Question: need two 1-second-pulses 30 seconds after power-on

Discussion in 'Electronic Basics' started by Christoph Ramm, Jan 6, 2004.

1. Christoph RammGuest

Hello newsgroup!

Maybe the question is a little confusing, that's why I drew a little
picture...

| ------ ------
| | | | |
|-//---------------------- -------- ------//--> output
|
| <------- 30s-----><-1s-><-1s-><-1s->
| <------- T1 -----><-T2-><-T3-><-T4->
|
| -----------------------------------------//--> power supply
| |
|-//----
|
--//--------------------------------------------//--> t

I need a simple circuit, that creates two one-second-signals 30 seconds
after turning the power on. I tried using the 555 timer IC, but I wasn't
successfull. Can you help me? Thanks a lot!

Greets, Christoph

PS: sorry for that bad english

3. Christoph RammGuest

not very good, 30 s may be 25..35 s, 1 s may be 0,75..1,25 s

5. Christoph RammGuest

Hello John!

"alt.binaries.schematics.electronic". Maybe you can send the content of

Thank you, Christoph

7. Anand DhuruGuest

You could use a small 8 pin PIC, the software would not be very
complex. Plus, you could change the pulse durations, nos etc. anytime
in the future if the requirements change.

Regards,

Anand Dhuru

8. Terry PinnellGuest

Method 1: 4 x 555 (attached)
----------------------------
http://www.terrypin.dial.pipex.com/Images/PulseTimer4x555.gif

I was pleased to get this working, despite its unimaginative approach.

Method 2: 4017 (attached)
-------------------------
http://www.terrypin.dial.pipex.com/Images/PulseTimer4017.gif

This is my preferred approach, as it requires only two simple,
independent adjustments: the 29.5s mono period and the 1s astable.
That odd duration of 29.5s was chosen because the clock won't
necessarily be closely synchronised with the mono outputs. That could
give rise to an extra delay of up to 1s. Circuit should ensure delay
between power up and first 1s pulse is between 29.5 and 30.5s,
'averaging' 30.0s.

If a slightly inferior output was acceptable, the OR gate could be
made from a couple of diodes and a resistor, and the half 4001 used to
make the monostable, eliminating the 555.

9. Fred BartoliGuest

Hi Terry,
I'm sure that you can achieve much lower part count (and BTW avoid the 2

Hint : use only 1x555, 1x74(HC)93.

Fred.

10. Christoph RammGuest

Hello John,

thanks a lot, I'll try this!

Greets, Christoph

11. Christoph RammGuest

Hello Anand,

to learn how to program PIS in assembler, I don't know how long this
would takt. I program C167-uC's in C, I don't know the traps of PICs...

But thank you anyway!

Christoph

12. John FieldsGuest

---
You're welcome.

As Terry has suggested, the adjustments might be a little tricky, but an
easy way to stay out of trouble would be to start with R3 at maximum
resistance, then adjust R4 (the pot) for the 30s delay from power-on to
the beginning of the first pulse. After that, adjust R3 until the
number of output pulses decreases to 2.

13. fpdGuest

"Fred Bartoli"
Nice drawings. What application do you use?

14. Terry PinnellGuest

"Terry Pinnell" <> a écrit dans le
message
Thank you. CircuitMaker.

15. Terry PinnellGuest

"Fred Bartoli"
Never heard any more from you on that Fred...

I eventually succeeded, but as I said it took a much *higher* part
count! Here's a breakdown:

1 x 74LS93 16-state binary counter (didn't have HC type)

2 x 4001 NOR gates for clock with 2s period and 50% duty cycle

15 x 4001/4011 gates to detect 3 states 13, 14 and 15 and deliver them
with appropriate polarities for subsequent logic

2 x NOR gates to OR states 13, 14 for required 1s output pulses

2 x NOR gates for bistable used to gate the clock (enabled at PU,
disabled on final state, 15)

I had a couple of spare gates left, but in total used 7 ICs.

So my 4017 approach at
http://www.terrypin.dial.pipex.com/Images/PulseTimer4017.gif
which uses only 3 ICs remains my recommended solution.

16. Christoph RammGuest

Thank you everybody!

I decidet to use a cheap PIC, programmable with BASIC. It's the simplest
application (only few extra parts), simple to program, flexible if I
need other pulses. Of course, a little overdone... Maybe I'll need
thousands of circuits some day (and I get rich and famous...), then I'll
take a look at a simpler, cheaper circuit. In this case, send me your
bench account, so I'll let you share with my euros )

Greetings, Christoph