One source I found says that Canon uses light from an LED--bounced from a prism at the bottom of the cartridge after ink is depleted--to trigger the "Empty" signal. Epson apparently counts the spurts of ink and calculates the arrival of "empty".
I couldn't find how HP do this. Anybody know?
Thanks.
I believe HP just estimates based on the cartridge type it detects, and the amount of ink it uses.
On Fri, 6 Mar 2015 23:03:13 -0800, DaveC wrote as underneath :
Any inkjet that uses chipped cartridges guestimates the emptiness. Old Canon printers certainly used the reflective prism, IP4000 was about the last that had unchipped carts. and thus had an accurate end level warning. I think most printers now would guestimate on the safe side judging by the complaints of half full carts being classed as empty. I dont know if Canon still uses the prisms on their modern chipped carts but I would think probably not as the guestimate method gets you to buy more ink earlier! Someone with one of the more modern Canons will know Im sure! ... HP have had chips since very early days so levels will be guestimated by software. C+
HP has two methods. One is to just guess based on usage: The other adds an expiration date to the cartridge: Both suck.
My old(?) Canon MP 620 uses chipped cartridges as far as I know and when I get an empty signal -the cartridge is fully emptied.
On my old Canon ip4300 printer the ink level can be seen through the clear plastic of the cartridge,unlike my Epson BX525WD multifunction printer.
Doug.
On Wed, 11 Mar 2015 19:03:25 -0700 (PDT), snipped-for-privacy@gmail.com wrote as underneath :
snip
Yep, any (prism) level measurement in the visible spectrum would need clear cartriges! Nearly all modern OEM carts. are black or an opaque colour! C+
Not exactly. There are more than a few problems.
Most older cartridges have open cell foam inside to prevent sloshing in transit. Kinda difficult to design a liquid level sensor that works in foam. Neither dye or pigment type inks are very conductive, so that's not going to work.
Some carts don't have any foam and are often clear or at least translucent. However, they are usually used with dye type inks, which are optically transparent. So, that's not going to work.
Older HP color carts have 3 colors in one cartridge. 3 sets of optical sensors in one cart isn't exactly economical or practical.
Optical sensing might work with pigment type inks, but I suspect the optical transmission characteristics will vary with the color. Also yellow is nearly transparent.
There is one place where optical sensing works... laser printers. The toner is optically opaque. Brother printers have windows on each end of the cartridge. Then the light can be seen through the cartridge, it's considered out of toner. The problem is they located the windows a bit too high on some printers. I forgot the model, but one of their older color laser printers leaves about 25% in the cartridge when it claims it's empty. The fix is to put some electrical tape over one of the windows.
Or a vertical light path from the led chip on the bottom of the cartridge, up through the (now) empty cartridge, reflecting off of a prism inside the top of the cartridge back to a receiver on the same chip as the LED is mounted.
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