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DVD Player Power Supply

BlueFusion

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They hook up a variable dummy load. Something they KNOW the curent draw from. I don't think it's that hard to work out.
If you connect a known load and measure the current, you get a reading. They simply hook up the biggest load they can before it blows, then rate it slightly lower than it's absolute max for safety.

Eg if you have a unknown psu, hook up a variable resistor across it (don't do that, it's probably not a good idea) with a meter, then read the current while turning the pot down. When you get to the end of the pot that's ikely the max output, and will also likely fry your meter if done that way. So please don't. However, the psu's max load is most likely the max current you can read with no load at all, just shorting the outpuit with the meter. Again, PLEASE DON'T DO THAT! Just an example!!!
 



Gazoo

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Yeah, Computers are used to design circuits...pretty much plug n play or plug n poof.. ;D But at least it's done in a virtual setting so if it goes poof it's easy to go back to the drawing board.
 

o_DEATH_ANG3L_o

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Oh ok I think I get it now, finally lol :p Anyways what would you guys suggest for a load to determine the max current output of my PSU? Keep in mind I am running 3.3 volts. I am wishing to use this PSU for a GB LD and want to know what I am dealing with as far as max current the PSU puts out at 3.3 volts.
 

Gazoo

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It looks like there is a fuse tucked under the wire in the upper right corner and the rating of the fuse is wrote on the board but I can't tell what it is.. but whatever it is this is the max the power supply can deliver. But the current ratings of the independent voltages may be different. So what is the current rating of the fuse?
 

o_DEATH_ANG3L_o

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The writing on the circuit board buy the fuse says 250V 2A. I just got back from Wal-Mart and I got a multimeter so I am gonna test some LEDs and the current I will post to let you know.
 

o_DEATH_ANG3L_o

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Ok so I tested some current finally. :) I hooked up a small blue LED from one of those little key chain things. The reading I was getting is like 20.5 to 22.0 mA. So what does this tell me?
 

ericab

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Death Angel said:
Ok so I tested some current finally. :) I hooked up a small blue LED from one of those little key chain things. The reading I was getting is like 20.5 to 22.0 mA. So what does this tell me?

the current of the L.E.D :p
 

BlueFusion

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You're looking at maybe 10 times that for a GB LD. Go to ratshack or fleabay and get a 1 or 3 watt LED, then hook that up. That will most likely tell you the max power of your PSU without breaking anything.
 

chimo

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As the others have stated, all it tells you is what the power supply will do with that particular LED.  Be careful with that power supply, the right half has main-level voltages.

At 3.3V, the SMPS will most likely be able to supply enough current to immediately fry the GB diode.
The big questions are:
- is it actually voltage regulated
- how much ripple voltage
- how much noise does it produce

If you don't have a scope to hook it up to, you are taking risks with your LD.

So what to do...

1. Work safely around energized circuits. On the right side of the PS, there is enough energy there to kill you.

2. Check if the 3.3 V output is regulated.  Measure the unloaded voltage and the voltage with several loads including a load that will draw the current you want to run your LD at. (e.g. if it's regulated (3.3V), try a resistor around 16 ohms for around a 200mA drive current - measure the actual resistance and voltage).

3. If #1 checks out, put a large capacitor and a 10k resistor across the output to help filter the output (actually the resistor is just to drain the capacitor).

4. Understand that this still may fry the LD because the PS may be noisy or produce spikes during start-up and shut-down. Ask yourself if it's worth using this PS.
 

o_DEATH_ANG3L_o

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Thanks Chimo I guess that makes a lot of sense to me. Yeah it would probably fry the LD. I was getting 125 to 130 mA readings from 2 white LEDs. Besides with Daedal's circuit, it is probably the safest way to go for the LD. So what is the operating voltage and current of those GB LD's?
 

chimo

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You will find the spec sheet in the GB thread.  You will also find numerous posts on mods using these LDs and the various operating currents chosen.

Death Angel said:
Thanks Chimo I guess that makes a lot of sense to me. Yeah it would probably fry the LD. I was getting 125 to 130 mA readings from 2 white LEDs. Besides with Daedal's circuit, it is probably the safest way to go for the LD. So what is the operating voltage and current of those GB LD's?
 







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