Archive for November, 2005
Capacitor Kit
Capacitor Kit
Doe putting a capacitor in series with an LED make the LED fade in and out, or is it not that simple?
I have a little kit that makes a row of LED’s light up back and forth, like the scanner thing on the front of kitt on knight rider. I was wondering if each LED could be made to fade in and out to make it flow smoother. would it work if I put a capacitor in series with each LED?
Yes, that would work. I’m sure your next question will be, “What value of capacitor should I use?” Well, I don’t know the frequency or duration that the LED will flash at, or the voltage and current used, or the resistance in-line with the LED, so I can’t help you further. The amount of time it takes to charge a capacitor like that depends on the resistance in series with it, and can be calculated. Here is an article on that formula:
http://en.wikipedia.org/wiki/RC_time_constant
So, the time constant for a particular capacitor-resistor in series is t = R x C.
If you are not sure what the resistance is (sometimes the resistor is built in to the LED), then you can measure the voltage and current between the LED and common, and calculate it with Ohm’s Law.
Figure that you want the LED to charge up for at least 3 time constants to achieve some good brightness, then remain on for a time before the LED turns off and the next one turns on, so I’d say that you would want a time constant that’s between 5% and 10% of the duration that the LED is turned on, but you may want to make it longer depending on how cool you want it to look.
Another thing that you need to consider is the bias voltage that the LED requires before it turns on. This will delay the LED from turning on immediately, but since the LED before it will also take longer to shut off, it won’t be very noticeable.
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TREBLE BLEED MOD KIT – CAPACITOR AND RESISTOR – DUNCAN $6.45 |
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2 x US made PIO Treble Bleed Capacitor Kit Guitar Parts $8.99 |
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2 x US made PIO Treble Bleed Capacitor Kit Guitar Parts $8.99 |
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.001 uf Treble Bleed Kit Capacitor 4 Fender Telecaster $1.95 |
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2 x US made PIO Treble Bleed Capacitor Kit Guitar Parts $8.99 |
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2 x US made PIO Treble Bleed Capacitor Kit Guitar Parts $8.99 |
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2 x US made PIO Treble Bleed Capacitor Kit Guitar Parts $8.99 |
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