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Step 9Another dimming method
ok, so maybe you don't want to use a microcontroller? here's another simple modification on "circuit #1"
the simplest way to dim the LED's is to change the current set-point. so we'll change R3!
shown below, i added R4 an a switch in parallel with R3. so with the switch open, the current is set by R3, with the switch closed, the current is set by the new value of R3 in parallel with R4 - more current. so now we've got "high power" and "low power" - perfect for a flashlight.
perhaps you'd like to put a variable-resistor dial for R3? unfortunately, they don't make them in such a low resistance value, so we need something a bit more complicated to do that.
(see circuit #1 for how to choose the component values)
the simplest way to dim the LED's is to change the current set-point. so we'll change R3!
shown below, i added R4 an a switch in parallel with R3. so with the switch open, the current is set by R3, with the switch closed, the current is set by the new value of R3 in parallel with R4 - more current. so now we've got "high power" and "low power" - perfect for a flashlight.
perhaps you'd like to put a variable-resistor dial for R3? unfortunately, they don't make them in such a low resistance value, so we need something a bit more complicated to do that.
(see circuit #1 for how to choose the component values)
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I've been looking at modifying to be adjustable.. I'm thinking you can use a 10ohm 25-turn trimpot:
3299P-100LF-ND
http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=3299P-100LF-ND
Then use the pot in "parallel" with the other values needed to create 1000mA, then turn the pot "up" to increase the ohms, therefore lowering the current. (4x) 2ohm redistors, in parallel.. gives 0.5ohms. As long as the trimpot goes down to 2ohm.. then you just need (3x) 2ohm resistors, as well as the trimpot.
http://www.1728.com/resistrs.htm
Sounds good anyways................ :)