Help building a 220 to 4 volts 3 Amps PSU

[HellasTechn]

Good day to all.

I need to build a 220v to 4v 3A psu.

Okay here is the story. On the ship that i work we have a submersible searchlight for when we dive at night. this light uses an 220v incandescent lamp. it is watertight but we have accidently broken the glass. We can not replace the light and we can not have an other one made. So we decided to replace it with a plastic one. Now we can no longer use the incandescent lamp because the heat that produces will destroy the plastic. On the other hand we could use a LED lamp but the led lapms i have found do not produce strong light So i thought maybe use a LED like this one http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Discrete-Directional/XLamp-XML
it is a cree XML-T6. The problem is that it runs on 4.2 volts and upto 3Amps.

Do you think it would be possible for me to build such a psu at a size no bigger than a E14 lamp ?

Or anyone could suggest something better ?

Thank you all !

 

[Gryd3]

I don't see why not... I guess it depends on what kind of space from the original lamp size you want to use... just the E14 socket, or a portion of the bulb as well?
Are you looking to construct this yourself, or have it sent out to get constructed?
Are you comfortable with a soldering iron?

You will need to build a 'constant current' driver for that LED.

 

[HellasTechn]

As long as it will not be bigger than a E14 candle lamp i am okay.

I will construct it myself and i can say that i am a pro as far as useing solderig iron. I have also experimented on makeing PCB's i have made several pcb's useing copper etching method.

I also think that i could manage with SMD's .

 

[HellasTechn]

You will need to build a 'constant current' driver for that LED.

Yes. that is for sure. I dont have any schematic though

 

[(*steve*)]

I guess you're saying that the lamp is powered from 220V.

Is there an option to change it so the power supply is external? If so, a 3A constant current source could be external to the unit.

On the other hand, you're using an approx 12W LED. I have a 12.5W commercially made bulb in my office that is pretty bright.

See here. Would that style of bulb fit? What is the wattage of the current bulb?

Oh, and if the lamp is submerged, wouldn't that keep the plastic cool?

 

[Gryd3]

Yes. that is for sure. I dont have any schematic though

It's always safer to bring the proper driving method for it anyway, but it sounds like you know what you are doing and just need help buttoning everything up with some design ideas.

I guess you're saying that the lamp is powered from 220V.

Is there an option to change it so the power supply is external? If so, a 3A constant current source could be external to the unit.

On the other hand, you're using an approx 12W LED. I have a 12.5W commercially made bulb in my office that is pretty bright.

See here. Would that style of bulb fit? What is the wattage of the current bulb?

Oh, and if the lamp is submerged, wouldn't that keep the plastic cool?

Can you elaborate on the use of this lamp?
I'm assuming it is tethered to the craft, if so, how long is the tether?
Also, depending on the construction, Steve bring up a good point about the external water cooling the plastic lens.. We do not know what you are actually using though

 

[Fish4Fun]

@ the risk of using the "easy button" why not just buy an LED driver? If you have trouble finding one that converts directly from 220V to 4V x 3A then why not just get a 220V to 12V "universal" SMPS then use any one of a number of "adjustable" CC/CV converters? Obviously it is easy enough to design/build a 220V to 3A DC Constant Current Driver, but I can't see there being a cheaper/easier way than using readily available existing products....If you MUST build one, then starting with ~12V (really anything between 9V and ~48V capable of continuous duty >> ~40VA) will greatly simplify the build....and make it a lot safer!

Of course you could just get a 12V submersible light, lol, they are readily available in a wide range of output wattages....I really don't like the idea of a 220Vac DIY submersible light for use where people are diving....and I am not even really the "cautious type"....

Fish

 

[HellasTechn]

One big thanks for your suggestions and interest.

I neglected to say that this light is fitted into a jet machine that we use to dive that is powered from the vessel through a thick cable. Yes the lamp runs under 220V. I dont remember the wattage of the lamp but i can find out tomorrow

External PSU is really not an option for me...

One other correction is that the lamp is not E14 but E11 !!!!

The water will cool the plastic but the surface from inside will become blurry.

So as far as my mind can get the only options i have is either to buy the glass wich is very expensive plus they ask minimum order of 50 pcs or buy the plastic and use the incandescent lamp and pray it doesnt get messed up or use a LED lamp somehow.

To be honest i think the LED with the appropriate psu will solve the problem

I am still open to suggestions.

 

[(*steve*)]

To be honest i think the LED with the appropriate psu will solve the problem

Given that LEDs a re already quite directional, you can probably use something like a COB LED module and have the space between it and the reflector for the power supply.

If everyone closes their eyes (except you HellasTechn), I have a quick and dirty solution:

Assuming that your 220V is clean, and that it is stable in frequency, you could simply use a capacitor to limit the current to the LED module. Essentially a capacitor in series with your 220V, then a bridge rectifier, some smoothing, and then straight to your LEDs.

This is a horrible solution (mostly due to safety) but you are building this in an enclosed space.

If you have motors and other things placing large spikes on your 220VAC, you'll need to filter the mains using a inductor to ensure these spikes don't damage your LEDs (they'll go straight through the series cap. A filter capacitor will help absorb some of the energy.

If you have a cap on the output of the bridge rectifier, ensure that the LEDs are always conected. If the LEDs get disconnected, the voltage on the filter cap will build up and can destroy the LEDs.

A proper design will also have some series resistance to limit initial current as well as resistors to leak away charge on the caps.

 

[HellasTechn]

What i am worried about it this case is that if for some reason the LED is off the circuit (if it burns or leads get desoldered) then dont we risk shorting the 220 ?
And yes there are large propellers so i assume there are voltage spikes but that is not for sure.

but i could build one psu like thar and test it before i put it to use.

Could you give me a schematic and parts list ?

Thank you !

 

[HellasTechn]

the last diagram looks ok to me But could i use a 4 volt zener ? and can it supply at least 2.5Amps ? and last if the LED gets hot and starts drawing more current ?

besides i think theese psu's cant deliver more than 150ma

 

[(*steve*)]

Here is a page describing the process. Note that in the calculation of the resistor he uses W instead of Ω (but an Ω symbol can be rendered as a W, so it may not be entirely his fault)

For a given frequency the capacitor determines the current (since the LED voltage is very small compared with the mains voltage). I recommend a capacitor across the LED

For higher currents I would also recommend a fuse rather than relying on the resistor to be a fuse (in fact I'd wire in a fuse anyway)

 

[HellasTechn]

Here is a page describing the process. Note that in the calculation of the resistor he uses W instead of Ω (but an Ω symbol can be rendered as a W, so it may not be entirely his fault)

For a given frequency the capacitor determines the current (since the LED voltage is very small compared with the mains voltage). I recommend a capacitor across the LED

For higher currents I would also recommend a fuse rather than relying on the resistor to be a fuse (in fact I'd wire in a fuse anyway)

Are you sure that it could handle more than 2.5 amps ?

I dont think it can.