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General Category => General Discussion => Topic started by: Vlk on April 16, 2015, 12:15:12 PM

Title: Can someone help a complete amateur with LED fading effect please? :-)
Post by: Vlk on April 16, 2015, 12:15:12 PM
Hi folks!

I just started a little project - a thing I need to do in order to finish up a gift for my fiancee. The problem is, I am totally new to electronics. :-) I've never build a single thing and all my electronic experience starts and ends with charging up my phone or my camera... :-D
So all these circuit plans I found on the web are really fun and nice, but I am very lost in them, although I can imagine they as clear and simple as they can get.
I found exactly the thing I need on Youtube, thus discovering this server. https://www.youtube.com/watch?v=DW2rFEZZJRs

However, I started this project with exactly the same components needed for this project: http://www.instructables.com/id/LED-Cube-Night-Light/?ALLSTEPS

Since I will be building something quite similar (it will be a small box), I need all the components to be quite small and 12v battery is not exactly the smallest and lightest.

So my goal is to build fade in and fade out LED effect. Slow fade in, when the switch is pressed and slow fade out, when the switch is pressed once again. All this with 3x LEDs (LED 5mm blue; 40?; 2300 mcd; 3,3 V; 20 mA) and 2x CR2032 3V batteries (I might add up one more if it will be needed).
Now I can see there is solution and I almost came to understand it, but I simply don't have enough engineering brain cells to grasp it completely. :-D I know I need capacitor, I need some resistors etc. But which kind of capacitor to fit my batteries and LEDs? Which kind of resistors? And when I will have all that, in which order to tangle them together? The Instructables project I linked above is easily understandable for me, because it is nicely visual. I am really quite lost in the circuit plans... And I know, I could go back to my high school years and try and learn it, but I don't really have tons of time to do it, since birthday of my fiancee is drawing near.

Could please anyone help me with this and give me directions of what I should do? It would be really greatly appreciated!

Have a great day guys!
Title: Re: Can someone help a complete amateur with LED fading effect please? :-)
Post by: cheerio on April 18, 2015, 20:52:00 PM
you can use the circuit on this page.

but your problem is that the button has to be hold to keep the leds on. there are 2 ways to fix that.
1. you use a switch like this one (stays in position):
http://www.conrad.de/medias/global/ce/7000_7999/7000/7090/7090/709061_LB_00_FB.EPS_1000.jpg (http://www.conrad.de/medias/global/ce/7000_7999/7000/7090/7090/709061_LB_00_FB.EPS_1000.jpg)
2. you use a small switch circuit:
you can use smth like this: http://www.pcbheaven.com/userpages/Bistable_relay/ (http://www.pcbheaven.com/userpages/Bistable_relay/)
or you use smth based on this: http://en.wikipedia.org/wiki/Multivibrator (http://en.wikipedia.org/wiki/Multivibrator) (i think you get an flipflop ic pretty easy and cheap)

with that you fix the switch problem.

get the electronics for the circuit on this side, play with it (get a few different resistors, capacitors) and when you are happy you can put it together.
Title: Re: Can someone help a complete amateur with LED fading effect please? :-)
Post by: Vlk on April 20, 2015, 14:41:17 PM
Thank you very much for your reply! I will try to get a different switch and get the different parts and try to get this working!

Do you think these parts might be suitable for me?

Resistors: http://www.gmelectronic.com/ru-2r7-0207-0-25w-5-p119-280
Capacitor: http://www.gmelectronic.com/ce-470u-10vt-jam-tk-6-3x11-rm2-5-bulk-p123-724
Transistor: http://www.gmelectronic.com/2sc1417-p215-457
Title: Re: Can someone help a complete amateur with LED fading effect please? :-)
Post by: cheerio on April 26, 2015, 12:45:27 PM
do you want to use the first or the second circuit? (http://pcbheaven.com/circuitpages/LED_Fade_In_Fade_Out_Dimmer/ (http://pcbheaven.com/circuitpages/LED_Fade_In_Fade_Out_Dimmer/))
either way you need more than one resistor. and i don't see where you need a 2.7Ohm resistor.
get the stuff that is listed in the table below the circuit you want to use and try it like that. when you are happy with it you can build the rest around it.