The Light in the picture I call the Star of Tucson. I had done a lot of experiments with 1-watt bead lights. when I looked up I had 18 wired units. I decided to solder the LEDs directly to each other. the 18 were waste, what a drag. I decided to make a light with them. I had made one years before. the light's characteristics were a piece of Romex, about a foot, for flexible light placement, LEDs for low power use, D cells for outrageous run time, and a big panel switch wrapped in Romex. unfortunately, 18 LEDs put out a lot of light and draw about 500 mA. it ate 3 batts in about 3 days, I did the math, that seemed about right so I projected 8 LEDs in parallel. the voltage drop is just over 3 volts so 2 batts in serries would drive an LED with no load resistor, on 4 Ds. 2 in series 2 in parallel. i think the real current is about 24 mA. I got like 1000 hours it would run continuously that's like 42 (The ultimate answer to the meaning of life) days. I did a quick cost analysis, $17.00 that's too much! the big cost was batt holders, $2.50 apiece, 4 is $10.00 bucks. I came up with a D cell holder for less than $0.50. The switch, a good one can be as much as $20.00. Switches are boring so I was looking for a way to "turn on" the light. I think a hall effect will drive the light directly It is just over. I could use an optoisolator to drive the 24 mA LEDs even if I did this the cheapest switches i could find were like 5 for $12 about 2 bucks. hall effect, magnet, and driver, less than $0.50. suddenly the price was like $4.00 my stained wooden batt holder is much cooler than the plastic one. moreover, the switch to the public is different. a washer under the turnon point will make for an eye-catching cheap device. that can be sold all day long at $20.00 bucks.
Schematic???????
It is pretty simple. the diodes can be connected to the power source directly in parallel. they draw around 5 to 10 mA I'm not sure. it works. the 18 one-watt beads draw like 500 mA. and drain the batts in like three days. the one I'm making for gifts. I project the 8 five-watt LED they have a different voltage drop of around 3 volts and will run 42 days continuously if I did the math right. the 5 watt and 1 watt are the amounts of light they make. so the 8 LEDs will look like a 40 watt light bulb but is actually about 25 mW. there is too long a piece of Romex. it should be about a foot. just enough to carry the light and bend to use.
Hi,
Thanks for the info, BUT what are the Hall Effect and Optocoupler devices.
Can you list part numbers and more clearly mark how they are connected, pin names etc.
That Opto has 3 pins, usually they have 4pins.
Tom... 
High Power Led Chip, 5w White Super Bright Intensity SMD Cob Light Emitter Components, Diode Bulb Lamp Beads for DIY Lighting (02)
Price: $8.89
Gikfun A3144/OH3144/44E/AH3144E Hall Effect Sensor Magnetic Detector for Arduino (Pack of 20pcs) EK1325
Gikfun OPTOCOUPLER DIP-4 PC817C PC817 for Arduino DIY (Pack of 20pcs) AE1143
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i have not done this yet. this was what i was going to use.
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