Quick and dirty halloween LED idea, best way?

[badlandsghost]

Our house has a fairly hefty stand of woods beside it, and I've had this idea bouncing around in my head for a couple of weeks, I'm just not sure of the best way to build it:
Basically I want to set up pairs of LED's in the woods to simulate glowing "eyes" looking out onto our street. My first idea was to use a string of blue christmas leds I got cheap last year (for models).

I trashed that idea in favor of individual sets (some of different colors) that I could attach anywhere (i.e. up high in trees, low to the ground and maybe a set or two peeking over the roof. ) Think "Evil Ed" from the end of Fright Night.

That much I can do with what little I know, but I got stumped when I added one additional bit to the plan: I want them to be able to "blink".

I read through all the stickies, and either I'm missing what I'm looking for, or the technical side of it overwhelmed my last few functioning brain cells.

Anybody got any ideas?
Thanks
J

[Sparky]

Once you pick your color LEDs, you'll now what size batteries you need. If you go with red or orange you could probably power them off a D pack. There are some 2 cell D pack battery holders. The D packs are nice and big to provide you with lots of runtime. Two Blue leds will need somewhere around 6.6 volts, a 4 cell AA pack would power those but not very long.

[en'til Zog]

Hi, badlandsghost

If'n you want a fairly fast blink with a bit of time between each blink, the easiest way is to use a self blinking LED. Since you want sets of eyes, use one SB LED in SERIES with two NON-SB LEDS. The SB will cause the two NON-SB LED to blink along with it. Try it, you might like it. Oh, you can bury the SB LED so it's not visible, you're just using it as the blinkificator.

If you want a longer ON time, you can use a 555 timer circuit. The chip is cheap, and if you use a C555 (the CMOS low power consumption version) you can use a 9 volt battery and get fairly long life out of the circuit. Good for hanging in trees. I think Sparky has that circuit somewhere in the announcements at the top of this forum.

Or you could use a cheeeep CMOS chip, the 4023, to do a nice 50/50 blink of whatever duration plings your inghams. Also in the aforementioned threads. The chip runs about $0.23 with a couple 'a "jelly bean" parts - one resistor and one capacitor. Total cost for blinkification, about half a buck, US.

Grab a few C555's and/or some 4023's and an experimenter's circuit board and plaly with 'em!

Go, scare some people.

[badlandsghost]

Thanks folks,
I'll probably check out all 3 options this weekend, once I can hit the "radio crap" (I don't think I'll have enough lead time to wait for mail order)
Roughly how much do the self blinkers go for retail?
Also, wouldn't it just be easier to use one SB and a non blinker? save an led? (or do the self blinkers just need enough voltage for 2 regular?) Finally, what should I base the resistor size off, the SB or the 2 non blinkers?

I've got the link for the LED "wizard", thats what I've always used to calculate battery's, resistors etc, but I know basically nothing about the self blinkers.

I do remember seeing stuff in the stickies about the 555 and the 4023, but apparently I missed the full possibilities (not hard for me, LOL)

Thanks for putting up with the newb questions.
J
(and if I can pull this off, I'll post some pics. Heck, I might even feel compelled to "share" by putting a few in my neighbors yards j/k )

[en'til Zog]

In the Box O' Stuff challenge, the idea of using SB LEDs came up and got explored a bit. Essentially, the SB lets through a little bit of power - that's what the internal circuit of the SB needs to keep operating - so the NON-SB tends to glow a bit. Using one SB to control two NON-SB LEDs keeps the intensity matched on the visible NON-SB LEDs.

Many SB LEDs need about 5 volts, but also limit current flow through themselves so I sometimes don't use any dropping or "safety" resistor. But, just in case, up in the trees, allow a voltage drop of 5 volts for the SB (or whatever the spec sheets say they need), add the voltage needs of the other LEDs, and calculate the resistor from that.

I use 9 volt batteries a lot so that leaves 4 volts or so for the other two LEDs.

The best way to figure all this out is to grab some LEDs, a cheap experimenter's 'bread board' and play with the suckers.

[badlandsghost]

Well for anybody thats interested heres a couple of pics of the finished "beasties". I tried the sb leds, but it didn't work out, so I just made them static, but I think they worked well, and now I've got a whole year to get the mkII's worked out, I'm thinking blinking, and maybe some kind of auto off during the day. (theyre already pretty stealthy, in daylight,even on, they are hard to spot)
You can't see all of them in the pics, but theres actually 6 sets outthere, in various colors.


Whaddya think?

J
http://i6.photobucket.com/albums/y221/M ... IM0737.jpg
http://i6.photobucket.com/albums/y221/M ... IM0736.jpg

[Sparky]

Those look great. If you're taking some time to get a blinking setup for next year, look at zogs, chip solution. You can easily reconfigure it to give you different rates of flash. Like 2 or 3 quick flashes followed by a longer pause.

here's a home brew style circuit board with field reconfigurable pins and cabling:
http://www.kc6sye.com/images/images_11_ ... L_pins.jpg
http://www.kc6sye.com/techmages_11_10_06.html

BTW I edited the post to link to the pics, last I checked we still had to link to images to reduce bandwidth consumption.

[badlandsghost]

Thanks:D ,
Sorry bout the img tags, my bad,

J

[en'til Zog]

WEll, the "EYES" certainly have it!

They look good, and that's what counts.

Now, about that owl, which really needs some glowing eyes....