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Re: Help needed please

Posted: Fri Sep 28, 2012 3:16 am
by kila2000
I found this set up on another forum, this is what you were meaning?
Instead of his push switch I would use a toggle so that the capacitor would stay charged until the switch turns off, does that sound right? Or is there an easier way still?

Re: Help needed please

Posted: Fri Sep 28, 2012 7:16 am
by csconsulting
Thats it yup.
You could replace the switch with a toggle no problems at all.

The only thing to watch out is how much current your LED string takes, beacuse during the fadein/fadeout the transistor may get a little warm depending on how many leds you have.

Re: Help needed please

Posted: Fri Sep 28, 2012 7:54 am
by effgee
kila2000 wrote:LEDs start dim and slowly get brighter, as if the core was powering up.
Have a look in the Arduino program, under "File > Examples > Analog > Fading"

Re: Help needed please

Posted: Fri Sep 28, 2012 8:49 am
by kila2000
csconsulting - the LED string this would go to is 4 2v 50ma LEDs. They run off a 12v power supply and so I have an 82ohm resistor wired to them. Is it possible for a capacitor to deliver more than 12volts from a circuit like that?

effgee - I'd love to use an Ardunino to do but they are pricey for me and building a circuit like this is not only cheaper but a good learning tool for me

Re: Help needed please

Posted: Sat Sep 29, 2012 2:20 am
by csconsulting
No, the capacitor in this circuit is only a timing element. It can not provide anymore then 12 volts.

In fact, due to that circuit being an "emitter follower" you wont get anymore then 11.4 volts due to the nature of the transistor.

Re: Help needed please

Posted: Sat Sep 29, 2012 3:56 am
by kila2000
That doesn't worry me too much as I was thinking of adding more resistance to make the lights dimmer anyway. Thanks for your help on this. I have the components now so am gonna play round with it, see what I can get.

Re: Help needed please

Posted: Thu Nov 08, 2012 3:43 am
by csconsulting
How did this work out for you?