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Electrical Engineering Help Needed
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Engineering & Manufacturing > Electrical

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Jul 29, 2012

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Jul 29, 2012
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Job Description

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  • Posted: Thu, Jul 26, 2012
  • Time Left: Closed
  • Location: Anywhere
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  • Start: Immediately
  • Hourly Rate: Not Sure
  • Hrs/wk: Not Sure | Duration: 1-2 weeks
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I am trying to convert a tact switch into a toggle switch and using that to turn on/off an 0.25W, 3V LED driving circuit. This is all fed off of a lithium-ion battery with a range of 3-4 volts.

There are a few ways to drive WLEDs. One way is to use a dedicated driving IC, which can come with shutdown pins. I'm very familiar with that solution and I am using a dual-D flip flop configuration to convert a tact switch into an on-off function. That toggle function feeds into the IC - so if I want to turn it on-off, I just push the switch. It works like a charm.

But what if one wanted to avoid using an IC? How do you link up that switching on-off output to the circuit that drives the LED? There are different ways you can go about driving an LED. Let's look at these categories:

1. LED to resistor to ground - inefficient, LED changes in brightness.
2. [1 MOSFET and 1 Transistor constant current source](  [obscured]  /id/Circuits-for-using-High-Power-LED-s/step6/The-new-stuff-Cons...

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