LED Lighting: One "Dead" D Cell at a Time.

Intro: LED Lighting: One "Dead" D Cell at a Time.

I currently have an ongoing supply of "Dead" (actually half used) alkaline D cells from a local manufacturing company. They use D cells in a couple of pieces of equipment as well as the automatic paper towel dispensers in all the restrooms. I understand from my friend who works there that they are charged a fee to dispose of them properly. So we are being green by completely depleting these batteries instead of buying new ones and also saving this company money. I believe the towel dispensers are the reason why so many of the batteries I get test at 1.1 to 1.4 volts. I assume the motor that turns the great big roll of towels draws a lot of current.

I bought a two pack of Eveready single D cell flashlights (model: EVEL152S). You can get these for under $5 if you shop around. They work well and I really like the click on / click off push button switch. I like mine (pictured above) better as a reading light and task light and emergency light around the house because of the following features:

Variable control for light intensity

RCA / Phono jack output for interchangeable LEDS.

The output jack also allows you to connect any length RCA cable to run the LED where needed.

Operates from 0.5 volts to over 3 volts input voltage under load.

Can be used to power other external 3 - 3.5 volt circuits (I have powered an LM386 amplifier circuit with it).

STEP 1: The Circuit

This circuit uses a circuit board removed from my favorite flashlight to hack. The Rayovac BRSLEDPEN-BA single AAA LED pen light. It is a nice little light as is. I believe the specs say 5.5 hours with the supplied zinc carbon battery. You should be able to find this flashlight for $3.50 - $4.00.

My testing shows that the circuit puts out about 3.5 volt with an input voltage all the way down to 0.5 volts under load (which is not much of a load). So this circuit makes a nice replacement for a joule thief. I plan on testing the circuit driving two LEDS to see how many hours it will run but I have been dragging my feet since I have dozens of free, half used ones. Doing the math based on the specs on the Rayovac packing, I come up with 160 hours with a new alkaline battery. We shall see starting this weekend. I will update. The lit up LEDS shown in the pictures are "Piranha" type LEDS. I bought these from Lighthouseleds.com.

We have the results.

Run time test: 144 hours (equal to 6 hours a day for 24 days).

Testing was done done with a new Rayovac "High Energy" alkaline D cell ($7.97 for a six pack).

Comments

[rafununu]

Something is wrong in your schematics, you can't have a 5k pot in serie with the Led and this for 2 reasons :

1) a white Led has a trigger voltage of 3v min. which leaves 0.5v max. for the 5k, implying an intensity of 0.1mA, this means 0.3mW for the Led, I don't think such Leds exist appart from special domains.

2) when the pot value decreases close to 0, the max available intensity, delivered by the converter, passes thru the pot and it simply burns.

[luxstar]

And yet is works. Try it.

1. The circuit works fine before being modified with the LED supplied with the flashlight, a new LED or multiple LEDS, So your first comment about knowing if this type of LED exists is invalid.

2. I am adding an additional resistor to the one in the original circuit so no problem there (and also no problem with anything burning).

I also run 4 LEDS in series with 12 volts and a resistor. Figure that one out.

Try it.