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Simplest 2-LED alternating flasher

P

Peter

Jan 1, 1970
0
I need the simplest possible circuit to make two LEDs flash
alternately. About 1/2 second on each. I envisage using one flashing
LED and one standard LED plus as few other components as possible.
Maybe the 2 LEDs, one resistor and a mosfet.

I have successfully used a flashing LED as the clock source for a 4017
decade counter. Now I just want to make it and another LED flash. Any
ideas much appreciated. Not interested in using 555's, NAND gates,
schmitt triggers etc.
 
T

Tom Biasi

Jan 1, 1970
0
Peter said:
I need the simplest possible circuit to make two LEDs flash
alternately. About 1/2 second on each. I envisage using one flashing
LED and one standard LED plus as few other components as possible.
Maybe the 2 LEDs, one resistor and a mosfet.

I have successfully used a flashing LED as the clock source for a 4017
decade counter. Now I just want to make it and another LED flash. Any
ideas much appreciated. Not interested in using 555's, NAND gates,
schmitt triggers etc.

Well you have imposed quite a few restrictions.
Maybe look at multivibrator circuits.
 
J

John Fields

Jan 1, 1970
0
I need the simplest possible circuit to make two LEDs flash
alternately. About 1/2 second on each. I envisage using one flashing
LED and one standard LED plus as few other components as possible.
Maybe the 2 LEDs, one resistor and a mosfet.

I have successfully used a flashing LED as the clock source for a 4017
decade counter. Now I just want to make it and another LED flash. Any
ideas much appreciated. Not interested in using 555's, NAND gates,
schmitt triggers etc.

---

If you successfully got the LED to drive the counter, then this
should work: (View in Courier)

+V
|
[R]
|
[LED]
|
D
FROM 4017 CLOCK INPUT>----G
S
|
GND
 
I need the simplest possible circuit to make two LEDs flash
alternately. About 1/2 second on each. I envisage using one flashing
LED and one standard LED plus as few other components as possible.
Maybe the 2 LEDs, one resistor and a mosfet.

I have successfully used a flashing LED as the clock source for a 4017
decade counter. Now I just want to make it and another LED flash. Any
ideas much appreciated. Not interested in using 555's, NAND gates,
schmitt triggers etc.


Does the clock input go high when the flashing led is off?
If it does connect a LED to the clk input and to GND...
something like this maybe...


VCC
+
|
|
.-.
| |
| |
'-'
|
|
|
V -> Flashing LED
-
LED | .--o--.
|-|<---|--|D S Q|
| | |
| -|> |
=== | R Q|
GND '--o--'
 
P

Peter

Jan 1, 1970
0
Sorry, I didn't mean I want it related to a 4017. This is a completely
separate exercise. I was just noting that I have successfully used a
flashing LED to drive a 4017. My circuit was published in Australian
Silicon Chip magazine in about 2004.

I now just want to make 2 LEDs flash. Need it quickly so was hoping
for a solution without having to experiment.
 
P

Puckdropper

Jan 1, 1970
0
Sorry, I didn't mean I want it related to a 4017. This is a completely
separate exercise. I was just noting that I have successfully used a
flashing LED to drive a 4017. My circuit was published in Australian
Silicon Chip magazine in about 2004.

I now just want to make 2 LEDs flash. Need it quickly so was hoping
for a solution without having to experiment.

Take a look at this:
http://mrollins.com/flash3.html

Oh, btw, when you need it fast it's best not to ask on Usenet...
Searching on the internet can get you results in less than 5 minutes. ;-)

Puckdropper
 
P

Peter

Jan 1, 1970
0
I did search the web but found nothing. That circuit you referred to
contains about 10 more components than I want to use. That looks like
a standard astable multivibrator for which I agree there are thousands
of circuits on the web. I am looking for something a bit unique.
 
L

Lionel

Jan 1, 1970
0
I did search the web but found nothing. That circuit you referred to
contains about 10 more components than I want to use. That looks like
a standard astable multivibrator for which I agree there are thousands
of circuits on the web. I am looking for something a bit unique.

The traditional method is an astable version of the classic 2
transistor flipflop. If you want anything simpler, with fewer
components (2x transistors, a couple of caps & a few resistors), &
more unique than that, you're going to have to design something
yourself.
(There's any number of ways of flashing two LEDs with a single chip,
but I can't think of any that are simpler than a 555.)
 
J

John Fields

Jan 1, 1970
0
Sorry, I didn't mean I want it related to a 4017. This is a completely
separate exercise. I was just noting that I have successfully used a
flashing LED to drive a 4017. My circuit was published in Australian
Silicon Chip magazine in about 2004.

I now just want to make 2 LEDs flash. Need it quickly so was hoping
for a solution without having to experiment.

---
1. When you reply to a post, don't snip all of the post you're
replying to, because that way no one knows what you're replying to.

2. When you reply to a post that you've left some of the poster's
text in for context, don't top post. So far you haven't been able
to, but if you snip properly you probably will want to since you're
a Google Grouper. For heaven's sake, read their stuff on posting to
USENET.

3. Pay attention when you read what someone gives you.

For example, I posted:

"If you successfully got the LED to drive the counter, then this
should work: (View in Courier)

+V
|
[R]
|
[LED]
|
D
FROM 4017 CLOCK INPUT>----G
S
|
GND"


Notice that the gate of the MOSFET is connected to the 4017 input,
which is also the output of the circuit you used to drive the 4017.

Since you didn't show the circuit, one would have to guess how it
was put together, but since you _know_ how it was put together all
you need to do is connect the point driving the counter to the gate
of the MOSFET.

So, to get your 2 flashing LED circuit all you need is the LED
flashing circuit you already have and the one I've given you.

Maybe this'll make it easier:


+V
|
[R]
|
[LED]
|
FROM THE PART OF THE D
FLASHING LED CIRCUIT------G 2N7000
WHICH WAS CONNECTED TO S
THE 4017 CLOCK INPUT |
GND
 
R

Rich Grise

Jan 1, 1970
0
Take a look at this:
http://mrollins.com/flash3.html

Oh, btw, when you need it fast it's best not to ask on Usenet...
Searching on the internet can get you results in less than 5 minutes. ;-)

Oh, ick! 2N3055s to flash LEDs? OP could use 2N2222s, PN2222s, 2N3904s,
2N4401s - practically any general-purpose tranny that will take the
supply voltage and maybe 25 mA. They're so common you could almost find
them lying in the street. ;-)

Here's a sort of generic thing on astables:
http://www.play-hookey.com/digital/experiments/rtl_astable.html

Have Fun!
Rich
 
J

jasen

Jan 1, 1970
0
Sorry, I didn't mean I want it related to a 4017. This is a completely
separate exercise. I was just noting that I have successfully used a
flashing LED to drive a 4017. My circuit was published in Australian
Silicon Chip magazine in about 2004.

I now just want to make 2 LEDs flash. Need it quickly so was hoping
for a solution without having to experiment.

---+--------+---- 5V
| |
| [220R]
self- | |
flashing V .---+
LED T / |
| |/ |
+-| V ordinary
| |\| T LED
| ~\ |
| | |
[1K] | |
| | |
----+----+---+- 0V

you may not need the 1K resistor.


Bye.
Jasen
 
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