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


"Jason S" <jst3712@xxxxxxxxxxxxxx> wrote in message
news:448aa43a$1_1@xxxxxxxxxxxxxxxxxxxxxx
Thanks guys heaps. You been a great help.
I haven't had a chance yet to try your schematic John (Petrus and ehsjr, I
have noted your observations and advice as well), but I'll let you know as
soon as I've totally rewired my breadboard...ugh.

However, do I really need to add another IC to my board (the 2nd 555)?
This board has to be as small as possible... I didn't think I'd need so
much electronics to do this simple task. Maybe 1x 556 (dual 555 IC)
instead of 2x 555 would save a little more space??

By the way - in relation to the way I configured the monostable.... is it
still a bad thing to want to be able to trigger the monostable at power on
(ignoring the reed switch for arguments sake)? Assume pins 1 and 8 were
connected directly to the supply rails... so when power is turned on, the
monostable triggers automatically (due to C2). I understand the correct
method of triggering pin 2 with a negative pulse, but then I would need a
separate circuit to achieve that as well - the negative pulse. That is
the only reason why I connected the reed relay the way I did - When the
magnet comes into contact with the reed, it triggers the 555, doesn't
matter how long the reed is in contact with the magnet for. In my
circuit, if I made it so that the reed switch triggers pin 2, the 555
would freeze (on 'high') because the motor would have turned off and
stopped right in front of the magnet indefinately. I was just wondering
that's all.

The two 15V zener diodes across the motor opposite each other is critical
yeah? Is my Q1 transistor overheating because these are absent? Or
because of the motor reactivating too soon before the relay switches
over??? The Q1 is rated 0.8A.

P.S: John, I really appreciate your schematics... makes it a lot easier
to understand what you are talking about =).

Ta
Jason.





*** Further to this, I have redone my schematic. Please check if everything
is correct as I may have missed something or misunderstood a bit here n
there.

Try this direct link :
http://www.jason3712.zoomshare.com/album/Electronics/images/61f79ebef160ea600b846b3e79e8f992_11499434750/:album?css=/lib/style/arial.css&css=/lib/style/type_editable.css&css=/lib/style/type_album.css

.... or find it manually by going to http://www.jason3712.zoomshare.com/
then clicking 'PHOTOS', 'Electronics', and clicking top (most recent) image,
"schemtaic_SL_v2".

I am yet to rewire my breadboard.

Regards,

Jason.





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