Need help designing multi-circuit for mod/contraption/thing

[Bimmerboy]

I'm still an real noob when it comes to electronics, but can learn quick. I'm hoping to build a driver for a new mod idea, and am guessing it's possible, but don't know for sure. Here's what needs to be done.

Imagine three banks of LED's, each bank a different color. First bank will be 8 reds, second will be 5 whites, and the third bank, from 1 - 3 blues (haven't decided yet. I'd like them to display a sequence where the red's come on first, they remain on while the white bank lights up, the 3 blues turn on last, and now all LED's are lit. Then they all turn off, and the process is repeated automatically. This is all to be run off either 6V (4 AA's), or 7.5V (5 AAA's)... whatever I can stuff in the housing along with electronics.

It'd be very cool if this could be done without pic programming, as I have no means to do so. Perhaps a few 555 timers could be used to acheive this? If this could be done, even in the most Rube Goldberg kind of way, I'll go for it.

I'll try to find a pic of the housing this is all going into.

Is something like this possible?

 

[Mr Happy]

Sure it sounds possible. You could use one timer as the base for the overall cycle. You would daisy-chain secondary delay timers off the base timer to light up the individual LED banks. Assuming the reds come on immediately, you would need three timers overall, and some transistors or something to provide the drive current to the LEDs.

 

[Bimmerboy]

Thanks for the reply, Mr. Happy, and sorry for the delay... a number of plans recently came to a screeching halt. However, I'm still interested in making this circuit when things are rolling again.

What you describe sounds fairly easy and do-able. Would you be able to provide some more detail to get me going in the right direction? Red coming on immediately is perfectly fine.

I'll see what I can find on the web also.

 

[Mr Happy]

I'm afraid I'm a bit of a noob at electronics myself. I tend to just dabble with circuits on a breadboard and adjust them until they do what I want.

But the 555 timers seem reasonable. You can get IC's with two (or even four maybe?) timers in them. For each timer you can adjust the on time independently of the off time. So to do the red LEDs you could make timer #1 be on for say 10 sec and off for 1 sec. You would make the timer output turn on a transistor that lights up the red LEDs for the duration of the 10 seconds.

For timer #2, you would configure it as a delayed turn on (say 3 secs), triggered by the first timer. That would turn on the whites.

Timer #3 would be a delayed turn on too, only for a longer delay than #2 (say 6 secs).

When timer #1 turns off, it would reset #2 and #3, turning off all the LEDs.

I can't help you more than this without building it myself, but if you experiment I'm sure you can figure it out.

 

[Bimmerboy]

Sounds like you're ahead of me in electronics so far. :nana: How does one adjust a 555? Different value resistors? :shrug: Heh... was hoping to have gotten around to learning more of this stuff last year.

I'll have to ensure each bank gets the proper current as well, and each one will require a different amount. As you said though, some experimentation will eventually get things sorted out.

...That, and asking for more help! :laughing:

 

[Mr Happy]

The best thing with the 555 (or any IC) is to download the manufacturer data sheet off the net. It will have a description of what the different pins do, and some example circuits showing how to wire it up.

The 555 uses a capacitor and a two resistors for a basic oscillator as I recall, but more complex circuits can use more resistors. It has different modes, and by using different pins in different ways you can make it be an oscillator, a delay timer, or do other things.

Heres a "thing" I made when I was experimenting with some 555's and other components a while ago: http://www.youtube.com/watch?v=oOovSCb50gA

I can't say enough about how valuable it is to try things out on a breadboard like that. You learn much more than just reading about the theory.

 

[uk_caver]

Another fairly simple way to achieve the original aims - a cycling between (off, red, red+white, red+white+blue) would use a single timer and a 4017

Each bank of LEDs would have power to it controlled by a FET or some other transistor, with the base of the transistor pulled low by a resistor.
A timer clocking driving a 4017 IC would cause a single output to go high in sequence. Connections between outputs of the 4017 and the transistors would be made by diodes.

For the simplest setup with equal times for 'off' and the 3 'on' states, 4017 output 0 wouldn't connect to anything, output 1 would have a single diode going to the 'red' transistor, output 2 would have 2 diodes, one going to each of the red and white transistors, and output 3 would have diodes running to all 3 transistors. Output 4 would connect to the reset input to give the chip a 4-output cycle.
Having different durations for different states is possible, but a little more complicated.

One advantage of having a single timer is that the speed can easily be varied without having to worry about any synchronisation issues.

 

[zipplet]

There is one other option which is to use a small PIC microcontroller. The small ones are very cheap but the problem is a programmer and needing to learn how to use them.

