Where can I find a small chaser circuit?

[MillenniumFalsehood]

I need one that chases 3 sets of LEDs for a warp engine in a 22" model of a Saladin class ship. The circuit need to fit inside an area no bigger than 2" x 3" and needs to have seamless transition between the last and the first LED in the chain. I would prefer a prebuilt circuit, like maybe from a toy laser pistol or something, but a diagram would be useful as well.

[Pat Amaral]

CultTVMan has a couple products from VoodooFX that would probably work for you but they're kind of pricey in my opinion.

[stevipop]

I can't provide a source for an off-the-peg prebuilt circuit, but here is a useful guide + diagrams to a rather simplistic version of what you seek.

For anyone else looking at the above link, the site provides an excellent intro to electronics in a very straightforward manner (if that's possible with electronics ).

Apologies in advance MF if it's not what you were looking for,

Steve.

[tetsujin]

For a "chaser" effect any kind of a microcontroller is overkill - but if "small" is your concern, you can't get much smaller than a microcontroller with its own oscillator built-in, and you can make any animation effect you like.

For instance, I'm doing animated nacelle lights for my Polar Lights Enterprise, by installing one PIC microcontroller in each nacelle. Because this particular PIC has a built-in oscillator and the reset line can be disabled, I only need to connect it to power and to the LEDs. I'm using the PDIP version because that's what I have on hand (about 1" long, .5" wide, .5" deep) But there are also surface-mount versions which are much smaller (but that makes them harder to hook up, too.) The PIC I'm using is the 16F628, which is an 18 pin package with 15 outputs. More compact PICs are also available, too, if you need fewer outputs. (I'm actually only using 10-12 on each PIC. Obviously if you just needed three outputs you could use something like an 8-pin PIC, which would likely have between 4-5 outputs and be a lot smaller. (About a half inch long.)

Of course, the complicated part of this is that you need to program the microcontroller. There are very cheap, simple circuits you can build to do that (particularly things that interface with the printer port - though personally I despise that kind of circuit because they never seem to work on my hardware) but I'd recommend something more along the lines of the programmers sold on kitsrus.com The PICs themselves cost around $2-$3 each, and the kitsrus programmers sell for around $30 (and some of them are pre-built) There are also microcontrollers out there which are even easier to program, but my experience is limited to PICs.

I apologize that this isn't a "ready-made" solution as you requested... But it's something that opens the way to a lot of possibilities. It's something that favors people who (like me) are better able to direct the desired actions of the circuit by writing software rather than building hardware. If you learn to work with microcontrollers then a lot of these problems of finding or building circuits to create model lighting effects and trying to fit them inside kits simply go away - and the answer to any such problem is usually a simple as "put a microcontroller in there".

When I was a kid I used to build chaser circuits using discrete single-purpose ICs - a 555 clock coupled with a 4017 decade counter, similar to the project on the page stevipop linked. You can tie an output of the 4017 to its "reset" line if you want to count through some number of steps less than 10. I'm not sure of the specs of the 4017 but it was at least able to direct-drive red, yellow, or green LEDs. So the whole circuit would be those two chips, a few resistors and capacitors, and the connections to the LEDs (and their resistors.) You could assemble the entire thing on a 2" square (or smaller) perforated circuit board, and it might even still be possible to buy all the components at a well-stocked Radio Shack (though it's getting harder to find RadShaks that sell ICs, a lot of them still sell resistors, caps, and experimenter's boards.) But naturally there are better deals elsewhere. Allelectronics.com sells 555 timers for around $0.75 and 4017 counters for $0.40, perf boards for around $0.75. The cost of all the components would likely approach $3.

Anyway, if you want to build something like this and you need help with directions and such let me know.

[MillenniumFalsehood]

Stevi, that is exactly what I am looking for! The blink rate looks good too. Thanks a bunch. I am going to Radio Shack later, so I can pick up all the components there. I have seen all of them, so I know they have them. The only question is of the 4017 chip. The last time I needed one they didn't have it. Must be popular.

Tetsujin, I know next to nothing of programming, so microcontrollers are out of the question for me. I got the Robotics Invention set from Lego, which is basically a microcontroller with easy to use software, but I could never get it to do what I wanted it to do. I got mad at it and sold it . Nope. no microcontrollers for me.

