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Is there a low-cost, less annoying alternative to a buzzer or LED for displaying the status of an operation? I want my clock radio on at night, but it has this really annoying power indicator LED. I'd like to keep some form of power indicator, so replacing the LED with an equivalent diode or just removing it isn't an option, but I also need to have it on. I have the LED removed, I just need some non-irritating indicator that I can still check if I want to, but without emitting any light.

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    \$\begingroup\$ Electrical Tape makes a dandy light filter. \$\endgroup\$ – Passerby Dec 12 '13 at 1:28
  • \$\begingroup\$ Yes, but I want to still see the indicator, just don't want it always on. I have used electrical tape on the stupid green LED that lights the 'enercell' logo on my old radioshack battery charger. I need this one to act as an indicator, though. \$\endgroup\$ – Wyatt8740 Dec 14 '13 at 23:10
  • \$\begingroup\$ Oh, trust me, some leds are so bright that e-tape just dims it. I have an external harddrive with a super bright blue led. With a bandage on top. Still plainly see the led even in daylight. \$\endgroup\$ – Passerby Dec 17 '13 at 20:17
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One indicator variety not mentioned in the other answer is flip-dot indicator: http://www.flipdots.com/electromagnetic-status-indicators.html

Those had been around for ages, and can easily be considered the most non-annoying indicator around, as they don't emit any light but are still perfectly readable under moon light conditions.

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    \$\begingroup\$ Like little solenoid/rc actuators. Pretty neat, never heard of those before. \$\endgroup\$ – Passerby Dec 12 '13 at 4:05
  • \$\begingroup\$ This will not do for the OP's application. The linked indicators retain their state without power. This means you need additional circuitry to flip it when power is lost! BTW, this is why these are so attractive for the correct application. \$\endgroup\$ – DoxyLover Dec 12 '13 at 4:30
  • \$\begingroup\$ I've first encountered those when disassembling an old Vax 750 power supply some 20 years ago - I felt compelled to pluck one out and play with it. For some reason, they never became very popular as stand alone indicators (yet, display matrices with those are pretty common). \$\endgroup\$ – oakad Dec 12 '13 at 4:34
  • \$\begingroup\$ @DoxyLover It can be trivially rectified with a simple edge detector (flip on power on, flip again on power off). \$\endgroup\$ – oakad Dec 12 '13 at 4:37
  • \$\begingroup\$ electronics.stackexchange.com/questions/52147/… \$\endgroup\$ – jippie Dec 12 '13 at 19:29
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Essentially, you'd like to know the status of the clock, when you need to. But, you don't want to see the LED when you don't need to.

Electrical

  • Add a momentary switch in series with LED. When you want to check the status, you can press the button and see the LED.
  • The LED should have a series resistor. Increasing the value of the resistor would dim the LED and make it less annoying, possibly.
  • Solenoid and spring as indicator. When the power is present, the solenoid is energized. When the power is not present and the solenoid is not energized, the spring pushes the armature out. The armature of the solenoid becomes an indicator.

Low tech

  • Tape the LED over. When you want to check the status, peel back the tape. Put the tape back, when you're done.

Humorous

  • Connect an electromagnet instead of the LED. When the LED is on, the electromagnet is energized. The electromagnet is holding a steel ball. Directly under the ball is a metal bowl, such that the ball will make loud noise when it falls. Julius Caesar style.
  • Yoga. The LED will seem less irritating, as might lots of other things.
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  • \$\begingroup\$ Why bother with a spring? A tiny solenoid can be fashioned as to use gravity to return the armature to the rest position. The active position would be held up against gravity. \$\endgroup\$ – Passerby Dec 12 '13 at 1:30

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