang:
I can't help the feeling that some of the LED lamps out there will probably work at 50V with no modifications - perhaps I'll try one or two - after all even if they don't work I can always use them somewhere else and save electricity which will pay for them.
Bill does your project mean that you've tried connecting straight to the 50V supply?
Russell
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So if you have a 50v supply that must be derived from a 415 transformer?
Either way you have 50v ac, so Bills voltage doubler circuit will work and led lights are a goer....
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all the machines I've seen with a low voltage work light
had a either 415V step down transformer with a 25 / 50V secondary
just for the "Lo Vo" light or
had 25/50V a winding on the machines control transformer
like this on a Bridgeport
John
PS
How about using a 24V automotive light run from the 25V tap
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My Harrison lathe was fitted with a 50volt step down LoVo transformer and was used in that state when I had it running on 3 phase.
Since moving workshop and converting the lathe to a single phase motor I took the step down transformer windings out of the switch box and managed to squeeze in a 240/12 volt toroidal transformer so I now use 12 volt spot bulbs or the LED equivalents......OZ.
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Bill does your project mean that you've tried connecting straight to the 50V supply?
Yes, the led bulb psu will run at 50vac ( about 70vdc when rectified internally) but it will not give full brightness and will likely over heat - The power o/p is almost constant ,so as input voltage drops current goes up and the losses will increase.
They seem to be ok down to about 65-70vac (the smpsu chips are typically rated from 90-250vac )
The doubler circuit gives the bulb about 128vdc (if memory serves) sufficient for the psu to run at constant power.
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Just a thought...
I have not tried the dim-able LED devices . These could potentially work down to a lower voltage but whether they will sense the lower input and will dim ,or only sense the phase start/ stop angle and remain full o/p , I don't know
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By the time you have bought all the bits to convert this, you might as well bite the bullet and just pay the £4.00 each for some GLS lamps surely?
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https://www.easy-lightbulbs.com/light-bulbs/general-household-lighting/gls-bulb/bayonet-22mm-diameter/gl5060bc-ca/?gclid=Cj0KEQiA4LCyBRCY0N7Oy-mSgNIBEiQAyg39thgQXTLCCxuRVE3NnZ2_rH446Vk3MKNatpSNl9IWfWsaAiI08P8HAQ
It's a shame really as i gave a load away last year with a load of festoon lights that used these bulbs
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By the time you have bought all the bits to convert this, you might as well bite the bullet and just pay the £4.00 each for some GLS lamps surely?
50v gls lamps are awful , they have a horrible yellow glow that barely lights the work and seem to darken the room when on.
I have working bulbs, just much prefer leds. I had previously had three 12v lamps in series with a small dropper resistance (12v lamps are fine up to about 20v)
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I would have to agree with you totally on that Bill
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I have to add my support for the voltage doubler circuit. Its so elegantly simple. I wish I had a need to use that solution somewhere just so I could.
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Thanks for all the suggestions - I'm thinking about it - and I'll need to talk to the machines owner. I think he might favour buying some 50V lamps - although if it were mine I think I'd go for Bill's voltage doubler.
Russell
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I'm a bit late to this party, but I recently converted my LoVo light to an MR16 12v led, replacing the 440v transformer with an led driver. Because the 3 phase motor is run off a vfd, I decided the easiest way was to run a seperate 240v supply to the lamp and the coolant pump, and this supplies the driver which sits in the transformer box in place of the old 440v transformer.
I wish I'd known that adaptors from BC to MR16 were available though - I spent far too long faffing about making up a plate to hold the new lampholder! It works a treat though, with a daylight led lamp in (6000k I think) and if it gets damaged or splashed with coolant there is only 12 v to worry about.
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If itm is a lovolite unit, some have different voltage tappings on the transformer unit.
Phil