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Old automatic gate controller question.

Discussion in 'Electronic Repair' started by David Farber, Jun 20, 2007.

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  1. David Farber

    David Farber Guest

    This 28 year old Stanley Vemco automatic gate uses mechanical relays. The
    problem is that the relays are noisy when either the opening or closing
    sensor switches are activated at the end of its travel. For example,
    somebody runs over the air hose to begin the open operation. You can hear a
    relay click with no problem, then the gate opens. Just before the gate is
    fully open, it enables a sensor switch which interrupts power to the motor
    relay. Then, you can hear one of the relays make a chattering noise which
    decays in about two seconds. The same thing happens when the gate closes. It
    seems to have gotten louder over the years. Since the entire circuit is AC,
     
  2. David Farber

    David Farber Guest

    Sorry about this incomplete message. It was erroneously sent. I think the
    solution will be to replace the noisy relays with new ones.
     
  3. Guest

    That, it would. Stanley makes (made) good stuff, and 28 years ain't
    nohow half-bad. If all it is is relays, count yourself lucky.

    Peter Wieck
    Wyncote, PA
     
  4. James Sweet

    James Sweet Guest

    Might be worth checking to see if there's a diode or rectifier bridge in
    there. A shorted diode could cause AC to be fed to relay coils expecting DC
    which will make them chatter or buzz.
     
  5. David Farber

    David Farber Guest

    I dismantled this thing last year. There are only switches and relays. But
    now that you mention it, maybe some of the relays were improperly replaced
    with dc relays or the diodes are missing? I'm not the original person
    working on this controller.

    Thanks for your reply.
     
  6. Ross Herbert

    Ross Herbert Guest

     
  7. David Farber

    David Farber Guest

     
  8. David

    David Guest

    These relays are all designed to be energized by an AC source. The copper
    shunt at the end of the pole piece is characteristic of AC relays. Is there
    a 24 volt transformer anywhere in there and do all of the relays chatter, or
    just one?

    David
     
  9. David Farber

    David Farber Guest

    Yes, there is a 24V transformer. The difficult part is figuring out which
    one(s) are chattering. They are not in a very convenient place to observe
    what's going on and all three of them are mounted side by side. I might need
    to extend the wires a bit so they can be moved into plain view and still
    have them electrically connected. Can you please explain in the picture of
    relay 1, http://www.pbase.com/mrfixit/image/81163240, what the rating of,
    "120VAC/28VDC"means? Is that the rating of the contacts?

    Thanks for your reply.
     
  10. Jamie

    Jamie Guest

    If you have a 24 volt supply then may I suggest you look for a rectifier
    or diode that has shorted and sending 24 volt ac instead of DC to the coil.
    those relays require DC volts if you're using voltages that low.
     
  11. indago

    indago Guest

    070620 1248 - David Farber posted:
    Relays work on a magnetic principle. When voltage is applied to the coil,
    the is created a magnetic circuit the engages. The magnetic pole pieces
    slam together. If there is a piece of dirt, or other foreign substance on
    the surface of the magnetic circuit where the pieces slam together, they
    will not engage properly, and with AC, the magnet will chatter. This is
    very annoying, and the poles should be cleaned. Just take a look in the
    relay and clean out any debris that has fallen into the magnetic circuit.
     
  12. David

    David Guest

    "David Farber"
    message
    The picture would indicate to me that
    the contacts are rated for 11 amps with
    either a 120v AC source a 28v DC source.
    It is not obvious what the coil voltage
    is supposed to be. Relay 2 appears to
    have a 110vac coil and relay 3 a 24vac
    coil.
    These look remarkably clean for such an
    old unit.

    David
     
  13. David Farber

    David Farber Guest

    As I found this unit, there is *no* dc power supply in this controller. One
    relay coil is connected directly to the 120VAC line voltage and is always on
    as long as the main power switch is on. All the other components are powered
    by the 24VAC. Those components are the two remaining relays, one self
    contained timer control device which delays the gate closing, and the
    contactor, which has two 24ACV solenoids that activate switches to enable
    the motor in either the forward or reverse direction.