I think I can take the diagram on the site Stevi linked to and make it a tad smaller. I am not going to use the IC sockets since it wouldn't fit in the Saucer section where I need because of the hieght of the interior of the saucer. I'll definitely use a soldering iron on 15 watts and a heat sink for the ICs.

[tetsujin]

Stevi, that is exactly what I am looking for! The blink rate looks good too. Thanks a bunch. I am going to Radio Shack later, so I can pick up all the components there. I have seen all of them, so I know they have them. The only question is of the 4017 chip. The last time I needed one they didn't have it. Must be popular.

Tetsujin, I know next to nothing of programming, so microcontrollers are out of the question for me. I got the Robotics Invention set from Lego, which is basically a microcontroller with easy to use software, but I could never get it to do what I wanted it to do. I got mad at it and sold it :evil: . Nope. no microcontrollers for me.

Yeah, around the time I got to writing up what you'd need to program the thing, I started thinking, "This really isn't as basic as he wanted..." I guess I just feel fortunate to be pursuing this area of the hobby at a point in time where microcontrollers and LEDs make things so easy. 4017's are fine for chasers, but as the animation gets more complicated, the circuitry required to create it without a microcontroller gets crazy. I'd hate to be trying to do a fancy nacelle lighting setup without a PIC... And being able to run a PIC with no external components (crystals, caps, resistors, anything) is great, too.

If you can't get your 4017's locally at Radio Shack try http://allelectronics.com or http://www.mouser.com - either place can hook you up with the part for less than a dollar. Also, for the 555/4017 circuit you can customize the speed of the display by adjusting one of the resistors on the 555.

I wouldn't say a heat sink is unnecessary - but I've never used one, so even if you weren't able to get one you'd probably be fine.

If you want to socket your chips for whatever reason, there is a way you can do it without increasing the height of your circuit. Just cut the socket in half, bend the IC's pins out so they're coplanar with the bottom of the IC, and attach each half-socket to one set of pins. Socketing certainly isn't necessary, but I often find it useful to keep a circuit modular while I'm building it, so I can test pieces separately, wire up a certain set of stuff and have that part be "done" even though it's not connected to anything else, etc. Of course, that makes your circuit wider - whether that's OK in the space you're installing, I couldn't say. But it's a socketing solution that requires no special or hard-to-find parts (like single-line sockets) - so if you want to socket, there you go.

[macfrank]

My only suggestion is to replace the 555 with its CMOS equivalent, the 7555. It seems counterproductive to use it in a battery operated circuit (or anywhere where current consumption is an issue). Yeah, it's a bit more expensive, but they're better overall than the 555.

Frank

[MillenniumFalsehood]

Not that I'm not going to use the 4017 chaser, but is there a way to make a transistor flip-flop that switches three times? I am using one for the formation lights, so Im am a bit curious as to how much you can acomplish using just transistors and capacitors.

Tetsujin, I feel the same way. I think we are all lucky to live in a point in time to see things like ICs, fiberglass, etc. come into common use. I would hate to be pursuing this hobby(if it even existed) around the forties when LEDs were not common, if they existed at all, and controllers consisted mainly of vacuum tubes and maybe a capacitor or two.

I am going to order all the components online at once, since I don't need to go to Radio Shack. All I had to do was screw in the lightbulb all the way into the socket. Boy do I feel stupid.

[stevipop]

Glad I could be of help MF. You are more than welcome

Me? I'm learning all this stuff from scratch, so I need a nice shallow curve, and sites like the one in the link aren't like earthquake pills! Who knows, maybe in two years time I may have even built myself the nav'n'strobe lights for the PL Refit! (Hang on! Isn't that how long it takes for the paint job? Doh!).

Hope yours goes better. Good luck.

[MillenniumFalsehood]

LOL! I hear ya on the paint job, Stevie. That's one of the prime reasons I prefer TOS craft to TMP and TNG vessels: mindbogglingly simple paint jobs!

One of these days we may get to be as inteligent in electronics as Tetsujin and Entl' Zog, but for now I'm going to continue reading "Electronics for Dummies". Thanks again for the site. It should be very useful.

Btw, I intend to use the chaser effect in conjunction with an orange LED and a rotating fan. Should look great when I finish. . .if I ever finish this thing. It's already taken six months to get this far, and it's not even halfway complete.