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Gallery, Projects and General => How do I?? => Topic started by: RussellT on November 17, 2015, 04:26:01 AM

Title: 48V lamp
Post by: RussellT 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
Title: Re: 48V lamp
Post by: awemawson 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
Title: Re: 48V lamp
Post by: RussellT 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
Title: Re: 48V lamp
Post by: awemawson on November 17, 2015, 08:18:28 AM
Here if you need it :)
Title: Re: 48V lamp
Post by: BillTodd 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
Title: Re: 48V lamp
Post by: John Rudd 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:
Title: Re: 48V lamp
Post by: RussellT 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
Title: Re: 48V lamp
Post by: John Rudd 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....
Title: Re: 48V lamp
Post by: John Swift 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


 

Title: Re: 48V lamp
Post by: Manxmodder 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.
Title: Re: 48V lamp
Post by: BillTodd 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.
Title: Re: 48V lamp
Post by: BillTodd 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
Title: Re: 48V lamp
Post by: Swarfing 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?
Title: Re: 48V lamp
Post by: Swarfing on November 18, 2015, 11:27:27 AM
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
Title: Re: 48V lamp
Post by: BillTodd 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)
Title: Re: 48V lamp
Post by: Swarfing on November 18, 2015, 03:15:09 PM
I would have to agree with you totally on that Bill
Title: Re: 48V lamp
Post by: sparky961 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.
Title: Re: 48V lamp
Post by: RussellT 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
Title: Re: 48V lamp
Post by: srp 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.
Title: Re: 48V lamp
Post by: hermetic on January 22, 2016, 04:32:24 PM
If itm is a lovolite unit, some have different voltage tappings on the transformer unit.
Phil