"Fred Bloggs" <
[email protected]> schreef in bericht
John Fields wrote:
On Wed, 26 Oct 2005 12:04:41 -0500, John Fields
That works- but is there an AC solution? Motor is heavily geared and
turns slowly- stops on a dime.
---
Yes.
Use an adjustable delay-on-make timer like an ICM Controls ICM102 or
a WW Grainger 4E233,(they're the same part) like this:
SWITCHED MAINS IN>---+------+
| | +-----+ |
|TIMER| | +-----+ | | O
| |K1
[COIL]- -|<---O
| |
O | |
S1 |<- - -[MOTOR]
O | |
| |
RETURN>--------------+-----------+
That way, If S1 is closed because the motor stopped when it (S1)
closed, the timer will block the flow of current into the coil of
K1, keeping K1 de-energized until the motor turns enough to release
S1.
---
Aarrghhh...
There's still a problem in that if the timer keeps the coil from
being energized for a while when the switched mains in goes hot
_and_ S1 is made, the same thing'll happen when S1 is made by the
motor riding over it, since it was open before that and the timer
was waiting for a current path to start its timeout. That is, when
the timer sees mains voltage across itself (and passes just enough
current to make its timer work without pulling in K1) K1 won't be
able to pull in until S1 is released, but by then it'll be too late,
and the motor will never stop.
Intrigueing problem to try to solve from just the AC side...
More tomorrow...
Si Dios quiere.
Right- I was wondering about that. The only way this can work is to
detect
a transition from open to close and and vice versa in S1, any control
relying on S1 static position or polarity of transition will fail.
Forgetting about any particular hardware for the moment, if you can
configure a detection circuit that is somehow "armed" by the sequence
of
S1 moving from initial to opposite state and then triggers the
self-latching NC power relay when S1 returns to the initial state, this
should do it. If power first comes up with S1 open, then the trigger
arms
when S1 closes and triggers motor off when S1 re-opens. If power comes
up
with S1 closed, the trigger arms when S1 opens, and triggers when S1
re-closes. The end result is that the motor always stops at the SW
position after making at most one revolution. If you want the motor to
fall into always stopping when S1 closes, then you could a timer that
applies to the arming logic so that if S1 was open initially, but the
motor has run a minimum predetermined time, the trigger logic will fire
on
first closure.
Can't help but giving it a second look. I'm sure all simple solutions may
run into timing or exception problems like I said before. The solution
below
is not very simple but should work always.
+--------+---------+---------+
| | | |
| | | |
.-. _|_ _|_ _|_
( M ) |_/_|- |_/_|- |_/_|-
'-' |A |B |S
| | | |
| | | |
+----------------------+ |
| | | | |
| | | | |
| | | | |
| +--------o / o / o /
| | / / /
| | /a1 /a2 / SW1
| | o o o
| | | | |
| | +----+----+ |
| | | |
| | | |
o /o /o |
/ / |
/ b / s |
o o |
| | |
+-------------+------------------+--
created by Andy´s ASCII-Circuit v1.24.140803 Beta
www.tech-chat.de
S can be omitted when SW1 has a normally closed contact that can stand
the
motor current, so SW1 can replace the s-contact. If you have to use the
S-relay, it should be fast with respect to the A- and B-relays.