Re: Need help with intermittent circuit failures - JK Flip Flops

[snip]


The circuit works fine most of the time (like 80%), but it's unreliable,
and
I don't know what I can do to make it work properly every time. Most of
the
time the relay changes state 1 sec after motor stops (which is correct),
but
other times it does other wierd things, like the relay would act as if
it's
connected directly to the 555's output pin. Also, llthough very rare,
the
JK Flip Flop would even ignore the clock signals it receives and
therefore
the relay would do nothing - only the motor would stop for the 1 sec.
Very
annoying, being intermittent faults.

I can forward a circuit schematic, but its too hard to draw in html
format
(it's a little too complex) to do. I have a proper schematic i could
email
though as a jpeg.

Anyone have any ideas? I need this thing to be reliable. I may be doing
something wrong?



Well, in addition to the bypassing and catch diodes that w2aew mentioned,
I'd say, go ahead and post the schematic on
news:alt.binaries.schematics.electronic ; I notice you're not posting from
google, so I'm assuming you have a real newsserver and a real newsreader.
Put something recognizable in the subject line, and call attention to it
here, or even copy/paste the message ID.

There are also free places where you can post an image, but you'd have to
look them up.

I'd really like to see this circuit, because it sounds like it could be
simplified. One question: does this magnet go past some switch, which
starts the "turn around" process, the motor coasts to a stop, the motor
goes the other way, what happens when the magnet passes the switch again?

Thanks,
Rich



Hi Rich,

Thanks for the reply.
To answer your question about the magnet switching, the motor (or should I
say 'Gearhead Motor', which spins maximum of 36RPM at the shaft) will be
spinning slow enough that by the time it fully stops (which doesn't take
long at all), the reed switch will still be magnetised. The magnet will be
fairly powerful to keep it magnetized, and depends on what type of magnet I
use and how. I think it won't be an issue for my project.... but it was a
very good question =)
Perhaps I should explain what sort of timer I am using and how the reed
switch is connected to it? Well I am using a 555 timer IC configured as a
monostable which self-triggers at power on. That is, when the timer circuit
is powered up via the reed switch when magnetized, the output of the timer
goes high for 1 sec, then goes low until power is reset.

I've had a look at the schematics.electronic newsgroup, but are attachments
allowed? I don't see too many of those so I'm a bit reluctant. Can I email
it to you directly? It's so much easier to see the circuit rather than
decsribe it right?

Thanks,
Jason.


.

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