Just a flashing circuit . . .

Discussion in 'The Projects Forum' started by Bluestribute, Jun 7, 2011.

1. Bluestribute Thread Starter New Member

Jun 7, 2011
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I'm a big n0000b when it comes to this stuff, so please bare with me as I have read up and tried to do some research but can't really find an answer to my question. Anyways, here's my question: How can I make a flashing LED circuit using a pot to control the flash rate?

I'm building a guitar and want it as unique as possible, so thought a little something like this would be cool and easy. I'd like to do it for the inlays (so maybe around 10 LEDs in this setup) so they flash, but have a knob (like the volume knob, tone knob, etc) to control the flash rate from slow to so fast it looks like they are just constantly on.

And I have googled it and searched it but nothing that would help my specific cause.

Apr 5, 2008
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3. Bluestribute Thread Starter New Member

Jun 7, 2011
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I read that and it seems more complex then what I'm going for. Isn't it possible to just add a variable resistor to the first figure (1.1) to achieve some sort of controllable LED series (even though I'm guessing that would control brightness and not flash rate, which I can deal with)? That's basically what I'm wondering- where/how do I add a variable resistor to a simple LED circuit to have some control over it (and hence, another "useless" knob on the guitar =)!)? So if I go and see a simple flashing circuit diagram, I can be like, "I'll just replace this with a potentiometer".

I'm assuming I just replace a resistor with the pot and then do some math to figure out what the other resistor needs to be?

Last edited: Jun 7, 2011
4. wayneh Expert

Sep 9, 2010
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Won't work, not easily anyway. LEDs are current devices, not like voltage devices for which pots work great. What I mean is that, near the voltage where they start to light up, say 3v, they will go from very little current (<5mA) to bright (20mA) to destroyed (>30mA) by, say, 3.5v. Those voltages depend on a lot of things including color of the LED, but the point is true for all of them. So dimming is usually done with a simple (eg. 1 transistor) current control or, preferably, a pulse-width-modulated PWM control. PWM is much more efficient and gives smooth control over brightness. To achieve flashing, you would use another 555 timer circuit. All this is described well in Bill's writings.

5. Bluestribute Thread Starter New Member

Jun 7, 2011
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Alright, I think I'm gonna bookmark that thread and do some more research on this

Mar 24, 2008
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