EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: viper on September 05, 2022, 06:52:44 am
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I have an application where I would like to blink or pulse light from a 12VDC LED light strip. The strip has 3 strips of LEDs, all wired to be separate circuits.
I realize simply blinking the lights is simple with a 555 and a pot, but I would like to get a bit more creative and have a few variations of frequency, duty cycle, etc. I would also like to do it differently for 2 of the 3 circuits of LEDs.
Basically all I need to do is switch 12VDC to the LEDs and I am not trying to get nuts with frequency, everything well inside of visual spectrum. Maybe 10hz or so. I figure a MOSFET is probably the best for the switching needs.
However, in all of this, I am trying to keep this simple without having to bring in a microcontroller. Basically for a mental picture, something like how Christmas lights may have different sequences, but they just repeat. Once I decide on a pattern, I probably won't change it.
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The problem is the highly complex circuit to do any sequencing without a MCU or other programmable chip. To do anything more complex that variable on and off time flashing, would require a whole mess of counters, gates and other logic and then you have the complexities of how to store and select the sequence.
However if you are willing to settle for simple variable on and off time flashing per channel, a CMOS 555 for each channel, with two pots and diode steering so the on and off times can be independently controlled, could be used to drive a MOSFET per channel to switch the LEDs.
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Take a look on CD40106 or any other similar IC , you can play a lot with it
(https://electro-music.com/forum/phpbb-files/40106_osc_with_mark_space_schematic_425.jpg)
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What’s your goal: a mental exercise on how to do this without a microcontroller, or the simplest circuit possible?
For the former, you have many options with varying levels of hardware complexity. For the latter, a microcontroller is undoubtedly the simplest (and the code for blinking isn’t hard, either).
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This should give you some ideas of how to blink LEDs in various ways ...
http://wunderkis.de/Blinkenlights/blinkedinger.html (http://wunderkis.de/Blinkenlights/blinkedinger.html)
http://wunderkis.de/Blinkenlights/blinkenlights.html (http://wunderkis.de/Blinkenlights/blinkenlights.html)
(I'm sorry, text is in German, but online translation exists ...)
There's no receipes anyway, just stuff for ideas.
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Hows about the ole classic 2 transistor astable multivibrator.
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A microcontroller is by far the simplest and most flexible choice if you want more than simple blinking off and on, that's exactly what most holiday lighting that has patterns uses. Another way that was once popular is using an EPROM, drive the address lines with a counter and then program your patterns into it.
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Hows about the ole classic 2 transistor astable multivibrator.
(https://www.eevblog.com/forum/projects/looking-for-simple-circuit-ideas-to-blinkpulse-led-strip/?action=dlattach;attach=1583032;image)
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I believe that simple battery-operated flickering LEDs (such as to emulate a candle flame) used cheap ICs programmed with simple tunes (e.g., Happy Birthday) designed for use in musical greeting cards.
https://www.halloweenforum.com/threads/interesting-fact-about-flickering-led-candles.104046/ (https://www.halloweenforum.com/threads/interesting-fact-about-flickering-led-candles.104046/)
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I believe that simple battery-operated flickering LEDs (such as to emulate a candle flame) used cheap ICs programmed with simple tunes (e.g., Happy Birthday) designed for use in musical greeting cards.
https://www.halloweenforum.com/threads/interesting-fact-about-flickering-led-candles.104046/ (https://www.halloweenforum.com/threads/interesting-fact-about-flickering-led-candles.104046/)
Some of them do, others use a LFSR. I don't remember where but somewhere I saw a detailed analysis of several different types of flickering LEDs.
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Thanks for all the thoughts and replies guys! We are moving forward with a microcontroller setup with mosfet switching so we can play around with the tuning a bit easier. Just a one off little project.