They are very versatile and multimode lights including fenix lights / etc use something very similiar.

Just my 2 cents/pence.

 

[uk_caver]

PICs are certainly nice for advanced applications (I use them in my lights), but there's a fair bit of learning to do up-front, especially if someone wasn't a C or assembler programmer, as well as the cost, and the possibility of a beginner significant hitting problems.

For a simple application, using simple chips on a breadboard does give the option of manually clocking, probing outputs with a voltmeter, etc, to get a fairly good idea of what is going on in all parts of the circuit.
This particular application sounds like a really good one for someone to start off with in electronics.

 

[Bimmerboy]

Thanks for the additional input, guys.

Offhand, it sounds like the 4017 idea could be a more simple layout than three timers, take possibly take a bit less space. Would that be true?

Also of possible concern is voltage overhead, as I may be limited to 6V due to space constraints. So if the 4017 layout stays operational on less Vin, all the better. Would that also be the case?

As you mentioned, uk, the single timer sounds great for adjusting speed without sync issues (Edit: unclear - I meant to say in whichever way they may occur... remember, I don't know a damn thing :nana. It'd be great if each step of the cycle could be easily made to be somewhere around 2 seconds or so.

Mr, Happy - Hahaha... I gotta' make one of those too! Perfect to give to my little nephew to annoy my bro, and sister-in-law with. :devil:

Edit: Just to make sure, since there will be three seperate banks of LED's, I'll need to make three different regulation circuits, right?

 

[Mr Happy]

On thinking about it a little more, you don't really need three 555 timers, just one is enough for the base clock. To achieve variable "on" delays you could take the sawtooth wave from the 555 and use voltage dividers and comparators to switch on different banks at different voltages on the up ramp of the sawtooth. This would have the advantage of synchronizing the various delays to the reference signal. Then to make the whole thing go twice as fast you would only have to change one resistor at the 555.

 

[uk_caver]

Offhand, it sounds like the 4017 idea could be a more simple layout than three timers, take possibly take a bit less space. Would that be true?

If you were looking for equal time-slices for the 4 states, space-wise things would probably be very similar
Voltage-wise the 4017 works down to ~3V and CMOS versions of the 555 possibly rather lower. The limiting factor for low voltage is likely to be the drive voltage for the LEDs.

Edit: Just to make sure, since there will be three seperate banks of LED's, I'll need to make three different regulation circuits, right?

You'd need some switching circuit for each bank, such as a transistor. (see http://www.kpsec.freeuk.com/trancirc.htm#chip )
If you're using 5mm LEDs, the simplest regulation is just picking appropriate resistors to limit the current, either in series with each LED, or in series with each group of two or more LEDs in parallel.

Are the LEDs going to be visible themselves, or used to light up something translucent from the inside?
If they're going to be directly visible, the precise current/brightness may not matter too much - looking directly at a red LED running at twice the current of one next to it, often the apparent difference in brightness is very small.

 

[MrAl]

Hello there,

I guess you may have already considered using a microcontroller, but
not sure if you want to get involved with programming one of them.
If you have some simple requirements perhaps i can program one for you.
You'd have to pay for the chip of course and shipping also.
One or two pieces would be ok i guess.

You'd have to tell me exactly the way you want the lights to flash
and the circuit would also depend on what power the LEDs are and
how many of each.

 

[Bimmerboy]

Mr. H - I'm somewhat lost on that last idea, but it certainly sounds cool! I have more to learn before understanding how that setup works though.

uk - Actually they are 5mm LED's, and will be directly visible through a clear plastic housing. Using resistors for regulation would be the simplest I assume, and to be honest, it's perfectly acceptable if it's a bit wasteful (as opposed to a switching design) as this will basically be a showpiece not run for long periods. Would resistor heat be a concern though? Perhaps even more so for the red section, as they have a Vf of around 2V, even more voltage would have to be dropped. The inside of this thing will have some very thin, heat sensitive plastic parts, and everything is fully enclosed.

Edit: The Electronics Club was a great link! Lot's of good stuff there.

MrAl - A highly interesting proposal! Thanks for the offer, and I may just take you up on it. Aside from being totally cool, would a pre-programmed chip simplify the rest of the design?

I now have a final LED count. It'll be 6 reds for bank one, 5 whites for bank two, and 4 blues for bank three. I assume everything will have to be in parallel (the LED's within each bank, then the banks themselves) in order to stay enough below Vbatt.

BTW, here's a pic of the housing, and the idea behind this build. It's going to be called The Liberty Bell (either that, or The Chocolaty Bell), hence the red, white, and blue LED's. Red will be the bottom deck, white in the middle, and blue on top.