TigerhawkT3
Flashlight Enthusiast
Does anyone know where to find an AC/DC adapter of around 80V, with at least a 2A rating? A CC driver with 120VAC input and Vmin<76VDC<Vmax ouput would also work.
High-voltage AC/DC adapter
- Thread starter TigerhawkT3
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TigerhawkT3
Flashlight Enthusiast
I'm hoping to avoid the need for an expensive battery and charger, BTW. Any leads?
TigerhawkT3
Flashlight Enthusiast
Anyone come across one?
Mr Happy
Flashlight Enthusiast
You could make one?
TigerhawkT3
Flashlight Enthusiast
I could, in theory, if I knew how to make one or where to get the components, which I dont. :candle: Do you know how, or where to find out how?
I'd like something reasonably efficient, around 80-90%.
I'd like something reasonably efficient, around 80-90%.
Mr Happy
Flashlight Enthusiast
You have given two alternative requirements: a fixed voltage regulator of about 80 V, or a constant current regulator (of how many amps?). Can you be more specific about what you need?
With a little electronic knowledge you could achieve either requirement with a suitable isolation transformer, a rectifier, a filter capacitor, a couple of resistors, and one of these parts: http://www.national.com/mpf/LM/LM317.html#General Description
[Edit: and fuses of course. Never forget the fuses...]
That web site has all sorts of application notes with advice on how to construct circuits using the part. Your main problem when operating at such high voltages will be to avoid letting the magic smoke out of the 317 by exposing it to the full voltage (i.e. shorting the output).
Unfortunately an isolation transformer capable of 80 V at 2 A will be a 160 VA component, which will be quite large and heavy. The lighter alternative would be some kind of switching power supply, but they are probably beyond the electronic beginner to design.
If you want to drive lots of LEDs in series off a mains power supply, maybe you can find one of the off-the-shelf LED drivers designed for fixed home or industrial lighting applications?
With a little electronic knowledge you could achieve either requirement with a suitable isolation transformer, a rectifier, a filter capacitor, a couple of resistors, and one of these parts: http://www.national.com/mpf/LM/LM317.html#General Description
[Edit: and fuses of course. Never forget the fuses...]
That web site has all sorts of application notes with advice on how to construct circuits using the part. Your main problem when operating at such high voltages will be to avoid letting the magic smoke out of the 317 by exposing it to the full voltage (i.e. shorting the output).
Unfortunately an isolation transformer capable of 80 V at 2 A will be a 160 VA component, which will be quite large and heavy. The lighter alternative would be some kind of switching power supply, but they are probably beyond the electronic beginner to design.
If you want to drive lots of LEDs in series off a mains power supply, maybe you can find one of the off-the-shelf LED drivers designed for fixed home or industrial lighting applications?
TigerhawkT3
Flashlight Enthusiast
I wanted to run 20 XR-E dice. Option 1 was an ~80VDC supply with an LM138 for a regulator, at 1.2A max, which explains the 2A rated current I wanted from the AC/DC adapter. Option 2 was a CC driver at 700mA or more that runs off mains power.
Rectifiers, capacitors, etc. are all parts I can get at RadioShack or something. The transformer, though, is something else - I don't even know where to look for something like that.
The highest-voltage AC/DC CC LED driver at DX has a max Vout of 68V, and it's been sold out for months. I can't find a Xitanium of a high enough Vout.
:thinking: :shrug:
Rectifiers, capacitors, etc. are all parts I can get at RadioShack or something. The transformer, though, is something else - I don't even know where to look for something like that.
The highest-voltage AC/DC CC LED driver at DX has a max Vout of 68V, and it's been sold out for months. I can't find a Xitanium of a high enough Vout.
:thinking: :shrug:
Mr Happy
Flashlight Enthusiast
This page has an idea that avoids complex regulation circuits: http://www.marcspages.co.uk/tech/6103.htm
You can work without the isolation transformer as shown in that link but you then have to be very careful about safety (protecting against both fire and electric shock).
I'm sure there are mains drivers from places other than DX but I can't find any links just at the moment.
You can work without the isolation transformer as shown in that link but you then have to be very careful about safety (protecting against both fire and electric shock).
I'm sure there are mains drivers from places other than DX but I can't find any links just at the moment.
qwertyydude
Flashlight Enthusiast
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If you're putting all the leds in series you'll end up with what I call Christmas light syndrome, one burns out and the whole string is dead.
