/diy/ - Do It Yourself

[Anonymous No.408829]

I live in the third floor of a guest house, and the stairs have no light and i'm a nocturnal animal, so everytime i need to get to the kitchen or the store i have to do it really slow since it's dark as fuck and the owner has no plans to waste more energy on a lamp, so i proposed him to use a single led to light up the stairs telling him that it would only need about 1 watt(i could use a flashlight, but fuck the place it's really dark and i'm not the only one that needs the light at night).

(Third world problems, i know)

So i wanted to turn an old cellphone charger to power a led, but i don't know if i need a resistor or something else, and also i need to know if the cellphone charger actually waste energy just for being pluged to the wall plus the energy needed to power the led.

Charged specs: 5.5v 550mA
Led ? dunno you guys tell me, there is a electronics store nearby so i guess i can get the one you guys tell me.

[Anonymous No.408855]

>if the cellphone charger actually waste energy just for being pluged to the wall
yes

Why not just use a switch?

To power an led, you need a resistor to "drop" the extra voltage.
The Voltage it needs to drop is (5.5V - LEDforwardVoltage)
Use 80% or less of the LED maximum current.
R = V / I
The resister value = (5.5V - LEDforwardVoltage) / (LEDmaxCurrent * 0.8)
Round up to the nearest common value

[Anonymous No.408862]

>>408855
Thanks.

[Anonymous No.408881]

>>408855
While the resistor does drop voltage, the true reason to use a resistor with an LED is to limit current so that the LED does not burn out. By determining the voltage drop across the resistor and how much current is going through the resistor, you can determine what wattage rating to use and how much power is being wasted.

[Anonymous No.408882]

honestly I'd suggest hanging a nail and just getting some sort of battery powered thing rigged together.

Hell, actually, is there a window or anything? and do you have access to any of those solar lamps? could lengthen the wire for one of those things a bit and hook the panel in the window

[Anonymous No.408896]

Runs off of AAAs
Or those round Tap On lights you see on TV

[Anonymous No.408899]

You can get a battery operated light at a dollar store. Or a night-light. Hardly seems worthy of a diy project.

[Anonymous No.408924]

>>408881
Six of one, half a dozen of the other

[Anonymous No.408936]

run a long extension cord along the wall and plug in a led night light that has a movement sensor.

[Anonymous No.408978]

one of these will do exactly what you want:
http://www.bunnings.com.au/products_product_nightlight-sensor-mort-bay-battery-operated-led-0765_P4350230.aspx?search=shed&searchType=any&searchSubType=products&filter=categoryname--Night+Lights

first link i found

[Anonymous No.408993]

Ask if you may also paint the walls and ceiling in the stairway. Any light color will help maximize the light you install. Even in the 3rd World a gallon of paint isn't that expensive. And sweep the steps while you are at it.

[Anonymous No.409005]

Why not just get a flashlight op?

[Anonymous No.409057]

>>408993
Yeah, white walls and ceiling will help enormously OP if you're installing one very small, faint, lightsource. The ceiling may be the most important as that'll be the primary reflector once someone's body occludes the passageway.