Re: 4017 Counter skips under load

On Jul 5, 2:00 am, jcargile2...@xxxxxxxxx wrote:
On Jul 4, 12:56 am, "David L. Jones" <altz...@xxxxxxxxx> wrote:



On Jul 4, 5:12 pm, jcargile2...@xxxxxxxxx wrote:

On Jul 3, 4:58 pm, "David L. Jones" <altz...@xxxxxxxxx> wrote:

On Jul 4, 8:54 am, jcargile2...@xxxxxxxxx wrote:

On Jul 3, 3:14 pm, "David L. Jones" <altz...@xxxxxxxxx> wrote:

On Jul 4, 6:50 am, jcargile2...@xxxxxxxxx wrote:

On Jul 3, 1:24 pm, Joerg <notthisjoerg...@xxxxxxxxxxxxxxxxxxxxx>
wrote:

jcargile2...@xxxxxxxxx wrote:
On Jul 2, 3:24 pm, "David L. Jones" <altz...@xxxxxxxxx> wrote:

On Jul 3, 7:11 am, jcargile2...@xxxxxxxxx wrote:

I have a fairly simple circuit that consists of a 4017 decade counter
and nine relay/LED combinations. The relays are very small and the
circuit operates just fine with no load, or when I connect an LED to
the relay output. But when I try to operate the circuit under load
(it is being used to fire nichrome ignitors), then the counter simply
skips the loaded relay and moves right to the next output. So if I
send the counter a series of 5 clock pulses, and put a load on the
relay attached to output 3, then the count goes 1,2,4,5,6. The final
count ends up being one off, so it's almost like the output in
question doesn't exist. What I don't understand is why this is
happening, since the relay is what bears the load, not the 4017.
Shouldn't the output requirement on the counter be the same regardless
of what the relay is switching?

Yes, it should be, but only if you have used proper circuit physical
circuit layout techniques to ensure that there is no ground or power
bounce.
Think "star grounding" and power decoupling.
Very common trap for young players.

Dave.

I installed the final power setup (on the tests I just had the board
jumpered onto the power supply) and now it will fire the ignitors.
The problem is that the counter is now behaving irratically. It will
skip several counts when receiving a clock pulse and will jump around
with the slightest change in ground (even connecting a single lead
from the multimeter to any point on ground advances the count). I've
tried several different caps (.01-10 uF) connected directly to the
power leads of the 4017 with no luck. All of the info I can find on
decoupling keeps talking about selecting the capacitor based on
frequency. But I'm only sending a single pulse of about 25 ns every
10-20 seconds. Does this mean I can use a larger cap? I'm seriously
freaking out at this point cause I only have 24 hours to get this
working. Thanks for the help!

How on earth do you get a 25nsec pulse out of a CD4017? That's like
clocking a moped at 100mph.

Anyhow, since things seem to become desperate over there I can only
suggest to build it up again on an experimental board that has a ground
plane. And no, you do not have to select decoupling caps based on
frequency. A 0.1uF plus a nice 10uF electrolytic should do, more if your
power supply is wimpy.

Can you post schematic plus photo?

--
Regards, Joerg

http://www.analogconsultants.com-Hidequotedtext-

- Show quoted text -

Sorry, I mistyped. The clock pulse coming into the 4017 from the PC
parallel port is 25 ms in length.

Ah, the alarm bells start ringing right there, no pun intended.
You probably have ringing on your clock line from the PC. Keep the
lead from the parallel port as short as possible.
Are you able to view the signal with an oscilloscope?

Classic problem with PC parallel port driven equipment.

Dave.- Hide quoted text -

- Show quoted text -

Unfortunately I don't have access to a scope. This is the kit that
I'm using. The board itself is plugged directly into the parallel
port. I then have leads soldered on to the board at the resistors so
that I get a clean 12 volt signal from the parallel port. From there,
that signal is run via ethernet cable to the firing controllers. In
my initial tests, this setup worked fine with just an LED as the
load. Because of safety reasons, I can't have the laptop and thus
myself any closer to the controllers themselves.

<img src="http://kitsrus.com/jpg/k74v2_1.jpg";>

Ah, a picture tells a thousand words.

The board should work just fine *if* you power your load from an
entirely separate and *floating* power supply relative to the plugpack
or power supply which powers the board. You've said the board works
just fine with an LED load, so obviously something is amiss with the
power supply wiring for the load.

