Help w/LEDs, batteries, and a lighting sequence

[rocketfodder]

Disclaimer: I'm pretty noobie, since it's been 4 or so years since I've taken any EE courses or thought about handling a soldering iron.

Is there a way I can link 8 red LEDs (not the fancy superbrights or anything enormous) to some combination of batteries (preferrably smaller than those big bricks--more like AAs or Ds, etc.)?

I'm trying to mod this.

I'd like it to run on an independent battery source rather than off the PSU. Any suggestions? Is it even possible, given the power constraints?

Provided any of you can tell me or show me where to learn how to link up 8 LEDs with a few batteries, is there a relatively easy way for me to get something where I could program a lighting sequence? I know it's possible with my enormous and old breadboard + programmable IC, but I figured I'd ask in case there's some new, fancy solution I don't know about.

Note: I'm looking for ALL help--like, down to which sort of LEDs would be good for this project, and whether I should put them in series or parallel, and what sort of resistor. I know enough to read specs and do some basic calculations, but other than that I'm lost.

Thanks if any of you can help at all.

 

[shadowlord]

wow that are a lot of questions, but maybe i'm able to answer some of them.

it's possible to use aa batteries, with two aa's you have a supply voltage of 3V.
you could wire the led's in parallel. given that you not use some of the fancy bright stuff you could calculate 8 led in parallel with a 3V source wich leads you to a 10ohm resistor.

hope this helps a bit.

 

[Mohonri]

Yes, you can control them with a programmable IC, but the programming's up to you--I'm not gonna do it for you!

As for hooking them up to batteries, there are several approaches. With red LEDs, you can hook up the LEDs like so:
Bat +-----^^^^----LED----Bat-
Just do eight of the above, with all the resistor-LED strings in parallel with each other, and running off the same battery. If you're using two AA's, C's, or D's, you'll have 3V to work with. The LED will drop 2V of that, leaving 1V @ 20mA, or 50Ohms for each resistor.

If you want to run them off a controller, then either hook the one end to Vcc and the other to the IC output pins, or hook the other end to GND and the positive end to the output pins. Just don't forget to invert the output if you need to!

 

[rocketfodder]

So it is possible, then? Great news guys

I wasn't asking you to program the IC for me, I know what a pain in the ass that is. I was just wondering if there was anything else that would provide a similar function before I started seeing what a mess I had on my hands.

Are you all using an online calculator of sorts for these general 2V = 8 LEDs = 50 Ohm resistor? I'm curious to learn, so that in the future I won't have to bug anyone.

I know one of them (series/parallel) is the inverse of the sum of the inverses, and one is just the sum, and blah blah it's all so foggy now. If only I hadn't tossed out my notes...

 

[cpemma]

Provided any of you can tell me or show me where to learn how to link up 8 LEDs with a few batteries, is there a relatively easy way for me to get something where I could program a lighting sequence? I know it's possible with my enormous and old breadboard + programmable IC, but I figured I'd ask in case there's some new, fancy solution I don't know about.

There's some old, plain solutions like a 555 clock and 4017 decade counter, where you can sequence up to 10 LEDs. Will run fine from a 9V PP3,

Example here.

The LED resistor calculation you can do in your head, (Supply Voltage - LED voltage)/LED current. Series LEDs, add the voltages, parallel add the currents.

 

[RancidWAnnaRIot]

programming an IC is no problem at all (at least for me it isn't).. it's just a HUGE waste of money...

 

[Mohonri]

programming an IC is no problem at all (at least for me it isn't).. it's just a HUGE waste of money...

That's what I meant earlier....man, oh man, how I want an STK500 dev kit.....

 

[agent420]

programming an IC is no problem at all (at least for me it isn't).. it's just a HUGE waste of money...

I find that they can be very cost effective. For example, the Atmel Tiny2313 costs less than $2 and offers a very wide array or hardware functions including 18 io lines, 4 channels of pwm, serial communication and multiple timers. It also has an internal oscilliator, so no additional hardware is needed, just a power supply. You can build a no parts programmer and there's a demo of my fav Bascom Basic compiler capable of programming up to 4k devices for free. There are excellent open source asm and C compilers as well should you feel the need to be more technical (I haven't needed to, Bascom has a large function library that compiles to very quick code; I've created several complex I2C & SPI projects with little effort).

A 555 + 4017 + associated caps & resistors probably costs around the same as a ucontroller that is much more flexible (and has a smaller footprint and parts count). Depending on the pattern you'd like to generate, conventional discrete parts could easily end up costing more.

The dev kits are nice, but you can accomplish the same thing on a breadboard for cheap. Actually, I prefer the breadboard because the prototyping area on most dev boards is too small for me, and I'd have to end up running long IO lines off the board to the connecting hardware. Really the dev boards aren't much more than a bunch of led's switches and maybe an lcd anyway...

[edit]

There's a better programmer schematic included in the Bascom Help file (IDE > Programmers > ISP programmer) that uses one cheap 74244 buffer chip. I've used this programmer for years, never let me down.

 

[agent420]

Forgot to mention the Picaxe chips... just a couple of bucks each with free Basic compiler software. I've not used them myself, but they seem an awfully cheap & easy way to get started with microcontrollers. Apparently they are being found in more and more commercial devices due to their rapid development abilities. Wiki