070620 1248 - David Farber posted:

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,



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.