On Fri, 23 Oct 1998, James Cameron wrote:

> The specifications of the relay are;
>         - 12V DC 400mW nominal coil power,
>         - two coil latching design,
>         - DPDT,
>         - Minimum set and reset power 180mW,
>         - Nominal set and reset power 360mW,
>         - Switching current maximum 2A,
>         - [Jaycar SY-4060 for the Aussies here].

A small question: Why use a latching relay for an application that can
certainly benefit from a self-resetting relay and where there is plenty of
power available.

A DPDT 5V relay can manage more than 3A and you can still use your
micro-switches to limit throw. Two such relays are cheaper than a latching
one and you can cunningly wire them (in series) such that they can't
auto-destruct even if both are turned on at the same time. If I were you
I'd use two micro-switches for each end, in series, each with its own
diode, just to be sure. Smoke from a cooking motor coil does not benefit
the health of a person that cannot move away from it.

For an existing latching relay, you can probably use 2 DTC124 digital
transistors and 2 kickback stopper diodes (1N4148) and that's it. It's a
good idea to fuse the relay coil power line with a micro thermo fuse.
Latching relay drive circuits are dimensioned for momentary operation and
have been known to 'cook' quite hot for a long time if failed.

my $0.02

Peter