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Hacking an HP C4780 printer — Parallax Forums

Hacking an HP C4780 printer

RS_JimRS_Jim Posts: 1,768
edited 2012-09-11 10:02 in General Discussion
Hi,
Has anyone connected a remote power switch and power lamp monitor to an HP C4780 wireless printer? My Printer is in a location far from where it is often needed and I want to power in on/off and monitor it's power state with a propeller. I thought I would ask here before I attempt to disassemble my printer.
Thanks.
Jim

Comments

  • RS_JimRS_Jim Posts: 1,768
    edited 2012-09-10 05:32
    Any thoughts?
    Jim
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2012-09-10 09:01
    You could go the X10 route:

    The original thread containing Jon's program.
    http://forums.parallax.com/showthread.php?136869-X-10-Firecracker-Object

    A recent project that I've completed using the code.
    http://www.instructables.com/id/Take-over-your-world-using-BASIC/
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-09-10 09:39
    You are a bit unclear about distance and your preference of wireless or wired.

    You could use the Propeller to act as a modem and work over telephone lines.
    You could use an XBee Professional for wireless of good distances.
    You could use RS-422/485 wire up to kilometers.

    The hardest part is to think of a way to hack the HP C4780 as Hewlett-Packard certainly won't help. You might find someone in the Linux community that has hacked and documented their results.

    These days, solid state relays for AC mains of a few amps are quite available for turning the printer off, but if you need to push a button for an ON condition, you may need to use a hobby servo or a solenoid.

    Not sure what to do if you have an out of paper condition or a printer jamb or an out of ink.
  • GadgetmanGadgetman Posts: 2,436
    edited 2012-09-10 22:16
    Maybe a Spinneret board, hooked up to a relay for powering the printer up and down, and possibly phototransistors to detect LED status?
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-09-11 00:33
    Yes, photo-transistors would indeed read the LEDs and monitor the printer's functionality. That makes the remoteness much less of a problem.

    There are lots of channels by which to communicate. Much depends on what you already have available.
  • RS_JimRS_Jim Posts: 1,768
    edited 2012-09-11 03:57
    Hi,
    what I was hopeing when I started this thread, was to come across someone who had experence with actual tying across the power switch on the printer and monitoring the power on circuit with opto-isolator etc. I already have a prop running on my network thanks to an Enc28J60, module I got from OBC at PropellerPowered. I can access the prop from both my laptop and ipad. when I log into the prop, I get a report on the state of the power to the printer. The relay to control the actual AC power just needs to be installed inside a box with the power outlet and connected via transister to the prop. I did not want to just pull the plug on the printer and reenable by by restoring the AC as it doesnot go through the manufacture's normal shutdown proceedure.

    I had thought about the hobby servo as a remote "finger" to push the power button, guess that will have to be the method I use. I wonder if the front panel LED generates enough lite to be read by a photo resister, or will I have to find a suitable photo transister.

    I will mark this as solved and eventually post the results on the project forum.

    Thanks for the input.
    Jim
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-09-11 10:02
    I'd skip considering a CdS photocell as they are slow and the cost of a photo-transistor is quite similar. These are likely to be more sensitive to the LEDs light as well.

    The problem with modern devices and their power switches is that there are essentially push buttons that toggle a flip-flop or some other logic. This makes them rather difficult to tie into and the behavior is not a simple on/off - maybe a pulse at a certain voltage. I suppose you could wire a parallel toggle, but it might require isolation of some sort - like an opto-isolator. You will have to figure out correct polarity as it is not a simple switching through a photo-transistor inside the opto-isolator - it is essentially a diode junction.

    The actual electrical connection is likely buried rather deep inside the chassis and unless you don't care about a warranty, you would have to open it up and suffer a voided one with no real assurance that you will accomplish what you want by opening the box. Of course, the worse case it that you actually damage the on/off and have no repair under warranty for your trouble.

    In other words, are you intrepid enough for this project? Can you afford to sail forth into the unknown and risk having to buy a replacement printer?

    The only problem with the photo-transistors is that they may require being attached in a manner when one can no longer see the actual LED as exposure to other lights might interfer with their correct function.

    So, you are going to end up with a rather unique worthless printer if you do the modificiations. I generally use something older and out of warranty for such projects
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