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one led, then 2, then 3, then 4......

steveharris

New Member
Hi guys...I don't know to much about electronics Ok. I am looking for a circuit that will light one then the next, then the next etc. each led comes on and stays on until the last one lights...after some time they all go off...after some more time it starts again
not even sure what this is called therefore my searching isn't finding what I'm looking for.
Thanks, Steve
 

HarveyH42

Banned
I've been thinking of something similar for a small wind generator project, but not quite what you are looking for but might find something useful. I'm think of hooking up an LM3914/3915 bar/dot driver IC up to the generator. It will drive 10 LEDs, but you can cascade them for more. The LEDs will be evenly spaced on the pole the wind generator is mounted. More power generated, more LEDs light up, sort of a wind speed gauge.

Yours might take 4 0r 5 logic chips, depends on how many LEDs, a clock source, and a timer. Probably simpler ways with fewer parts. Have to see what othe suggestions you get. Might want to give a few more details on what it will be used for, power source, type of LEDs, and how much electronic experience you have. Guessing you don't use microcontrollers (this would make a great starter project). So basicly you'll be using logic chips (flip-flop/shift register), I prefer the 4xxx CMOS series over the older 74xxx, wider voltage range.
 

bananasiong

New Member
I think this is suitable if you don't need many LED: twisted ring counter or Johnson counter. Then you can use extra logic gate to force them to the initial (all off) when all are light on.
 

3v0

Coop Build Coordinator
Forum Supporter
It may be easier to use a microcontroller. If you only need a few LEDs then use the pins to drive the LEDs. For a lot of LEDs use the processor to shift 1s into a chain of shift registers.

Either way the code and the hardware is very simple. A bonus would be that you could generate any pattern you wanted
 

HarveyH42

Banned
steveharris said:
Hi guys...I don't know to much about electronics Ok. I am looking for a circuit that will light one then the next, then the next etc. each led comes on and stays on until the last one lights...after some time they all go off...after some more time it starts again
not even sure what this is called therefore my searching isn't finding what I'm looking for.
Thanks, Steve
Think he's looking for something simple to construct. I would (have) use the MCU, mostly for the single chip solution. But since he's inexperienced in electronics, likely a little too advanced to start with, unless he already knows how to program, like on a PC. In which case, he might consider taking up microcontrollers.

Waiting to hear a few more details on what he wants, before getting too serious on throwing something together with logic chips.
 

Bob Scott

New Member
Hey, you seem to be describing the operation of the sequential tail lights of an early '60's Ford T-bird, or the same circuit the highway construction arrow signs work. Would you be able to search for lots of predesigned similar circuits just by googling "sequential tail laights"?

Bob
 

steveharris

New Member
Ok...say a line of 50 leds,,, led 1 lights, led 1 stays on, led 2 lights, now led 1 and 2 are on together. Led 3 lights, now 3 leds are on, led 4 lights, now 4 leds are on,,,,, keeps going until all 50 leds are on... after a time they all go off...then the procees restarts...1 led, then 2, then 3, then 4 and so on.
hope that this is clearer..
a line of leds lighting one after another until they are all on..then all of at once,,,,the repeats
Thanks again, Steve
 

on1aag

New Member
Hi Steve,

Add six extra CD4015's and connect them all as the second
half of the CD4015 is connected to the first half. Connect
all clock and all reset inputs together and move the reset
which is connected to Q1B to Q3M. (from the seventh CD4015)
That's it.

on1aag.
 

sheldonstv

New Member
Try this for controlling your leds via a 4017,set the 4017 to reset using the Q5 output and it will work as you want
 

Attachments

on1aag

New Member
The man specifically asked for a line of 50 leds, this would mean
a total of 1275 diodes. The last transistor doesn't actually need
a diode, 1274 diodes will do ! :D

on1aag.
 

Hero999

Banned
50 LEDs is a lot, are there any PICs with enough pins?

I think logic gates are probably a more sensible option here.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Hero999 said:
50 LEDs is a lot, are there any PICs with enough pins?

I think logic gates are probably a more sensible option here.
Probably not?, you only need 16 pins (8x8) and multiplex the outputs to feed 64 LED's - check my tutorial which does exactly that with a 16F628 (18 pin PIC).
 

3v0

Coop Build Coordinator
Forum Supporter
Hero999 said:
50 LEDs is a lot, are there any PICs with enough pins?

I think logic gates are probably a more sensible option here.
There are 80 pin pics with 70 IO channels in the 18F line but I am thinking the TQFP package is not an option for this his project.

You could do it with a PIC and 6 or 7 74HC595s. Total part count would be 7 or 8 chips the LEDs and resistors. Code is trival.

If you used two 16F877As with 34 IO lines each you could do it with 2 chips. In general most types run and hide when one mentions more then one processor but this is not difficult.
 

Hero999

Banned
Nigel Goodwin said:
Probably not?, you only need 16 pins (8x8) and multiplex the outputs to feed 64 LED's - check my tutorial which does exactly that with a 16F628 (18 pin PIC).
I would agree. I forgot you could do that, it's pretty obvious!
 

on1aag

New Member
Hi Charlie,

It won't work because the voltage drop accross a transistor junction
and nine diodes . . . . . and two leds is higher than your supply voltage.
And even if you increase the supply voltage the leds will become much
fainter as the number of voltage drops accross the diodes increases.

on1aag.
 

charlie_r

Member
oops, forgot to change the supply to 7.2V

ok, it was worth a cheap shot.

guess we really don't have much choice but to go to a uC setup.

personally, i have no experience with micros, but am willing to try anything at least once.

thanks for your input


C
 
Last edited:

charlie_r

Member
Here's another go at trying to figure this out.

If I'm reading the logic gate thing right, if I use a nand gate between the 4017 and the switching transistors, I still would need to invert that signal. If I could have someone look this over and tell me what I'm doing wrong or right.....
 

on1aag

New Member
Hi Charlie,

You're wrong again, if you insist on using a 4017 you gonna need OR
gates to drive the transistors. For the first transistor you need one
with 10 inputs, for the second one you need one with nine inputs,
shall I go on ?
What's wrong with my circuit ?



on1aag.
 

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