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


"John Fields" <jfields@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:umqo821htuqem9a1kaqp8hgm4u9g9h5o64@xxxxxxxxxx
On Sun, 11 Jun 2006 07:45:09 -0500, John Fields
<jfields@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Sun, 11 Jun 2006 19:25:07 +1000, "Jason S"
<jst3712@xxxxxxxxxxxxxx> wrote:


--------- Hi John, I don't see the new schematic on adse =( Remember
how
you couldn't see mine? Looks like the same thing is happening. Please,
I
would like to see it =)

---
OK, I've emailed it to you.

If you don't have access to abse it's probably because your ISP
doesn't carry abse. If you want it, let them know and maybe they'll
start carrying it.

BTW, I'm working on a version of the circuit with _no_ 555s which
looks pretty good. I'll post it to abse and email you a schematic
when I'm done. Sometime today, I think.

---
Better than that, an LTSPICE simulation follows that uses only two
chips for the logic, a "D" type flip-flop and a NOR. I used a
MOSFET bridge instead of a relay for the motor rotation reversal,
but if you want to use a relay you can hook it up like you've shown
on your schematic. Same thing for the power ON-OFF to the motor.

[snip]
John Fields
Professional Circuit Designer


Hi again John,
Thanks, I received your email with your PDF attachment. I have also added
this to my website so everybody else can see what you have posted to me, if
that's ok.

Click this link to view the schematic John Fields emailed to me :
http://www.jason3712.zoomshare.com/album/Electronics/images/faa493dae822fb12905ac558c67fc35e_11500904500/:album?css=/lib/style/arial.css&css=/lib/style/type_editable.css&css=/lib/style/type_album.css).

I rewired my breadboard and the attached circuit works quite well, although
I couldn't hook up the gearhead motor because I broke one of its terminals
=S ... I'll have to pull it apart and resolder it. Besides, I don't have
any 15V zeners on me at the moment, so I don't want to pop another BC338!
But at least I can tell what is happening by the 3 LED's, "Motor On",
"Direction A" and "Direction B". So it appears now there is that extra
delay before the motor turns back on.

I've noticed a potential problem though!!! You know how this thing pans 180
degrees and then changes direction shortly after the reed switch is
magnetized? This thing would break on me if it was left the way it is (not
the circuit, but the outer structure because it's not designed to spin
beyond 180 degrees).

- I'll give you an example:
Imagine the motor is turning in Direction "A", and the reed switch just made
contact with the magnet. Then I shut down the whole circuit intentionally
(at this stage, it has already panned 180 degrees, which is the max). If
you then turn the circuit back on, *sometimes* the motor starts to spin in
the same direction (A) it was before - when it should be turning the
opposite direction (B) straight away. So somehow the circuit will need to
know that it reached the end from the previous time and should be turning in
the correct direction. I'm not sure how this will need to be hooked up, but
maybe a second reed switch is needed (one for each direction)???

Other than that it seems to be working fine. I can't wait to see your next
version John.... no 555!

Regards
Jason.


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