After refilling a Canon ip4200 or similar, with the newer-type chipped
cartridges, one loses the ability to monitor the ink levels using the
printer's cirquitry and software. This is unfortunate.

It occurred to me that it would be quite easy to design and produce a
low-cost add-on ink level warning device - comprising a sensor that
detects when the rear portion of the cartridge (the chamber with no
sponge inside) runs dry. This could be achieved with a two-terminal
sensor that detects increased electrical resistance when there is no
longer any ink between the terminals. The terminals could project from
the end of a rod that extends down into the cartridge from the top. It
could be inserted after drilling a hole - one for each cart. The
sensors could cause an LED to light up (one for each cart). It could
also set off a beeper.

If anyone ends up building one, please send me one ..or at least, some
instructions and a component list!

I'd design it myself, but my knowledge of electronics is too scant.

Al D