    Thanks for your reply.
     
  14. David Farber

    David Farber Guest

    The pictures are about two years old. The unit itself is located in a
    protected box and that probably has helped to preserve the looks of the
    components.

    Thanks for your reply.
     
  15. m kinsler

    m kinsler Guest

    You've got a bad pair of contacts feeding the coil of one of the
    relays. The chattering relay is probably not the one that is at
    fault; the difficulty might well lie in that sensor switch. I've had
    difficulties with magnetic reed switches in the past, and if there's
    one there I would see about it. There may also be a bad connector
    associated with the sensor switch. Find the wires that go to the
    sensor switch and use a jumper across them to simulate the operation
    of that switch. If the relays operate but do not chatter, then the
    difficulty lies in the sensor switch or its wiring.

    M Kinsler
     
  16. David Farber

    David Farber Guest

    The sensor switches are regular microswitches. I'll do the jumper test and
    see what happens.

    Thanks for the good suggestion.
     
  17. Ross Herbert

    Ross Herbert Guest

     
  18. Ross Herbert

    Ross Herbert Guest


    PS. Since you say there is no DC power supply then it would appear
    that photo 1 also shows an ac coil relay.
     
  19. David Farber

    David Farber Guest

    Perhaps whoever worked on it before was replacing parts and not too picky
    about what types of relays were put in.

    I have uploaded a schematic of the electronics which I drew from tracing all
    the wires. I'd like to know if anybody can find any mistakes in the wiring
    diagram.

    http://www.pbase.com/image/81266775

    Secondly, there is a bell hose that opens the gate from the inside of the
    garage and a key that opens the gate from the outside. There is a second
    hose whose sensor is not hooked up which runs underneath the gate when in
    the closed position. I think this is a safety factor in case somebody drives
    in and the gate starts to close and would prefer not having their car
    smashed. As a security precaution, I think it would be smart to have this
    second hose sensor only allowed to be activated if the gate is actually
    closing. Where would be the correct spot, assuming one exists, to insert the
    second hose sensor that would *only* open the gate if the gate is in the
    process of closing?

    Thanks for your reply.
     
  20. Ross Herbert

    Ross Herbert Guest


    Yipes! All those uninsulated terminals look dangerous to me....

    Drawing out schematics of relay equipment is an art in itself. You
    have to establish conventions (ie, moving and stationary contact sets,
    coil relationships and status of the total mechanism). You must draw
    the whole system when it is in a defined state, such as "gate closed",
    and then draw the state of each relay and its associated contacts in
    this condition, remembering that the moving and stationary contact
    springs must also be drawn to reflect the associated relay situation.

    For example your notes say that Relay A is shown de-activated but the
    schematic is drawn such that its coil IS activated via the limit close
    switch (ie. the gate is closed). Also, the schematic shows the timer
    relay is activated from GND at C/9-3 (deactivated) via A/8-3
    (deactivated) to 24Vac, yet the timer relay contact is shown as being
    open.

    The schematic also shows the main power switch is ON and the B relay
    is activated. I assume those B contacts are supposed to be normally
    open when the relay is deactivated, so if this assumption is correct
    and the relay is drawn in its activated position, then the contacts
    should be drawn with the moving contact at the top being pulled
    towards the coil and making contact with the stationary contact. As
    drawn the contacts are shown as opening when the coil is activated but
    I assume you meant to draw it with the contacts making when the coil
    is activated.

    Also, where is the motor connected and what voltage supply powers the
    motor?

    Unless you can clearly define the status and show things as they
    really are in that condition, then it is difficult to work out how
    things are meant to work.

    Having said that, your first effort is to be commended, considering
    you probably haven't had to do this sort of thing before.
     
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