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controlling lights by short switch-offs


Julian Bradfield

Jan 1, 1970
I've been mulling the following problem, and would appreciate any
bright ideas.

I have light fitting with five bulbs (being replaced by compact
fluorescents as they burn out).

Sometimes, but rarely, I would like a dim or very dim light, with,
say, only three and only one of the bulbs lit.
However, having just redecorated, I'm not in the business of running
any extra cables (and since I'm putting in compact fluorescents, I
can't just use a dimmer to get less light!).

So I thought it should be possible to put a device into the light
fitting with the following properties:
it switches AC mains to two outputs, and has three states, with 0, 1
or 2 outputs switched on;
the usual state is 2; however, if power is removed for a short time,
it drops to state 1, then to 0, then to 2, so that the 1 and 0 states
can reached by removing power for (say) 2 and 4 seconds respectively,
and then re-applying power.

Now, given no constraints, this is easy enough to do with standard
electronics, but how feasible is it given the following constraints:
the 240 V AC mains supply to the fitting is the only power supply (and
no batteries can be used); and
the entire circuitry has to fit in a small space
(say 2cm x 2cm x 1cm); and
no non-trivial heatsinking is available (unless I'm creative, I