On Sun, 07 Aug 2005 22:31:59 +1000, Peter Hendra
wrote:


=What is best - solenoids or relays? What is the difference please?

A relay is a mechanical arrangement of electrical contacts actuated by
a coil. Run current through the windings of the relay coil and it
becomes a magnet. The magnetic force attracts a soft-iron armature,
which then moves and imparts its motion to the contacts, making (or
breaking) the circuit, depending on the arrangement of the contacts.

A solenoid is also a coil, usually with a hollow center into which is
inserted a soft-iron rod. Current through the coil generates a
magnetic field, as in the relay coil, and the rod (armature) is either
pulled into the coil or expelled from the coil, depending on the
design. Mechanical springs would normally hold the armature in some
de-energized (power-off) position, either in or out of the solenoid
core.

If your winch has two heavy-duty electrical terminals (+ and -) then
you would probably want to use a relay close to the winch with its
heavy-duty contacts in series with the battery supply to the winch for
control. As you had planned, energize the relay coil from the cockpit
over an appropriate circuit.

If your winch has two heavy-duty terminals and one lighter-duty
terminal, chances are it has its motor contacts inside the housing.
You would connect battery to the heavy-duty terminals, and energize
the lighter-duty terminal from the cockpit through an appropriate
circuit.

Your engine starter is a good example of a solenoid-actuated
high-current switch.

Of course, most winches are reversible, and now you're getting into
another can of mollusks!

Cheers--
Terry--WB4FXD
Edenton, NC