Author Topic: 48V lamp  (Read 7930 times)

Offline RussellT

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48V lamp
« on: November 17, 2015, 04:26:01 AM »
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
Common sense is unfortunately not as common as its name suggests.

Offline awemawson

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Re: 48V lamp
« Reply #1 on: November 17, 2015, 07:35:53 AM »
Russell I have a feeling that I have some 48v bulbs tucked away somewhere, let me do a search after lunch
Andrew Mawson
East Sussex

Offline RussellT

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Re: 48V lamp
« Reply #2 on: November 17, 2015, 08:16:27 AM »
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
Common sense is unfortunately not as common as its name suggests.

Offline awemawson

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Re: 48V lamp
« Reply #3 on: November 17, 2015, 08:18:28 AM »
Here if you need it :)
Andrew Mawson
East Sussex

Offline BillTodd

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Re: 48V lamp
« Reply #4 on: November 17, 2015, 09:22:13 AM »
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
« Last Edit: November 17, 2015, 11:04:11 AM by BillTodd »
Bill

Offline John Rudd

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Re: 48V lamp
« Reply #5 on: November 17, 2015, 10:35:50 AM »
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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Offline RussellT

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Re: 48V lamp
« Reply #6 on: November 17, 2015, 03:24:33 PM »
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
Common sense is unfortunately not as common as its name suggests.

Offline John Rudd

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Re: 48V lamp
« Reply #7 on: November 17, 2015, 03:47:19 PM »
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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Offline John Swift

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Re: 48V lamp
« Reply #8 on: November 17, 2015, 04:46:08 PM »

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


 


Offline Manxmodder

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Re: 48V lamp
« Reply #9 on: November 17, 2015, 07:02:30 PM »
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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Offline BillTodd

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Re: 48V lamp
« Reply #10 on: November 18, 2015, 12:56:50 AM »
Quote
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.
« Last Edit: November 18, 2015, 10:20:21 AM by BillTodd »
Bill

Offline BillTodd

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Re: 48V lamp
« Reply #11 on: November 18, 2015, 11:08:05 AM »
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
Bill

Offline Swarfing

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Re: 48V lamp
« Reply #12 on: November 18, 2015, 11:21:46 AM »
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?
Once in hole stop digging.

Offline Swarfing

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Re: 48V lamp
« Reply #13 on: November 18, 2015, 11:27:27 AM »
Once in hole stop digging.

Offline BillTodd

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Re: 48V lamp
« Reply #14 on: November 18, 2015, 12:07:27 PM »
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)
Bill

Offline Swarfing

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Re: 48V lamp
« Reply #15 on: November 18, 2015, 03:15:09 PM »
I would have to agree with you totally on that Bill
Once in hole stop digging.

Offline sparky961

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Re: 48V lamp
« Reply #16 on: November 18, 2015, 10:03:32 PM »
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.

Offline RussellT

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Re: 48V lamp
« Reply #17 on: November 23, 2015, 11:02:02 AM »
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
Common sense is unfortunately not as common as its name suggests.

Offline srp

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Re: 48V lamp
« Reply #18 on: January 22, 2016, 03:56:35 PM »
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.

Offline hermetic

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Re: 48V lamp
« Reply #19 on: January 22, 2016, 04:32:24 PM »
If itm is a lovolite unit, some have different voltage tappings on the transformer unit.
Phil