Dave.- Hide quoted text -

- Show quoted text -

I tried that earlier, but couldn't get the firing boards (running
4017) to recognize the clock pulses from the parallel port interface
unless the grounds were connected. Am I doing something wrong there?

I don't get the whole picture here, so let's see if I have this
correct...
The 4017's are located on your own board at the end of a long ethernet
cable connected connected to this relay interface board?

Please explain in detail what the relay interface board does, what
your 4017 board does, how they are connected together, how they are
powered, and what lengths of cable are used. Unless you do that we'll
all be going around in circles.

Dave.- Hide quoted text -

- Show quoted text -

Hopefully these pics will show the full set up.

http://a548.ac-images.myspacecdn.com/images01/105/l_9f67b69cc9c5093d7...

This is the inside of the firing box. The barrier strip at the top
brings the +12V and ground for the firing control boards (at bottom)
as well as a separate ground for the igniters that is controlled by a
safety switch. I added the cap to the barrier strip last night in an
attempt to help stiffen the power supply to be boards, but have not
yet tested it.

http://a340.ac-images.myspacecdn.com/images01/79/l_d358560b9c651a8da6...

The second pic is the top side of one firing control board. There are
5 of these in total. The IC at the top is the 4017. The black
rectangular boxes at the bottom of the board are the SPST reed relays
that activate the igniters.

http://a502.ac-images.myspacecdn.com/images01/82/l_86a86c8ec7313a72a4...

The underside of the firing board. The wide trace on the right side of
the board is the +12V and the left side is ground. Are these too
small?

http://a861.ac-images.myspacecdn.com/images01/82/l_5aafdf9e0837402f36...

This is the Kit74 parallel port interface as well as the power
supply. I only have them sitting this close in order to fit them into
one picture. I have wired leads onto the Kit74 that goes to an RJ45
jack. That ethernet cable then goes to an identical jack where each
line is connected to the clock pin of one firing control board.

So in theory the operation goes like this:
The system is powered up and all counters and parallel port are
reset. The ignitor ground is then connected via a remote switch.>From there the software on my laptop plays the soundtrack and at set

intervals activates a single channel output on the parallel port.
That signal is then sent from the Kit74 interface via an ethernet
cable to the firing boards in the display. The 4017 in the firing
controller advances one count, activating the next relay in line. The
wire connected to the relay receives +12v which passes through the
nichrome igniter and returns to ground through the safety switch. The
wire heats, igniting the fireworks. The igniter typically burns up in
less than 1 second. The process repeats until all 9 cues have been
used.

Problems:
1) You are driving the relays directly with a 4017, that's *bad*. A
4017 will not have enough output current to do that. You are using low
power reed relays, but it's still too much for a 4017.

2) You can't use a relay driver board to provide clock pulses to a
4017, in fact this probably the worst possible way I can think of to
do this. You'll get ridiculous amounts of contact bounces causing
multiple pluses.

3) You are feeding power to the remote boards via the long ethernet
cable that is also the same ground line as the 4017. Power for the
4017 board should be local.

I'm surprised it even worked at all with no load.

At the very least, this might help until you can design the whole
thing properly from scratch - add a single-shot circuit to the 4017
board clock input so you are guaranteed to only generate one clock
pulse from how ever many erroneous input pulses.

Dave.

.

Relevant Pages

  • Re: 4017 Counter skips under load
    ... But when I try to operate the circuit under load ... skips the loaded relay and moves right to the next output. ... Think "star grounding" and power decoupling. ...
    (sci.electronics.design)
  • Re: 4017 Counter skips under load
    ... But when I try to operate the circuit under load ... skips the loaded relay and moves right to the next output. ... with the slightest change in ground (even connecting a single lead ... The second pic is the top side of one firing control board. ...
    (sci.electronics.design)
  • Re: 4017 Counter skips under load
    ... But when I try to operate the circuit under load ... skips the loaded relay and moves right to the next output. ... with the slightest change in ground (even connecting a single lead ... lead from the parallel port as short as possible. ...
    (sci.electronics.design)
  • Re: 4017 Counter skips under load
    ... But when I try to operate the circuit under load ... skips the loaded relay and moves right to the next output. ... Think "star grounding" and power decoupling. ... lead from the parallel port as short as possible. ...
    (sci.electronics.design)
  • Re: 4017 Counter skips under load
    ... But when I try to operate the circuit under load ... skips the loaded relay and moves right to the next output. ... Think "star grounding" and power decoupling. ... lead from the parallel port as short as possible. ...
    (sci.electronics.design)