Homemade 9 Volt LED Nightlight

Bmccue1964

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Dec 31, 2001
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Based upon prior postings, I took an old 9 volt battery and removed the clip portion. I then soldered in a 270 ohm resistor and 1 single white LED to the connections. The whole works were then potted in epoxy. The light puts out enough light for close up reading and also enough light to "bump proof" an average sized room in the dark. Provides enough light in a bathroom to enable "functions".

As of 8:30am this morning, the light has been running for 2 WEEKS without any noticeable decrease in output (new 9volt alky battery at start).

Simple to make and very useful in an emergency.
 

WildRice

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Nov 30, 2003
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Just out of curisoty, can you check what the current pull is. I have seen whites draw 1mA or less and still put out enough light to be usefull for the above purpose...
Jeff
 

paulr

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Mar 29, 2003
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Led VF = about 3.6 volts, so when the battery is new there's 9-3.6=5.4 volts across the 270 ohm resistor, which would be 20 mA. I don't think an alkaline 9v cell can supply 20 ma for two weeks nonstop. If you measure the battery voltage with a meter I bet you'll find it's dropped a lot and the light is actually much dimmer now. It's quite hard to notice differences in brightness when the color doesn't change. It really doesn't take much light to see around a bathroom once you're dark adapted.
 

Bmccue1964

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Voltage at battery terminals is now 6.65 volts. I can't measure the amperage since it won't register, so perhaps a slight reduction in output has occurred. However, my rough "reading in the dark test" still works.
 

Bmccue1964

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Well the light ran over 3 weeks before it lost its usefulness.

I then assembled 2 white LEDs in series with a 50 ohm resistor between them and assembled like above. They were very bright and ran for 2.5 days at an uncomfortable intensity to look at.

My next goal is to use the same 2 LED approach, but use a 1K ohm resistor instead. In addition, I'd also like to bridge the 1K ohm resistor with a 50 ohm resistor attached to a momentary SPST switch. This should allow the light to glow for quite some time so it can be found, and then the light can jump up in intensity when a flashlight is needed.
 

paulr

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Mar 29, 2003
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Why not use an spdt switch so you can flip between low and high intensity. That's pretty much what Paklite charges $20+ for.
 
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