th0mas Posted January 26, 2007 Report Share Posted January 26, 2007 Totally unrelated to midiboxing, but this is the forum I know and love.For my girlfriend this valentine's day I'm thinking about taking a little mint container (hello kitty to be precise), dremelling a heart out ot the top and inserting a semitransparent plastic layer underneath, then having a little red LED fade in and out.I don't have much time so I cannot require ordering parts, and if I can help it want to stick to radioshack since there's one three blocks away VS about an hour bussing during my work hours for any real electronics store.The two suggestions I've seen are using two 555 IC's with very slightly different oscillation frequencies (but 50/50 duty cycle) fed through an XOR gate. The effect would be sorta like PWM. I at least understand how this one works.The other suggestion I've seen is from http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#eyes.gif (scroll down to the "Fading Red Eyes" header), involving a 1458 opamp.I really have one question: can I swap the 1458 for a TL082 opamp? I have no clue what opamp's do so I can't really tell based on datasheets, and am wondering if anyone knows.Thanks guys.Tom Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted January 26, 2007 Report Share Posted January 26, 2007 how about a 555 turning it on and off, and putting a capacitor across the terminals of the LED. i'll have a look round see if i can find something. Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted January 26, 2007 Report Share Posted January 26, 2007 http://www.bit-tech.net/modding/2002/08/27/rainbow_led/1.htmlmight help? Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted January 26, 2007 Report Share Posted January 26, 2007 http://brunningsoftware.co.uk/Capacitr.htmthat's what i was talking about i think, exchange the switch for a transistor fed from the 555 square wave output. Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted January 26, 2007 Report Share Posted January 26, 2007 possibly something in here too:http://www.parallax.com/dl/docs/cols/nv/vol6/col/nv126.pdfgood luck. Quote Link to comment Share on other sites More sharing options...
th0mas Posted January 26, 2007 Author Report Share Posted January 26, 2007 If I understand correctly, the capacitor will make it so that it comes on at full brightness and then fades off instead of turning off abruptly? That would work pretty well, I don't really need to ramp into it. Thanks! ;D Quote Link to comment Share on other sites More sharing options...
AndrewMartens Posted January 26, 2007 Report Share Posted January 26, 2007 The other suggestion I've seen is from http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#eyes.gif (scroll down to the "Fading Red Eyes" header), involving a 1458 opamp.I really have one question: can I swap the 1458 for a TL082 opamp? I have no clue what opamp's do so I can't really tell based on datasheets, and am wondering if anyone knows.It doesn't look like there's any particular reason that the designer used the 1458, other than it being a dual opamp. A TL082, 072, pair of 741s, etc. should work just fine. Whatever you have on hand. If you've got a breadboard handy, it should only take a few minutes to test. If you don't have a breadboard... why not? Go get one, they're only a few bucks! :-) Heck, you can probably even find a small cheapish one at Radioshack... Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted January 26, 2007 Report Share Posted January 26, 2007 If I understand correctly, the capacitor will make it so that it comes on at full brightness and then fades off instead of turning off abruptly? That would work pretty well, I don't really need to ramp into it. Thanks! ;Dno probs Quote Link to comment Share on other sites More sharing options...
th0mas Posted January 26, 2007 Author Report Share Posted January 26, 2007 It doesn't look like there's any particular reason that the designer used the 1458, other than it being a dual opamp. A TL082, 072, pair of 741s, etc. should work just fine. Whatever you have on hand. If you've got a breadboard handy, it should only take a few minutes to test. If you don't have a breadboard... why not? Go get one, they're only a few bucks! :-) Heck, you can probably even find a small cheapish one at Radioshack...Thanks! I'm actually going to try the capacitor across the LED first, I think the sudden on/decay might actually look cooler than fading in and out - but I'm glad to know if I'm not happy with that I can substitute op-amps :D Quote Link to comment Share on other sites More sharing options...
Jaicen Posted January 26, 2007 Report Share Posted January 26, 2007 Why don't you get a 40106 hex schmitt trigger and build a couple of square wave oscillators. This has the advantage not only of outrageously low parts count, but also extremely low current, (You can get PWM using just two inverters if you're so inclined). Quote Link to comment Share on other sites More sharing options...
th0mas Posted January 27, 2007 Author Report Share Posted January 27, 2007 Why don't you get a 40106 hex schmitt trigger and build a couple of square wave oscillators. This has the advantage not only of outrageously low parts count, but also extremely low current, (You can get PWM using just two inverters if you're so inclined).I actually already have the 555 circuit built! Thanks for this option though, I might look at it for some other ideas. Now to tweak my resistor values! Quote Link to comment Share on other sites More sharing options...
th0mas Posted February 1, 2007 Author Report Share Posted February 1, 2007 Having seen:http://compiler.kaustic.net/machines/apc.htmlI'm thinking about integrating this into her gift - she likes things that go beyoowoooppppp. AFAIK the circuit is basically two 555's, with one of them controlling the other's oscillation frequency or duty (or both.. or something).Could I integrate the LED into the controlling 555's output so it also flashes while modulating the second 555? I figure it might work since the frequency will be low enough to be visible (I think - I'm going to have to analyze the circuit to guarentee that). Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 2, 2007 Report Share Posted February 2, 2007 Yeh I've been eyeing those off as a first electronics project for my g/f. It's as much for my benefit as hers, I just think they sound cool ;)she likes things that go beyoowooopppppheheheh I bet she does ;) Quote Link to comment Share on other sites More sharing options...
th0mas Posted March 8, 2007 Author Report Share Posted March 8, 2007 Hey guys,I'm sure you aren't, but just to wrap up this thread here is a picture of what I ended up giving her (only a couple days late, too! whew!)Her description of the picture: "happiness is BEEEEYYYYYSQUEEEEEEEEEEEeeeeeeeeee!!!YYYOWWWBBRRRRRRDDDDDD RRRRRRRRRRRREEEEEEEEEOOOOOOO " and she says thanks for answering my questions :DCheers,Tom Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.