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I was hoping someone could help me understand a very simple approach to creating a flashing led. While many simple examples exist, I cant quite find one that allows me to control both the pause rate and display duration times.. for example: led on (emitting) "10ms" led off "30ms" (repeat forever). Or perhaps I swap out a capacitor to creat "led on 500ms" led off "2ms" (repeat forever). Anyhow, I have capacitors to work with, 555 times, resistors, diodes. I'm a real beginner obviously, and do not know how to design around the 555 - but if someone has a very easy suggestion I can attempt I'd appreciate it. I'm attempting to study the effect of "charging" a glow in the dark object with a 3.3v UV Led and thought it would be neat to see the minimal amount of strobing required to energize the glow. Thanks!

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    \$\begingroup\$ for example: led on (emitting) "10ms" led off "30ms" (repeat forever). Or perhaps I swap out a capacitor to creat "led on 500ms" led off "2ms" (repeat forever). That will be a challenge using 555 ICs. Flashlights you can buy that have these functions use a microcontroller which is a cheaper solution than anything 555. There's no need to explain how to make a flashing LED with a 555, there are plenty of tutorials to be found if you look for them. \$\endgroup\$ Oct 8, 2019 at 13:35
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    \$\begingroup\$ This is exactly the sort of thing that Arduino is perfect for. You have a specific application in mind, and don't want to get bogged down in the technical details. \$\endgroup\$
    – Dave Tweed
    Oct 8, 2019 at 13:55
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    \$\begingroup\$ 555 astable oscillator. Two resistors in parallel in charge/discharge circuit with a diode in series with each resistor, opposite polarity for each diode. One controls charge and the other discharge. \$\endgroup\$
    – Russell McMahon
    Oct 8, 2019 at 19:56
  • \$\begingroup\$ Much appreciated thank you all, I'm going to look more into Arduino and micro controllers for future projects - makes a lot of sense since I know programming. I'm also going to give the 555 timer ideas here a try for learning \$\endgroup\$ Oct 8, 2019 at 23:55

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Just Googling "555 astable circuit" will list plenty of web sites. This one: 555 Oscillator Tutorial gives the equations for the on time and off time.

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  • \$\begingroup\$ thanks this really nailed the question because this link outlines exactly how the t1 and t2 times can be produced! \$\endgroup\$ Oct 8, 2019 at 23:58

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