Recent content by Revolvr

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    LEDs and resistors

    SparkFun sells a little boost regulator circuit board using the NCP1402 chip. It outputs a fixed 3.3V with an input as low as 1V. It can source up to 200mA but that depends on the input voltage. You might still need a small resistor depending on the Vf and If. This and one D cell and you can't...
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    opinions on ways to wire led series in "high/low" mode/ and cooling question

    Re: opinions on ways to wire led series in "high/low" mode/ and cooling question I agree. The easiest way to do it is to have the switch select between two different resistances. Then just worry about the right resistance on each branch. So in your case you need about 0.68 for 2300 mA, and...
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    opinions on ways to wire led series in "high/low" mode/ and cooling question

    Re: opinions on ways to wire led series in "high/low" mode/ and cooling question I am not sure I see any need for that diode. Electricity will either flow thru the yellow wire or the orange wire.
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    how can I power these led in the house?

    Often a single 5mm LED can be powered directly off a 3V button cell battery like a CR2016. The battery has enough internal resistance to keep the current down. But it won't last too long. My wife has a few simple LED decorations around powered by button cells but they don't last. So I end up...
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    Powering 12V Strip with 16v laptop supply possible?

    Each of the 3 LEDs are in series with one current limiting resistor, probably 100 Ohms to give about 20mA at 12V, assuming a 3.3V drop across each resistor. 16V would up the current from 20mA to about 60mA. This probably won't fry the LEDs but it will certainly shorten their life. I suppose you...
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    power supply for LEDs

    12V LED strips are wired with every 3 LEDs in series with a current limiting resistor to make up the difference between the 12V and the LED Vf. This is why the cuttable segments will have 3 LEDs and their resistor.
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    First Build: Need HELP matching drivers & batteries to the LED

    One host that might work well is the Dorcy 41-4750. This is a yellow plastic flashlight I've seen on Amazon for around $15. It uses a Cree XR-E on a 20mm star at a nominal 700mA, and 4 AA batteries. The good thing about it is that there is lots of room behind the LED for a circuit board or two...
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    First Build: Need HELP matching drivers & batteries to the LED

    Thanks for the feedback. I might give one a try. Did you decide on a driver and host? BTW, like the idea of testing these with currency. I have quite a few bills from several countries I could try. But I need to catch me a scorpion. ;)
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    First Build: Need HELP matching drivers & batteries to the LED

    Not necessarily. This LED will draw 700mA at some voltage between 3.9V and 4.5V. If it happens to be 3.9V there's a fair chance a fully charged 18650 will smoke it. If 4.5, probably not. First thing I'd do when I got the LED would be to test it on a variable power supply with an ammeter and...
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    Inexpensive little AA light Sipik68 & Clones.

    You're right of course, who would mod a cheap $4 flashlight? Well probably a lot of us, just for the fun of it. I wouldn't mind making an UV version if I could find a decent high powered UV LED. For scorpion hunting. BTW, like the pop pop boat. I had not heard of these until I saw your sig.
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    Inexpensive little AA light Sipik68 & Clones.

    The one on the left looks like a Cree XP-G. I don't recognize the others. I have 2 of these, one branded UltraFire, the other Sipik. My UltraFire has the same LED as the one on the left. The Sipik has the other. I've see the Sipik web page, and I'm convinced my Sipik isn't a real Sipik. The...
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    Inexpensive little AA light Sipik68 & Clones.

    An AA battery provides at most about 1.5 volts, decreasing to 1 volt as it nears end of life. Meanwhile the LED typically requires around 3.1V. So the driver has to boost the voltage to provide the current and often will provide up to around 500mA. The Li-Ion 14500 provides about 3.6V or more...
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    Inexpensive little AA light Sipik68 & Clones.

    If one were to eliminate the requirement to run off AA batteries and use the 14500 only, then there are lots of options. Assuming it uses a standard 17mm driver that is. Probably a 3,4, or 6x AMC7435 would do, though I forget off-hand what current I can draw from a 14500. I have several of...
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    Need Fast Help With My UltraOK(really budget) flaslight

    I have one budget light that won't work if the tail cap is screwed in tightly. I loosen it slightly and it works. I haven't figured that one out yet.
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    XM-L-sized SK98 clones; any good?

    Re: XM-L-sized SIPIK68 clones; any good? Thanks. BTW, my Ultrafire branded 68 doesn't have the indents in the LED retainer ring, but the Sipik branded unit does. Frankly I'm not convinced either one are actually UltraFire or Sipik. But still, not bad lights for the price.
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