How about a series parallel combination? you can't do 20 as easily but if you can do series strings of 3 and parallel them you can easily use a computer power supply, available rather cheaply. A 3 series string would run 4 volts/bulb, a little high but you can just put a resistor inline. So 7 strings is 21 bulbs.
How about a series parallel combination? you can't do 20 as easily but if you can do series strings of 3 and parallel them you can easily use a computer power supply, available rather cheaply. A 3 series string would run 4 volts/bulb, a little high but you can just put a resistor inline. So 7 strings is 21 bulbs.
Illum
Flashaholic
David, whats with you and ubermassive LED arrays?
If I need a portable flood light you would be first on my list
If I need a portable flood light you would be first on my list
TigerhawkT3
Flashlight Enthusiast
I remember reading that capacitors in an AC circuit act as a DC circuit's resistors, but with less energy loss. Is that what that link is talking about doing? It looks like he's just running it DD off that. I've been reading through it a couple times, trying to figure out what values of cap and resistor would be needed to get a particular voltage. I think the biggest hurdle would be the peak voltage, as 80V RMS would be 113V peak, which would handily fry any 80V device... or does that only refer to current, which would be regulated by an LM? :thinking:
I'll do some more reading about AC, but I think I'd still be happier at this point with a commercially manufactured 120VAC>80VDC adapter, so any leads on that would be nice.
I'll do some more reading about AC, but I think I'd still be happier at this point with a commercially manufactured 120VAC>80VDC adapter, so any leads on that would be nice.
Mr Happy
Flashlight Enthusiast
How about something like the [FONT=Arial, Helvetica, sans-serif]Xitanium LED Driver LED120A0700C24F on this page? http://www.theledlight.com/led_drivers.html
[/FONT]
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TigerhawkT3
Flashlight Enthusiast
I haven't come across any Xitaniums with enough power for this project.
TigerhawkT3
Flashlight Enthusiast
I've been racking my brain and searching the Internet for an efficient way to get a smooth 80VDC from mains 110VAC, but haven't come up with anything. If not that, maybe it'd be easier/cheaper to boost 12VDC (i.e., a single car battery) to 80V. I have no idea where to start with that, either.
Any ideas?
Any ideas?
Mr Happy
Flashlight Enthusiast
Perhaps you may need to think outside the box a little. Do you need to run 20 LEDs all on one 20S series chain? Maybe you could run four parallel chains in a 4P5S arrangement, and then you would only need a 20 volt supply instead of an 80 volt supply. At 700 mA per string you would need 2.8 A in total, and you could manage that using an LM138 as a linear current regulator.
TigerhawkT3
Flashlight Enthusiast
The whole point of a high-voltage array was to increase efficiency. Using an LM at an even lower voltage than the TVL2 (36V, 9-LED) I already have would be nonsensical to me, not to mention current balancing issues.
How feasible would it be to make my own 120VAC>60VAC 2-3A transformer? I'd just need half the windings on one side as were on the other, if I understand them correctly. Does anyone know how to actually go about building one?
Illum
Flashaholic
60Vac? why not just buy a cheap variac?
TigerhawkT3
Flashlight Enthusiast
How cheap? I've found one for $50, but that doesn't seem very cheap. Still, something like this could be handy to have.
Illum
Flashaholic
I was looking at a 3 amp model for $50
I try to avoid werking with AC whenever I can, due to the reason that I don't seem to be able to isolate all my LEDs from the heatsink...it only takes one closed circuit to permit a "hot" plate that could kill if I brushed against the heatsink
I try to avoid werking with AC whenever I can, due to the reason that I don't seem to be able to isolate all my LEDs from the heatsink...it only takes one closed circuit to permit a "hot" plate that could kill if I brushed against the heatsink
TigerhawkT3
Flashlight Enthusiast
Why would you have AC near an LED heatsink? :thinking:
Would the following work?
1. 120VAC>60VAC transformer (variac)
2. Full-wave rectifier (picture is from Wikipedia)
3. Big 300V capacitor
4. LM138 as a driver
5. 20S1P LED array
I'm thinking about getting that variac, especially since it could (in theory, if I've got it right) provide a high-voltage source to run other big LED arrays, chargers, and so on.
Would the following work?
1. 120VAC>60VAC transformer (variac)
2. Full-wave rectifier (picture is from Wikipedia)
3. Big 300V capacitor
4. LM138 as a driver
5. 20S1P LED array
I'm thinking about getting that variac, especially since it could (in theory, if I've got it right) provide a high-voltage source to run other big LED arrays, chargers, and so on.
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