Re: Mast wiring

On Sat, 19 Dec 2009 14:41:02 GMT, Ronald Raygun
<no.spam@xxxxxxxxxxxxxxxxxxxxx> wrote:

Mas Dubh wrote:

Interested in the "Rayguns" 2 wire approach - whazisdis?

Two wires for two bulbs:

Basic method: You need two diodes. In the case of a combined
anchor/tricolour light, depending on its design, there is usually
room in the socket unit to fit these.

Connect both diodes to wire A. They should go in opposite directions,
so that the arrow or stripe on one diode faces towards wire A, while
that on the other diode faces away from wire A.

Connect the other end of diode 1 to one end of bulb 1.
Connect the other end of diode 2 to one end of bulb 2.
Connect the other ends of the two bulbs to wire B.

If wire A is positive and wire B negative, one bulb comes on.
If you reverse the polarity, so that wire A is negative and
wire B positive, the other bulb comes on instead.

One disadvantage of having the diodes in series with the bulbs is
that you will get a voltage drop across the diodes, of about 0.6V,
which can be significant (though you can get special diodes with
lower drops) since this is in addition to the drop you get in the
wiring itself. This problem can be avoided (as Ian pointed out
recently) by using an...


Enhanced method: You need one diode and a relay which operates a
single pole changeover switch. It may not be as easy to fit this
into the space available without improvising.

Connect wire A to the diode, the other end of the diode to the relay
coil, the other end of the relay coil to wire B. That way the relay
will energise only if the the wires are polarised one way, not the
other.

Also connect wire A to the moving contact of the switch in the relay.
The two fixed contacts of the switch are connected to the two bulbs
respectively, the other ends of the two bulbs being connected to wire
B as before. This way the switch in the relay connects either bulb 1
or bulb 2 to wire A, depending on whether the coil is energised.


What to do at the bottom:

The obvious way is to use a two-way changeover switch (known as DPDT)
with a centre off position. This works like two mechanically linked
but electrically independent single changeover switches, i.e. there
are 6 contacts usually arranged in two rows of 3, thus:

123
456

and with the switch in one position, 2 is connected to 1, and 5 is
connected to 4, while in the other position, 2 is connected to 3, and
5 is connected to 6. In the centre off position, no contact is connected
to any other.

Wire the battery supply to the centre contacts 2 and 5, for example
minus to 2 and plus (from a fuse) to 5.

Then connect 1 to 6 and this becomes wire A.
Then connect 4 to 3 and this becomes wire B.

An alternative method which "feels" like you are switching each
bulb independently, i.e. makes you use two switches, one for the
tricolour and one for the anchor light, needs two DPDT switches,
but not of the centre-off variety.

Wire the battery supply so that negative goes to terminal 1 on both
switches, and fused positive goes to terminal 4 on both switches.

Wire 2 on one switch to 2 on the other.
Wire 3 on one switch to 3 on the other.
Wire 3 on one switch to 6 on the other, and this becomes wire A.
Wire 3 on the other switch to 6 on the first, this becomes wire B.

This way when one or both switches are "off" (2 and 5 to 1 and 4),
negative is on both 1s and both 2s, and positive is on both 4s and
both 5s. When both switches are "off", then of course both 3s and 6s
are disconnected from the supply.

When one switch is "on", its 2 and 5 get connected to its 3 and 6,
and if this is the first switch, wire A becomes - and wire B becomes +.
If you switch the other switch instead, the polarity is reversed.
If you try to switch both of them on, the supply gets disconnected.


Three wires for four bulbs:

One method (there are others) is to apply the 2-wire recipe twice.
Use wires A and B to control bulbs 1 and 2 as above, and then in
a similar way use wires B and C to control bulbs 3 and 4.

This does give you the option of having bulb 1 or 2 on at the same
time as 3 or 4, but that might not be desirable.

Wiring up the switches at the bottom is less straightforward. It might
be better to use a 5-position rotary switch than a number of two or
three way ones.




Great description but anybody using Light Emitting Diodes does need to
be aware that they *are* diodes and polarity is important.

This could of course be very useful in the above
.

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