"PoP" wrote
| This only leaves the issue of emptying the dustbin of sawdust.
| Perhaps not such a difficult task to shimmy up the ladder every
| so often to do that, but knowing my aptitude for laziness I'll
| probably overlook the emptying until the cyclone starts filling
| the vacuum cleaner and I hear the vacuum whining that it maybe
| needs emptying, exacerbating the problem with a vacuum dustbag
| which now also needs emptying. So I've thought of the following
| to solve this problem.....

Put an infra-red led on on side of the bin and an infra-red photocell on the
other side an appoprriate distance from the bottom. It doesn't matter if
they're in-line or if the photocell picks up light scattering inside the
bin, because you are relying on the settled sawdust blocking the led
completely. However the surface should be smooth so that 'ambient' sawdust
doesn't settle on the components causing a false 'full' indication

Owain