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Current contents:
EUR0 (about $0), some lint and a button.
There are a few aspect of the circuit that could be improved. Firstly, the nozzles that have been used are not spread evenly across the cartridge. It is however quite a lot of work to figure out exactly how to drive all the nozzles and the pins used here already produce a quite legible text. Secondly, the current consumption is not really suited to a little 9-V battery. With long texts this battery is temporarily exhausted quite quickly. It is of course possible to replace it with a 9-V NiCd or NiMH battery. These have no problems delivering short-duration current spikes. Thirdly, the text that the stamp produces is fixed, defined by the code in the microcontroller. With a little bit of work it can be changed to use the EEPROM instead and be made adjustable via, for example, a serial cable.
All this is not necessary for vandalising someone else's whiteboard and is left as an exercise for the reader. The author is keen to see any improvements in the circuit or firmware, so that others can also benefit from these. The firmware, source code and any potential updates are available for free downloading, of course.
Now a final remark: inkjet cartridges are not really designed to be used continuously in the open air. It can happen that the head becomes blocked with dried ink. In that case it helps to shake the whole thing vigorously a few times (watch out for splattered ink everywhere) and to suck up the ink with a tissue from the head afterwards. It certainly helps if the cartridge is stored with the print head facing downwards as much as possible.
This article featured in the magazine 'Elektor'. Their English site is here. They also have a Dutch, German and French edition of their wonderful magazine.
Last 10 comments Show allthere was/is a swedish company "printdreams" who developed a device called "Xyron Design Runner" (check on the usual channels) where in the end you could also upload your own files to print on ANY surface. used hp cartdridges aswell. i saw them on the cebit computer fair 6-10 years ago. their sites are down now unfortunately, i hope they didn't go bankrupt...
It still is, under 'electronic stamp'. I agree that I have to make everything a bit more readible; the current setup worked fine when I had only 5 or 6 projects but the site is kinda growing out of its jacket now :)
Hi, it seems this project isn't listed in the menu anymore? Here's another handheld printer, but their homepage seems to be dead. http://www.ohgizmo.com/2009/11/04/printbrush-looks-like-magic-makes-printing-not-suck/
i can't find this cartridge type in my country,can anyone to show me about pinout for new cartridge, like hp21, thnks
Oh no, I've got even more HP26 cartridges! Now, if only I could find some time, and some text to print on some object...
have anyone interfaced epson head? My boss has reverse engineered it? I want to interface that too can any one help? If so mail me at awasoft@hotmail.com
Thank you very much for your information, I build a circuit based on yours, with the addition of an RS232 interface to plot with commands from a PC in order to mount the printer head to my homemade CNC router. Unfortunately I put a transistor array instead of direct connection to the CPU before I saw your comment. Despite of this, it printed some ink, so I guess the head has internal pull up resistors, although the transistors reversed the pollarity of the signals, so the printing was strange (I activated more than one nozles at a time instead of one). Anyway I have to find the exact timing of ON and OFF to achieve a fast and decent printing and not to burn the head. Thanks for everything!
That's not an issue - the printer head itself seems to have transistors or mosfets in place: the lines are active-high iirc.
In the low driving end, when the high end is activated there is current flowing to the internal ESD diodes of the microcontroller even when high (I guess that the 15V in the nozzle driving mechanism is not enough for ink to flow, but you should consider using a transistor array or an array of diodes instead of direct drive from the microcontroller)
i forgot: here a video of their 2006 prototype: http://www.youtube.com/user/PrintDreams#p/a/u/2/fSM5z5vL-Qo