Backlight LED Switch

[rceckspurt13]

Ok heres what im thinking:

This is all based on the assumption that the connections here (in the red circle) are the positive and negative of the backlight:

My idea is to connect the trigger leds up to the positive and negative of the screen. This would make it so that you could control the brightness of the led swith the screen button. Also when the backlight is off, the leds will be too.

also if it wont work to hook it up that way, could you hook it up to just the positive point of the backlight connector and then a seperate ground?

let me know if this will work. Thanks.

[psp339]

Use a multimeter and test which pins gives out power.

[rceckspurt13]

I dont have a multimeter that i can us efor this kind of testing. thats why i had to ask.

[cameron14]

the two pins in the middle are nothing
but it is 40volts dc so thats probably to much
i even tryed it with two multimeters

[gr8npwrfl]

You could use two n channel mosfets to switch the gate with 40 volts and yet the drain would
be able to run at 3.3 volts.

Yes you could use it to switch if you want.

[ryan0]

You could do it without risking losing brightness from the backlight simply by using an lm386,do not use the same size resistors as the sound mod,I'd recommend attaching a 20 ohm on the +,hook that up to the lm386,put a another 20 or so ohm on the output of the lm386,this is so there will be a noticable difference in the led's between each brightness level,because the backlight will provide half the current and the psp will provide the rest,this stops or severely reduces the risk of the led's draining any brightness from the screen

[ryan0]

woah 40 volts?I didn't know it was that high,I thought it was only 5!I learn something new everyday XD,if thats the case you will need a step down converter which is a pain in the ass cos theres heatsinks and other annoying things involved (not that I don't like heatsinks,but they'd be hard to get into a psp)

[rceckspurt13]

Couldent you use resistors to get it down to a managable voltage? And I dont understand how it gets 40 volts from a 3.6 volt battery? Could someone explain it? I'd like to know.

[Bhawan]

for that you need something called a transformer(no it wont transform into a robot and stall shooting stuff, if it does try to be kind and cool with it). ..... resistors are just to control the flow or amount of electricity that flows through the circuit but for voltage, you need transformer... a transformer has four legs coming of of it one pair for input (+)and(-) input and other for (+)and(-) output........ i hope that helps

[rceckspurt13]

so this won't be as easy as I thought.  Sounds like I would need a transformer or step down converter, lm386, and resistors. If I'm getting this correctly, I would have to take the positive and negative from the backlight and run it through the transformer and then to the inputs of an lm386. Then connect the lm386 power supply to a +5 point and a ground. Then I need to connect the LEDs to the output of the lm386. Well it was a good thought I think. I didnt know it would be so complicated. I figured I'd just solder some LEDs to the + and- of the backlight. Well thank you all forletting me know how wrong I was.

[ryan0]

to sum this project up,get a suitable step down converter (40vac-5vdc),then do what I said above,if you need me to draw a diagram then just pm me,
ryan0

[gr8npwrfl]

You can step down with a zener diode and a resistor running into an n channel mosfet. The zener would clamp
the input voltage down to a manageable level and the fet would isolate it. It would then only be
an on off switch at whatever level you want.

[ryan0]

You can step down with a zener diode and a resistor running into an n channel mosfet. The zener would clamp
the input voltage down to a manageable level and the fet would isolate it. It would then only be
an on off switch at whatever level you want.

would that also convert it to dc?

[gr8npwrfl]

one more diode in series would make it close enough to DC so you
would not see a flicker

[ryan0]

would a capacitor not do the job better?

[gr8npwrfl]

The capacitor will not rectify like a diode. It will only smooth out the waveform.

Full wave rectifiers use capacitive filtering on the output to remove spikes
that are short duration.

The waveform that a capacitor would create is just a longer period sine wave.