Help with simple LED sequence

Hi all, I want to make 4 LED's light up in the following sequence (looping): O O _ _ _ O O _ _ _ O O O _ _ O O O _ _ _ O O _ _ _ O O O _ _ O

the above shows it has gone through two sequences, I'll want it to be continuous and with variable frequency (a potentiometer?)

I've read up on 555 oscillators, logic gates (nand, nor, etc.), flip-flops, op-amps.......... I don't know where to start. I DO have a nine volt battery and some LEDs. Any guidance is greatly appreciated, Bart

A 555 can be used as a variable frequency source. The traditional setup is to use the output pin to drive a resistor, which then feeds a capacitor which is connected to ground. The junction of the resistor and capacitor can then be used to drive the trigger and threshold inputs, thus causing an oscillation that has the frequency proportional to R * C. If you replace the R with a pot, you can have a nice clock which can be adjusted using a pot. This only works well with cmos 555s, since the older ones have too much leakage into their threshold and trigger inputs, and can thus cause problems. Search on the Internet for a datasheet for a 555, and look up the values. There are also suggested circuits for this kind of thing in most datasheets.

That can drive a 4017, which is what is called a 'johnson counter'. It is basically a set of flipflops, all connected in sequence, so the output of one changes the state of the next one on low to high transitions. There are 10 output pins, and they are each brought high, one at a time, when a clock (such as the one above) is applied. There is a reset input that will reset the counter back to 0 when applied, so, for counts less than 10, one usually just connects an output to this reset. Then, when the chosen output goes to 1, it'll reset the chip back to the beginning.

Generating your output pattern can be easily accomplished by using either logic gates, or simply using diodes from the appropriate outputs. You might be able to drive the LEDs directly from these diodes for certain classes of logic chips. An example would be for diodes to point from Q0 to both the first and second LED's anodes, the LED's cathodes each to small resistors to ground. Then when Q0 is high, LEDs one and two will glow, when Q1 is high, LEDs 2 and 3 will glow, etc.

If the LEDs are the standard ones, it'll only take about 5mA to light them up, so you can use the scheme above. If they are those high powered ultra bright ones, it may take more. In that case, skip the driver, and use the output of the 4017 + diodes to power the base of an NPN transistor (one for each LED). The NPN transistor should have its emitter grounded, and have the LED, plus current limiting resistor, between the collector and positive voltage source. The LED may have a forward voltage drop of anywhere between 1.4 and 3.4 volts, so you'll need to calculate the resistor size by

1) determining the LED Vf (look at the datasheet, or measure it) 2) Subtract this number from the volts supplied by your voltage source 3) Take the result, and subtract 0.2 from it for the voltage drop of the NPN transistor. 4) Decide on the current you need, and take the result of 1-3 above, and divide it by that current. The result will be a number like 53 or something like that. Buy resistors that are near that value.

As an example, assume your led has a Vf of 3.4V, and your power supply is

9V. Also, assume the LED datasheet says you need 20mA. Then, you need a resistor which is

R = (9 - 3.4 - 0.2) / 0.020 = 270 ohms.

You can use a resistor (say 100 ohms) between the diode output junction and the NPN transistor for safety's sake, although a CD4017 won't allow more than about 5mA though the base anyway, so it is probably safe to omit.

Bob Monsen

When Fields calls you rude, you know you've stepped over the line. Please accept my apology.

--
Your manners are fine and Jeff\'s rudeness was out of line.  This is
seb, a starting point where newbies aren\'t supposed to know
anything, where they\'re not supposed to be bullied because of their
ignorance, and where there are no stupid questions but, often, lots
of stupid responses to those questions.

Anyway, welcome to the group!

I apologize to the group. What Jeff calls stupid is actually my unfamiliarity with newsgroup "netiquette". It won't happen again, Jeff is correct that I should crosspost. I found

and my manners will improve exponentially.

Bart

"Bart" schreef in bericht news:c5052$432c5c26$d8442b04$ snipped-for-privacy@FUSE.NET...

Bart,

I don´t say electronics to be difficult but you *do* need some basic knowlegde. As you know about the 555 you may start to build an astable multivibrator with a low frequency. Let´s say 1 or 2Hz. You can connect a LED to the output (use a series resistor to limit the current) so you made a blinking LED. Examples all over the net. Google on "555 blinking LED". Once you made that you can learn to vary the frequency using a potentiometer. If you made that you need only two flipflops and some XORgates to make the walking light you want to have. I can make the schematic for you, but can you read it? Personally I'd program a smal PIC micro for a job like this but I guess you're not in for that.

petrus bitbyter

--
I think the high part of "D" is too short by one clock.

This should do what you want. I've shown waveforms too.

If LEDs are not bright enough, drive them with transistors as Bob described.

--
Terry Pinnell
Hobbyist, West Sussex, UK

You're right, thanks. Found several other careless mistakes too. Hope it is now correct.

BTW, I *think* that -ve spike on B (Q0 output) is just a simulation artifact, but I'm not entirely sure.

--
Terry Pinnell
Hobbyist, West Sussex, UK

LOL!

Cheers! Rich

Terry Pinnell wrote on 18th Sep:

And here's THE MOVIE! (Tee-shirt to follow.)

Posted also to alt.binaries.schematics.electronic, as 'Help with simple LED sequence: The Movie'

--
Terry Pinnell
Hobbyist, West Sussex, UK

Text! Music! Video! Awesome!! :-)

Ed

Terry Pinnell wrote on 18th Sep:

should do what you want. I've shown waveforms too.

enough, drive them with transistors as Bob

And here's THE MOVIE! (Tee-shirt to follow.)

Posted also to alt.binaries.schematics.electronic, as 'Help with simple LED sequence: The Movie'

--
Terry Pinnell
Hobbyist, West Sussex, UK

on

18th Sep:

here's THE MOVIE! (Tee-shirt to follow.)

Text! Music! Video! Awesome!! :-)

Ed

Have you got anything I can play that with? Windows Media Player keeps insisting that it can't find a decoder. Xine doesn't like it either, but that doesn't surprise me much.

If I have to spend money for some third-party coded (Which turned out to be the most likely possibility after screwing around for about two hours with Microsoft's "help" pages.), then screw it, it ain't worth it.

Or, could you put it in a format that's compatible with a plain vanilla WMP?

Or, what's it a movie _of_? (I can hear the gal singing on the Victrola, but no video).

Thanks, Rich

Download Quicktime Alternative, it plays just about anything.

I'm no video expert (just started dabbling with it), but I'm surprised WMP can't play the MS proprietary WMV format. I think that's also probably WMP's 'native' video format? Can you play *any* WMV?

You didn't say which version of WMP you have, so I'll assume it's fairly recent. I have WMP9; haven't got around to the latest yet. Under Tools|Options|File Types, presumably all looks OK? For example, WMV is checked?

Out of curiosity, what happens if you try Open With|your browser?

FWIW, I can play that WMV (video and sound) here in the following players:

- WMP9

- IrfanView

- Nero ShowTime

- RealPlayer

- PowerDVD

I'm trying to convert it to an AVI file, but so far can't get it below

8MB.

--
Terry Pinnell
Hobbyist, West Sussex, UK

That's frustrating. It plays for me with Windows Media Player. Wish I knew the magic incantation you need to use to get it to play for you.

Ed

6.0

So have I, now.

Never mind. ;-) (what's the smiley for "tail between legs"?)

Cheers! Rich