I'm planing out my circuits so I can do them later. I was just wondering if this will work or is there a better way. Doing 2 diode fan controllers for 4 120 mm fans http://www.cpemma.co.uk/sdiodes.html. Controller goes form OFF, High-Low. I want the bar graph indicator LEDs to fade as I turn them off and on.
It will work (fade out, not in) but you'll have to experiment with capacitor values to get the effect you want.
I'll take a rough stab in the dark and guess that ~50-100uf would give a nice fade off effect for a single led, like ~1 second or so maybe? So to have a fade in effect, we're gonna need to make an rc circuit... it would be cool to have a single rc circuit per led, that is used for both fade on and fade off!
Can go for the RC circuit but I am not to sure on how. I know a little bit on electronics. Just looking for a1 sec or so fade in then when turned off 1 sec fade off. The aqua LEDs are 3.6fv. Also will the rotary switch fan controll work with 2 fans each? I am using AC Ryan Blackfire 120mm fans that are 2.8W each.
You can use a few fans like that on each rotary switch if you wish, but as Cpemma was saying, with higher current draw, a slightly higher voltage drop will be had with each step on the switch, so you'll have a slightly less fine speed control, but you probably won't notice the difference without looking at rpm monitors. With only 2 fans each the difference would be even smaller, so go for it. I'd be spending a fair bit of time just to attempt designing an RC circuit like what i mentioned... there are a few guru's here that could probably whip one up easily though So who's up for the challenge guys? E-cookies await you!
It's covered here somewhere, Simplest method is to split the LED resistor into two with the capacitor from the midpoint. It also helps when fading to use very low LED current, say 1mA max. A SPICE simulator is handy for estimating values.
There's a sneaky way of using a 2-letter search term, add the wildcard * to make it 3 characters. Trouble is, RC* picks up RCA as well as just RC. But 'fade led' might be better.
That might be it. How would you do it for 12v and just 1 LED. I was thinking about just doing the capacitor now, something like 1000uf or 2200uf.
I think this should give about ~1 second fade on, and about ~1 second fade off, for a 3.6v led running at 20ma, which is fairly bright. If you want to just fit a cap for now, to give about 1 second fade off but instant on, then try about 10uf, assuming you are gonna use around ~470 ohm resistor to run the led at ~20ma. I think 1000uf would last about 1 minute or close to it. I might be wrong here, it's been years since i had a little play with RC circuits. I confess that the previous pic i posted is actually Cpemma's
Thanks mvagusta,What program is that? Also for doing each LED would you need a diode after the 1K resister to keep the capacitor from discharging to the other circuits.
I just used paint to mod cpemma's diagram, which was probably made using pspice or something like that? I don't think you'd need those extra diodes you've thrown in, as only one of the circuits is connected at any time via the rotary switch anyway. I also previously mentioned that if you just used a cap by itself for now, so you'd get fade off only, that 1000uf would give close to a minute. I didn't take into account that the cap would be the power supply not just part of an RC circuit, so a 1000uf might only be like ~10 seconds, maybe 100uf would be close to 1 second, not 10uf like i said just before. Either way i'm just guessing on this, i can't remember the formula to work it out exactly Make sure you do some experimentation on a breadboard or something before you build! I haven't made these circuits we've drawn here so i can't garantee they will work the way i think they will!
I really need to take a electronics course. I will play around with this. I have one of those old radio shack 100 in 1 electronics boards that I could use as a breadboard.
OK I see how this works. Messed around with this last weekend doing 3 volts and different capacitors.
So far at 9v (caps are only rated to 10v) to get the fade in fade out at ~one second I'm using a 470K resister for R1 and a 3.3 uF cap for C1. If there is a another combination, the 1k resister is off unless it would work better at 12v.
I am looking at around $45 with out s/h or the LEDs to build the controller with the RC circuit on digikey. With out the RC circuit it is $35 Knobs that I'm going to use are these.http://media.digikey.com/photos/Kilo International Photos/OESA-50 CLR.jpg
Looks cool. I hate it when i go to the hardware store for a couple of little things, and then i get this big bill by the time i get to the register
LoL Now is just need to talk parents int letting me get all of the stuff. I added a few more things and now im at 57 without shipping.
I know how you feel! I'm trying to do something similar, sure wish I had one of those old kits now. I like how you've come up with this. Nice sketchup skills as well. What program did you use to create your wiring diagrams? Good luck with the parents, tell em you'll cover the shipping! I'd like to know how this comes out, pics/video too!
