So I was chatting with Sean and Alex last night about projects we could do for Halloween this year.
Last year's extreme pumpkin carving was pretty cool. Apparently because of the flooding pumpkins may be a bit pricey this year, but I'm up for doing them again this year anyway.
We were also brainstorming about a small soldering project to be done jointly with the Scouts, and we're going to prototype a small variable speed blinker that could be soldered up on a small piece of perfboard and worn over a costume to make the wearer more visible when out in the dark. We're shooting for a target price per set of $5 or so when we order parts in quantity.
So far the plan looks like to build a board with a couple of 555 timers and some trimpots that could adjust the speed and fade time for several LEDs. We haven't settled on single RGB LEDs or clusters of individual color.
Post more ideas or good parts you find in this thread.
Patrick
Cool idea. I designed/built a circuit last year using a 74HC14 chip that cycles colors nicely through one RGB.
Chip + LED = around $1.25 for small quantities. I buy my RGBs on eBay - the problem is that they take a few weeks to arrive from China. I do have quite a few lying around though (maybe like 30 or 50).
I would be into helping out on this project! When would you have the scouts build?
I also designed a 555 timer circuit w/ 5" long slider pots for lighting control. This turned out to be pretty expensive. I didn't look at using trim pots but I think they will be expensive too and put us out of the $5 price range.
Sophi
Electronics Goldmine has these:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G3279
10k sliders for $0.25/ea. If we can work with that value, that should be a pretty good option but we'll have to order soon.
I might have a couple 74HC14s lying around to play with. Do you have the schematic for that?
Also, Mouser has some smd rgb leds for ~$0.33 but I think we'd either have to pre-solder them, put them on a breakout, or something. With time getting tight, I'm not sure how feasible that is, though. Maybe we could just get 3 individual color leds?
Here's the HC14 circuit. I used this simply to cycle through the colors on autopilot, no potentiometer necessary. The trouble with using 10k resistors is that not much changes. Or you have to use gigantic capacitors. Worth experimenting with though- I did quite a bit of RC mixing to get the correct values. We could use an RGB in a thru-hole package.
http://mix-engineering.com/2011/04/oscillating-with-the-74hc14/
In the open source section you can get the 555 timer circuit http://mix-engineering.com/wp-content/uploads/2011/07/555-timer-light.pdf it's in Eagle too.
This is a good project in general for the Scouts, Halloween or not!
Sophi
Just found a 100pk of 5mm rgbs @ Sparkfun for $60. That seems like a pretty good deal and Sparkfun is usually pretty quick to ship.
http://www.sparkfun.com/products/9985
Make sure you buy common anode ones http://www.sparkfun.com/products/10818 otherwise you'll need more IO.
I have a 40-pack common cathode RGBs...sigh
Sophi