Been searching around for LED Fader circuits i could use for a project i'm working on and not found anything due to the size of the circuits in general. I have to fit 2 lithium cell batteries, the socket for them, a 555 timer + associated bits, 2 minature button push switches and and whatever im going to use for the fader in a 4cm diameter x 8mm depth circular space, not easy. Not gonna give away what i'm working on, just leave you to guess from the two shots below, more fun hehe . This Image shows the base piece, with the leds around the edge, resistors in the channels and 12 contact points for power points from the fade circuit and to ground. Need 6 fade channels, 2 LEDs per channel, 2 channel with 2 second, 2 with 3 second and 2 with 4 second fades. I Also need to rig the circuit either with two switches one for continous current to the led's and one for the fade circuit, after pressing either there is then a 2 minute delay and the circuit shuts off. This may be easier to do with a double pole push switch to just switch between the two circuits, straight passthrough to the 555 then the leds on one position and the fader, 555 then the leds on the other, thoughts ? This image shows a rough base of the unit, skewed a bit when i was doing the top channels so it isnt a great render but you get the idea, it's not to scale either but i dont often do max work thats exactrly to scale, mech desktop job if it needs that much detail. In there needs to go the batteries and connector, a 555 timer, one or two micro push switches, and the fader circuit. The cell batteries are the best for the task i think. I've considered other batteries but there all 1.2-1.5v which doesnt help although nimh batteries would last longer than cells theres still not as much juice. Plus theres size to consider, two of the largest cells on maplin would be 600maH or something close to it which is more than i need for 12 LEDs averaging 20ma each. So need some help, i can think of several solutions none of which i'm particularly keen on using, and i'm sure someone will say use a PIC which is what i may end up doing but i'm not particularly fond of PICs, we dont get on *looks at tub of dead ones that he gave a one to a friend from to work into one of her dreads*. Remember the key is small, 4cm diameter circular area, 8mm deep, leds and resistors housed above. So if anyone has any suggestions or guides they can link me to that might fit the bill please do, after searching and going through old links most of the day i have ended up at the place i should have begun really hehe .
i do believe StevieG was selling preprogrammed PICs that did just this, might be worth chattign to him...
Did you look at SMD parts? You can mount them with conductive Epoxy instead of solder. A sharp tool, like the hooked utensils that dentists sometimes use to poke your teeth, are good for putting small beads of Epoxy on the little legs. Check if a CMOS version of 555 (like 7555) conserves battery power in your circuit. There are dual (556) and quad (558) versions of the basic 555 that could some space.
Hi there ! I'm working on the same thing THis is the best circuit I found for fading LED's : http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm Scroll half way down to "Fading Red Eyes" I found an old modem of mine had an SMD version of the 1458 Op Amp IC the guy recommends in it, so I'm using that and SMD LED's and other parts this should be small enuff for your needs too ? THe same circuit is here http://www.metku.net/index.html?sect=view&n=1&path=mods/colorfade/index_eng but with less clear info. Good luck !
THANK GOD! I've been looking for that site for days, lost all my links a while back and i knew japala had some on his site just could'nt remember the address. I'll have a go playing with that and 12 leds, see what i can fit in to that space, have all the parts for that lying around already. I May have a go with a PIC aswell, might save me a little space in the end. SMD parts are all i'm using anyway, with the exception of the battery clip and the LEDs, both of which you can mount SMD style. And solder epoxy is like gold dust in the UK, dont know of an online reseller that sells it, or any local stores, not anymore anyway. Got one tube left i use for modding playstations and stuff with. Hmmmm now how am i going to integrate a 2 minute 555 into that circuit, also may need to alter the resistors for a 3v source..... http://www.metku.net/mods/colorfade/1.png
Just had a thought, since i'm gonna be running 4v and 4.2v LEDs from a 3v source i'm not gonna need resistors am i. Not sure if they'll be weak on 3v though now that i'm thinking about it, using the standard 3mm and 5mm UV and Bright Whites from Maplin atm which should be alright, might need to get some UV 5s though. Gonna have to go out and get some of those cell batteries and give this a go today, still looking for a cell battery connector socket though, if anyone know of one, and please god dont say farnell, i hate looking through that site hehe .
Bugger Farnell !! Who can afford to buy from them ? RE: THe CR2032 batt clip, could you pull one from a dead PC motherboard ?A lot of the ones I've seen could easily be modified to take 2 cells and a dead M/B can be had for free at a lot of S/H PC shops
Could try to pull one from a dead board but as its smd the legs would be extremely short, maybe too short, but you can get them on maplin and rapid so i'll have a check see if they fit just by ripping one from one of the ... 4 dead or retired boards i have here atm. Tip for anyone who gets through a lot of big capacitors or mosfets, rip them off old mobos, older the better it seems for capacitors, usually much larger. Founds some really nice mosfet heatsinks on one set which i ripped off and now use on my current board, never know what you might find when someone donates their dinosaur of a machine to you.
4v and 4.2v LEDs? are you sure you have that right? o.0 either way, youre going to want a resister there as without it the current will not be limited and your LEDs will die much faster.
I dunno about the LEDs. With that low a supply voltage versus forward voltage, I don't think they will light at all. Also, where are you getting your LED from? 4.2v seems rather high for an LED. _C
