Mobile Printerserver

Intro: Mobile Printerserver

for some reason i needed a mobile printer one day. it had to be movable, reliable and plug'n'print. to be more specific here's an unordered list of what it should be able to do:

- print on endless paper
- plug in into an existing network (with dhcp configuration) and print all new mails from a specific account each 10 minutes
- be heavy enough not to slide around all the time
- be light enough to be easily moved around
- no configuration, no login or whatever on startup, just push the button and it works
- easy maintenance (in case e.g. the cartridge is empty)
- low cost

STEP 1: Setting Up the Printer

(sorry no pic. i'll keep this step short since i don't want to go too much into technical details - you guys who know linux are able to do this better anyway ;-) )
after purchasing a cheap old dot-matrix printer on ebay and checking for the matching drivers i installed a very basic debian system (non-graphical, just textbased) on an old computer i had lying around (400 mhz, 250 mb, 4 gb from 1998). configuration was easily done in cups via a textbased www-browser on the machine. as you can see here i'm quite a noob - didn't know how to do it better (but i'm sure there is a better way). after setting up and configuring a mailclient i wrote a simple script that invokes the client, converts the incoming mails the way i needed them and sends them to the printer. a cronjob then runs the script every ten minutes. so far so easy.

STEP 2: What Not to Do: Start/stop the Whole Machine With a Switch

everything had to be as easy to start and stop as possible. starting it is easy: press the start button of the computer. the machine will boot and verything runs fine. the problems start when one wants to stop the machine: pushing the button again turns off the machine, but it also can crash the harddisk. at the moment the machine is still running that way, but any hints how to do it better would are greatly apprechiated (shutting down just with a single button)!

STEP 3: Disassembling the Hardware

after measuring the dimensions of the printer and the parts of the computer i decided to mount everything on a single piece of mdf with wheels on the bottom. i wanted to take away the original cases to improve cooling. this was easy with the computer: take out a few screws and you're done. the printer was the harder part to disassemble (and, of course, to be able to reassemble it again without it's case).

STEP 4: Reassembling and Mounting

after disassembling the hardware got mounted on the bottom of the case. cables and switches were added to allow everything to be put inside the case and to have just a switch and a wall-plug on the outside.

STEP 5: Building the Case

the top part of the case was built with mdf and dowels. since i don't have a drill-stand with possibilities for adjustment i just wrapped a tape around the drill to know how deep i can go without going through.

STEP 6: Wheels

after drilling all holes needed the wheels were mounted to the bottom and loose cables and the transormer of the computer were fixed with cable ties.

STEP 7: Test-assembling

next thing to do was to test-assemble the whole thing to see if everything is in place

STEP 8: Cutting Holes

test assembling was successfull so i took everything apart again to cut the holes for the fans, switches and the wall-plug

STEP 9: Paper In- + Outlet

at this point i ran into troubles: i needed to makes slots for the paper transport through the printer. thinking i would be able to do it simply by using a milling machine i ended up with a slot like you see in the picture below.
thinking over it again i decided to add some kind of tracks to the inside of the panel to keep the milling machine in line. this worked out perfectly.

STEP 10: Glueing

glueing it alltogether was quite easy. i used cheap paper tape to keep it all in place.

STEP 11: Assembling and Testing

the last thing to do was to screw some pieces of wood to the bottom to prevent the top from sliding around. after this everything was put together and the printer was tested successfully. to keep it as nice as it was the case was painted (clear) afterwards.

Comments

[munchman]

You seem to have a lot of dead space above the pc - why not change the HDD to a CF card, and mount it above some of the printer circuit boards. Would make the entire thing a lot thinner.

[carkat]

right. but i don't know if it's possible to boot from a cf-card since the computer is quite old (from 1998) and the bios would only boot from hdd and floppy. maybe one could flash a new bios but i guess that wouldn't be worth it. if i would have spent more time in optimizing the placement of the parts i surely could have saved quite some space, but i'm fine with the size of it since it stands quite stable and doesn't slide or tilt.

[munchman]

I think CF cards have the same pinout as an IDE hard drive, I know you can buy converters for a couple of bucks online. But I agree, it looks nice as a square.

[crapflinger]

"everything had to be as easy to start and stop as possible. starting it is easy: press the start button of the computer. the machine will boot and verything runs fine. the problems start when one wants to stop the machine: pushing the button again turns off the machine, but it also can crash the harddisk. at the moment the machine is still running that way, but any hints how to do it better would are greatly apprechiated (shutting down just with a single button)!" if you ran the PC off a "smart" UPS (one with USB support) inside the case instead of just straight off power...then you could have the PC set to shutdown as soon as the UPS looses wall power...then plug the UPS into some form of switched outlet that connects to the main power cord coming out of the case...then you press the power button on the case and it turns everything off safely...also set the PC to resume on return of power and it will boot once the power comes back on... i don't have any knowledge of working with UPS systems in linux though....i know there are ways to do it though a side note on that possibility is that most UPS devices will beep on power loss so you may need to bypass the beeper or something

[carkat]

yeah, thanks. that would be a possibility. also in linux. though i guess there are some other -less expensive- possibilities :-) what i was thinking of is a script that constantly checks the serial port and shuts down the computer when triggered somehow. but i don't know a) how to use the serial port / how to connect something to it and b) how to write a script that is capable of checking the port for changes but possibly there are even more easier solutions...

[crapflinger]

that would work too (assuming you figured out how to do it)

http://mercury.chem.pitt.edu/~sasha/LinuxFocus/English/January2001/article186.shtml maybe that?

[carkat]

wow, this is great, thanks a lot!