Help needed please

The "Eleven" is our Uno-equivalent Arduino-compatible board, but with a number of improvements including prototyping area, a mini-USB connector, LEDs mounted near the edge, and the D13 LED isolated using a FET. [Product page]
kila2000
Posts: 8
Joined: Fri Sep 21, 2012 12:44 pm

Re: Help needed please

Post by kila2000 » Fri Sep 28, 2012 3:16 am

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?
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csconsulting
Posts: 62
Joined: Fri Sep 21, 2012 7:22 am

Re: Help needed please

Post by csconsulting » Fri Sep 28, 2012 7:16 am

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.

effgee
Posts: 64
Joined: Tue Aug 07, 2012 2:41 am

Re: Help needed please

Post by effgee » Fri Sep 28, 2012 7:54 am

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"

kila2000
Posts: 8
Joined: Fri Sep 21, 2012 12:44 pm

Re: Help needed please

Post by kila2000 » Fri Sep 28, 2012 8:49 am

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

csconsulting
Posts: 62
Joined: Fri Sep 21, 2012 7:22 am

Re: Help needed please

Post by csconsulting » Sat Sep 29, 2012 2:20 am

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.

kila2000
Posts: 8
Joined: Fri Sep 21, 2012 12:44 pm

Re: Help needed please

Post by kila2000 » Sat Sep 29, 2012 3:56 am

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.

csconsulting
Posts: 62
Joined: Fri Sep 21, 2012 7:22 am

Re: Help needed please

Post by csconsulting » Thu Nov 08, 2012 3:43 am

How did this work out for you?

vaiybora
Posts: 5
Joined: Mon Sep 25, 2017 3:28 pm

Re: Help needed please

Post by vaiybora » Tue Sep 26, 2017 12:49 pm

Thank for the good topic,Thanks for your sharing. :P :P

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