Controlling an HP #27cartridge

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Paul Wilkins

Dear all,

I've spent the last couple of days trying to reverse engineer an HP
inkjet cartridge - it's a black #27 (C8727A) that I'm using in a
Deskjet 3745. I now have a fairly good idea of the circuitry
connecting the 37 pins but was wondering if any of you have a better
idea of what they're doing (which shouldn't be hard, I'm no electronic
engineer!)

I need to control the nozzle addressing matrix system and would like
to be in a position where I can remove the cartridge from the printer
carriage and simply connect to it to a signal generator to release a
known number of droplets. I could go into far more detail about the
motivation for this project but I'll leave it there for the time
being!

Any help (be it emails, URLs, posted ramblings) would be much
appreciated.

Thanks,
Paul Wilkins
 
I've spent the last couple of days trying to reverse engineer an HP
inkjet cartridge - it's a black #27 (C8727A) that I'm using in a
Deskjet 3745. I now have a fairly good idea of the circuitry
connecting the 37 pins but was wondering if any of you have a better
idea of what they're doing (which shouldn't be hard, I'm no electronic
engineer!)

I need to control the nozzle addressing matrix system and would like
to be in a position where I can remove the cartridge from the printer
carriage and simply connect to it to a signal generator to release a
known number of droplets. I could go into far more detail about the
motivation for this project but I'll leave it there for the time
being!

Any help (be it emails, URLs, posted ramblings) would be much
appreciated.
Click to expand...

Unless you have a particular reason to want to use the #27 you would probably
be better with a different cartridge. The #27 cartridge uses a rather complex
multiplexing and timing method to fire the nozzles and it is unlikely that you
can reverse engineer it without some trouble. The previous generation such as
the #45 cartridge has an X-Y addressing scheme that is easier. Easier still
would be on of the "TIJ 2.0" cartridges such as the #29 cartridge. It has a
series of firing resistors with individual contact pads and a common return
pad. This would be the easiest to fire with minimal electronics.

You might search for US patent 6,347,868 which describes a handheld printing
tool based on rather simple electronics to fire a #41 cartridge. It may have
information that would help you; see
http://patft.uspto.gov/netacgi/nph-...L&s1=6347868.WKU.&OS=PN/6347868&RS=PN/6347868

In any case it will be non-trivial. One thing you will need to be careful with
is the energy applied to the cartridge; pulses of more than a few microseconds
in duration could damage the printhead. The #29 cartridge would be more
forgiving in this regard than later cartridges.

A bit more description of what you would like to do would probably be helpful.

Regards,
Bob Headrick, not speaking for my employer HP
 
pulses of more than a few microseconds in duration could damage
the printhead.
Click to expand...

Bob, with hindsight, I can only agree! I've just got some ink out but
then a little smoldering suggested I might want to be a little more
subtle with my drive signals!

Thanks very much for your post. I am looking to adapt a printhead to
give me a well controlled dispersion of small water droplets. This is
part of a Engineering Masters project. I'm a thermodynamicist and am
not really all that good with electronics. Regardless, the plan is to:

- gain control of a printhead to selectively fire, one nozzle, a group
of nozzles or an entire row
- switch ink for water and adjust the signals as necessary to account
for the differences in viscosity.

Best wishes,
Paul W
 
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